Article: 222155 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <28826-4412519C-544@storefull-3255.bay.webtv.net> <1142073802.408256.64360@i40g2000cwc.googlegroups.com> <8_CQf.55899$Jd.1369@newssvr25.news.prodigy.net> <1216e3dskf72sa3@corp.supernews.com> <1bj7129btemua297vutapmnrhc1kn4l73f@4ax.com> <0M1Rf.53582$H71.9935@newssvr13.news.prodigy.com> Message-ID: Date: Mon, 13 Mar 2006 00:05:36 GMT Tom Donaly wrote: > that sounds like Cecil's theory, which he's always ready to > defend with his strong right arm. I can't believe all the fuss he's made > over something as trivial as a loading coil. As long as someone asserts that there is no phase shift through a 75m mobile bugcatcher coil, I will continue pointing out that they are wrong. The phase shift through a 75m bugcatcher coil is approximately the same as it is at the bugcatcher coil's self-resonant frequency. That's simply a law of physics that some people wish didn't exist but it does in spite of their wishes. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222156 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142043207.752336.206250@j52g2000cwj.googlegroups.com> <28826-4412519C-544@storefull-3255.bay.webtv.net> <1142073802.408256.64360@i40g2000cwc.googlegroups.com> <8_CQf.55899$Jd.1369@newssvr25.news.prodigy.net> <1216e3dskf72sa3@corp.supernews.com> <1142119851.274292.127420@j33g2000cwa.googlegroups.com> <1142162882.986318.46180@j52g2000cwj.googlegroups.com> <4a-dnWqZ766NGonZnZ2dnUVZ_vidnZ2d@adelphia.com> Message-ID: Date: Mon, 13 Mar 2006 00:09:50 GMT John Popelish wrote: > Cecil Moore wrote: >> We may understand the results of Tom's latest >> measurement by considering the following: >> >> 50 ohm source===1 WL 50 ohm lossless coax===8+j2500 load > > I am not sure I understand this. As I understand an S parameter tester, > both source and load are 50 ohms. Tom says he fed and monitored the > signal with a pair of current transformers. I don't think he fed the coil with a current transformer. I think he simply had the coil across the signal generator's output terminals with current pickup devices at each end of the coil. The above diagram doesn't change anything about his configuration but does point out the conceptual mistake he made which is the identical conceptual mistake that he and Roy have been making for years. Their model presupposes their measured results. How could their results be anything else? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222157 of rec.radio.amateur.antenna Message-ID: <4414C080.6050601@fuse.net> Date: Sun, 12 Mar 2006 19:44:48 -0500 From: jawod Subject: Re: Safety ground versus RF ground for a 2nd Floor shack References: <26f31$44110069$42a1bfc2$15706@FUSE.NET> <1141986196.902379.179470@e56g2000cwe.googlegroups.com> w8ji@akorn.net wrote: > jawod wrote: > >>I know this has been addressed on the group before but I remain confused. > > >>My own gut says safety first, lower risk of RF issues after-the-fact by >>? what ? >> >>I remember suggestions of coiling the ground wire in an RF choke, >>multiple ground lines of various lenghts to mess with harmonics. >>Ferrite beads? Chicken blood and a black cat? > > > > John, > > You have been misled and confused by bad information. > > > > Richard Clark has given you good advice. > > > The only antenna that requires an RF ground is an antenna with a single > conductor feedline worked against ground, or an antenna that is poorly > designed or constructed. > > The only reasons to have a hamshack ground, unless you are trying to > band-aid an antenna that is improperly constructed or feed a longwire, > are electrical safety and lightning. > > Electrical safety can be taken care of by using a three wire outlet > with grounding to the sagfety ground, and by following national codes. > National codes require your station ground be bonded to the power mains > entrance ground. We are not suposed to have two isolated grounds > according to NEC, and it is a bad idea to have isolated grounds for > lightning, safety, and RFI reasons. > > I'm afraid all the talk about ground loops and such have confused you. > > Try reading this: > > http://www.w8ji.com/ground_systems.htm > > 73 Tom > My apologies to Richard and Tom. Your advice IS appreciated. Just got my ego bruised a bit. john Article: 222158 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1141864325.153022.145680@p10g2000cwp.googlegroups.com> <18782-440FBF35-53@storefull-3252.bay.webtv.net> <1141929188.910581.171220@p10g2000cwp.googlegroups.com> <1211ig3hafcm451@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Mon, 13 Mar 2006 00:47:36 GMT "Richard Clark" wrote in message news:r3f912drbusfdugh59rd8o3e3ip2vr4llr@4ax.com... > On Fri, 10 Mar 2006 03:12:11 GMT, "Jerry Martes" > wrote: > >> I have a HP8405A Vector Voltmeter I'll give you and even pay the >> shipping >>if that is of any help with the measurements. > > Hi Jerry, > > So, any taker? > > 73's > Richard, KB7QHC Hi Richard No takers. No replies. Jerry Article: 222159 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Radiation Resistance Date: Sun, 12 Mar 2006 19:59:22 -0600 Message-ID: <2813-4414D1FA-1068@storefull-3257.bay.webtv.net> References: <23728-44146513-657@storefull-3254.bay.webtv.net> Roy, W7EL wrote: "There`s even a picture Fig 5-1" Yes, exactly as I speculated. Reg`s question that I tried to answer was: "What is the value of the constant C?" My answer is 395 and I`nm sticking with it until someone shows me the error in my ways. Best regards, Richard Harrison, KB5WZI Article: 222160 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142073802.408256.64360@i40g2000cwc.googlegroups.com> <8_CQf.55899$Jd.1369@newssvr25.news.prodigy.net> <1216e3dskf72sa3@corp.supernews.com> <1142119851.274292.127420@j33g2000cwa.googlegroups.com> <1142162882.986318.46180@j52g2000cwj.googlegroups.com> <4a-dnWqZ766NGonZnZ2dnUVZ_vidnZ2d@adelphia.com> <1142209619.304856.265010@j33g2000cwa.googlegroups.com> Message-ID: Date: Mon, 13 Mar 2006 02:22:01 GMT w8ji@akorn.net wrote: > http://www.w8ji.com/inductor_current_time_delay.htm Don't you think it only fair to to the readers to indicate on that new web page that you measured the current in the midst of of a 16000:1 SWR? That's what I get for 8+j2500 being fed by a 50 ohm source. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222161 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141864325.153022.145680@p10g2000cwp.googlegroups.com> <18782-440FBF35-53@storefull-3252.bay.webtv.net> <1141929188.910581.171220@p10g2000cwp.googlegroups.com> <1211ig3hafcm451@corp.supernews.com> Message-ID: Date: Mon, 13 Mar 2006 02:23:52 GMT Jerry Martes wrote: > No takers. No replies. > > Jerry Jerry, I've sent you two emails. Did you not get them? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222162 of rec.radio.amateur.antenna Message-ID: <4414DAA3.5792458B@shaw.ca> From: Irv Finkleman Subject: Re: Safety ground versus RF ground for a 2nd Floor shack References: <26f31$44110069$42a1bfc2$15706@FUSE.NET> Date: Mon, 13 Mar 2006 02:36:04 GMT One way to beat this is to tune with low power and touch the rig. Every few days increase the power until you have built up a tolerance to the RF tingle. You could also try this with the household power, starting at 2 or three volts, and increasing it gradually over time until you build up your immunity to electric shock as well. Irv VE6BP :-) Article: 222163 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1141864325.153022.145680@p10g2000cwp.googlegroups.com> <18782-440FBF35-53@storefull-3252.bay.webtv.net> <1141929188.910581.171220@p10g2000cwp.googlegroups.com> <1211ig3hafcm451@corp.supernews.com> Subject: Re: Current through coils Message-ID: <8V4Rf.4714$o41.3612@trnddc06> Date: Mon, 13 Mar 2006 02:36:52 GMT "Cecil Moore" wrote in message news:YI4Rf.38223$_S7.21255@newssvr14.news.prodigy.com... > Jerry Martes wrote: >> No takers. No replies. >> >> Jerry > > Jerry, I've sent you two emails. Did you not get them? > -- > 73, Cecil http://www.qsl.net/w5dxp No Cecil, I didnt. Maybe I wrote my address wrong. I figured you realized that the HP Vector Voltmeter wasnt capable of providing the data needed for this discussion. Jerry KD6JDJ j.jmartes@verizon.net Article: 222164 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Radiation Resistance Date: Sun, 12 Mar 2006 20:56:05 -0600 Message-ID: <24187-4414DF45-859@storefull-3251.bay.webtv.net> References: <1219clp27lvpu79@corp.supernews.com> Roy, W7EL wrote: "Do the proper substitutionn and you`ll get the correct answer." Yes. The warning also appears on page 137: "In developing the field expressions for the short dipole, which were used in obtaining (5-56), (5-56) is the value of radiation resistance, the restriction was made that lambda is much larger than the length of the dipole L." No problem there, Reg specified a short monopole. Kraus does a sample calculation for a short dipole. I used Kraus` data and got the same answer when duplicating his calculation. But Reg was not asking for an answer to a specific problem. Reg was asking for the value of the constant in a formula of the same form. Kraus gives it as 80 pi squared for a dipole.. This is 790. We know that a monopole has half the resistance of a dipole. Example: 73 ohms and 36.5 ohms. 790 / 2 = 395. That`s not a resistance, it is only the value of a constant which must be multiplied by (L/lambda) squared to give the radiation resistance of a very short monopole. Best regards, Richard Harrison, KB5WZI Article: 222165 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Yagi Antenna Question References: <1142213036.108163.297200@e56g2000cwe.googlegroups.com> Message-ID: <4414e0f4_4@newsfeed.slurp.net> Date: 12 Mar 2006 22:03:16 -0500 ORIGINAL MESSAGE: chris wrote: > Also, on many multi-element Yagi designs, the norm seems to be just > one reflector, and many director elements. Does this mean that the > reflector is more "effective" than the directors at modifying the > radiation field? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In a sense, yes it is more effective. Think about it this way: If the reflector does its job, there is no more energy behind it to be reflected any further. Just the opposite with a director. The more it directs the energy, the more there is to be further directed. When yagis first became popular there were designs published with two or more reflectors. People soon realized the second one added little or nothing and they disappeared. I suppose if you want really exceptional F/B ratio you could use a second reflector, but most people don't bother. One is enough. Bill, W6WRT Article: 222166 of rec.radio.amateur.antenna Message-ID: <4414E21C.9080503@fuse.net> Date: Sun, 12 Mar 2006 22:08:12 -0500 From: jawod Subject: Re: Safety ground versus RF ground for a 2nd Floor shack References: <26f31$44110069$42a1bfc2$15706@FUSE.NET> <4414DAA3.5792458B@shaw.ca> Irv Finkleman wrote: > One way to beat this is to tune with low power and touch the > rig. Every few days increase the power until you have built up > a tolerance to the RF tingle. > > You could also try this with the household power, starting at > 2 or three volts, and increasing it gradually over time until > you build up your immunity to electric shock as well. > > Irv VE6BP :-) I tried this approach several years ago...got up to about half a kilovolt... but my wife complained that my glow was keeping her up at night. Article: 222167 of rec.radio.amateur.antenna Message-ID: <4414E987.8090501@fuse.net> Date: Sun, 12 Mar 2006 22:39:51 -0500 From: jawod Subject: Re: Safety ground versus RF ground for a 2nd Floor shack References: <26f31$44110069$42a1bfc2$15706@FUSE.NET> <4414DAA3.5792458B@shaw.ca> <1142217753.842244.236260@v46g2000cwv.googlegroups.com> w8ji@akorn.net wrote: > There is absolutely no reason to have an RF ground unless: > > 1.) You are end feeding a single wire antenna that is brought into the > shack > > 2.) The two conductor feedline you have brought in, be it coax or open > wire, is connected to an antenna that is not properly designed or > installed > > The safety ground is required. The RF ground is a band-aid for > something else being wrong. > > 73 Tom > Tom, If we assume that there is a well matched antenna: twin line to balun, coax to transceiver. My RF concern was that a long line to ground would serve as an antenna to bring RF into shack. If this is not the case, or if this is easily dealt with, great. The mains box is on the opposite side of the house...that ground is not conveniently located. My coax will go thru a lightening arrestor (Polyphase) which will be earth grounded. If I run a low gauge wire from that earth ground to the main box ground, then this is prevents ground loop? What if the distance to the mains box is 60 feet? John Article: 222168 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141864325.153022.145680@p10g2000cwp.googlegroups.com> <18782-440FBF35-53@storefull-3252.bay.webtv.net> <1141929188.910581.171220@p10g2000cwp.googlegroups.com> <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Mon, 13 Mar 2006 03:41:34 GMT Jerry Martes wrote: > No Cecil, I didnt. Maybe I wrote my address wrong. I think the feature on my newsreader must not be working. I didn't get any notice that it didn't go through. I'll send you a regular email. > I figured you realized that the HP Vector Voltmeter wasnt capable of > providing the data needed for this discussion. Here's the procedure for measuring the electrical length of a base loading coil. That's the same as the delay through the coil. 1. Mount your base loading coil on your vehicle and remove the stinger. Note that the current is zero at the top of the coil with the stinger removed. 2. Use an antenna analyzer, like an MFJ-259B to locate the self-resonant frequency. It will be the first frequency going up in frequency for which the reactance is zero and the resistance is very low. My 75m bugcatcher coil has a self-resonant frequency of 6.6 Mhz which is an electrical 90 degrees at 6.6 MHz. 3. Calculate the length of the RF cycle at the self-resonant frequency. 1/6600000 = 152 nS for 360 degrees at 6.6 MHz. The coil is an electrical 90 degrees long on its self-resonant frequency so the delay through the coil is 152/4 = 38 nS. 38 nS is also the approximate delay through the coil when used as a base loading coil on 4 MHz. One RF cycle on 4 MHz takes 250 nS so 90 degrees (1/4WL) of that cycle is 62.5 nS. The coil is providing 38/62.5 = 61% of the antenna on 4 MHz. Forget the bogus coil delays posted by the "experts". They are measuring standing wave current which is known not to change phase on either end of the coil and it doesn't do a bit of good to measure something that doesn't ever change. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222169 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Sun, 12 Mar 2006 21:38:12 -0600 Message-ID: <2814-4414E924-271@storefull-3257.bay.webtv.net> References: <8V4Rf.4714$o41.3612@trnddc06> Jerry Martes wrote: "I figured you realized that the HP Vector Voltmeter wasn`t capable of providing the data needed for this discussion." More likely necessary. It is dead simple. You have a whip with a loading coil somewhere in the circuit under it. The r-f energy is reflected by the open circuit at the tip of the antenna. It must return toward the sender. There is no place else to go. Anything feeding the antenna is in the path. Volts and amps at any and all points along the way are acted upon by the incident and the peflected waves. Straight wire or coil, the effect is the same as there is a periodic variation in volts and amps due to the combination of the effects of volts and amps from both directions. Should the current at both terminals of a loading coil happen to be the same, it would likely be a rare coincidence. Best regards, Richard Harrison, KB5WZI Article: 222170 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radiation Resistance References: <23728-44146513-657@storefull-3254.bay.webtv.net> <2813-4414D1FA-1068@storefull-3257.bay.webtv.net> <1142217483.531237.70100@j52g2000cwj.googlegroups.com> Message-ID: Date: Mon, 13 Mar 2006 03:46:25 GMT w8ji@akorn.net wrote: > Is everyone from Texas like this? Before you jump the gun, we should probably wake Reg up and ask him what he really meant. I don't think he was asking about an infinitessimal vertical. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222171 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radiation Resistance References: <1219clp27lvpu79@corp.supernews.com> <24187-4414DF45-859@storefull-3251.bay.webtv.net> Message-ID: Date: Mon, 13 Mar 2006 03:55:11 GMT Richard Harrison wrote: > We know that a monopole has half the resistance of a dipole. Example: 73 > ohms and 36.5 ohms. 790 / 2 = 395. That`s not a resistance, it is only > the value of a constant which must be multiplied by (L/lambda) squared > to give the radiation resistance of a very short monopole. Does it matter that for a vertical that is 1/2 of the length of the dipole, (L/lamda)^2 is different by a factor of 4? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222172 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Radiation Resistance Date: Sun, 12 Mar 2006 21:53:33 -0600 Message-ID: <2813-4414ECBD-1075@storefull-3257.bay.webtv.net> References: <1142218986.976512.61520@i39g2000cwa.googlegroups.com> Gene Fuller wrote: "However, you overlooked the fact that "L" is gifferent for the dipole and monopole." L is not a constant. L is a variable in another part of the formula. The difference in radiation resistance between a dipole and a monopole is a constant. It equals 2, not 4, not 8, or not 16. Best regards, Richard Harrison, KB5WZI Article: 222173 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Vertical vs Horizontal shootout part one Date: Sun, 12 Mar 2006 23:09:05 -0500 Message-ID: <1219ru8so8fp2f@corp.supernews.com> References: <120ngtl3drs574@corp.supernews.com> The hour is growing late and the urge to tell a story is upon me. Note, that unlike others, I never imbibe alcoholic beverages. This is a true story. A large, expensive, rotatable LPDA was erected on a tall tower and tested in an informal way with a receiver and short-wave broadcast transmitters as signal sources. Nulls were where they were supposed to be. F/B was roughly what was expected. Front lobe seemed about right. A month went by and it was time to perform more careful measurements. A 180 swing while listening to a distant carrier suggested that there was more gain off of the back than off of the front! Wise men pondered that this must be a measurement error. Impedances were very close to expected. The scheme that was used to determine that the antenna needed to be brought back to earth were these: (Keep in mind that this is a LPDA and not a Yagi.) A 6db pad was put in the line to ensure that the nonexistent impedance changes with no change in frequency would not affect things. An accurate, step attenuator was then added in the line. (Should sound familiar.) Antenna was pointed towards a known very high power broadcast station with a known location such that the expected receiving take-off angle was about 6 degrees. Bandwidth was made very narrow and centered on the carrier. Enough attenuation was added to get the S-meter to average either side of a mark. The attenuation was varied by one db up and down with several minutes at each level. Then the antenna was rotated 180 degrees and the change in attenuation to return to the same indication was noted. Ouch. Repeated several times it became clear that the antenna had reversed direction and (are you listening?) a number for the difference in gain (at the angle involved) and the uncertainty in that number was crafted. Lord K. should have said - and may have said - that all measurements comprise at least two numbers: an estimate expressed as a number and an estimate of the uncertainty in the first number expressed as a number. The evidence was conclusive that something had happened. A search for causality took place with the assistance of NEC. With a good deal of speculation and noting how the largest elements were constructed, it was speculated that one of the rearmost elements (or a part of one of the rearmost elements) may have become detached electrically. An NEC simulation was produced that fit the data. No, this is not proof, but it did furnish additional support for the need to lower the antenna. More support came >from measurements at the high end of the frequency range where no anomalies were noted and where the long elements would not be expected to play much of a role. At significant cost and effort, the antenna was lowered and it was found that one of the mechanical connections of a sleeve with normal screw had not been tightened in a rear element. The conclusive proof was that the screw had not "cut." Apparently, a month of very sight corrosion had isolated part of an element. So, be my students and find the lessons in this tale. Make a list. 73 and I am off to bed, perchance to dream of antennas, Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net " Article: 222174 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <8V4Rf.4714$o41.3612@trnddc06> <2814-4414E924-271@storefull-3257.bay.webtv.net> Message-ID: Date: Mon, 13 Mar 2006 04:06:04 GMT Richard Harrison wrote: > Should the current at both terminals of a loading coil happen to be the > same, it would likely be a rare coincidence. All one has to do to see radical changes in the currents at the ends of the coil is move the coil up and down a 3/4WL radiator. One can find a place where current at the top of the coil is five times the current at the bottom of the coil. That's just the way standing wave current works. Too bad there are so many myths and old wives' tales being spread about it by alleged "experts" who have forgotten EE201. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222175 of rec.radio.amateur.antenna From: stananger < stananger@********.***> Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? References: Message-ID: Date: Mon, 13 Mar 2006 05:04:27 GMT Robert11 wrote: > Hello: > > Anyone have any thoughts on (hopefully not experiences) whether putting a > loop of, e.g. 1 foot in diameter, > on a coax run from an outdoor receive-only antenna has any merit as far as > helping any emf lightning induced pulses from traveling into a house ? > > Have heard about this, but it's hard to believe it would actually do > anything in practice. > But,... ? > > B. you been hanging out on 11 meters? Article: 222176 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Radiation Resistance Date: Sun, 12 Mar 2006 23:17:07 -0600 Message-ID: <28826-44150053-804@storefull-3255.bay.webtv.net> References: Cecil, W5DXP wrote: "Does it matter that for a vertical that the length of a dipole (L/lambda)squared is different by a factor of 4?" It doesn`t make a ratio different than two to one in the ratio of resistances of the 1/2-wave dipole to the 1/4-wave monopole. We are not comparing a monopole that is the the length of a dipole with the dipole. We are comparing a monopole that is 1//2 the length of a dipole to the dipole when we make the resistance ratio. The small dipole is working against a perfect ground in Reg`s specification. It would see its reflection in that perfect ground, so its equivalent length is doubled. Kraus` dipole is presumed to be in free space. Best regards, Richard Harrison, KB5WZI Article: 222177 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Subject: Re: Current through coils Message-ID: Date: Mon, 13 Mar 2006 06:39:03 GMT "Richard Clark" wrote in message news:dpr91293ecf5lellnaup410gdb80m4f8jc@4ax.com... > On Mon, 13 Mar 2006 03:41:34 GMT, Cecil Moore wrote: >>I'll send you a regular email. > ... >>Use an antenna analyzer, like an MFJ-259B to locate the >>self-resonant frequency. > > Vector VOLTmeter? > VECtor Voltmeter?!!! > > I don' need no stinkin' VECtor VOLTmeter! > > Hi Jerry, > > Can you take another dumpster dive and see if you can find a Raster > Ammeter? > > 73's > Richard Clark, KB7QHC Hi Richard There are sooo many things I dont know anything about. Raster Ammeter is one of the many things I havent even heard about. I sure would like to learn how to use a Vector Voltmeter. Right now, I cant measure impedance (with any confidance of accuracy) when their VSWR is below about 1.5 to 1 on a 50 ohm line at 137 MHz. Jerry Article: 222178 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Subject: Re: Current through coils Message-ID: <_O8Rf.6000$o41.751@trnddc06> Date: Mon, 13 Mar 2006 07:03:22 GMT "Richard Clark" wrote in message news:kt4a12l0rm1e7m20d5nje4k1c9k793pi07@4ax.com... > On Mon, 13 Mar 2006 06:39:03 GMT, "Jerry Martes" > wrote: > >> Raster Ammeter is one of the many things I havent even heard about. > > "It's a joke, son." > Foghorn Leghorn Hi Richard The "raster" had all the earmarks of an imaginary device. I sensed it was a put on. The problem I have is my inexperience requires that I dont assume *anything*. I feel like Rip Van Winkle. The engineering community has developed a whole lot of nice things since I left it in 1969. And, its like I've been sleeping for 37 years. Jerry Article: 222179 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Date: Mon, 13 Mar 2006 00:50:06 -0600 Message-ID: <23730-4415161E-24@storefull-3254.bay.webtv.net> References: <1142219157.314335.180560@j52g2000cwj.googlegroups.com> W_Tom wrote: "Do you think the loop will stop what three miles of sky could not?" Depends on what kind of loops and how many. I`ve worked in several broadcast stations that often got struck by lightning. Their towers were the tallest things around. None of these stations got significant damage from lightning. In addition, none of the station equipment powered from the mains or appliances plugged into the mains at the station ever was damaged. All these stations used tower lighting chokes, one coil for each tower lighting wire including the neutral going up the tower. Three wires, beacon, side lights, and neutral were usually accommodated with tower lighting chokes. Their primary function is to avoid sapping any of the r-f energy from the tower. Another benefit is that the chokes reject lightning too. They are substantial and all turns are wound side by side (trifiler?) around a large ceramic coil form. The wire is large enough to easily handle the load current. I never worked at a station that used Austin tower lighting transformers instead of chokes, but I`ve seen enough of them to suppose they must isolate about as well as chokes do. One station I worked in had an FM antenna atop one if its AM broadcast towers. Its FM coax was coiled at ground level to isolate the AM r-f and it rejected lightning too. So, if you have enough of the right turns the choke does effectively reject lightning. Inductance is proportional to the size of the coil. Best regards, Richard Harrison, KB5WZI Article: 222180 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Radiation Resistance Message-ID: References: <1219clp27lvpu79@corp.supernews.com> <24187-4414DF45-859@storefull-3251.bay.webtv.net> Date: Mon, 13 Mar 2006 08:16:32 GMT On Sun, 12 Mar 2006 20:56:05 -0600, richardharrison@webtv.net (Richard Harrison) wrote: >Roy, W7EL wrote: >"Do the proper substitutionn and you`ll get the correct answer." > >Yes. The warning also appears on page 137: >"In developing the field expressions for the short dipole, which were >used in obtaining (5-56), (5-56) is the value of radiation resistance, >the restriction was made that lambda is much larger than the length of >the dipole L." No problem there, Reg specified a short monopole. > >Kraus does a sample calculation for a short dipole. I used Kraus` data >and got the same answer when duplicating his calculation. > >But Reg was not asking for an answer to a specific problem. Reg was >asking for the value of the constant in a formula of the same form. >Kraus gives it as 80 pi squared for a dipole.. This is 790. > >We know that a monopole has half the resistance of a dipole. Example: 73 >ohms and 36.5 ohms. 790 / 2 = 395. That`s not a resistance, it is only >the value of a constant which must be multiplied by (L/lambda) squared >to give the radiation resistance of a very short monopole. > Is all that to mean that you used the formula given by Kraus for a short thin dipole and applied your own rule to halve the coefficient. In your original response you said "395 It is found on page 137 of Kraus` 1950 edition of "Antennas"." Is that correct, or did you make the number 395 up according to your own rules and then attribute it to Kraus? Owen -- Article: 222181 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Mon, 13 Mar 2006 13:01:15 GMT Richard Clark wrote: > Cecil Moore wrote: >>Use an antenna analyzer, like an MFJ-259B to locate the >>self-resonant frequency. > > Vector VOLTmeter? > VECtor Voltmeter?!!! > > I don' need no stinkin' VECtor VOLTmeter! Actually, unlike Tom (who rushes in where angels fear to tread) I cannot figure out how to use the VVM to make a valid measurement of what we are trying to measure. If I cannot figure that out, then the VVM won't do me any good as Tom's setup didn't do him any good and just confused him all over again by tricking him into making his measurement in an SWR = 16000:1 environment. I'm truly surprised his standing-wave current delay measurement wasn't zero. Guess everyone sees the danger in trying to guess what the results of someone else's measurement will be. Tom should have measured something around 15.6 degrees. The fact he didn't sends up a very large red flag. Another problem is that the delay through the coil changes drastically between bench isolation and being installed directly above a GMC pickup's ground plane because of the enormous increase in coil capacitance to that ground plane. So the delay through the coil needs to be measured in the physical environment in which it is operated. It is virtually impossible to eliminate reflections from a 75m mobile bugcatcher system so the VVM can't measure what we are trying to measure. The question is: For a well-designed coil, is the self- resonance method valid for determining the delay through a coil at HF frequencies below the self-resonant frequency? Since that's been an accepted way of doing it for more than a century, I don't see how anyone could object. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222182 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? References: Message-ID: Date: Mon, 13 Mar 2006 13:09:44 GMT stananger wrote: > Robert11 wrote: >>Anyone have any thoughts on (hopefully not experiences) whether putting a >>loop of, e.g. 1 foot in diameter, >>on a coax run from an outdoor receive-only antenna has any merit as far as >>helping any emf lightning induced pulses from traveling into a house ? > you been hanging out on 11 meters? Reminds me of what I once told my secretary back in the 70's. Our lab soldering irons were simple AC devices with standard AC cords attached. We tied a half-hitch knot in them and used that loop to hang them on nails on the wall. I was at the bench one day and my secretary asked me what the knot was for. I told her that by tightening the knot, I could regulate the flow of electrons and thus control the temperature of the soldering iron. Later that night, over drinks at Charlie Brown's, she and I had a good laugh about that. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222183 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radiation Resistance References: <28826-44150053-804@storefull-3255.bay.webtv.net> Message-ID: Date: Mon, 13 Mar 2006 13:13:22 GMT Richard Harrison wrote: > Cecil, W5DXP wrote: > "Does it matter that for a vertical that the length of a dipole > (L/lambda)squared is different by a factor of 4?" > > It doesn`t make a ratio different than two to one in the ratio of > resistances of the 1/2-wave dipole to the 1/4-wave monopole. We are not > comparing a monopole that is the the length of a dipole with the dipole. > We are comparing a monopole that is 1//2 the length of a dipole to the > dipole when we make the resistance ratio. Richard, Balanis doesn't say that the 'L' in the monopole formula is 1/2 the 'L' in the dipole formula. Does Kraus? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222184 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <_O8Rf.6000$o41.751@trnddc06> Message-ID: Date: Mon, 13 Mar 2006 13:17:34 GMT Jerry Martes wrote: > I feel like Rip Van Winkle. The engineering community has developed a > whole lot of nice things since I left it in 1969. And, its like I've > been sleeping for 37 years. Ever heard of a "Triactuated Multicomplicator"? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222185 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Radiation Resistance References: <1142218986.976512.61520@i39g2000cwa.googlegroups.com> <2813-4414ECBD-1075@storefull-3257.bay.webtv.net> Message-ID: Date: Mon, 13 Mar 2006 14:22:24 GMT Richard Harrison wrote: > Gene Fuller wrote: > "However, you overlooked the fact that "L" is gifferent for the dipole > and monopole." > > L is not a constant. L is a variable in another part of the formula. The > difference in radiation resistance between a dipole and a monopole is a > constant. It equals 2, not 4, not 8, or not 16. > > Best regards, Richard Harrison, KB5WZI > Richard, I guess this must be the week for basic math explanations. Let's try it with numbers. The equation shown in Kraus "Antennas", 2nd edition, page 216, for the radiation resistance of a short dipole with constant current is: Rr = 80 pi^2 (L/lambda)^2 80 pi^2 is about 790, so the equation is rewritten as: Rr = 790 (L/lambda)^2 In the convention used by Kraus, "L" is the total length of the dipole. I presume the equivalent discussion is contained in the 1950 edition of "Antennas". As a test case, let's suppose that L is 8 meters, and lambda is 80 meters. We immediately see that Rr is 7.9 ohms. OK, now take the monopole over perfect ground that Reg mentioned. The monopole length that corresponds to one half of the test case dipole is 4 meters. The radiation resistance of the monopole is 3.95 ohms. So, the question becomes determining the correct coefficient for the Rr equation. (L/lambda) is now 0.05, not 0.10. Therefore, Rr = 3.95 ohms = X (0.05)^2 I believe you will discover that "X" must be 1580. This is set up using the definitions for L as stated in Kraus (dipole) and as stated by Reg in his monopole query. Of course you can set up your own rules, but that would be addressing a different problem. 73, Gene W4SZ Article: 222186 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Radiation Resistance Date: Mon, 13 Mar 2006 15:04:25 +0000 (UTC) Message-ID: References: <12180orrngmfn42@corp.supernews.com> "Roy Lewallen" wrote > C = 160 * pi^2 ~ 1579. ==================================== Thank you Roy. ---- Reg Article: 222187 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> Message-ID: Date: Mon, 13 Mar 2006 15:09:31 GMT w8ji@akorn.net wrote: > Cecil Moore wrote: >>Guess everyone sees the danger in trying to guess what >>the results of someone else's measurement will be. Tom >>should have measured something around 15.6 degrees. The >>fact he didn't sends up a very large red flag. Tom, I am going to ask you some relatively simple technical questions. If you continue to refuse to answer those questions, I and the other readers of r.r.a.a will draw a logical conclusion about your unwillingness or inability to answer questions, i.e. a non-technical answer or no answer at all will cause you to lose credibility. I was wrong about the radiation resistance equation. See how readily I admitted my mistake? (When was the last time you admitted a mistake?) First question is a short one: Please explain why a century old method of determining the phase shift through a coil by measuring its self-resonant frequency is not good enough for you. Do you really expect us to believe that the phase shift through a well-designed coil can change by 81% from 16 MHz to 4 MHz? > Translation of what Cecil actually is saying: > > "Whenever multiple measurements by independent sources disagree with me > the measurements others made must be wrong." I make mistakes but I seem to be on a solid technical footing here. A number of readers agree. Maybe you can convince me and them otherwise if you stop refusing to answer technical questions about your measurements. Your 100 uH coil is the 8+j2500 ohm load in the following fixed font example. That's at 3.98 MHz with a Q of 313. Current probes are at X and Y. How is the following circuit different from your test setup? +---one wavelength lossless 50 ohm coax-----+ | X source coil 8+j2500 load | Y +-------------------coax braid--------------+ The one wavelength of lossless coax doesn't change any values in the steady-state situation so the current probes at X and Y read the same value of currents as yours. The SWR on the coax is about 16000:1. There is virtually zero net current flowing through the load because of the *extreme* mismatch. Virtually all of the current at the coil is standing-wave current which is known to have unchanging phase. Roy measured the unchanging phase of standing wave current and reported close to zero. You measured the unchanging phase of standing wave current and got close to zero. It is no wonder you guys get the same value of current phase delay since you are making exactly the same error in your measurements spanning a number of years. I'm surprised that you didn't measure a 0 nS delay. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222188 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Radiation Resistance Date: Mon, 13 Mar 2006 09:07:05 -0600 Message-ID: <28826-44158A99-847@storefull-3255.bay.webtv.net> References: Owen Duffy wrote: "Is that correct---?" No, I don`t think so. Kraus` formula is: Radiation resistance = 80 pi squared L squared L is the fraction of a WL made by a tiny dipole. For the same wavelength, a monopole is only 0.5 the length of a dipole and it has 0.5 the radiation resistance. If we use its length in the formula abbove, the radiation resistance would calculate as only 1/4 that of a dipole because the constant is the same and L squared is 0.5 squared. I speculrte from the resistance ratio of a normal dipole to a normal monopole that the answer should be 0.5. So I erred by halving the constant. I should have doubled it to offset the quartered answer an unchanged constant would produces when L = 0.5. My new and improved answer to what the value of C is: 1580 Best regards, Richard Harrison, KB5WZI Article: 222189 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radiation Resistance References: <1142218986.976512.61520@i39g2000cwa.googlegroups.com> <2813-4414ECBD-1075@storefull-3257.bay.webtv.net> <1142261146.942721.125300@z34g2000cwc.googlegroups.com> Message-ID: <33gRf.616$tN3.309@newssvr27.news.prodigy.net> Date: Mon, 13 Mar 2006 15:18:23 GMT w8ji@akorn.net wrote: > This newsgroup, like any public forum, allows anyone to say almost > anything without censorship. Because of that two things none of us like > to see will happen: > > 1.) Incorrect information is posted By gurus as well as everyone else. I asked some technical question in another posting, Tom. In the past, you simply ignored my technical questions by trimming them from my posting and then you objected to my style which is all that was left. Let's see if you are still unwilling to answer my technical questions one of which is: Why isn't a century old method of determining the phase shift (delay) through a coil by measuring the self- resonant frequency good enough for you? How do you explain an 81% difference between this old accepted method and your recently measured results? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222190 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Date: Mon, 13 Mar 2006 09:36:48 -0600 Message-ID: <28826-44159190-848@storefull-3255.bay.webtv.net> References: <1142235977.589666.141840@j33g2000cwa.googlegroups.com> W_Tom wrote: "How does a microhenry stop or divert lightning?" Alone, not effectively. I think "driploops" are almost usless in lightning protection. W_Tom is right. You need to make a path unattractive to protect and divert the lightning to an easier path to earth. Best regards, Richard Harrison, KB5WZI Article: 222191 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> Message-ID: Date: Mon, 13 Mar 2006 17:45:20 GMT w8ji@akorn.net wrote: > Cecil Moore wrote: > >>Guess everyone sees the danger in trying to guess what >>the results of someone else's measurement will be. Tom >>should have measured something around 15.6 degrees. The >>fact he didn't sends up a very large red flag. > > Translation of what Cecil actually is saying: > "Whenever multiple measurements by independent sources disagree with me > the measurements others made must be wrong." Other multiple measurements by independent sources agree with me and disagree with you, Tom. Wonder why you neglected to post this reference from your own server? http://lists.contesting.com/archives/html/Towertalk/2003-11/msg00540.html It is a posting to TowerTalk by Jim Lux, W6RMK. I'll just extract some excerpts. "For closewound coils, with length to diameter ratios around 5:1, a series of fairly careful measurements have been made with the coils arranged vertically above a ground plane, fed at the base, with a capacitive load on the other end, and the driving frequency arranged to be at the resonant frequency of the whole assembly." Sure sounds like your 100 uH 10"x2" coil installed in a mobile ham radio antenna environment. "In most cases, the phase shift in the current at top and bottom [of the coil] was on the order of 10-20 degrees." Contrary to the assertions of W8JI. Funny, I predicted 16 degrees for your coil on 4 MHz based on the self-resonant frequency. "For inductance the signficant thing is that the magnetic field of one segment pretty much links to the adjacent segments, and less so for the rest." Contrary to the assertions of W8JI. "At this time, the models are sufficiently well developed that they predict the actual currents and voltages to substantially better than one percent ..." As opposed to W8JI's "accuracy". "The take home message here, regarding loading coils, is that simple lumped approximations of a loading coil may do just fine for an initial design cut, but do not adequately reflect reality." "I think it's best to leave it at: Loading coils are not isolated lumped elements and cannot be modeled as such." To which I add: Since a lumped element model is a subset of the distributed network model, if the lumped element results disagree with the distributed network results, the lumped element results are simply invalid. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222192 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Message-ID: <9oiRf.176$4L1.60@newssvr11.news.prodigy.com> Date: Mon, 13 Mar 2006 17:57:25 GMT John Popelish wrote: > Cecil Moore wrote: >> Since that's been an accepted way of doing it for more >> than a century, > > How did you learn about this as the accepted way? I'm a part-time teacher and it is described in a physics history book that is, unfortunately, at work. Interesting book as it gives a biographical treatment of the major famous physicists from Galileo to Einstein. The Maxwell and Heavyside sections are particularly interesting to me. For more information, take a look at: http://lists.contesting.com/archives/html/Towertalk/2003-11/msg00540.html -- 73, Cecil http://www.qsl.net/w5dxp Article: 222193 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Mon, 13 Mar 2006 11:53:49 -0600 Message-ID: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> References: Cecil, W5DXP wrote: "Please explain why a centuries old method of determining phase shift through a coil by measuring its self-resonant frequency is not good enough for you?" A coil is an RLC circuit. At resonance, L offsets C and all that is left is R. In a resistance, the current is in-phase with the applied voltage. But, in a physical length of a tuned circuit or in a straight conductor in its place, in a circuit with reflections, you have energy coming from both directions creating an interference pattern, which is repeated every 1/2-wave (180-degrees) in the line Peaks are 1/2-wave apart, considering the velocity factor of the line. To determine the phase shift, count the maxima. The wavelength of a line is the distance a wave must travel for one complete cycle (360-degrees). If you want the phase shift for a line, take the length of line required for one degree of phase retardation and multiply it by the length of line you have. Best regards, Richard Harrison, KB5WZI Article: 222194 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Message-ID: <2ldb125et5j4cgg3l9ogu153t1agkplbl5@4ax.com> References: Date: Mon, 13 Mar 2006 18:33:39 GMT On Sun, 12 Mar 2006 10:59:56 -0500, "Robert11" wrote: >Hello: > >Anyone have any thoughts on (hopefully not experiences) whether putting a >loop of, e.g. 1 foot in diameter, >on a coax run from an outdoor receive-only antenna has any merit as far as >helping any emf lightning induced pulses from traveling into a house ? > >Have heard about this, but it's hard to believe it would actually do >anything in practice. >But,... ? Your station can be thought of as a cluster of "black boxes" with interfaces (eg power, audio in, rx RF in, control, etc) that are suceptible to damage if large voltages are impressed across those interfaces. Hardening a station against lightning usually involves minimising the voltage impressed across those interfaces in the event of lightning, and two main approaches are followed (usually together): 1. - reducing the current that enters the station in a strike; and 2. - reducing the voltage drop in conductors within the station that would cause high voltages across interfaces. Item 1 is usually done by diverting the bulk of the lightning current via an alternate path to ground. This means shunting the current through a low impedance path to ground before it enters the station. Series impedance on the path to the station may assist in increasing the portion of the strike current that flows by the alternate shunt path to ground, but series impedance without the upstream shunt path is not likely to have much effect. The series impedance you propose is very small, so its effect will be quite limited. Item 2. is usually addressed by the design of the earthing system and equipotential bonding (eg single point earthing). In summary, a one turn loop in the coax alone is not going to provide a significant improvement in lightning protection in a station that is not otherwise hardened against lightning or EMP. Owen -- Article: 222195 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> Message-ID: Date: Mon, 13 Mar 2006 18:53:22 GMT Richard Harrison wrote: > The wavelength of a line is the distance a wave must travel for one > complete cycle (360-degrees). If you want the phase shift for a line, > take the length of line required for one degree of phase retardation and > multiply it by the length of line you have. If you want to know the velocity factor of a piece of transmission line, the easiest thing to do is find its first self-resonant frequency. A little math will yield the VF which allows prediction of the phase shift through any reasonable length of tranmission line. If you want to know the velocity factor of a coil, the easiest thing to do is find its first self- resonant frequency. A little math will yield the VF of the coil which allows prediction of the phase shift through any reasonable length of coil. Not disagreeing - just expanding. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222196 of rec.radio.amateur.antenna From: aRKay Subject: Re: Description of W9INN 40/80 dipole References: <4414a523_1@newsfeed.slurp.net> Message-ID: Date: Mon, 13 Mar 2006 19:11:00 GMT In article <4414a523_1@newsfeed.slurp.net>, "Bill Turner" wrote: > The word was "resonactor". I have one of his antennas and it works > fine. > > I have not examined the resonactor in detail, but I believe it is just > an inductor which is carefully wound to be self-resonant at the desired > frequency, thereby eliminating the need for a separate capacitor to > resonate it. A clever idea, since eliminating the separate capacitor > easily allows full legal power without the expense of a very high > voltage capacitor. > > W9INN's trap dipoles are the only ones I know of which advertise full > legal power handling, and that's why I purchased one. I've been running > full power RTTY on mine for five years with no problems. > > Since I purchased mine there may have been other full power trap > dipoles come on the market. If anyone knows of one, please reply. I'm > always curious about such things. > > Bill, W6WRT Bill, That for the memory jog... the correct term W9INN used was resonactor and like you said it works FB with or without power. My two resonactors have been in use since 1978 at three different locations. 73, Dick AA5VU Article: 222197 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Mon, 13 Mar 2006 19:26:10 GMT Richard Clark wrote: > Well, I for one note that your call for a reference to that one point > (coil self resonance) was met by a "link" to a mailing list on another > point (assembly self resonance). Give us a break, Richard. Those two subjects were in different paragraphs and completely unrelated. I looked up the reference and it is, "The Great Physicists From Galileo To Einstein, Biography of Physics", by George Gamow, (ISBN: 0486257673) I was going to furnish that information on Thursday when I go back to work. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222198 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Mon, 13 Mar 2006 11:39:04 -0800 Message-ID: <121biitcvt2a85@corp.supernews.com> References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> John Popelish wrote: > > If the inductor in question does not take much advantage of mutual > induction across its length nor has much capacitance across its length > (say, a straight conductor, strung with ferrite toroids), then I can see > the similarity with a transmission line. But as the inductor approaches > a lumped inductance with significant inter winding capacitance and > mutual inductance coupling the current across a significant part of its > winding length, I see on reason to assume the transmission line method > (delay independent of frequency) strictly applies. It might, but it > would take more than you saying so to assure me that it is a fact. > > In other words, transmission line concepts like uniform inductance per > length and uniform capacitance per length get rather muddled in a real > inductor. Tom W8JI posted a good description and summary of inductor operation a little while ago, but it looks like it could bear repeating, perhaps with a slightly different slant. In a transmission line, a field at one end of the line requires time to propagate to the other end of the line. As the EM fields propagate, they induce voltages and currents further down the line, which create their own EM fields, and so forth. These propagating fields and the currents and voltages they produce make the whole concept of traveling voltage and current waves useful and meaningful. But in a tightly wound inductor, a field created by the current in one turn is coupled almost instantly to all the other turns (presuming that the coil is physically very small in terms of wavelength). Consequently, output current appears very quickly following the application of input current. The propagation time is nowhere near the time it would take for the current to work its way along the wire turn by turn. Once again it's necessary to point out that I'm speaking here of an inductor which has very good coupling between turns and minimal field leakage or radiation, for example a toroid. If you make an air wound inductor and slowly stretch it out until it's nothing more than a straight wire, it'll begin by resembling the toroid -- more or less, depending on how well coupled the turns are and how much its field interacts with the outside world -- then slowly change its characteristics to resemble a straight wire. There's no magic transition point. So by choosing the inductor, you can observe behavior anywhere along this continuum. Roy Lewallen, W7EL Article: 222199 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Current through coils Date: Mon, 13 Mar 2006 13:44:19 -0600 Message-ID: <121bisltdp0m6ef@corp.supernews.com> References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> John Popelish wrote: > Cecil Moore wrote: > (snip) > >> Other multiple measurements by independent sources agree with >> me and disagree with you, Tom. Wonder why you neglected to post >> this reference from your own server? >> >> http://lists.contesting.com/archives/html/Towertalk/2003-11/msg00540.html >> >> It is a posting to TowerTalk by Jim Lux, W6RMK. I'll just extract >> some excerpts. >> >> "For closewound coils, with length to diameter ratios around 5:1, a >> series of fairly careful measurements have been made with the coils >> arranged vertically above a ground plane, fed at the base, with a >> capacitive load on the other end, and the driving frequency arranged >> to be at the resonant frequency of the whole assembly." >> >> Sure sounds like your 100 uH 10"x2" coil installed in a mobile ham >> radio antenna environment. > > (snip) > > The tantalizing part from my perspective is this: > > "The measurements were made with carefully designed fiberoptic probes > that were specifically designed to avoid perturbing the magnetic and > electric fields." > > I would like to read a full description of this instrumentation. Like many others I don't know everything. In line with reducing my ignorance could you amplify on how the phenomena is measured with a "fiber optic probe". What type of transducer is used to convert energy of an electrical nature to energy of an optical nature with out "perturbing the magnetic and electric fields". Dave WD9BDZ Article: 222200 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <9oiRf.176$4L1.60@newssvr11.news.prodigy.com> Message-ID: <62kRf.659$tN3.307@newssvr27.news.prodigy.net> Date: Mon, 13 Mar 2006 19:50:26 GMT John Popelish wrote: > I also note that the opening statement: > > "For closewound coils, with length to diameter ratios around 5:1, a > series of fairly careful measurements have been made with the coils > arranged vertically above a ground plane, fed at the base, with a > capacitive load on the other end, and the driving frequency arranged to > be at the resonant frequency of the whole assembly." > > This definitely specifies only a single frequency for the test. Yes, a 75m mobile base-loaded antenna is a single frequency antenna. Why are you surprised? Those guys have figured out something that I haven't, probably because they have better tools at their disposal than I do. They seem to have a 1% accurate model at frequencies other than the self-resonant frequency. I, OTOH, am only sure of my accuracy at the self-resonant frequency due to the limited tools at my disposal. > So I don't see how this reference > supports your claim that measuring the delay at resonance tells you the > delay at other frequencies. It also contradicts your claim about how a > standing wave makes it difficult to measure the current delay through > the coil. What have I missed? You missed the complete point, John. If one cannot eliminate reflections from the measuring process, then use them to your advantage in the measurements. Self-resonance means that the forward wave is in phase with the reflected wave. The first time that happens is when the wave has made a 180 degree round trip to the tip of the antenna and back, i.e. it happens first at self-resonance, when the coil is electrically 90 degrees long. For a well-designed coil, like a well-designed transmission line, it doesn't vary by much over HF frequencies. In short, the self-resonance velocity factor should extend pretty well to all HF frequencies below that self-resonance point. I need to think about the frequencies above the self-resonance point, but that doesn't apply to the present discussion. I guess I should re-phrase my statement. Standing waves make it difficult for *ME* and W8JI to measure the current delay through the coil. I ran essentially the exact experiment that W8JI ran with identical results. I even used the current pickups that W8JI kindly furnished to me. The only difference between W8JI and me is that I recognized the results to be bogus. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222201 of rec.radio.amateur.antenna From: chuck Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> Message-ID: <68kRf.3771$k75.1205@newsread3.news.atl.earthlink.net> Date: Mon, 13 Mar 2006 19:56:50 GMT David, Could it be something as simple as the use of a fiber optic cable as an alternative to a shielded coax cable? I suspect the "without perturbing . . ." part may be innocent overstatement. Wish I had a set of high-frequency probes with fiber optic cables! Chuck David G. Nagel wrote: > John Popelish wrote: > >> Cecil Moore wrote: >> (snip) >> >>> Other multiple measurements by independent sources agree with >>> me and disagree with you, Tom. Wonder why you neglected to post >>> this reference from your own server? >>> >>> http://lists.contesting.com/archives/html/Towertalk/2003-11/msg00540.html >>> >>> >>> It is a posting to TowerTalk by Jim Lux, W6RMK. I'll just extract >>> some excerpts. >>> >>> "For closewound coils, with length to diameter ratios around 5:1, a >>> series of fairly careful measurements have been made with the coils >>> arranged vertically above a ground plane, fed at the base, with a >>> capacitive load on the other end, and the driving frequency arranged >>> to be at the resonant frequency of the whole assembly." >>> >>> Sure sounds like your 100 uH 10"x2" coil installed in a mobile ham >>> radio antenna environment. >> >> >> (snip) >> >> The tantalizing part from my perspective is this: >> >> "The measurements were made with carefully designed fiberoptic probes >> that were specifically designed to avoid perturbing the magnetic and >> electric fields." >> >> I would like to read a full description of this instrumentation. > > > > Like many others I don't know everything. In line with reducing my > ignorance could you amplify on how the phenomena is measured with a > "fiber optic probe". What type of transducer is used to convert energy > of an electrical nature to energy of an optical nature with out > "perturbing the magnetic and electric fields". > > > Dave WD9BDZ Article: 222202 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Coax To Coax Noise transfer ? Date: Mon, 13 Mar 2006 19:56:37 -0000 Message-ID: <121bjjll54og800@corp.supernews.com> References: In article , Robert11 wrote: >Hello: > >Am about to start stringing some coax from an outside Receive-Only antenna's >Balun up to >my study where the receiver is. (30 MHz on down listening) > >The easiest thing for me is to run it alongside an existing (looks like >coax, but am not sure) wire >that Comcast has strung for my broadband service to the PC. Actually to >their always-on modem which is then >connected to the PC. > >Was wondering about coax to coax noise transfer into the receiving antennas >coax from being right alongside >this Comcast stuff. > >Think there's any reason for concern ? If the Comcast cable was installed properly, there shouldn't be a problem. Coax cable with high-quality shielding leaks very little signal, and the cable companies have to use well-shielded cable in their plants in order to avoid leakage of channels whose fall into the airband, amateur, and public-safety allocations. Also, I don't think that Comcast's plant is likely to carry much, if any content below 30 MHz. There's some possibility, I suppose, of some leakage of noise from the cable modem itself back up along the outside of the Comcast coax. You might want to consider buying a few snap-on interference-suppression ferrites, and snap 'em onto the outside of both cables (e.g. where the Comcast cable leaves the building, where your receiver coax enters the building, and maybe a few more scattered along one or both coaxes). This would help block or dissipate any RF currents flowing on the outsides of the coaxes. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 222203 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: ANTENNA SHARING References: <1142271577.733440.280370@p10g2000cwp.googlegroups.com> Message-ID: Date: Mon, 13 Mar 2006 13:06:38 -0600 I'll let others delve into the real depths here... It is possible (some would say likely) that if you dont separate the radios by some antenna line filtering (eg diplexer) one transmitter could damage the others receiver. This will happen even if they are on differing frequencies because it is likely the first amplifying device in line will be made to work across a broad range of frequencies. There is a good chance that you may not notice the damage if the signals you normally listen to are strong, only to find that the blown front device is needed when they get weak. If you wanted to consider a diplexer you have another big problem in that your operating frequencies overlap and are very wide. Most of these filters tend to work on a fairly narrow band or widely separated wider bands. If you segment the transceivers to specific operating frequencies you can bet that one day you'll want to use the "wrong" transceiver... You also want to retain a good antenna/transceiver line match. Adding a T piece and more equipment tends to upset that somewhat. The (extra) coax length itself will be a load that best case will reduce the effective power output. The input impedance of the receiver wont vary as a fucntion of the receiver operating frequency. Unless of course there is some front end filtering which is switched in and out. (Thats unusual nowadays - not having filters keeps the cost down) I'd suggest that a cheaper path is to use 2 antennas as a diplexer/filter system will be quite expensive. The other way to do it might be via coaxial relays that switched the unused receiver antenna to an attenuator or "open" whilst the other radio is transmitting. This would take some figuring because you want the relays to changeover before the radio starts transmitting. Hope this is of some help. Cheers Bob Big Nose wrote: > > Currently I am looking into the problem of using a common antenna for > two VHF transceivers. One operates 30 - 90 MHz and the other from 30 - > 512 MHz. They would both be tuned into seperate frequencies and need > to share a common broadband, omni directional, vertical monopole. > > I think I am getting myself a bit confused (or should I say more > confused), do I need to used a diplexer? Would a T piece not suffice > as both sets would be tuned to different frequencies and seperation and > harmonics would be considered? Would these factors not mean that the > input impedance to the set tuned into the different frequency would > remain high thus not effect matching? > Article: 222204 of rec.radio.amateur.antenna From: "Old Ed" References: <2%HQf.12296$wH5.7544@trnddc02> Subject: Re: Dipole Extension (done) Message-ID: Date: Mon, 13 Mar 2006 20:04:46 GMT Bottom posted... "Dick, AA5VU" wrote in message news:aa5vuNOSPAM-76F3DC.19575711032006@newsclstr02.news.prodigy.com... > In article <2%HQf.12296$wH5.7544@trnddc02>, > "Dale Parfitt" wrote: > > > Absolutely zero reason to place that wire in series with the dipole- in fact > > it will not yield the same results if you do so- you will end up having to > > redo the length. It will also mechanically weaken the antenna and also > > change 80M resonance. There is no current in that short stub-i.e. no effect > > on radiation. Let it dangle. > > Dale W4OP > > Thanks..... going to let it dangle. Not hurting anything and it has a > good attachment. Hi Dick, Dale has got it EXACTLY right here! Variable-length stubs from the inboard screws on the "resonactors" is how Bill (W9INN) INTENDED his antennas to be tuned! He called this--logically enough--"stub tuning." The obvious advantages of stub tuning are: 1. It's much easier than changing the length of the primary antenna wire, and 2. The two (or more) bands can be adjusted INDEPENDENTLY of each other; i.e., changing the length of the 40m stubs does not affect 80m tuning; and changing the length of the 80m stubs does not affect 40m tuning. This is absolutely the right way to build dipoles in which precise tuning of resonance is desired. Now that you've got your 40m resonance set to mid-band, you're pretty much done on 40m; you can get the full band under 2:1. But 80m is another story. Because of the "resonactor" loading (which conveniently reduces overall length), your 2:1 BW is probably 90 to 140 kHz. By changing the 80m stubs, you can put this wherever you want in the 80m band; but it's still pretty narrow. I made a small mod on my W9INN 80/40/17 dipole by putting Rat Shack banana sockets on the ends of the primary 80m stubs. This enables me to swap stubs (each with its own banana plug), to move the 80m resonance around in the band. Because my antenna is in an inverted vee configuration with fairly low ends, it's easy for me to change the stub(s). My normal tuning point is 3950 kHz, where I get 1:1 SWR. To move to 3850 kHz, I plug in ONE stub of appropriate length. (Absolute mechanical symmetry isn't necessary; in fact, asymmetry in the preferred direction can actually lower SWR.) It takes me 90 seconds to go from my second-floor shack out to the antenna, make the change, and come back again. Naturally, the WX is sometimes such that I don't want to go outside and play with stubs. That's one reason I just replaced my trusty W9INN with a Buckmaster OCF; but the Buckmaster is a subject for another thread. 73, Ed, W6LOL Article: 222205 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> Message-ID: Date: Mon, 13 Mar 2006 20:44:31 GMT David G. Nagel wrote: > Like many others I don't know everything. In line with reducing my > ignorance could you amplify on how the phenomena is measured with a > "fiber optic probe". What type of transducer is used to convert energy > of an electrical nature to energy of an optical nature with out > "perturbing the magnetic and electric fields". Like you (unlike W8JI) I don't know everything. :-) I have hardly any idea how they used a "fiber optic probe" to make their measurements. I suspect they superposed local RF phasors and used a fiber optic system to report the results. That's what I would do. I have invited Jim, W6RMK, to join the discussion. Maybe he can answer your questions. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222206 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <121biitcvt2a85@corp.supernews.com> Message-ID: Date: Mon, 13 Mar 2006 20:45:42 GMT Roy Lewallen wrote: > But in a tightly wound inductor, a field created by the current in one > turn is coupled almost instantly to all the other turns ... "All the other turns"? Here's what Jim Lux, W6RMK, had to say about that: "For inductance the signficant thing is that the magnetic field of one segment pretty much links to the adjacent segments, and less so for the rest." Less to the 3rd, less than that to the 4th, even less than that to the 5th. What do you think it might be by the time it gets to the 80th turn on Tom's coil? Seems that we can assume that the linkage between coil #1 and coil #80 is negligible. > Once again it's necessary to point out that I'm speaking here of an > inductor which has very good coupling between turns and minimal field > leakage or radiation, ... So was W6RMK. > There's no magic transition point. Indeed there isn't. I repeat, in case your didn't understand - indeed there isn't. So you can discard your magic lumped- circuit model for a system containing reflections. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222207 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Mon, 13 Mar 2006 20:47:53 GMT Richard Clark wrote: > Cecil Moore wrote: >>Those two subjects were in different paragraphs and completely unrelated. > > 'xactly my point. So if your point and my point are exactly the same, what is the point in disagreeing? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222208 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Yagi Antenna Question Date: Mon, 13 Mar 2006 16:24:41 -0600 Message-ID: <16561-4415F129-38@storefull-3256.bay.webtv.net> References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> Tom, W8JI wrote: "A reflector does not reflect anything. It radiates." Call a parasitic element anything you like, but the convention has already set in. Kraus tells the Yagi-Uda story on page 246 of his 3rd edition of "Antennas". He writes: "He (Uda) found the highest gain with the reflector about lambda/2 in length (they must be near resonance to get excited properly) and spaced about lambda/4 from the driven element, while the best director lengths were about 10% less than lambda/3." Uda`s reports were published between March 1926 and July 1929. There has been much fine tuning since then. On page 245, Kraus writes: "When the parasitic element is inductive (longer than its resonant length) it acts as a reflector. When it is capacitive (shorter than its resonant length) it acts as a director." Shortwave broadcast station I worked in about a 1/2 century ago used parasitic arrays of horizontal antennas. They were called "curtains". We did the adjustments of reflector phasings near the earth. The reflectors had feedlines like the driven elements, but were connected to short-circuit stubs instead of a transmitter. The shorting bar location was adjusted for the proper phase lag behind the driven element. It`s easier than trimming the reflector. We hung sampling loops from the driven element and reflector and fed them to an RCA WM-30-A phase monitor exactly as were used in medium wave broadcast stations for maintenance of directional arrays. You could have used such a phase monitor to check the phase difference introduced by a mobile loading coil. It is an oscilloscope fitted with a precision phase shifter which identifies which of the 4 quadrants the phase difference falls in and the number of degrees. The parasitic reflector performs the function of reversing the direction of much of the energy traveling toward it. Someone in this thread said it can be 99% effective. I also recall reading somewhere that if you are constructing a 2-element parasitic array, you`ll get more gain from a director than from a reflector. Our broadcast plant was behind our reflectors so it made sense to protect it in spite of perhaps a slight gain penalty. Best regards, Richaed Harrison, KB5WZI Article: 222209 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> Message-ID: Date: Mon, 13 Mar 2006 22:51:27 GMT Cecil Moore wrote: > I have > hardly any idea how they used a "fiber optic probe" to make > their measurements. I suspect they superposed local RF phasors > and used a fiber optic system to report the results. That's > what I would do. Make sure you set those "superposed local RF phasors" on stun before you make the measurement. Otherwise you might hurt someone. 73, Gene W4SZ Article: 222210 of rec.radio.amateur.antenna From: Barry OGrady Subject: Re: Concord,ca Police Department gives people tickets that have 820lbs. in a 1 ton pu truck Date: Tue, 14 Mar 2006 11:51:32 +1100 Message-ID: References: <1141922578.317968.87630@u72g2000cwu.googlegroups.com> <441453c3_2@news.bluewin.ch> On Sun, 12 Mar 2006 18:00:49 +0100, paul wrote: >blackhca@hotmail.com wrote: >> Concord,ca Police Department Officer... > > >This is only the work of a troll, google >"Ron Turner" Concord Police< >and have a look at his mayhem. Obviously they are not going to give tickets that weigh 820 lbs! Barry ===== Home page http://members.iinet.net.au/~barry.og Article: 222211 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Date: Tue, 14 Mar 2006 01:21:57 -0000 Message-ID: <121c6lln9k19924@corp.supernews.com> References: In article , Larry Benko wrote: >Bob, > >Go to h > >http://www.dowcorning.com/content/etronics/etronicsseal/etronics_aas_1ptov.asp > >for just about everything you would ever want to know. We use several >grades of electronics RTVs at work in contact with coaxial cable jackets >and all kinds of components to meet DO-160E vibration requirements for >airplave use. The stuff we use does not have the characteristic acetic >acid smell which I think is actually stearic acid. According to the labels I've read, much of the consumer-grade RTV does in fact release acetic acid as it cures. Not good stuff to use around electronics or other metals. The noncorrosive, "moisture cure" or "neutral cure" RTVs are a better choice for use around electronics. The ones marketed as "electronics- grade" are the surest bet in this regard, and usually need to be mail-ordered. A possible compromise would be the consumer-grade RTVs which are specifically advertised as being noncorrosive for use on metals - the labels on these say that they release methanol and ammonia during cure. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 222212 of rec.radio.amateur.antenna From: "Steve" References: Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Date: Mon, 13 Mar 2006 18:28:20 -0800 Message-ID: <44162a45$0$58071$742ec2ed@news.sonic.net> I wouldn't think anything but extremely good grounding at the antenna will do much. Long ago, when I lived on the west central coast of Florida (lightning alley), I had a 6-meter repeater on a tall building. The transmit and receive antennas were at diagonal corners of the building (no duplexer). We got a direct hit on BOTH antennas. The damage was something to see. Antennas had no damage except some scorch marks, but the coax was another matter. There would be 2-3' of coax, then 2-3' of nothing but scorched roofing. This repeated across the entire 150' or so length of the coax! A whole bunch of RG-8 simply vaporized. Steve Article: 222213 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Mon, 13 Mar 2006 18:35:54 -0800 Message-ID: <121cb0eh5hhc230@corp.supernews.com> References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> It's my policy to keep all email confidential. However, Cecil persists in sending me unwelcome email. I've requested several times, first politely then bluntly, that he stop sending it, but he ignores my requests and persists. I assume this is driven by the same compulsion that keeps him promoting his alternate theories. Because this email comes after repeated requests that it not be sent, I don't feel bound to give it the same level of privilege as all other email and keep it private. I believe it's relevant to the discussion at hand on this group, so I'll share it here, verbatim and without editing. The subject is "Can't resist". ---- Beginning of quote ---- Sorry, Roy, I forgot to delete your email address from my email address file. When your house of cards based on out and out lying comes tumbling down, exactly how are you going to handle the obvious deliberate attempt at misinformation that you and Tom have been distributing to the unwashed masses for so many years? Did you think you would never get caught in your lies during your lifetime or what? After 20 years of evidence to the contrary, you can hardly plead ignorance. -- no 73 for the "gobbledygook" guy, Cecil, W5DXP ---- End of quote ---- This is from the person who so loudly complains about people making personal attacks in place of reasoned arguments. I've done my best to explain basic theory, and even spent a day carefully constructing and making measurements and honestly reporting the results. I'll continue to do my best to present factual information in spite of these juvenile attacks, and will try my best to remain objective, although it's awfully hard sometimes in an environment that brings responses like this email typifies. Anyone who doesn't want to read what I post should add me to his newsgroup reader filter, as I did Cecil to mine two years ago. Those who do read what I post should know that I have absolutely no reason nor desire to mislead anyone in any way. Roy Lewallen, W7EL Article: 222214 of rec.radio.amateur.antenna Date: Mon, 13 Mar 2006 20:38:38 -0600 From: Tom Ring Subject: Re: Safety ground versus RF ground for a 2nd Floor shack References: <26f31$44110069$42a1bfc2$15706@FUSE.NET> <4413AA19.7090101@fuse.net> Message-ID: <44162cd9$0$3764$39cecf19@news.twtelecom.net> jawod wrote: > > Reading the two responses so far...I'll get my advice elsewhere. Typical > internet group response...mildly insulting and of no direct value. I > first have to know what ground means? Whatever. > Imaginary numbers apparently require imaginary minds. Richard wrote a very detailed response which covered pretty much everything you need. Perhaps you did not read it all. What didn't you understand? If you didn't understand something, you should have asked about what you did not, and he would gladly (I'm assuming, but I'm pretty sure on this) have answered your question. tom K0TAR Article: 222215 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Mon, 13 Mar 2006 18:38:53 -0800 Message-ID: <121cb615o4isf77@corp.supernews.com> References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> John Popelish wrote: > > I wish I could, but this is the first I have heard of such > instrumentation. That is why I would like to read more about it. Hopefully the poster mentioning the optical probe will explain a bit more. But I recall seeing optically coupled instrumentation used in an EMI screen room to couple signals in and out. To my knowledge, though, the probes themselves were conventional, and fiber optics were used only to replace connecting wires. Roy Lewallen, W7EL Article: 222216 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Yagi Antenna Question References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> <16561-4415F129-38@storefull-3256.bay.webtv.net> Message-ID: <44162d6d_4@newsfeed.slurp.net> Date: 13 Mar 2006 21:41:49 -0500 ORIGINAL MESSAGE: > Tom, W8JI wrote: > "A reflector does not reflect anything. It radiates." *********** REPLY SEPARATOR *********** Tom could have said "it reflects by radiating". Semantics count here. 73, Bill W6WRT Article: 222217 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Description of W9INN 40/80 dipole References: <4414a523_1@newsfeed.slurp.net> Message-ID: <44162f8d_2@newsfeed.slurp.net> Date: 13 Mar 2006 21:50:53 -0500 ORIGINAL MESSAGE: John Ferrell wrote: > > You may want to check out the antenna advertising here: > http://www.alphadeltacom.com/ > > It seems like your description. > I do not have an antenna for 160-80. > The DX-LB at $130 looks pretty good. *********** REPLY SEPARATOR *********** Yes, that looks very similar to the W9INN design. Should be a good one. 73, Bill W6WRT Article: 222218 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? References: <121c6lln9k19924@corp.supernews.com> Message-ID: <441630ac$1_4@newsfeed.slurp.net> Date: 13 Mar 2006 21:55:40 -0500 ORIGINAL MESSAGE: Dave Platt wrote: > > The noncorrosive, "moisture cure" or "neutral cure" RTVs are a better > choice for use around electronics. The ones marketed as "electronics- > grade" are the surest bet in this regard, and usually need to be > mail-ordered. *********** REPLY SEPARATOR *********** Your local pet shop will have RTV made for sealing glass aquariums which does not release acetic acid or anything else harmful to fish. If it won't harm fish, it surely won't harm your hardware. 73, Bill W6WRT Article: 222219 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Current through coils Date: Mon, 13 Mar 2006 21:15:47 -0600 Message-ID: <121cdb7cihv2t1e@corp.supernews.com> References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> Roy Lewallen wrote: > John Popelish wrote: > >> >> I wish I could, but this is the first I have heard of such >> instrumentation. That is why I would like to read more about it. > > > Hopefully the poster mentioning the optical probe will explain a bit > more. But I recall seeing optically coupled instrumentation used in an > EMI screen room to couple signals in and out. To my knowledge, though, > the probes themselves were conventional, and fiber optics were used only > to replace connecting wires. > > Roy Lewallen, W7EL Roy and John; The fiber optic leads are used in the experiment mentioned in the story linked by the URL that was recently mentioned in this thread. I think the whole thing is hilarious and was especially struck by the use of glass fiber to measure an electrical/magnet phenominum with no indication how the measurement is made. Sort of in line with someone's line of thinking in this thread. Dave N Article: 222220 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Yagi Antenna Question Date: Mon, 13 Mar 2006 19:26:19 -0800 Message-ID: <121cdv08ruvo207@corp.supernews.com> References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> <16561-4415F129-38@storefull-3256.bay.webtv.net> <44162d6d_4@newsfeed.slurp.net> Bill Turner wrote: > ORIGINAL MESSAGE: > >> Tom, W8JI wrote: >> "A reflector does not reflect anything. It radiates." > > > > *********** REPLY SEPARATOR *********** > > Tom could have said "it reflects by radiating". > > Semantics count here. > > 73, Bill W6WRT That's an interesting point. Suppose you have a two-element driven array with the elements spaced a quarter wave apart and fed 90 degrees out of phase. This produces a cardioid pattern, which has a deep null. Is the element toward the direction of the null "reflecting" and the other one "directing"? If so, what are they "reflecting" and "directing"? Each element intercepts considerable energy from the other and reradiates it, if that makes a difference. Here's another one: Build a 4 square array, assuming the ground is perfect. (The EZNEC example file 4Square.EZ or demo equivalent d_4Square.EZ can be used to illustrate this.) If you disconnect the feedline to the rear array element and short circuit the feedpoint (by deleting Source 1 in the EZNEC model), you'll still have a moderately good directional pattern with about 15 dB front-back ratio. The rear element is now a parasitic element, which we like to call a "reflector". You've said it "reflects by radiating". Now connect the rear element feedline as in the original antenna. The front/back ratio improves. But the feedpoint resistance of the rear element is negative. This isn't particularly unusual in driven arrays -- it means that the element in question is absorbing power from the other elements and sending down the feedline toward the source. The element is still radiating, because current is flowing on it. But it's absorbing more power from the surrounding region than it's giving back in the form of a field. (Again, the excess is being sent back along the feedline to be used by the other elements.) So, is that element now "reflecting"? If so, is it "reflecting by radiating"? Roy Lewallen, W7EL Article: 222221 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Description of W9INN 40/80 dipole Message-ID: <25ec1250g0ssd441qmsl4hrkqqq8lskdmh@4ax.com> References: <4414a523_1@newsfeed.slurp.net> <44162f8d_2@newsfeed.slurp.net> Date: Tue, 14 Mar 2006 03:31:28 GMT On 13 Mar 2006 21:50:53 -0500, "Bill Turner" wrote: >ORIGINAL MESSAGE: > >John Ferrell wrote: > >> >> You may want to check out the antenna advertising here: >> http://www.alphadeltacom.com/ >> >> It seems like your description. >> I do not have an antenna for 160-80. >> The DX-LB at $130 looks pretty good. > > > >*********** REPLY SEPARATOR *********** > >Yes, that looks very similar to the W9INN design. Should be a good one. > >73, Bill W6WRT I had one of the Alpha Delta antennas many years ago; the inductors were wound on ceramic or plastic forms, I forget which, but it was a very well-built antenna. bob k5qwg Article: 222222 of rec.radio.amateur.antenna From: Harry Gross Subject: Re: Phase shift circuits Message-ID: Date: Mon, 13 Mar 2006 22:44:26 -0500 Hi all, I'm toying with the idea of an 'electronically rotatable' dipole setup. Consider: a dipole oriented N/S another dipole oriented E/W They cross each other at the mid-point of each, forming a big plus sign, like so: | | ----+---- | | If you feed the N/S dipole, you get an E/W radiation pattern. Similarly, if you feed the E/W dipole, you get a N/S radiation patter. If you feed the N/S and E/W dipoles simultaneously, you get a NW/SE radiation pattern (for example), and if you flip the feed of either one of them 180 degrees, then you get a NE/SW radiation pattern. So far, so good. Now for the fun part. If you feed one of the dipoles with a signal that is only 90 degrees out of phase (or 270 degrees), you can get radiation patterns that take of in the NNW/SSE or WNW/ESE directions, and if you feed the other dipole 90 or 270 degrees out of phase, you get NNE/SSW and ENE/WSW directions. What I am looking for is a circuit that can perform the necessary phase delays, without having to use miles of coax coiled up in the shack. Ideally, the circuit would be able to perform the phase shift on all (or at least several) ham bands, so that it could feed into a pair of fan-dipoles for operation on multiple bands. Anyone have any suggestions on just how to accomplish this? In the extreme case, you could have a continuously adjustable system, that would permit you to point the 'virtual dipole' in any direction at all, which might be useful when attempting to null out an interfering station off to the side of the desired signal. However, in practice, I suspect that the eight positions mentioned above would be sufficient to do the same thing (albeit with the possibility of somewhat more signal loss due to fixed aiming directions). I seem to recall seeing a quote in the ARRL Handbook (or the ARRL Antenna Book) from Roy Lewallen, indicating that there is no simple way to do this. Am I mis-remembering (or mis-interpreting) what I read? I know that the military does this sort of thing with radar systems, and has for some time. However, their budget is quite a bit bigger than mine, so perhaps their solution isn't 'simple':-) Any thoughts on this, anyone? Harry Gross Article: 222223 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <9oiRf.176$4L1.60@newssvr11.news.prodigy.com> <62kRf.659$tN3.307@newssvr27.news.prodigy.net> Message-ID: Date: Tue, 14 Mar 2006 03:56:10 GMT John Popelish wrote: > I don't think so. Your claim is that one can use a resonant condition > to find the current delay at that frequency, and then, assume that that > delay holds for all other, lower frequencies. At other *HF* frequencies and within reason, John, within reason. A two to one range wouldn't surprise me. Tom's five to one range >from 16 MHz to 4 MHz is surprising. If the frequency kept going to 1 MHz, would the delay go below 3 nS? If Tom measured the delay at the self-resonant frequency of 16 MHz, would he measure 16 nS? If one plots the delay from 1 MHz to 16 MHz would there be any nonlinear points on the curve as implied by Tom's measurements? > I am skeptical that this > is the case for any device that is not inherently a constant delay > device. I didn't mean to imply that it was an absolutely constant delay device. If it is well designed and if the environment is held constant, it should exhibit approximately the same delay over HF below its self-resonant frequency. Tom's measurements implied a 5 to 1 range shift in delay from a 4 to 1 range shift in frequency. Delays changing faster than the frequency certainly don't make sense to me. What would be the cause? From 16 Mhz to 4 Mhz: Does L vary much with frequency? Why? Does C vary much with frequency? Why? Does R vary much with frequency? Why? Does G vary much with frequency? Why? These are the parameters in the "phase constant" equation. Let's take a look at my measured data where I changed the stinger by 2 feet from zero to 12 feet. The 75m bugcatcher coil is mounted on a mobile antenna mount on my GMC pickup. For clearence purposes, it has a one foot bottom section. The stinger goes from 0' to 12': 0, 2, 4, 6, 8, 10, 12 The resonant frequency goes from: 6.7, 5.1, 4.3, 3.8, 3.5, 3.2, 3.0 MHz I just don't see any nonlinear changes such as Tom reported. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222224 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Yagi Antenna Question References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> <16561-4415F129-38@storefull-3256.bay.webtv.net> <44162d6d_4@newsfeed.slurp.net> <121cdv08ruvo207@corp.supernews.com> Message-ID: <44163f90_3@newsfeed.slurp.net> Date: 13 Mar 2006 22:59:12 -0500 ORIGINAL MESSAGE: Roy Lewallen wrote: > That's an interesting point. Suppose you have a two-element driven > array with the elements spaced a quarter wave apart and fed 90 > degrees out of phase. This produces a cardioid pattern, which has a > deep null. Is the element toward the direction of the null > "reflecting" and the other one "directing"? If so, what are they > "reflecting" and "directing"? *********** REPLY SEPARATOR *********** Trying to bridge the gap between engineering and English, I would suggest this analogy: A mirror reflects light energy fed to it, while a light bulb takes electricity and turns it into light. Either a mirror or a light bulb can be used to send light in a desired direction, but only one is "reflecting" that energy in the usual sense of the word. Likewise, only the mirror is "re-radiating" energy, much like a yagi's reflector does. The analogy is not perfect but that's what the words mean to me. 73, Bill W6WRT Article: 222225 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Vertical vs Horizontal shootout part one References: <120ngtl3drs574@corp.supernews.com> <1219ru8so8fp2f@corp.supernews.com> Message-ID: <441640db_5@newsfeed.slurp.net> Date: 13 Mar 2006 23:04:43 -0500 ORIGINAL MESSAGE: Mike Coslo wrote: > So, be my students and find the lessons in this tale. Make a list. *********** REPLY SEPARATOR *********** My very first thought was you were receiving an LP signal instead of SP. Shows how a DXer thinks. :-) 73, Bill W6WRT Article: 222226 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> Message-ID: <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> Date: Tue, 14 Mar 2006 04:09:35 GMT John Popelish wrote: > ... I see no reason to assume the transmission line method > (delay independent of frequency) strictly applies. It might, but it > would take more than you saying so to assure me that it is a fact. Assume the environment of the coil is fixed like the variable stinger measurement I reported earlier. Besides the frequency term, the phase constant depends upon L, C, R, and G as does the Z0 equation. Why would the L, C, R, and G change appreciably over a relatively narrow frequency range as in my bugcatcher coil measurements going from 6.7 MHz to 3.0 MHz? And I didn't mean to imply that the delay is "independent" of frequency, just that it is not nearly as frequency dependent as Tom's measurements would suggest. If Tom made his measurements >from 1 MHz to 16 MHz, what do you think the curve would look like? Freq 1 2 4 8 16 MHz Delay ___ ___ 3 ___ 16 nS That looks non-linear to me. How about you? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222227 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 14 Mar 2006 04:09:08 +0000 (UTC) Message-ID: References: <8V4Rf.4714$o41.3612@trnddc06> Addressed to nobody in particular. >From basic transmission line theory, the velocity of propagation along a coil is estimated by - V = 1 / Sqrt( L * C ) metres per second, where L and C are henrys and farads per metre respectively. The formula for L and C can be found in your Bibles from coil dimensions, numbers of turns, etc. The velocity factor = V / c and Zo = Sqr( L / C ). Attenuation (loss) = R / 2 / Zo nepers, where R is wire resistance plus radiation resistance. >From which other interesting facts can be deduced. ---- Reg. Article: 222228 of rec.radio.amateur.antenna From: Owen Duffy Subject: Powerline trap Message-ID: Date: Tue, 14 Mar 2006 04:13:06 GMT You probably haven't thought of powerlines as an antenna, the BPL industry pretends they aren't, but they are. A recent news item is about a new patent for a "Filter for segmenting powerlines for communications" (US 7,005,943). It is described: "There is provided a method for blocking a portion of energy of a signal in a power line. The method includes equipping a high frequency magnetic core with a coil, connecting a capacitor across terminals of the coil to create a resonant circuit that resonates at a frequency of the signal, and placing the magnetic core around the power line, at a location where the blocking is desired." Hmmm, a trap! Without getting bogged down in the details of the coil and the current / phase relationships, is this likely to be effective? A parallel resonant trap in an antenna doesn't eliminate current beyond the trap at the frequency of trap resonance. Will it make the region of the powerline between the injector and the trap a better radiatior for the same injector power? Thoughts? Owen -- Article: 222229 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb0eh5hhc230@corp.supernews.com> Message-ID: Date: Tue, 14 Mar 2006 04:21:39 GMT Roy Lewallen wrote: > It's my policy to keep all email confidential. Apparently not. That was a private email. Publishing it in public without my permission is unethical but seems you and Tom will seemingly stop at nothing to keep promoting your myths. You have, over and over, rejected the distributed network model even though you know it is a superset of the lumped- circuit model. Would you agree with me that after all this time, you cannot possibly plead ignorance? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222230 of rec.radio.amateur.antenna From: "Dan, danl, danny boy, Redbeard, actually Greybeard now" Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Message-ID: References: Date: Mon, 13 Mar 2006 22:11:13 -0600 On Mon, 13 Mar 2006 18:59:34 -0500, "Robert11" sent into the ether: >>>Hello: >>> >>>Is it safe to use the typical GE RTV silicones against a Polyethylene (PE) >>>coax outer jacket ? >>> >>>I know the RTV's use some type of acid (acetic ?) to cure the stuff, and I >>>was wondering if >>>anyone might have any first hand experience if there is any kind of >>>interaction with a coax outer jacket ? >>> >>>Thanks, >>>Bob >>> Bob, I have been using GE 1200 on coax and connectors since the early seventies and have never had a problem with it affecting good silver plated or cheap connectors or the varying grades of coax I have used. If you want to be fussy cover the connector with electrical tape and then cover with silicone. This makes it easier to remove but is not necessary for protecting the connector or the coax. I would not use it inside of a radio or other electronic equipment but outside of that it will not hurt and will keep the connection free of moisture, BTW, if you do wrap it with tape first be sure to coat the coax past the tape to ensure a good waterproof seal. N9JBF I've learned that I don't suffer from insanity, I enjoy it! danl4x@charter.net Remove the x for e-mail reply www.outdoorfrontiers.com www.SecretWeaponLures.com A proud charter member of "PETAF", People for Eating Tasty Animals and Fish!!! Article: 222231 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <121cdb7cihv2t1e@corp.supernews.com> Message-ID: Date: Tue, 14 Mar 2006 04:31:21 GMT David G. Nagel wrote: > The fiber optic leads are used in the experiment mentioned in the story > linked by the URL that was recently mentioned in this thread. I think > the whole thing is hilarious and was especially struck by the use of > glass fiber to measure an electrical/magnet phenominum with no > indication how the measurement is made. Sort of in line with someone's > line of thinking in this thread. There exist transducers that will convert RF to light on one end of a fiber optics cable and back to RF at the other end. It's no big deal and keeps the transfer of information from being affected by EM fields. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222232 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 14 Mar 2006 04:32:28 +0000 (UTC) Message-ID: References: <8V4Rf.4714$o41.3612@trnddc06> Oops! Zo = Sqrt( L / C) Article: 222233 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Tue, 14 Mar 2006 04:37:58 GMT Reg Edwards wrote: > From basic transmission line theory, the velocity of propagation along > a coil is estimated by - > > V = 1 / Sqrt( L * C ) metres per second, So Reg, for a fixed installation, why would L and C change much with frequency, like from 16 nS at 16 MHz to 3 nS at 4 MHz? If we took it down to 1 MHz, would the delay go below 3 nS? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222234 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb0eh5hhc230@corp.supernews.com> Message-ID: Date: Tue, 14 Mar 2006 05:13:52 GMT Roy Lewallen wrote: > I believe it's relevant to the discussion at > hand on this group, so I'll share it here, ... So you believe my personal feelings about you are relevant to a technical discussion???? Exactly which technical parameters are affected by my feelings about you? Every time this subject comes up, more and more people realize that the r.r.a.a gurus are not omniscient. Here's a smattering of the email I've received over the past week. Unlike you, I won't mention any names. "I hope ... that [X and Y] will acknowledge the validity of your approach." [X and Y are posters to r.r.a.a] "You are moving pretty fast, but nothing that you are saying sounds like there are any glaring errors." "Distributed constants not lumped constants prevail." "I, too, am skeptical of that 3 ns delay." " ...your Corum reference certainly ends the debate." "I want to let you know your dedication to principle and rational analysis ... are inspiring to many of us." "The unwillingness of the "gurus" to answer specific technical questions is pretty disappointing." Roy, are you listening to that last comment? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222235 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 14 Mar 2006 06:11:43 +0000 (UTC) Message-ID: References: <8V4Rf.4714$o41.3612@trnddc06> "Cecil Moore" wrote in message news:GMrRf.750$tN3.463@newssvr27.news.prodigy.net... > Reg Edwards wrote: > > From basic transmission line theory, the velocity of propagation along > > a coil is estimated by - > > > > V = 1 / Sqrt( L * C ) metres per second, > > So Reg, for a fixed installation, why would L and C change > much with frequency, like from 16 nS at 16 MHz to 3 nS at > 4 MHz? If we took it down to 1 MHz, would the delay go > below 3 nS? > -- > 73, Cecil http://www.qsl.net/w5dxp ========================================== Sorry Cec, I havn't the foggiest idea. Having started it, I havn't been taking much notice of this long-winded thread. Its all too clever for poor little me! ;o) ---- Reg. Article: 222236 of rec.radio.amateur.antenna From: "Hal Rosser" References: <1142271577.733440.280370@p10g2000cwp.googlegroups.com> Subject: Re: ANTENNA SHARING Message-ID: <_itRf.1568$Tv6.617@bignews5.bellsouth.net> Date: Tue, 14 Mar 2006 01:25:58 -0500 Well, one thing for darn sure - those 2 radios sharing the antenna should be able to hear each other really really good - (till they destroy each other's front end.) Given the parameters (sharing some of the same frequencies) - the only way to share the antenna is by unplugging the coax from one radio and pluggin it into the other. - Or using a good coax switch - (which could conceivably be a relay) But I may be wrong. My 2¢ w4pmj Hal "Big Nose" wrote in message news:1142271577.733440.280370@p10g2000cwp.googlegroups.com... > Currently I am looking into the problem of using a common antenna for > two VHF transceivers. One operates 30 - 90 MHz and the other from 30 - > 512 MHz. They would both be tuned into seperate frequencies and need > to share a common broadband, omni directional, vertical monopole. > > I think I am getting myself a bit confused (or should I say more > confused), do I need to used a diplexer? Would a T piece not suffice > as both sets would be tuned to different frequencies and seperation and > harmonics would be considered? Would these factors not mean that the > input impedance to the set tuned into the different frequency would > remain high thus not effect matching? > Article: 222237 of rec.radio.amateur.antenna From: "Hal Rosser" References: <1142219157.314335.180560@j52g2000cwj.googlegroups.com> Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Message-ID: <0ttRf.1569$Tv6.867@bignews5.bellsouth.net> Date: Tue, 14 Mar 2006 01:36:40 -0500 That's right - a bolt of lightning comes streaking across several miles of dry air, finds the antenna with no problem, then upon seeing the loop, ducks back into the ground. But at least the loop will make the rain drip outside. It not useless. "w_tom" wrote in message news:1142219157.314335.180560@j52g2000cwj.googlegroups.com... > Do you think a loop will stop what three miles of sky could not? > Effective protection is not about stopping a transient. That does not > work and is they myth even used to promote plug-in protectors. A most > trivial earth ground is a massive improvement in protection. That > incoming wire must be earthed - directly or through a protector - > before entering the building. That simplest earthing is many times > more effective than 100 loops. Effective for direct strkes - which > means induced trasnients would be made irrelevant. > > The US Forestry Service has documented that most direct strikes to > trees do not leave appreciable indication. Even a standard household > earth ground in conductive soil will provide protection from most > lightning strikes. Then we enhance that earthing for other, more > violent and less frequent direct strikes. > > Quality of earthing determines how many direct strikes will be > earthed without damage. Even some earthng to a single point is a > massive improvement in transistor protection. But the loop is about > as useful as bad science fiction. For loop to be effective, then loop > also must seriously degrade radio reception. How many reasons why that > loop is useless? Five? > > Robert11 wrote: > > Hello: > > > > Anyone have any thoughts on (hopefully not experiences) whether putting a > > loop of, e.g. 1 foot in diameter, > > on a coax run from an outdoor receive-only antenna has any merit as far as > > helping any emf lightning induced pulses from traveling into a house ? > > > > Have heard about this, but it's hard to believe it would actually do > > anything in practice. > > But,... ? > > > > B. > Article: 222238 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Powerline trap Date: Mon, 13 Mar 2006 23:04:03 -0800 Message-ID: <121cqn82o4udt51@corp.supernews.com> References: Owen Duffy wrote: > You probably haven't thought of powerlines as an antenna, the BPL > industry pretends they aren't, but they are. > > A recent news item is about a new patent for a "Filter for segmenting > powerlines for communications" (US 7,005,943). It is described: > > "There is provided a method for blocking a portion of energy of a > signal in a power line. The method includes equipping a high frequency > magnetic core with a coil, connecting a capacitor across terminals of > the coil to create a resonant circuit that resonates at a frequency of > the signal, and placing the magnetic core around the power line, at a > location where the blocking is desired." > > Hmmm, a trap! Without getting bogged down in the details of the coil > and the current / phase relationships, is this likely to be effective? > A parallel resonant trap in an antenna doesn't eliminate current > beyond the trap at the frequency of trap resonance. Will it make the > region of the powerline between the injector and the trap a better > radiatior for the same injector power? > > Thoughts? > You're correct that a trap doesn't stop current -- or energy -- at the trap. The lines on both sides couple with each other, allowing substantial current to flow on the side away from the source. All the trap does is guarantee a current null at some point. A quarter wave away, a current maximum will occur. In fact, a trap can increase current coupled into a wire if it breaks a formerly non-resonant wire into pieces of which one or more are near resonance. Roy Lewallen, W7EL Article: 222239 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Date: Mon, 13 Mar 2006 23:14:29 -0800 Message-ID: <121craq3ed95h91@corp.supernews.com> References: The advice to avoid acetic-acid smelling RTV because of corrosion is passed along from person to person like an urban legend, but like an urban legend it's just about impossible to find anyone who's actually seen any corrosion result from its use. (A number of queries I've made over the years has produced just one, using a very early version of RTV.) I've used the acetic-acid smelling stuff for decades on a variety of metals including tinned and untinned wire, aluminum, nickel, and copper circuit boards, and never seen a hint of corrosion. But formulations vary widely, and my experience certainly isn't exhaustive. I'm not entirely convinced, though, that among the many formulations there aren't others, which don't have that smell, which might be corrosive to some materials. People who worry about this should buy an industrial product and stay with it, since there's a much better chance the formulation won't change in the future without notice. Roy Lewallen, W7EL Article: 222240 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Phase shift circuits Date: Mon, 13 Mar 2006 23:20:27 -0800 Message-ID: <121crm0eijembda@corp.supernews.com> References: The two dipoles don't couple to each other, so you have a lot of options for feed systems. Transmission delay lines are one. Another is lumped circuit networks -- an L network can be designed to effect a range of phase shifts. I think you'll find, though, that you'll hardly be able to tell when you rotate the array in any increment smaller than 90 degrees, and unless a signal is pretty close to a null, even that rotation won't make a striking difference. It's a problem that's easily modeled, so I'd start by seeing just what I might gain from it before going to the trouble. Roy Lewallen, W7EL Harry Gross wrote: > Hi all, > > I'm toying with the idea of an 'electronically rotatable' dipole setup. > > Consider: a dipole oriented N/S > another dipole oriented E/W > They cross each other at the mid-point of each, forming a big plus > sign, like so: > > | > | > ----+---- > | > | > > If you feed the N/S dipole, you get an E/W radiation pattern. Similarly, > if you feed the E/W dipole, you get a N/S radiation patter. > > If you feed the N/S and E/W dipoles simultaneously, you get a NW/SE > radiation pattern (for example), and if you flip the feed of either one > of them 180 degrees, then you get a NE/SW radiation pattern. > > So far, so good. Now for the fun part. If you feed one of the dipoles > with a signal that is only 90 degrees out of phase (or 270 degrees), you > can get radiation patterns that take of in the NNW/SSE or WNW/ESE > directions, and if you feed the other dipole 90 or 270 degrees out of > phase, you get NNE/SSW and ENE/WSW directions. > > What I am looking for is a circuit that can perform the necessary phase > delays, without having to use miles of coax coiled up in the shack. > Ideally, the circuit would be able to perform the phase shift on all (or > at least several) ham bands, so that it could feed into a pair of > fan-dipoles for operation on multiple bands. > > Anyone have any suggestions on just how to accomplish this? In the > extreme case, you could have a continuously adjustable system, that > would permit you to point the 'virtual dipole' in any direction at all, > which might be useful when attempting to null out an interfering station > off to the side of the desired signal. However, in practice, I suspect > that the eight positions mentioned above would be sufficient to do the > same thing (albeit with the possibility of somewhat more signal loss due > to fixed aiming directions). > > I seem to recall seeing a quote in the ARRL Handbook (or the ARRL > Antenna Book) from Roy Lewallen, indicating that there is no simple way > to do this. Am I mis-remembering (or mis-interpreting) what I read? > > I know that the military does this sort of thing with radar systems, and > has for some time. However, their budget is quite a bit bigger than > mine, so perhaps their solution isn't 'simple':-) > > Any thoughts on this, anyone? > > Harry Gross Article: 222241 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Powerline trap Message-ID: References: <121cqn82o4udt51@corp.supernews.com> Date: Tue, 14 Mar 2006 07:34:47 GMT On Mon, 13 Mar 2006 23:04:03 -0800, Roy Lewallen wrote: >You're correct that a trap doesn't stop current -- or energy -- at the >trap. The lines on both sides couple with each other, allowing >substantial current to flow on the side away from the source. All the >trap does is guarantee a current null at some point. A quarter wave >away, a current maximum will occur. In fact, a trap can increase current >coupled into a wire if it breaks a formerly non-resonant wire into >pieces of which one or more are near resonance. Thanks Roy, Given that BPL band plans often have a link bandwidth of several MHz, one wonders also about the effectiveness of a trap in compromising depth of notch vs bandwidth. Perhaps the magic bullet is really a band stop filter, I didn't look the patent up. But no matter, it seems it serves more to organise the location of standing waves rather than eliminate current past the trap. Of course, we are all scratching our head about the technical elegance or even feasibility of BPL (or lack of it, more to the point). Owen -- Article: 222242 of rec.radio.amateur.antenna From: Big Endian Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? References: <1142219157.314335.180560@j52g2000cwj.googlegroups.com> <0ttRf.1569$Tv6.867@bignews5.bellsouth.net> Message-ID: Date: Tue, 14 Mar 2006 10:06:34 GMT In article <0ttRf.1569$Tv6.867@bignews5.bellsouth.net>, "Hal Rosser" wrote: > That's right - a bolt of lightning comes streaking across several miles of > dry air, finds the antenna with no problem, then upon seeing the loop, ducks > back into the ground. > But at least the loop will make the rain drip outside. It not useless. I've read that most of the lightning starts at the ground first and reaches into the sky to find the other end. > > > "w_tom" wrote in message > news:1142219157.314335.180560@j52g2000cwj.googlegroups.com... > > Do you think a loop will stop what three miles of sky could not? > > Effective protection is not about stopping a transient. That does not > > work and is they myth even used to promote plug-in protectors. A most > > trivial earth ground is a massive improvement in protection. That > > incoming wire must be earthed - directly or through a protector - > > before entering the building. That simplest earthing is many times > > more effective than 100 loops. Effective for direct strkes - which > > means induced trasnients would be made irrelevant. > > > > The US Forestry Service has documented that most direct strikes to > > trees do not leave appreciable indication. Even a standard household > > earth ground in conductive soil will provide protection from most > > lightning strikes. Then we enhance that earthing for other, more > > violent and less frequent direct strikes. > > > > Quality of earthing determines how many direct strikes will be > > earthed without damage. Even some earthng to a single point is a > > massive improvement in transistor protection. But the loop is about > > as useful as bad science fiction. For loop to be effective, then loop > > also must seriously degrade radio reception. How many reasons why that > > loop is useless? Five? > > > > Robert11 wrote: > > > Hello: > > > > > > Anyone have any thoughts on (hopefully not experiences) whether putting > a > > > loop of, e.g. 1 foot in diameter, > > > on a coax run from an outdoor receive-only antenna has any merit as far > as > > > helping any emf lightning induced pulses from traveling into a house ? > > > > > > Have heard about this, but it's hard to believe it would actually do > > > anything in practice. > > > But,... ? > > > > > > B. > > Article: 222243 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 14 Mar 2006 12:09:12 +0000 (UTC) Message-ID: References: <8V4Rf.4714$o41.3612@trnddc06> > > Reg Edwards wrote: > > > From basic transmission line theory, the velocity of propagation > along > > > a coil is estimated by - > > > > > > V = 1 / Sqrt( L * C ) metres per second, > > > > So Reg, for a fixed installation, why would L and C change > > much with frequency, like from 16 nS at 16 MHz to 3 nS at > > 4 MHz? If we took it down to 1 MHz, would the delay go > > below 3 nS? > > -- > > 73, Cecil http://www.qsl.net/w5dxp > > ========================================== > > Sorry Cec, I havn't the foggiest idea. > ---- > Reg. > =========================================== On second thoughts, since L and C are functions of a coil's physical dimensions it must be something else which is changing with frequency. ---- Reg. Article: 222244 of rec.radio.amateur.antenna From: Harry Gross Subject: Re: Phase shift circuits References: <121crm0eijembda@corp.supernews.com> Message-ID: <%rzRf.14$ny.6@fe10.lga> Date: Tue, 14 Mar 2006 08:22:03 -0500 I guess I'll have to break down, buy a copy of EZ-NEC and play with it:-) By the way, are you suggesting that 90 degree rotation is all I'd need, simply because the dipole radiation pattern is so wide, broadside to the radiator? If that turns out to be true, then the problem becomes vastly easier to deal with, and could even be done mechanically by simply switching around the feed line to one dipole (easier to do with ladder line - the preferred feed line to a dipole - than coax, of course) although that might not be the BEST way to do it. Harry Roy Lewallen wrote: > The two dipoles don't couple to each other, so you have a lot of options > for feed systems. Transmission delay lines are one. Another is lumped > circuit networks -- an L network can be designed to effect a range of > phase shifts. > > I think you'll find, though, that you'll hardly be able to tell when you > rotate the array in any increment smaller than 90 degrees, and unless a > signal is pretty close to a null, even that rotation won't make a > striking difference. It's a problem that's easily modeled, so I'd start > by seeing just what I might gain from it before going to the trouble. > > Roy Lewallen, W7EL > > Harry Gross wrote: > >> Hi all, >> >> I'm toying with the idea of an 'electronically rotatable' dipole setup. >> >> Consider: a dipole oriented N/S >> another dipole oriented E/W >> They cross each other at the mid-point of each, forming a big >> plus sign, like so: >> >> | >> | >> ----+---- >> | >> | >> >> If you feed the N/S dipole, you get an E/W radiation pattern. >> Similarly, if you feed the E/W dipole, you get a N/S radiation patter. >> >> If you feed the N/S and E/W dipoles simultaneously, you get a NW/SE >> radiation pattern (for example), and if you flip the feed of either >> one of them 180 degrees, then you get a NE/SW radiation pattern. >> >> So far, so good. Now for the fun part. If you feed one of the >> dipoles with a signal that is only 90 degrees out of phase (or 270 >> degrees), you can get radiation patterns that take of in the NNW/SSE >> or WNW/ESE directions, and if you feed the other dipole 90 or 270 >> degrees out of phase, you get NNE/SSW and ENE/WSW directions. >> >> What I am looking for is a circuit that can perform the necessary >> phase delays, without having to use miles of coax coiled up in the >> shack. Ideally, the circuit would be able to perform the phase shift >> on all (or at least several) ham bands, so that it could feed into a >> pair of fan-dipoles for operation on multiple bands. >> >> Anyone have any suggestions on just how to accomplish this? In the >> extreme case, you could have a continuously adjustable system, that >> would permit you to point the 'virtual dipole' in any direction at >> all, which might be useful when attempting to null out an interfering >> station off to the side of the desired signal. However, in practice, >> I suspect that the eight positions mentioned above would be sufficient >> to do the same thing (albeit with the possibility of somewhat more >> signal loss due to fixed aiming directions). >> >> I seem to recall seeing a quote in the ARRL Handbook (or the ARRL >> Antenna Book) from Roy Lewallen, indicating that there is no simple >> way to do this. Am I mis-remembering (or mis-interpreting) what I read? >> >> I know that the military does this sort of thing with radar systems, >> and has for some time. However, their budget is quite a bit bigger >> than mine, so perhaps their solution isn't 'simple':-) >> >> Any thoughts on this, anyone? >> >> Harry Gross Article: 222245 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 14:28:35 GMT w8ji@akorn.net wrote: Before I comment on your posting below, I think you can prove to yourself that your measurements are flawed. You measured 3 nS delay through your coil at 4 MHz. Now perform the same measurement at the self-resonant frequency. The delay through the coil is known to be 15.6 nS at the self-resonant frequency. If your delay measurement isn't 15.6 nS, then there is something wrong with your methods. Better yet, measure the delay at 1, 2, 4, 8, &16 MHz and report the results. > ... it is unlikely anyone can prove Cecil wrong. That's because in order to prove me wrong, you have to prove yourself right. You simply haven't done that because you refuse to engage me at a technical level. You have ignored my technical questions and refused to discuss the technical details. Many readers have noticed that, wonder why, and have commented on it in emails to me. > This all seems logical to me, because Cecil has asked for measurements. > The pattern has been after he gets measurement results and finds they > disagree with his theory, he has to blame the difference on something. Tom, your measurements agree perfectly with my theory. You are measuring standing wave currrent. That standing wave current magnitude is pictured in every good book on antennas. Kraus also shows the phase which, for a thin wire dipole, is fixed at zero from tip to tip on the antenna. It is understandable why you measured zero standing wave current phase shift through the coil. THE STANDING WAVE CURRENT PHASE SHIFT IS ZERO WHETHER THE COIL IS IN THE CIRCUIT OR NOT! Since the phase of the standing wave current is fixed and unchanging whether the coil is in the circuit or not, why do you think measuring that unchanging phase around a coil proves anything? > I proposed antenna losses were swamped out by ground losses in a > vehicle, and because of very high ground losses the effects of coil > resistance were diluted. I agree with that and have never argued otherwise. > I measured the inductor and found as quite logically anyone would > expect that current ratio depended on the ratio of stray C from the > coil to load C at the open end of the coil. Yuri K3BU argued the coil > replaced a certain number of degrees electrical height, and I > disagreed. The following reports a 10-20 degree phase shift through most coils. http://lists.contesting.com/archives/html/Towertalk/2003-11/msg00540.html > Most people experienced in systems like this from an engineering > standpoint agreed with me. Somewhere about that time Cecil brought > reflected waves into the discussion. Those "most people" don't understand forward and reflected waves on a standing-wave antenna. You have proven by your postings here that you do not understand forward and reflected waves on a standing- wave antenna like a 75m bugcatcher mobile antenna. Worse yet, you refuse to discuss the antenna at a technical level and have simply sandbagged your misconceptions. I remember when you were using the lumped inductance feature of EZNEC to try to prove your point, certainly an invalid proof. When we started this thread, it was obvious that you didn't know the standing wave current phase is fixed near zero degrees so measuring it is futile. > After a series of "what happens if" Cecil wanted measurements. When > they were made, he and Yuri announced the measurements proved their > points. Yes, they did prove that the current at the ends of the coil were NOT equal. You said they were. I said they were not. Out of all of your and Roy's measured results, the current was equal in only the case of the small toroidal coil and that's because it was located at a standing wave current maximum (loop). > When the person making the measurements corrected those > misstatements and pointed out the measurements didn't support their > claims, the only logical course was to discredit the measurements and > ask for new ones. You sure have selective memory, Tom. I fully accepted your standing- wave current measurements. But standing-wave current measurements cannot be used to measure the traveling-wave delay through a coil. That should be obvious to everyone by now. The delay through the coil causes a phase shift in the forward wave and the reflected wave, not in the standing wave. THE PHASE OF THE STANDING WAVE CURRENT IS KNOWN NOT TO CHANGE AND THAT'S EXACTLY WHAT YOU MEASURED, VIRTUALLY NO SHIFT. Kraus agrees. Figure 14-2 of "Antennas For All Applications", 3rd edition shows a graph of the phase of the standing wave current. That phase is zero tip-to-tip for a thin-wire 1/2WL dipole. > When new measurements again disagreed with the concept of huge current > or phase delay of current that was tied to degrees the coil replaces, > the only course was to reject those measurements. THOSE MEASUREMENTS WERE NOT REJECTED! They were accepted as perfectly valid measurements of standing wave current. Those characteristics are pictured in Kraus and your measurements agree perfectly with them. Your argument is a strawman. The fact is that a standing wave measurement CANNOT yield the current delay through the coil any more than it can yield the current delay through a wire. YOU CANNOT MEASURE THE DELAY THROUGH THE COIL USING CURRENT KNOWN NOT TO CHANGE PHASE! > So here we are today, two or three years later, still trying to find a > measurement that will agree with what Cecil and Yuri proposed or for > another person of reasonable engineering experience to agree with the > notion the coil behaves as a coiled up antenna or transmission line > rather than behaving more like a lumped component in a small heavily > loaded mobile antenna. This is not about you or me or Yuri. It is about getting down to the truth. Yet you rave on and on about personalities. Why don't you discuss technical issues instead of personalities? There is a phase shift in the forward current through the loading coil. There is a phase shift in the reflected current through the loading coil. Those phasors are rotating in opposite directions so the net phase is fixed. You can measure standing wave current phase in thousands of experiments from now to kingdom come and you will not be measuring the phase shift of the forward and reflected current through the coil. Your measurements, so far, are meaningless. You have NEVER measured the delay through the coil. I guess I'm going to have to draw you some pictures and post them on my web page. > Since dozens of hours of measurements acceptable to most people were > rejected, the only solution would be to require a measurement with > instrumentation no one has. I fully accept your standing wave current measurements, Tom, but standing wave current measurements will not yield the information that we are after. We need to know the phase shift in the forward and reflected currents through the coil. Standing wave measurements simply will not yield that information. Self-resonance measurements will yield that information. The delay through a coil that is self-resonant on 16 MHz is 15.6 nS. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222246 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Tue, 14 Mar 2006 14:34:46 GMT Reg Edwards wrote: > Having started it, I havn't been taking much notice of this > long-winded thread. Its all too clever for poor little me! ;o) Just curious, Reg, are you familiar with phasors used to represent traveling waves where the phasor has a rotation about the origin proportional to the frequency? Are you familiar with the phasor addition of two of those waves traveling in opposite directions forming standing waves? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222247 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Phase shift circuits References: <121crm0eijembda@corp.supernews.com> Message-ID: <%yARf.535$4L1.80@newssvr11.news.prodigy.com> Date: Tue, 14 Mar 2006 14:37:47 GMT Roy Lewallen wrote: > Another is lumped > circuit networks -- an L network can be designed to effect a range of > phase shifts. Don't you find it strange that lumped-circuits cause phase shifts sometimes (above) and sometimes not (loading coils)? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222248 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <8V4Rf.4714$o41.3612@trnddc06> Message-ID: Date: Tue, 14 Mar 2006 14:45:51 GMT Reg Edwards wrote: > On second thoughts, since L and C are functions of a coil's physical > dimensions it must be something else which is changing with frequency. Or maybe nothing is changing appreciably over relatively small frequency excursions. Maybe the measurements are not measuring what someone thinks they are measuring. The only experiment so far that has actually measured the delay through a coil is the self-resonant frequency measurement. Tom's and Roy's results are perfectly consistent with the measurement of standing wave current whose phase is known to be constant and unchanging. That measurement yields no new information. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222249 of rec.radio.amateur.antenna From: Mike Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? References: <121craq3ed95h91@corp.supernews.com> Message-ID: <67BRf.873$tN3.831@newssvr27.news.prodigy.net> Date: Tue, 14 Mar 2006 15:16:18 GMT I was visiting a local SGC dealer years ago as he was troubleshooting a brand new antenna tuner that was not working. When he opened the plastic case, that special RTV acidic smell almost knocked us over and all the tinned circuit board traces and exposed wiring were corroded and black. SGC claimed they used the wrong type of RTV on a batch of tuners that was not for electronics use. Mike Roy Lewallen wrote: > The advice to avoid acetic-acid smelling RTV because of corrosion is > passed along from person to person like an urban legend, but like an > urban legend it's just about impossible to find anyone who's actually > seen any corrosion result from its use. (A number of queries I've made > over the years has produced just one, using a very early version of RTV.) > > I've used the acetic-acid smelling stuff for decades on a variety of > metals including tinned and untinned wire, aluminum, nickel, and copper > circuit boards, and never seen a hint of corrosion. But formulations > vary widely, and my experience certainly isn't exhaustive. I'm not > entirely convinced, though, that among the many formulations there > aren't others, which don't have that smell, which might be corrosive to > some materials. > > People who worry about this should buy an industrial product and stay > with it, since there's a much better chance the formulation won't change > in the future without notice. > > Roy Lewallen, W7EL Article: 222250 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <8V4Rf.4714$o41.3612@trnddc06> <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142339226.575932.283830@p10g2000cwp.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 15:22:21 GMT w8ji@akorn.net wrote: > The pattern has been after Cecil gets measurement results and finds > they disagree with his theory, he rejects the measurements. Not true, Tom, please stop saying such. I fully accept and embrace your measurements of standing wave current, already known to possess unchanging phase. Kraus has a graph of exactly that. Your measurements are PERFECTLY consistent with standing wave current measurements. What they are not consistent with is traveling wave current which undergoes a phase shift through the coil as yet unmeasured by you. Why don't you stop talking about you and me and discuss the technical issues? > The most logical thing any person can do when they repeatedly reject > any disagreeing data supplied by multiple people using different > equipment and methods is to come up with a measurement device no one > has or can build. That's not true either. A lot of hams can measusre the self-resonant frequency of a coil and know the coil exhibits a 90 degree phase shift at that self-resonant frequency. > The only recourse for Cecil and Yuri was to dismiss those measurements > and my measurements and demand new measurements. This is ancient history, Tom. I have learned a lot since then and would appreciate you dragging yourself back into the present so we can discuss technical issues, rather than personalities. For the present discussion, what happened in the past simply doesn't matter as I don't believe the same thing I believed three years ago. Things are not as simple as I first thought. > So here we are today, two or three years later, still trying to find a > measurement method that will agree with what Cecil and Yuri proposed, > that a loading coil behaves as a coiled up antenna or transmission line Three years ago, one could not use constant phase standing wave current to measure the delay through a coil. Today, one cannot use constant phase standing wave current to measure the delay through a coil. Nothing has changed. Standing wave current is what it is. Making the same measurements three years apart doesn't prove anything new. > Since no one has them and > that is all Cecil will accept, Cecil can not be proven wrong by a > method Cecil will accept. Again, a false statement. I am not asking for fiber optic measurements. All I am asking is that you measure the delay through your coil using exactly the methods as before, and report the results for 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz, the self-resonant frequency for which the delay is already known. When you do that, you will probably know what is wrong with your conclusions. There's nothing wrong with your experiment if you really want to measure the phase shift of a standing wave current known to have unchanging phase. Your measurements are perfectly consistent with the laws of physics. Please stop re-hashing the past. This is three years later. I've learned a lot in those 3 years and have changed my mind about a lot of things. Please just discuss the technical details and leave the personalities out of it. If the only way you and Roy can dispatch me is at a personal ad hominem level, doesn't that speak volumes about not being able to dispatch me at a technical level? Are you guys engineers or just attack dogs? For instance, compare the ad hominem stuff in your above posting to the technical content. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222251 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Tue, 14 Mar 2006 11:25:20 -0600 Message-ID: <2814-4416FC80-304@storefull-3257.bay.webtv.net> References: Cecil, W5DXP wrote: "Kraus agrees." Pity the fool that argues with Terman or Kraus! In Kraus` Figure 14-2 of the 3rd edition of "Antennas", the 1/2-wave is resonant and shows no phase shift from end to end. In Figure 14-4, phase is shown to make an abrupt phase transition at a point 1/2-wave back >from the open circuit at the tip of the antenna. This is predictable >from the behavior of an open-circuited transmission line as shown by Terman in Fig. 4-7 in his 1955 edition. Kraus` Figure 23-21 shows how a self-resonant coil can replace a short-circuited 1/4-wave stub in a phase-reversing trap. If you don`t have the 3rd edition of "Antennas", get it. Cecil wrote: "I am not asking for fiber optic measurements." Very likely they aren`t necessary. I`ve measured currents along antennas draging a sampling loop along them with a rope. A transit determined the position and its telescope made the r-f ammeter in the loop readable. Surely a loop and its ammeter can be small enough not to upset the measurements if you use enough power and have a low enough frequency. As Richard Clark might say: "We don`t need no stinkin` fiber optics." Best regards, Richard Harrison, KB5WZI Article: 222252 of rec.radio.amateur.antenna From: Bob Bob Subject: Modeling question Message-ID: Date: Tue, 14 Mar 2006 11:44:30 -0600 On a learning curve here. I'll admit I am after a fast answer or two. Using 4nec2 to model what will likely be a 2m antenna used at the home QTH. Its an extended double zepp. ie two 5/8's in phase with a hairpin like centre section, the whole thing made of 1/2" copper and fed at 200 ohms with a 4:1 balun or 100 ohm Q section. I have also included the mast but havent really adjusted for best gain. There will be a quad on the other side that isnt modeled yet. Looking good so far but; - Is the diameter of the source wire an issue? - How do I allow for the use of copper pipe 90 degree elbows used in construction. If I model them as (say) a extra single wire at 45 degrees to mimic the radious I run into segment len/diameter limits. Any thoughts or feedback welcome. Nec file attached inline. (Apologies for the line breaks) I have yet to go through convergence testing and playing with numbers of segments in the shorter sections. Cheers Bob W5/VK2YQA CE GW 1 13 0 0 15.19 0 0 16.38 0.012 GW 2 3 0 0 16.38 0.28 0 16.38 0.012 GW 3 3 0.28 0 16.38 0.41 0 16.38 0.012 GW 4 1 0.41 0 16.38 0.41 0 16.45 0.012 GW 5 3 0.41 0 16.45 0.28 0 16.45 0.012 GW 6 3 0.28 0 16.45 0 0 16.45 0.012 GW 7 13 0 0 16.45 0 0 17.64 0.012 GW 8 1 0.28 0 16.45 0.28 0 16.38 0.012 GW 9 81 0.501 0 0 0.501 0 17.7 0.025 GE 1 EK EX 0 8 1 0 1 0 GN 2 0 0 0 14 8.e-3 FR 0 1 0 0 146 0 EN Article: 222253 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Phase shift circuits References: <121crm0eijembda@corp.supernews.com> <%yARf.535$4L1.80@newssvr11.news.prodigy.com> <1142355638.246812.259970@e56g2000cwe.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 18:25:48 GMT K7ITM wrote: > Get a life, Cecil. Take the impedance at a point on a transmission line with reflections. Install a series inductor. It causes an arc on a Smith Chart. How can an arc on a Smith Chart equate to a phase shift of zero degrees? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222254 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> Message-ID: Date: Tue, 14 Mar 2006 18:35:31 GMT John Popelish wrote: > We are not talking about L, C, R, or any other inherent property > changing with frequency. The velocity factor of the coil is based on those quantities and can be calculated. The velocity factor of a transmission line is based on those quantities and can be calculated. >> Freq 1 2 4 8 16 MHz >> Delay ___ ___ 3 ___ 16 nS >> >> That looks non-linear to me. How about you? > > Definitely nonlinear, just like impedance is very nonlinear as the > frequency passes through any resonance. Care to fill in the blanks above? > This is why I am suspicious of > a measurement made at resonance, being extrapolated to non resonant > conditions. Self-resonance is simply where the round trip delay through the coil puts the forward and reflected voltages and the forward and reflected currents either at zero degrees or 180 degrees. That's what happens at an open-ended 1/4WL stub. That's also what happens at the feedpoint of a resonant standing wave antenna like a 75m mobile bugcatcher antenna. Resonant mobile antennas are "self-resonant antenna systems". -- 73, Cecil http://www.qsl.net/w5dxp Article: 222255 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <1142363038.740587.153310@v46g2000cwv.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 19:22:48 GMT jpopelish@rica.net wrote: >>The velocity factor of a transmission line is based on those >>quantities and can be calculated. > > Not quite. The velocity factor in transmission lines is based on > ratios: capacitance per length, and inductance per length. There exist formulas for calculating the Z0 and VF of helical transmission lines. I'll bet Reg can do it. A coil has a capacitance per length and inductance per length. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222256 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Yagi Antenna Question Date: Tue, 14 Mar 2006 13:24:47 -0600 Message-ID: <28826-4417187F-1058@storefull-3255.bay.webtv.net> References: <121cdv08ruvo207@corp.supernews.com> Art Unwin wrote: "I read as far as the word "tho a" and you made my day, you confirmed what I suspected that all antennas are based around yagis and not about antennas in general which is exactly the point I made earlier." Glad to see you posting again, Art. Kraus produced an organization chart of antennas on page 56 of the 3rd edition of "Antennas". In the Kraus plan, the "Yagi-Uda" is among the "End Fires". The topic is: "Yagi Antenna Question". Roy responded with: "Suppose you have a two-element driven array with the elements spaced a quarter wave apart and 90 degrees our of phase." This driven antenna produces a nice null to the rear as a Yagi can, but the Yagi is a parasitic array, not a driven array. In this forum, a participant is free to take the discussion in any desired direction and other participants are just as free to respond or not any way they want to. It`s freedom of choice! Best regards, Richard Harrison, KB5WZI Article: 222257 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Powerline trap Date: Tue, 14 Mar 2006 20:23:43 -0000 Message-ID: <121e9ifn2nqlocb@corp.supernews.com> References: In article , Owen Duffy wrote: >"There is provided a method for blocking a portion of energy of a >signal in a power line. The method includes equipping a high frequency >magnetic core with a coil, connecting a capacitor across terminals of >the coil to create a resonant circuit that resonates at a frequency of >the signal, and placing the magnetic core around the power line, at a >location where the blocking is desired." > >Hmmm, a trap! Without getting bogged down in the details of the coil >and the current / phase relationships, is this likely to be effective? Might well be. A classic method of blocking single-frequency interference current from flowing down a feedline is to stick a parallel-resonant trap next to it. The commonest variety I've seen described is a wire loop with tuning capacitor. I have no reason to believe that a core-based version would not work. >A parallel resonant trap in an antenna doesn't eliminate current >beyond the trap at the frequency of trap resonance. Will it make the >region of the powerline between the injector and the trap a better >radiatior for the same injector power? Could easily do so. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 222258 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Loop In Coax Help Prevent Lightning Induced Surges ? Date: Tue, 14 Mar 2006 14:23:26 -0600 Message-ID: <9127-4417263E-1072@storefull-3253.bay.webtv.net> References: <44162a45$0$58071$742ec2ed@news.sonic.net> Steve wrote: "I wouldn`t think anything but extremely good grounding at the antenna will do much." That helps. Company I retired from had radios all over the world. Most base stations used Andrew 1/4-wave stainless steel folded monopoles. These were securely grounded to the tower. The tower had a separate ground rod connected outside the base to each leg of the tower by heavy strap or cable. These radios suffered no lightning damage, despite repeated hits. Kraus has this to say in kis 3rd edition of "Antennas" on pages 719 and 720: "---a short-circuited lambda/4 section of coaxial line is connected in parallel with the antenna terminals. This widens the impedance bandwidth and also places the stub antenna at dc ground potential. This is desirable to protect the transmission line from lightning surges." Whenever we could not use a folded antenna with a single-frequency radio, we connected the shorted stub directly across the antenna and grounded the coax at the tower top. It works. Best regards, Richard Harrison, KB5WZI Article: 222259 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> Message-ID: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Date: Tue, 14 Mar 2006 20:56:31 GMT Cecil Moore wrote: > John Popelish wrote: > >> We are not talking about L, C, R, or any other inherent property >> changing with frequency. > > > The velocity factor of the coil is based on those quantities > and can be calculated. > > What's the formula, Cecil? Also, what is the dominant mode of a single wire, loading-coil transmission line: TE, TM, TEM, or what? If not TEM, how do you calculate the cutoff frequency? If I terminate one of these things in the right impedance will it act like an infinite transmission line? Given your loading coil terminated in a given impedance, what is the expression for the impedance looking into it? I suppose you also have something that will tell us how to find your coil's characteristic impedance; o.k., out with it. All this bluster and threatening rhetoric aren't advancing the acceptance of your crackpot theory one inch, Cecil. I don't see anything wrong with at least attempting to characterize a loading coil as a transmission line as long as the attempt is done dispassionately with real theory and an acceptance of the possibility of failure as part of the effort. Desperately thinking up excuses for an idea you made up in your head, and becoming emotionally distraught when people don't buy those excuses, is a waste of your time and everyone else's. 73, Tom Donaly, KA6RUH Article: 222260 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Phase shift circuits Date: Tue, 14 Mar 2006 14:52:57 -0600 Message-ID: <9127-44172D29-1073@storefull-3253.bay.webtv.net> References: <1142312610.017971.218740@v46g2000cwv.googlegroups.com> Tom, K7ITM wrote: "I tried "quadrature variometer" with no real luck." I found a posting from qsl net that looked interesting. You might look at the goniometer on page 1050 of Terman`s 1955 edition. Best regards, Richard Harrisn, KB5WZI Article: 222261 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Tue, 14 Mar 2006 21:45:06 GMT Tom Donaly wrote: > What's the formula, Cecil? http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (32) The velocity factor can also be measured from the self- resonant frequency at 1/4WL. VF = 0.25(1/f) > I suppose you also > have something that will tell us how to find your coil's characteristic > impedance; o.k., out with it. http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43) The characteristic impedance can also be measured at 1/2 the self-resonant frequency at 1/8WL. For a lossless case, the impedance is j1.0, normalized to the characteristic impedance so |Z0| = |XL|. For a Q = 300 coil, that should have some ballpark accuracy. We don't need extreme accuracy here. We just need enough to indicate a trend that the velocity factor of a well-designed coil doesn't increase by a factor of 5 when going from 16 MHz to 4 MHz. In "Antennas for All Applications", Kraus gives us the phase of the standing wave current on standing wave antennas like a 1/2WL dipole and mobile antennas. 3rd edition, Figure 14-2. It clearly shows that the phase of the standing wave is virtually constant tip-to-tip for a 1/2WL dipole. It is constant whether a coil is present or not. There is no reason to keep measuring that phase shift over and over, ad infinitum. There is virtually no phase shift unless the dipole is longer than 1/2WL and then it abruptly shifts phase by 180 degrees. I agree with Kraus and concede that the current phase shift in the midst of standing waves is at or near zero. There is no need to keep providing measurement results and references. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222262 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 21:58:47 GMT Tom, Whenever Cecil gets in a total lather I am reminded of John Belushi in Animal House. "Were you there when the Germans bombed Pearl Harbor?" This entire saga has been greatly extended and quite thoroughly confused by imprecise and flat-out-incorrect terminology. It probably won't get better any time soon. Currents, waves, and fields are used interchangeably as the mood strikes. Phase shift can refer to almost anything, it seems. Free-space optics are used as an analog to current in a wire. Descriptions that almost certainly have little transferability from one human to another abound, such as "superposed local RF phasors". Oh well, it's entertaining, at least for a while. 73, Gene W4SZ w8ji@akorn.net wrote: > With all the respect I can muster, here we go again Cecil. > > Current is current. Voltage is voltage. > [snip] > > In every single device we would be able to build, we would never be > able to sort reflected current from forward because current is current. > There really isn't any such thing as current traveling two directions > at one past one point in a system. > > You have taken this argument to an absolute dead end, because you > insist current can flow two directions at the same time at one single > point in a system. > > You are demanding a measurement method that uses a device that cannot > be built to measure something that does not exist. That is either > humorous, sad, or frustrating. It sure isn't science. > > 73 Tom > Article: 222263 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Powerline trap Date: Tue, 14 Mar 2006 14:08:53 -0800 Message-ID: <121efnr3vn09h64@corp.supernews.com> References: <121cqn82o4udt51@corp.supernews.com> Wes Stewart wrote: > > Hmmm. Interesting. I'm too busy to think much about this at the > moment but Devoldere has something in his book (p. 9-27 in my old > Third Edition) about decoupling a tower from ground using a "linear" > parallel-tuned trap. > > Does this not work? This sounds like the "resonance breaker" someone mentioned recently. It resembles a gamma match. You put a wire parallel to the tower for a few feet, then connect the top to the tower through a capacitor. The bottom of the wire is connected to the (grounded) bottom of the tower. This alters the effective height, and therefore the resonant frequency, of a tower. It's a technique used in the broadcast industry to reduce undesired coupling which distorts antenna patterns. I don't think this method will do more or less than a trap. There's nothing which will stop current or energy at some point, as long as there's mutual coupling from the wire on one side to the wire on the other. I recall an EMI control class I took long ago, where they told how a brute force power line filter was installed to reduce radiation from circuitry inside a device via the power line. Worked fine in the lab but failed in production. The filter was physically placed where there was room near the front of the unit, and they found that the production folks had neatly bundled the filter input and output wires for some distance, providing a good path around the filter. The same sort of thing happens on a wire with a trap, although the coupling is of course not as strong as between the bundled wires. Roy Lewallen, W7EL Article: 222264 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Phase shift circuits Date: Tue, 14 Mar 2006 14:11:49 -0800 Message-ID: <121efta7fb7jqcf@corp.supernews.com> References: <121crm0eijembda@corp.supernews.com> <%rzRf.14$ny.6@fe10.lga> Harry Gross wrote: > I guess I'll have to break down, buy a copy of EZ-NEC and play with it:-) The free demo program is adequate for what you're doing. > By the way, are you suggesting that 90 degree rotation is all I'd need, > simply because the dipole radiation pattern is so wide, broadside to the > radiator? Yes. If that turns out to be true, then the problem becomes vastly > easier to deal with, and could even be done mechanically by simply > switching around the feed line to one dipole (easier to do with ladder > line - the preferred feed line to a dipole - than coax, of course) Why is ladder line preferred over coax? I suggest reading http://eznec.com/Amateur/Articles/Baluns.pdf. Take a good look at Figure 2. > although that might not be the BEST way to do it. Roy Lewallen, W7EL Article: 222265 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Tue, 14 Mar 2006 22:29:28 GMT w8ji@akorn.net wrote: > I've solved the measurement problem. I measured current and voltage > levels and phase of each. There you go again, "I, I, I". This is not about you. This is about valid measurements. I concede that when one measures the current phase shift in a standing wave environment, that the result will be zero or close to zero. But we are not interested in measuring a constant phase whether the coil is in the circuit or not. We are interested in measuring the phase shift through the coil and it is NOT zero. Reference: Kraus' "Antennas for All Applications", 3rd edition, Figure 14-2. Kraus clearly shows if you measure the phase shift between any two points on a 1/2WL dipole, that measured shift will be close to zero degrees whether a coil is present or not. There is no need to keep performing those same measurements. I agree with Kraus. We know a 1/2WL dipole is 180 degrees long. The fact that the standing wave current doesn't change phase from end to end doesn't mean the 1/2WL dipole is zero degrees long. The fact that the standing wave current doesn't change phase on each side of a coil doesn't mean the coil is zero degrees long. > I've measured time delay of current appearing at the coil output > compared to input. There you go again, "I, I, I". It doesn't matter who does the measurement or whether a coil is in the circuit or not. The standing wave current's phase doesn't change in the antenna's 180 degrees of length. That has nothing to do with anybody's measurements. That's just a fact of physics. One cannot use standing wave current to measure the delay through a coil OR A WIRE in a standing wave environment. If one takes a known 30 degrees of a 1/2WL dipole and uses standing wave current to measure the phase shift through that 30 degrees of wire, the measurement yields zero degrees. Does that mean the phase shift in 30 degrees of wire in a 1/2WL dipole is zero? Of course not. One simply cannot ascertain the phase shift in a piece of wire (or coil) by measuring the phase of the standing wave current. > Current is current. On the contrary, one can look at the formula for standing wave current and see that standing wave current is NOT like traveling wave current. Traveling wave current is of the form f(z+wt) or f(z-wt) depending upon the direction of travel. Standing wave current is of the form f(z) + f(wt) so they are quite different and therefore have *different* characteristics. As you can see from the functions, magnitude and phase are interlocked for a traveling wave. Magnitude and phase are unlocked for a standing wave. With a phasor fixed at zero degrees, how does a standing wave phasor manage to flow? As is my custom, I am going to trim the part of your posting with which I agree. > In every single device we would be able to build, we would never be > able to sort reflected current from forward because current is current. On the contrary, we do it all the time for transmission lines with a known Z0. We separate forward power from reflected power. It is trivial to take forward power in a certain Z0 feedline and convert that value of power into forward current. It is trivial to take the reflected power in that same line and convert that power into a reflected current. Here are the formulas: |Ifor| = SQRT(Pfor/Z0) |Iref| = SQRT(Pref/Z0) In our directional couplers, we throw away the phase when we rectify it, but we don't have to throw away the phase. We can look ahead of the diodes with an o'scope probe and actually compare the phases of the two waves. > You have taken this argument to an absolute dead end, because you > insist current can flow two directions at the same time at one single > point in a system. There you go again, "you, you, you". Everyone has requested that we cease and desist from the personal attacks. "We" means "you and me". But it is well accepted in the distributed network model that two currents can flow in opposite directions at the same time. There's probably no other way to get standing waves and a 75m mobile bugcatcher antenna system *IS* a standing-wave antenna. > You are demanding a measurement method that uses a device that cannot > be built to measure something that does not exist. That is either > humorous, sad, or frustrating. It sure isn't science. There you go again, "you, you, you". This is not about you or me or our feelings. We can certainly measure the two currents flowing in opposite directions in a transmission line. Not having a voltage reference common is why it's hard to do in an antenna but I suspect it could be done with E-field and H-field probes and a little superpositioning. We are sometimes a rational species. We can perform our experiments on a transmission line with known Z0 and if we are careful, project out results on a standing wave antenna with an unknown Z0. Actually, the Z0 for a 1/2WL dipole made >from #14 wire at 30 ft. from the ground is pretty well known to be about 1200 ohms. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222266 of rec.radio.amateur.antenna From: "James F. Mayer" Subject: Digikey phishing Message-ID: Date: Tue, 14 Mar 2006 23:12:41 GMT Someone or a group of persons are phishing with the subject header "CC Pending Order Letter from Digi-Key for salesorder 16642643" I have received 2 (two) of them in the last two days and I have forwarded them to Digikey. They are investigating. If you receive any, please notify Digikey so thay can trsck down the culprits and prosecute them to the fullest extent of the law. Article: 222267 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Tue, 14 Mar 2006 17:03:49 -0600 Message-ID: <24188-44174BD5-266@storefull-3251.bay.webtv.net> References: <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Tom, W8JI wrote: "A traditional directional coupler works by comparing voltage across the line at any one point to current in the line at that same point." Almost. It compares a voltage sample to a current sample, both of which have been converted into d-c voltages. These have been carefully crafted to be exactly equal d-c voltages regardless of the power level in the line. I`m giving up on correcting line by line. Important fact is that a reflection reverses the phase between the voltage and current produced by a wave. So when the samples from the forward wave are siummed, their total is exactly 2x the value of either the voltage-derived sample or the current-derived sample. When the samples from the reflected wave are summed, being equal but opposite in polarity, they add to ZERO. Calibration is so the total produces the correct value on the power scale for the wave in the forward direction. To get the power in the reverse direction, the input and output are effectively exchanged so that the forward power indication cancels and the reverse power indication is produced by the sum of its voltage and current d-c sample outputs. Best regards, Richard Harrison, KB5WZI Article: 222268 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Tue, 14 Mar 2006 23:24:41 GMT Cecil Moore wrote: > Tom Donaly wrote: > >> What's the formula, Cecil? > > > http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (32) > > The velocity factor can also be measured from the self- > resonant frequency at 1/4WL. VF = 0.25(1/f) > >> I suppose you also >> have something that will tell us how to find your coil's characteristic >> impedance; o.k., out with it. > > > http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43) > > The characteristic impedance can also be measured at > 1/2 the self-resonant frequency at 1/8WL. For a lossless > case, the impedance is j1.0, normalized to the > characteristic impedance so |Z0| = |XL|. > For a Q = 300 coil, that should have some ballpark accuracy. > > We don't need extreme accuracy here. We just need enough to > indicate a trend that the velocity factor of a well-designed > coil doesn't increase by a factor of 5 when going from 16 > MHz to 4 MHz. > > In "Antennas for All Applications", Kraus gives us the phase > of the standing wave current on standing wave antennas like > a 1/2WL dipole and mobile antennas. 3rd edition, Figure 14-2. > It clearly shows that the phase of the standing wave is virtually > constant tip-to-tip for a 1/2WL dipole. It is constant whether > a coil is present or not. There is no reason to keep measuring > that phase shift over and over, ad infinitum. There is virtually > no phase shift unless the dipole is longer than 1/2WL and then > it abruptly shifts phase by 180 degrees. > > I agree with Kraus and concede that the current phase shift in > the midst of standing waves is at or near zero. There is no > need to keep providing measurement results and references. You load your antennas with a Tesla coil? Did you read the part about a Tesla coil going to a lumped inductor when it was shortened? 73, Tom Donaly, KA6RUH Article: 222269 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Current through coils Message-ID: <09ke125ae6sgljfk808u0vesdka361li2g@4ax.com> References: <1142371307.650160.117590@j33g2000cwa.googlegroups.com> <24188-44174BD5-266@storefull-3251.bay.webtv.net> Date: Tue, 14 Mar 2006 23:36:34 GMT On Tue, 14 Mar 2006 17:03:49 -0600, richardharrison@webtv.net (Richard Harrison) wrote: >Tom, W8JI wrote: >"A traditional directional coupler works by comparing voltage across the >line at any one point to current in the line at that same point." > >Almost. It compares a voltage sample to a current sample, both of which >have been converted into d-c voltages. These have been carefully crafted >to be exactly equal d-c voltages regardless of the power level in the >line. When you convert a sample of the RF voltage at a point to DC voltage you have a DC voltage proportional to the magnitude of the RF voltage at the point. When you convert a sample of the RF current at the same point to DC voltage you have a DC voltage proportional to the magnitude of the RF current at the point. You cannot use these two samples to determine generally the magnitude of the reflection coefficient (and hence VSWR), much less independent samples of the travelling waves. No, neither a directional coupler nor a common reflectoter work as you describe Richard. Owen -- Article: 222270 of rec.radio.amateur.antenna From: chuck Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 00:25:23 GMT Hello Tom, I understand that on page 6, the reference qualifies the statement in the abstract by saying that for heights " . . . less than 15 degrees . . . one passes to the lumped element regime . . ." I thought Cecil was drawing examples for heights greater than 15 degrees. Have I misunderstood? 73, Chuck, NT3G Tom Donaly wrote: > Cecil Moore wrote: > >> Tom Donaly wrote: >> >>> What's the formula, Cecil? >> >> >> >> http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (32) >> >> The velocity factor can also be measured from the self- >> resonant frequency at 1/4WL. VF = 0.25(1/f) >> >>> I suppose you also >>> have something that will tell us how to find your coil's characteristic >>> impedance; o.k., out with it. >> >> >> >> http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43) >> >> The characteristic impedance can also be measured at >> 1/2 the self-resonant frequency at 1/8WL. For a lossless >> case, the impedance is j1.0, normalized to the >> characteristic impedance so |Z0| = |XL|. >> For a Q = 300 coil, that should have some ballpark accuracy. >> >> We don't need extreme accuracy here. We just need enough to >> indicate a trend that the velocity factor of a well-designed >> coil doesn't increase by a factor of 5 when going from 16 >> MHz to 4 MHz. >> >> In "Antennas for All Applications", Kraus gives us the phase >> of the standing wave current on standing wave antennas like >> a 1/2WL dipole and mobile antennas. 3rd edition, Figure 14-2. >> It clearly shows that the phase of the standing wave is virtually >> constant tip-to-tip for a 1/2WL dipole. It is constant whether >> a coil is present or not. There is no reason to keep measuring >> that phase shift over and over, ad infinitum. There is virtually >> no phase shift unless the dipole is longer than 1/2WL and then >> it abruptly shifts phase by 180 degrees. >> >> I agree with Kraus and concede that the current phase shift in >> the midst of standing waves is at or near zero. There is no >> need to keep providing measurement results and references. > > > You load your antennas with a Tesla coil? Did you read the part > about a Tesla coil going to a lumped inductor when it was shortened? > 73, > Tom Donaly, KA6RUH Article: 222271 of rec.radio.amateur.antenna Date: Tue, 14 Mar 2006 18:52:46 -0600 From: Tom Ring Subject: Balun Question Message-ID: <4417658a$0$3760$39cecf19@news.twtelecom.net> If one has a sealed balun, such as you would pick up at your FLARPS or a fles market, and the label has disappeared from environmental exposure, is it possible to easily determine - 1) - if you are sure it's a 1:1 whether it's voltage or current type 2) - given it's totally unknown, anything about it. Instruments available would be a standard multimeter and an MFJ 259 or something equivalent. I think I know the answer to 1), but 2) has me stumped. Yes, dummy loads are a start, but is there an efficient way to get all unknowns absolutely resolved. tom K0TAR Article: 222272 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1142379642.765519.168180@p10g2000cwp.googlegroups.com> Subject: Re: Good coax for WiFi (2.4 & 5 ghz)? Message-ID: Date: Wed, 15 Mar 2006 01:39:57 GMT "KG0WX" wrote in message news:1142379642.765519.168180@p10g2000cwp.googlegroups.com... > I'm trying to setup a homebrew WiFi (802.11b/g) antenna for my IBM > Think Pad laptop. The coax run will be about 15" going to some home > brew antennas. I don't know the name of the antenna but it can be seen > at this url: > > http://wireless.gumph.org/content/4/3/011-mini-wireless-antenna.html > > I plan on running coax (2 lines) from the 802.11 card (internal mini > PCI) > to the rear top of the LCD display. I'll terminate with connectors and > attach the antennas when the laptop is open. Great plan but what about > coax losses? The output of the 802.11 card is 250mw. > > Most WiFi antennas use RG174 coax - I've even seen mobile antennas > for WiFi with 10' runs of the stuff. Correct me if I'm wrong but > wouldn't > 10' of rg174 at 5 ghz be so lossy that it would defeat the purpose of > the > mag mount mobile antenna? > > Like I said, I only need about 15" from the output of the 802.11 card > to the antennas. What coax would be good? I'm worried about losses > but I also need to route the coax through the laptop and up the back > of the LCD display so size (dia) matters. I guess I'm stuck with RG174 > but are there better choices? What would be the losses with 15" of it > into a matched load at 5ghz? > > Basically, given the above conditions and with the need for both small > coax and teeny connectors, what would be your recommendations? > > 73's de Ken KG0WX Hi Ken Could you use a USB connected wireless adapter?? You can dismantel some USB wireless adapters so their antennas are available to you for attaching a coax and even a SMA if you have the ability to work with that small stuff. Jerry Article: 222273 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 01:39:54 GMT Tom Donaly wrote: > You load your antennas with a Tesla coil? Did you read the part > about a Tesla coil going to a lumped inductor when it was shortened? A minimum Tesla coil is 1/4WL. My 75m bugcatcher coil mounted on my pickup as a base-loaded coil with no whip is 1/4WL on 6.6 MHz. Going from 6.6 Mhz to 4 MHz is only 40% shortening. I think the lumped inductor crossover point is probably pretty far below 4 MHz. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222274 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Balun Question Date: Tue, 14 Mar 2006 17:40:03 -0800 Message-ID: <121es3p5el3u5fb@corp.supernews.com> References: <4417658a$0$3760$39cecf19@news.twtelecom.net> Tom Ring wrote: > If one has a sealed balun, such as you would pick up at your FLARPS or a > fles market, and the label has disappeared from environmental exposure, > is it possible to easily determine - > > 1) - if you are sure it's a 1:1 whether it's voltage or current type Measure between the input terminals with an ohmmeter. A voltage balun will show a DC short, a current balun an open. > 2) - given it's totally unknown, anything about it. Connect the input terminals together and the output terminals together. Connect it to your antenna analyzer as a plain series load -- that is, connect the balun input terminals to the analyzer center conductor and the balun output terminals to the analyzer connector shell (or reverse the two -- it doesn't matter). Measure the impedance at frequencies of interest. You generally need a minimum of around 500 - 1000 ohms for an effective balun. The angle of the impedance doesn't matter unless you're running a lot of power, in which case a low angle (that is, a primarily resistive impedance) might result in objectionable balun heating. You can also connect resistors of various values across the balun output and measure the input Z with your analyzer. With a 50 ohm load, you should see close to 50 ohms in over a wide frequency range. As the load gets farther from 50 ohms, you'll see more variation between the input and output Z and it'll change more rapidly with frequency. This can be corrected if necessary with a matching arrangement. > Instruments available would be a standard multimeter and an MFJ 259 or > something equivalent. > I think I know the answer to 1), but 2) has me stumped. Yes, dummy > loads are a start, but is there an efficient way to get all unknowns > absolutely resolved. Roy Lewallen, W7EL Article: 222275 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Tue, 14 Mar 2006 19:56:30 -0600 Message-ID: <9128-4417744E-274@storefull-3253.bay.webtv.net> References: <1142383426.398750.259860@v46g2000cwv.googlegroups.com> Tom, W9JI wrote: "It is only after the voltages, one proportional to current and one proportional to voltage, are added that the voltage is rectified and used to drive the meter." Obviously a power determination must use voltage and current samples taken at the same place at the same time. We can`t use today`s voltage and yesterday`s current nor can we use the voltage over here and the current over there. Everything happens simultaneously and at the same sampling point. A single loop terminated in a diode is coupled to the center conductor of the coax. Its magnetic coupling produces the current sample. Its capacitive coupling produces the voltage sample. These are tweaked for identical deflection of the power meter. Best regards, Richard Harrison, KB5WZI Article: 222276 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 02:08:24 GMT chuck wrote: > I understand that on page 6, the reference qualifies the statement in > the abstract by saying that for heights " . . . less than 15 degrees . . > . one passes to the lumped element regime . . ." > > I thought Cecil was drawing examples for heights greater than 15 > degrees. Have I misunderstood? You understand, Chuck, for example, my 75m bugcatcher coil, base- mounted on my GMC pickup with no whip is 1/4WL self-resonant at 6.6 MHz, i.e. it is 90 degrees on 6.6 Mhz. By ratio and proportion, the height on 4 MHz is 90(4/6.6) = ~54.5 degrees, 3.6 times the transition height for passing to the lumped element regime. One would have to divide the self-resonant frequency by 6 to get down to the 15 degree maximum for the lumped element regime so 1.1 MHz would be the highest frequency for which the lumped element regime could be considered valid. As the paper says: "Of course, the uniform current assumption has no validity for coils operating anywhere near self-resonance." Even the 100 uH test coil, 90 degrees self-resonant at 16 MHz, when used on 4 MHz is 90(4/16) = ~22.5 degrees, still above the 15 degree limit. One would have to go down to 2.7 MHz for the lumped element regime to be valid for that 100 uH coil and that is for an excellent coil with a Q of around 300. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222277 of rec.radio.amateur.antenna Date: Tue, 14 Mar 2006 20:37:08 -0600 From: Tom Ring Subject: Re: Yagi Antenna Question References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> <16561-4415F129-38@storefull-3256.bay.webtv.net> <44162d6d_4@newsfeed.slurp.net> <121cdv08ruvo207@corp.supernews.com> <44163f90_3@newsfeed.slurp.net> <1142388810.162667.101490@z34g2000cwc.googlegroups.com> Message-ID: <44177e00$0$3754$39cecf19@news.twtelecom.net> w8ji@akorn.net wrote: > Thinking a reflector "reflects" and a director "directs" will doom you > to failure if you are trying to understand how a Yagi works. > > 73 Tom > Thanks for the nice synopsis. I would add that, because of how the physics works, the pattern that evolves doesn't happen during the first cycle, or the first few. It takes a while, and the more elements involved, the longer it takes. There were some nice online "movies" (simulations) of an antenna "building" its near and far field patterns a year or so ago. I will have to do some googling to find them again, they were quite interesting. tom K0TAR Article: 222278 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <1142387880.537934.100710@p10g2000cwp.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 02:47:40 GMT w8ji@akorn.net wrote: > Cecil Moore wrote: >>is only 40% shortening. I think the lumped inductor >>crossover point is probably pretty far below 4 MHz. > > There isn't any "crossover point". That point has been made several > times by different people. One of those people supporting a "crossover point" is Dr. Corum in his IEEE peer reviewed paper at: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf (page 6) Dr. Corum is pretty clear about 15 degrees, i.e. 4% of a wavelength, being the "crossover point". He considers 15 degrees to 90 degrees to require a distributed network analysis while below 15 degrees, "one passes to the lumped- element regime ..." The "crossover point" would be the same rule as for a transmission line. How long does a transmission line with reflections have to be before it is no longer valid to consider it a lumped piece of wire. 15 degrees is 4% of a wavelength and sounds reasonable. However, under the right conditions, one could arrange a current node at the halfway point of that 15 degrees of feedline thus causing current to flow into both ends of the feeline at the same time. 1/2 cycle later, current would be flowing out of both ends. How would a lumped-circuit model handle those conditions? The "crossover point" is obviously arbitrary but if one locates it very far above 15 degrees, according to Dr. Corum, one risks invalid analysis results such as have been reported here. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222279 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 03:17:02 GMT Cecil, (No smiley faces this time. No trolls or tricks either.) The assertion that there is some important difference between a standing wave and its component traveling waves has been made on a number of occasions in this thread. Indeed, that concept seems pretty central to the entire issue. It may be worth examining the importance of this distinction further. Basic assumptions: * System is linear, with no diodes, saturating cores, etc. * System is steady-state, with no startup transients. * System is lossless, including a lack of radiation * Superposition applies, i.e., scaling works and we can add subcomponent functions without error. The whole is precisely equal to the sum of the parts, no more and no less. If any of these assumptions are not operative, then what follows may not be correct. As you have stated, including references from Hecht, it is customary to mathematically show traveling waves in the form: cos (kz +/- wt) Through straightforward addition and simple trigonometry is is seen that the standing wave corresponding to the sum of equal magnitude forward and reverse traveling waves has the form: cos (kz) * cos (wt) The key question then becomes, what information has been lost in adding the traveling waves to form a standing wave? All of the parameters and variables are still in the standing wave equation, namely, k, z, w, t. The numerical values and definitions for these terms have not changed. One can add constant phase offsets in the traveling wave equations, but those don't really add any new information, and in any case they are not lost in converting to the standing wave format. Are there some hidden variables that have not been considered? If so, what are they, and where do they show up in the original traveling wave equations? If not, why does the analysis and measurement of the traveling wave components give one iota more information than the analysis and measurement of the standing wave? There is little doubt that real world conditions will violate some of the assumptions, but that does not seem to be the issue in the debate at this time. Again, what extra information would be gained if somehow the traveling wave components could be measured? 73, Gene W4SZ Cecil Moore wrote: > w8ji@akorn.net wrote: [snip] > >> Current is current. > > > On the contrary, one can look at the formula for standing wave > current and see that standing wave current is NOT like traveling > wave current. Traveling wave current is of the form f(z+wt) or > f(z-wt) depending upon the direction of travel. Standing wave > current is of the form f(z) + f(wt) so they are quite different > and therefore have *different* characteristics. > > As you can see from the functions, magnitude and phase are > interlocked for a traveling wave. Magnitude and phase are > unlocked for a standing wave. With a phasor fixed at zero > degrees, how does a standing wave phasor manage to flow? Article: 222280 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1142379642.765519.168180@p10g2000cwp.googlegroups.com> Subject: Re: Good coax for WiFi (2.4 & 5 ghz)? Message-ID: Date: Wed, 15 Mar 2006 04:11:19 GMT "Chuck Olson" wrote in message news:XI6dnTsPL4Rm54rZRVn-gQ@comcast.com... > > "Jerry Martes" wrote in message > news:NfKRf.7774$%e1.6453@trnddc05... >> >> "KG0WX" wrote in message >> news:1142379642.765519.168180@p10g2000cwp.googlegroups.com... >> > I'm trying to setup a homebrew WiFi (802.11b/g) antenna for my IBM >> > Think Pad laptop. The coax run will be about 15" going to some home >> > brew antennas. I don't know the name of the antenna but it can be seen >> > at this url: >> > >> > http://wireless.gumph.org/content/4/3/011-mini-wireless-antenna.html >> > >> > I plan on running coax (2 lines) from the 802.11 card (internal mini >> > PCI) >> > to the rear top of the LCD display. I'll terminate with connectors and >> > attach the antennas when the laptop is open. Great plan but what about >> > coax losses? The output of the 802.11 card is 250mw. >> > >> > Most WiFi antennas use RG174 coax - I've even seen mobile antennas >> > for WiFi with 10' runs of the stuff. Correct me if I'm wrong but >> > wouldn't >> > 10' of rg174 at 5 ghz be so lossy that it would defeat the purpose of >> > the >> > mag mount mobile antenna? >> > >> > Like I said, I only need about 15" from the output of the 802.11 card >> > to the antennas. What coax would be good? I'm worried about losses >> > but I also need to route the coax through the laptop and up the back >> > of the LCD display so size (dia) matters. I guess I'm stuck with RG174 >> > but are there better choices? What would be the losses with 15" of it >> > into a matched load at 5ghz? >> > >> > Basically, given the above conditions and with the need for both small >> > coax and teeny connectors, what would be your recommendations? >> > >> > 73's de Ken KG0WX >> >> Hi Ken >> >> Could you use a USB connected wireless adapter?? You can dismantel >> some >> USB wireless adapters so their antennas are available to you for >> attaching > a >> coax and even a SMA if you have the ability to work with that small >> stuff. >> >> Jerry >> >> > Hi, Jerry and Ken > > Pardon me for getting into this, but we would all like to know which USB > adapters (and cardbus adapters currently manufactured) can be taken apart > and fitted with an antenna connector. There are a number of PC card > adapters > that have appeared in websites showing these modifications but the units > are > mostly no longer manufactured. With metropolitan Wi-Fi coming in to > various > municipalities lately, it is becoming more desirable to put up an antenna > to > guarantee 100% connection when the AP is half a block away or behind a big > house or dense foliage. > > Thanks for your help. > > Chuck Hi Chuck Although I dont have a part number for a USB wireless adapter, I can get the number from my buddy's adapter. He replaced the built in antenna the USB wireless adapter with a short coax to his Wireless antenna. I assummed the adapters are available at places like Fry's. I am using a different approach here at home. I put a Bridge behind small satellite TV dish and suffered the loss associated with foot and a half of coax loss to the illuminator. That allows me to run CAT 5 to the computer. Jerry > Article: 222281 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 04:24:21 GMT Gene Fuller wrote: > As you have stated, including references from Hecht, it is customary to > mathematically show traveling waves in the form: cos (kz +/- wt) > Through straightforward addition and simple trigonometry is is seen that > the standing wave corresponding to the sum of equal magnitude forward > and reverse traveling waves has the form: cos (kz) * cos (wt) I see I made a typo and typed a '+' sign in my previous equation. Of course, it should have been a '*' sign for multiply. > Are there some hidden variables that have not been considered? Not a hidden variable, but there seems to be a hidden mathematical concept, at least hidden from some individuals. In case some might not know, 'z' is the position up and down the wire, omega (w) is our old friend 2*pi*f, and 't' is, of course, time. In the traveling wave equation, cos(kz +/- wt), the position on the wire and omega*time are added or subtracted *before* the cosine function is taken. That means that the position on the wire and the phase velocity are inter-related. One cannot have one without the other. And that is indeed a characteristic of a traveling wave. Physical position, frequency, and time all go into making a traveling wave. It is modeled as a rotating phasor. However, in the equation, cos(kz) * cos(wt), the physical position, 'z' is disconnected from the phase velocity, 'wt'. The standing wave is no longer moving in the 'z' dimension. If you pick a 'z' and hold it constant, i.e. choose a single point on the wire, the standing wave becomes simply some constant times cos(wt). Thus at any fixed point on the line, the standing wave is not moving - it is just oscillating at the 'wt' rate and a current probe will certainly pick up the H-field signal. The phase of the standing wave current is everywhere, up and down the 1/2WL thin-wire, equal to zero. The sum of the forward phasor and reflected phasor doesn't rotate. Its phase doesn't change with position. Only its magnitude changes with position and if the forward wave magnitude equals the reflected wave magnitude, it is not flowing in the real sense that current flows. It is a standing wave and it is just standing there. The main thing to realize is that the standing wave equation divorces the position of the standing wave from its phase velocity such that the phase velocity is not active in the 'z' dimension, i.e. up and down the wire. The standing wave current "pseudo phasor" is not rotating. The standing wave is not going anywhere. It is not flowing along a wire or through a coil. Measuring its phase is meaningless because the phase is already known to be constant and unchanging from tip to tip in a 1/2WL dipole or across a loading coil in a mobile antenna. Thinking that standing wave current flows from the middle of a dipole to the ends is just a misconception. The equation for a standing wave indicates that it doesn't flow. What is flowing are the forward and reflected waves. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222282 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 04:48:26 GMT Gene Fuller wrote: > Again, what extra information would be gained if somehow the traveling > wave components could be measured? Here's a pretty good animation of forward, reflected, and standing waves. http://users.pandora.be/educypedia/electronics/applets/ph14e/stwaverefl.htm -- 73, Cecil http://www.qsl.net/w5dxp Article: 222283 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 04:52:54 GMT That's probably what he has in mind: using longer coils to get the correct phase shift. He'll have to use the formulas in the reference to make coils that will test his ideas. I don't understand why he uses a coil at all, in that case, since he could just as easily use a length of coiled up transmission line to accomplish the same thing. I think he's been trying to prove that coils, as people currently use them, are really transmission lines that automatically shift the current phase the correct amount to cancel antenna reactance. If he applies his reference formulae to one of Tom's coils and it doesn't show the correct phase shift, though, his theory is in trouble. 73, Tom Donaly KA6RUH chuck wrote: > Hello Tom, > > I understand that on page 6, the reference qualifies the statement in > the abstract by saying that for heights " . . . less than 15 degrees . . > . one passes to the lumped element regime . . ." > > I thought Cecil was drawing examples for heights greater than 15 > degrees. Have I misunderstood? > > 73, > > Chuck, NT3G > > > Tom Donaly wrote: > >> Cecil Moore wrote: >> >>> Tom Donaly wrote: >>> >>>> What's the formula, Cecil? >>> >>> >>> >>> >>> http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (32) >>> >>> The velocity factor can also be measured from the self- >>> resonant frequency at 1/4WL. VF = 0.25(1/f) >>> >>>> I suppose you also >>>> have something that will tell us how to find your coil's characteristic >>>> impedance; o.k., out with it. >>> >>> >>> >>> >>> http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43) >>> >>> The characteristic impedance can also be measured at >>> 1/2 the self-resonant frequency at 1/8WL. For a lossless >>> case, the impedance is j1.0, normalized to the >>> characteristic impedance so |Z0| = |XL|. >>> For a Q = 300 coil, that should have some ballpark accuracy. >>> >>> We don't need extreme accuracy here. We just need enough to >>> indicate a trend that the velocity factor of a well-designed >>> coil doesn't increase by a factor of 5 when going from 16 >>> MHz to 4 MHz. >>> >>> In "Antennas for All Applications", Kraus gives us the phase >>> of the standing wave current on standing wave antennas like >>> a 1/2WL dipole and mobile antennas. 3rd edition, Figure 14-2. >>> It clearly shows that the phase of the standing wave is virtually >>> constant tip-to-tip for a 1/2WL dipole. It is constant whether >>> a coil is present or not. There is no reason to keep measuring >>> that phase shift over and over, ad infinitum. There is virtually >>> no phase shift unless the dipole is longer than 1/2WL and then >>> it abruptly shifts phase by 180 degrees. >>> >>> I agree with Kraus and concede that the current phase shift in >>> the midst of standing waves is at or near zero. There is no >>> need to keep providing measurement results and references. >> >> >> >> You load your antennas with a Tesla coil? Did you read the part >> about a Tesla coil going to a lumped inductor when it was shortened? >> 73, >> Tom Donaly, KA6RUH Article: 222284 of rec.radio.amateur.antenna From: "Hal Rosser" References: <4417658a$0$3760$39cecf19@news.twtelecom.net> Subject: Re: Balun Question Message-ID: Date: Tue, 14 Mar 2006 23:57:17 -0500 "Tom Ring" wrote in message news:4417658a$0$3760$39cecf19@news.twtelecom.net... > If one has a sealed balun, such as you would pick up at your FLARPS or a > fles market, and the label has disappeared from environmental exposure, > is it possible to easily determine - > > 1) - if you are sure it's a 1:1 whether it's voltage or current type > > 2) - given it's totally unknown, anything about it. > > Instruments available would be a standard multimeter and an MFJ 259 or > something equivalent. assuming its a wound balun... attach some alligator clips to a variable resistor, and set it to around 50 ohms or so - then attach it to one side of the balun. and attach coax from the mfj259 to the other side. turn on the mfj and adjust the resistor for low swr (you'll have to measure it later) turn it off and measure the resistance you had to adjust it to. Dividing that value by 50 will probably be the balun's impedence ratio (4-to-1 - or whatever) Change freqs on the MFJ and go it over again till you determine the bandwidth. (If you adjusted the resistor to 200 ohms and it shows SWR of 1:1, then its a 4 to 1 balun) my 2¢ Hal W4PMJ Article: 222285 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 05:03:42 GMT Cecil Moore wrote: > Tom Donaly wrote: > >> You load your antennas with a Tesla coil? Did you read the part >> about a Tesla coil going to a lumped inductor when it was shortened? > > > A minimum Tesla coil is 1/4WL. My 75m bugcatcher coil > mounted on my pickup as a base-loaded coil with no > whip is 1/4WL on 6.6 MHz. Going from 6.6 Mhz to 4 MHz > is only 40% shortening. I think the lumped inductor > crossover point is probably pretty far below 4 MHz. Why don't you crunch the numbers using your reference and find out for sure? (If your reference is correct, that is. Some of the papers by academics on the web don't always give information that corresponds to reality.) You should be able to analyze your bugcatcher easily and report what you find. It sure beats sitting around drinking Ripple and feeling persecuted. 73, Tom Donaly, KA6RUH Article: 222286 of rec.radio.amateur.antenna From: Dave Heil Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? References: <121craq3ed95h91@corp.supernews.com> Message-ID: Date: Wed, 15 Mar 2006 05:00:55 GMT Dan Richardson adelphia wrote: > On Mon, 13 Mar 2006 23:14:29 -0800, Roy Lewallen > wrote: > >> The advice to avoid acetic-acid smelling RTV because of corrosion is >> passed along from person to person like an urban legend, but like an >> urban legend it's just about impossible to find anyone who's actually >> seen any corrosion result from its use. (A number of queries I've made >> over the years has produced just one, using a very early version of RTV.) > > [snip] >> Roy Lewallen, W7EL > > HI Roy, > > I have been using a different product for over a decade that works > great - liquid vinyl tape. It does a heck of a job for sealing > water-tight connections and, like RTV, doesn'g get hard and crack. > You can buy it a most hardware stores. > > Its easy to use and, like was suggest earlier in this thread, I first > wrap the connection with regular vinyl tape (a single layer) before > appling the liquid compond - its makes for much easier removal when > needed. I've pretty much switched completely to the Plasti-Dip stuff myself. It is readily available in at least two colors--red and black--at Lowe's. I used RTV, both the acetic acid and non-acetic acid varieties through the years. After a couple of unpleasant corrosion experiences with the acetic acid type, I began either wrapping connectors with vinyl electrical tape or spraying with acrylic sealant and then applied the RTV. Either way works well. I recall seeing cautions that one should be wary of black RTV in that it could conduct. I don't know whether it can break down but I've used the clear product. Dave Heil K8MN Article: 222287 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 05:04:34 GMT Tom Donaly wrote: > If > he applies his reference formulae to one of Tom's coils and it > doesn't show the correct phase shift, though, his theory is in trouble. His reference formulae are for traveling waves, not standing waves. We already know that the phase of the standing wave current on a 1/2WL thin-wire dipole varies not one degree over that entire 180 degrees. Yet we know the forward wave undergoes a 90 degree phase shift from feedpoint to tip and the reflected wave undergoes a 90 degree phase on the trip back to the feedpoint. Standing wave phase is virtually unchanging and is therefore useless for trying to determine the electrical length of a wire or a coil. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222288 of rec.radio.amateur.antenna From: "Sal M. Onella" References: <_1GPf.17539$992.17494@tornado.socal.rr.com> Subject: Re: Military ships fan antenna Message-ID: Date: Tue, 14 Mar 2006 21:10:38 -0800 "J. B. Wood" wrote in message news:wood-0903060744300001@jbw-mac.itd.nrl.navy.mil... > In article , Richard Clark > wrote: > > > On Wed, 08 Mar 2006 19:14:02 GMT, "NA" > > wrote: > > > > >Can anyone tell me about "fan antennas" like those used on the large navy > > >ships. > > > > Hi Jim, > > > > It is an array of co-planar, parallel monopoles driven at the same, > > common point. The size of each in the array is different spanning > > from short to long such that at least one is resonant within a wide > > band of frequencies. > > > > > Hello, and the only fan antenna that I have any experience with is the > venerable 2-6 MHz twin fan transmitting antenna used on USN combat ships. > This antenna consists of two sets (port, starbaord) of three sloping wires > strung from a yardarm on the stack to the feedpoint on the deck. A VSWR > of 3 or less is typically achieved using a fixed passive LC network. By > design, most of the radiation actually comes from RF currents induced on > the stack by the fan wires. Sincerely, > > John Wood Supplementing, if I may, many fan-wire antennas are fed from the mast. (I've climbed most of the ships in the Pacific Fleet at one time or another.) Coax into the matching network box and port/starboard feedwires out. The traditional design used the fan from 2-6, another antenna, maybe a cage for 4-12 and a third, maybe a discone or trussed whip, from 10-30. These are fed by four- or eight-channel multicouplers in Radio. A newer design, called HFRG, for HF Radio Group, uses a 2-9 fan and maybe twin whips from 8- 30. HFRG tolerates a 4:1 SWR ... I don't think you can get a match of 3:1 over a wide range like 2-9 or 8-30. (In a lab, maybe.) I Googled for AN/URC-131 and got: http://www.rfcomm.harris.com/products/integrated-communications/anurc-131v.p df It's mostly a Harris puff piece, but there's a little techie stuff. I have to say "maybe" a lot because of differences between classes and even between different levels of modernization within a single ship class. John KD6VKW US Navy since Jan, 1962, in many capacities. Article: 222289 of rec.radio.amateur.antenna From: Bob Subject: Re: Good coax for WiFi (2.4 & 5 ghz)? References: <1142379642.765519.168180@p10g2000cwp.googlegroups.com> <1142394311.679500.186730@i40g2000cwc.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 05:54:32 GMT Did you know the USSS investigates many types of computer fraud and hacking? Do you think it’s wise to state your intent to maliciously invade other peoples computer systems and mention a traceable Ebay purchase of the goods to do so? USB type adaptors generally do not work with the popular freeware that you wanna be hackers use to commit your heinous crimes. Belden RG-174 has about .6dB loss/ft @ 5.6GHz. Your 15ft chunk would have about 9dB loss, not too impressive. Bob KG0WX wrote: > Well, I'm not just building *any* WiFi setup - I researched a bit and > found > on eBay what is generally agreed on to be one of the top 5 internal > 802.11 > cards. With up to 250mw output and external antenna, I plan on diving > into > a new hobby - wardriving. > > I could just buy a USB WiFi adapter and crack open the case and hack it > with an external antenna but from what I've seen, both the low output > and > poor rx sensitivity seem to be quite common with these devices and that > is not what I want. > > I did remember a bookmarked site which calculated the info I needed. > Turns > out that my coax in question will have about 1.7 db loss at 5ghz. Not > too bad. > > Still, if anyone knows of a coax that is better than RG174 while being > about > the same size, please chime in with your comments! > > Ken KG0WX > Article: 222290 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Modeling question References: <3FIRf.28313$M52.20709@edtnps89> Message-ID: <18qke3-do6.ln1@p400bob.personal.cox.net> Date: Wed, 15 Mar 2006 00:53:21 -0600 Hi Frank The pgm I was using complained about Seg.Len/Rad < 6 for which I adjusted the seg lengths for accordingly. I guess the warnings are different for each software front end. More reading and expermenting to do! Tnxs for your input. Cheers Bob Frank's wrote: > > Bob, while your model does not produce any errors with NEC 2, the > "Average Gain Test" (AGT) returns: > > Freq.(MHz) Wavelength(m) Avg. Power Avg. Power (dB) Comments > ------------------------------------------------------------------------- > 146.00000 2.05340 0.78364 -1.05885 > Questionable > > All GW cards return a warning: " Seg.Len/Rad < 8. Also the pole > segmentation is considered too large. > > It appears that accurate modelling of such a structure in NEC 2 is not > possible unless you reduce the size of your conductors. > > 73, > > Frank > > Article: 222291 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 15 Mar 2006 06:23:45 -0600 Message-ID: <23730-44180751-57@storefull-3254.bay.webtv.net> References: <1142403032.631680.97570@j33g2000cwa.googlegroups.com> Tom, K7ITM wrote: "FWIW, the "aingle loop terminated in a diode" that provides both magnetic and electric coupling at the same time" is not the only way to make a directional coupler." Agteed, but the Bird Electronic Corporation has been successful making the plug-ins for their "Thruline Wattmeter" that way for about 50 years. Best regards, Richard Harroison, KB5WZI Article: 222292 of rec.radio.amateur.antenna From: Harry Gross Subject: Re: Phase shift circuits References: Message-ID: Date: Wed, 15 Mar 2006 08:18:11 -0500 Thanks for all the input. I'll be playing with the idea for the next few weeks/months, and I'll let you all know how it works out. Article: 222293 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> Message-ID: <30WRf.738$4L1.193@newssvr11.news.prodigy.com> Date: Wed, 15 Mar 2006 15:02:23 GMT Richard Clark wrote: > Cecil Moore wrote: >>A minimum Tesla coil is 1/4WL. My 75m bugcatcher coil >>mounted on my pickup as a base-loaded coil with no >>whip is 1/4WL on 6.6 MHz. > > An 11.4 meter tall bugcatcher coil - sure.... Such are the rewards of > a Xerox based education. The physical height of my 75m bugcatcher coil is about 0.167 meters. Dividing 0.167m by 11.4m gives the velocity factor equal to 0.015. Your 11.4 meter value assumes a VF of zero. Multiply the 11.4 meters by the VF of the environment and you will obtain the physical length for something with an electrical length of 90 degrees. To obtain an electrical 90 degrees using RG-213: 11.4m * 0.66 = 7.5m To obtain an electrical 90 degrees using my 75m bugcatcher coil: 11.4m * 0.015 = 0.167m -- 73, Cecil http://www.qsl.net/w5dxp Article: 222294 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 15:06:52 GMT Objection, your Honor! Answer is unresponsive to the question. Sustained. 8-) Gee Cecil, how does one learn of such a "hidden mathematical concept", when it does not seem to be embodied in the formalism? Let's try again. Suppose the standing wave is examined to perfection. Everything that can be determined is measured without error. Now we take the superposition in reverse; specifically we divide the standing wave into forward and reverse traveling components. It would seem that we have a complete and accurate definition for the two traveling wave components. The interrelations, as you call them, between the variables and parameters are fully defined by the basic math and the carefully measured standing wave. What else is needed to describe the traveling waves? Additional variables? Additional coefficients or parameters? Additional hidden mathematical concepts? There seems to be a lack of understanding and appreciation for what the concepts of "linear" and "superposition" really mean. These are not just mathematical concepts. When they apply it means that the system under study is fully and completely described by ** either ** the individual functional subcomponents ** or ** the full superimposed functional component. It is not necessary to use both formats, and there is no added information by doing so. Take a look at any of your favorite antenna references with an eye toward the treatment of standing wave antennas. I believe you will find only passing discussion of traveling waves. There will be some mention of the equivalence between the two types of waves, but little else. It is unlikely that you will find anything that says you will get more information if you take the time and trouble to analyze traveling waves. 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> As you have stated, including references from Hecht, it is customary >> to mathematically show traveling waves in the form: cos (kz +/- wt) >> Through straightforward addition and simple trigonometry is is seen >> that the standing wave corresponding to the sum of equal magnitude >> forward and reverse traveling waves has the form: cos (kz) * cos (wt) > > > I see I made a typo and typed a '+' sign in my previous equation. > Of course, it should have been a '*' sign for multiply. > >> Are there some hidden variables that have not been considered? > > > Not a hidden variable, but there seems to be a hidden > mathematical concept, at least hidden from some individuals. > > In case some might not know, 'z' is the position up and down > the wire, omega (w) is our old friend 2*pi*f, and 't' is, of > course, time. > > In the traveling wave equation, cos(kz +/- wt), the position on > the wire and omega*time are added or subtracted *before* the cosine > function is taken. That means that the position on the wire and the > phase velocity are inter-related. One cannot have one without the > other. And that is indeed a characteristic of a traveling > wave. Physical position, frequency, and time all go into > making a traveling wave. It is modeled as a rotating phasor. > > However, in the equation, cos(kz) * cos(wt), the physical position, > 'z' is disconnected from the phase velocity, 'wt'. The standing wave > is no longer moving in the 'z' dimension. If you pick a 'z' and hold > it constant, i.e. choose a single point on the wire, the standing > wave becomes simply some constant times cos(wt). Thus at any fixed > point on the line, the standing wave is not moving - it is just > oscillating at the 'wt' rate and a current probe will certainly pick > up the H-field signal. The phase of the standing wave current is > everywhere, up and down the 1/2WL thin-wire, equal to zero. The sum > of the forward phasor and reflected phasor doesn't rotate. Its phase > doesn't change with position. Only its magnitude changes with position > and if the forward wave magnitude equals the reflected wave magnitude, > it is not flowing in the real sense that current flows. It is a > standing wave and it is just standing there. > > The main thing to realize is that the standing wave equation > divorces the position of the standing wave from its phase > velocity such that the phase velocity is not active in the > 'z' dimension, i.e. up and down the wire. The standing wave > current "pseudo phasor" is not rotating. The standing wave > is not going anywhere. It is not flowing along a wire or > through a coil. Measuring its phase is meaningless because > the phase is already known to be constant and unchanging from > tip to tip in a 1/2WL dipole or across a loading coil in a > mobile antenna. > > Thinking that standing wave current flows from the middle of a > dipole to the ends is just a misconception. The equation for > a standing wave indicates that it doesn't flow. What is flowing > are the forward and reflected waves. Article: 222295 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142403032.631680.97570@j33g2000cwa.googlegroups.com> <23730-44180751-57@storefull-3254.bay.webtv.net> Message-ID: <4cWRf.742$4L1.590@newssvr11.news.prodigy.com> Date: Wed, 15 Mar 2006 15:15:12 GMT Richard Harrison wrote: > Tom, K7ITM wrote: > "FWIW, the "aingle loop terminated in a diode" that provides both > magnetic and electric coupling at the same time" is not the only way to > make a directional coupler." > > Agreed, but the Bird Electronic Corporation has been successful making > the plug-ins for their "Thruline Wattmeter" that way for about 50 years. My old Heathkit HM-15 SWR meter has a short slotted through-line with two parallel pick up wires located about halfway between the center conductor and the shield. A 50 ohm resistor to ground at one end kills the voltage in that direction. A diode at the other end rectifies the voltage in the opposite direction. With two resistors and two diodes on opposite ends of the two pickup wires, they separate the forward wave from the reflected wave. The operation of the slotted line + pickup wires seems to be a lot like the Thruline element in a Bird but with no slug to rotate. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222296 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Yagi Antenna Question Date: Wed, 15 Mar 2006 09:13:20 -0600 Message-ID: <2813-44182F10-1461@storefull-3257.bay.webtv.net> References: <1142220621.801581.310250@u72g2000cwu.googlegroups.com> Tom, W8JI wrote: "The shorter element doesn`t direct. It reradiates energy." On page 905 of Terman`s 1955 edition he writes: "If resonant at a higher frequency than is being transmitted, the parasitic antenna acts as a "director" and tends to concentrate the radiated field in its direction." "Director" in quotation marks means: that is what they are called. Pity the fool who argues with Terman! Best regards, Richard Harrison, KB5WZI Article: 222297 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 15:27:48 GMT Cecil, WOW! Thanks! I took all of those endless physics and math classes before the Internet arrived, so I had no idea how a standing wave was formed. 8-) 8-) 8-) OK, the same question. It is a pretty picture, but what extra information would be gained if somehow the traveling wave components could be measured? 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> Again, what extra information would be gained if somehow the traveling >> wave components could be measured? > > > Here's a pretty good animation of forward, reflected, > and standing waves. > > http://users.pandora.be/educypedia/electronics/applets/ph14e/stwaverefl.htm Article: 222298 of rec.radio.amateur.antenna From: "Juergen Kosel" Subject: 1 Million Visitors to your Website Message-ID: <_RWRf.578$Yr.20@nntpserver.swip.net> Date: Wed, 15 Mar 2006 17:00:41 How To Get 1 Million Visitors On Your Web Site Without Paying A Dime In advertising ! Are you frustrated by the lack of traffic coming to your site? If I would tell you that after months of research, I just got my hands on the most hidden secrets... very sneaky tricks ! Click here : http://freeadguru.com/cgi-bin/i.pl?c=a&i=32460 Hurry, before the page gets banned! --- MAF Anti-Spam ID: 20060315091657M9n6YrV1 Article: 222299 of rec.radio.amateur.antenna From: "Frank" References: <3FIRf.28313$M52.20709@edtnps89> <18qke3-do6.ln1@p400bob.personal.cox.net> Subject: Re: Modeling question Message-ID: Date: Wed, 15 Mar 2006 16:20:04 GMT > Hi Frank > > The pgm I was using complained about Seg.Len/Rad < 6 for which I adjusted > the seg lengths for accordingly. I guess the warnings are different for > each software front end. > > More reading and expermenting to do! Tnxs for your input. > > Cheers Bob Hi Bob, you are probably right about the different software standards. The NEC-2 Users Manual, p8, first paragraph, states: "Delta/a must be > 'about' 8 for errors < 1%". I guess the developers of 4nec2 considered the error for Delta/a > 6 to be acceptable. Your model, in free space with no pole, does deviate a little from a thin wire dipole of the same length. Possibly the stub effects the pattern some. Both of Cebik's books make excellent reading for NEC modeling, although oriented to Nittany's products. Also www.cebik.com is a good source of information. 73, Frank Article: 222300 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 16:47:26 GMT Gene Fuller wrote: > ... how does one learn of such a "hidden mathematical concept", > when it does not seem to be embodied in the formalism? The standing wave function equation, cos(kz)*cos*wt), is different in kind and function from the traveling wave function equation, cos (kz ± wt). When two traveling waves are moving along the same path in opposite directions, their two phasors are rotating in opposite directions. It is the sum of their phase angles that is a constant number of degrees. It is that constant phase angle that has been measured and reported here. Kraus shows a plot of the standing wave angle for a 1/2WL thin- wire dipole. It is zero from tip to tip. Kraus has already told us that its value is zero degrees. For a non-thin-wire, it deviates from zero degrees, but not by much. There's no good reason to keep measuring it over and over. A quantity whose phase is fixed at zero degrees cannot tell us anything about the phase shift (delay) through a coil or even through a wire. Given: The phase shift in the standing wave current through 1/8WL of wire in a 1/2WL thin-wire dipole is zero degrees. What valid technical conclusions can be drawn from that statement? That there is no phase shift in 45 degrees of wire in a 1/2WL dipole? > Suppose the standing wave is examined to perfection. Everything that can > be determined is measured without error. Now we take the superposition > in reverse; specifically we divide the standing wave into forward and > reverse traveling components. It would seem that we have a complete and > accurate definition for the two traveling wave components. The > interrelations, as you call them, between the variables and parameters > are fully defined by the basic math and the carefully measured standing > wave. No argument. What some individuals seem to have missed are key concepts involved in that process. In fact, that very process is what I am presenting here. > What else is needed to describe the traveling waves? Additional > variables? Additional coefficients or parameters? Additional hidden > mathematical concepts? What else is needed is already there but unrecognized by a number of individuals. The equations for the forward and reflected waves are different in kind and function from the equations for the standing wave. Assuming equal magnitudes and phases for the forward and reflected waves, the superposition of those two phasors yields a result that is really not a bona fide phasor because it doesn't rotate. One cannot use a quantity whose phasor doesn't rotate to measure phase shifts (delays) through coils or through wires. Pardon me for having to state the obvious. Picture one end of the 1/2WL thin-wire dipole and set the reference phase of the forward current at 90 degrees. This is for reference only to make the math easy. When the forward current hits the end of the dipole, it undergoes a 180 degree phase shift and starts traveling in the opposite direction as the reflected current. For ease of math, let's assume the magnitude of the forward current and reflected current at the end of the dipole is one amp. Here's what the standing wave current will be at points along the dipole wire looking back toward the center. The first column is the number of degrees back toward the center from the end of the dipole, i.e. the end of the dipole is the zero degree reference for 'z'. The center of the dipole is obviously 90 degrees away >from the end. Back forward current reflected current standing wave current 0 deg 1 at 90 deg 1 at -90 deg zero 15 deg 1 at 75 deg 1 at -75 deg 0.52 at 0 deg 30 deg 1 at 60 deg 1 at -60 deg 1.00 at 0 deg 45 deg 1 at 45 deg 1 at -45 deg 1.41 at 0 deg 60 deg 1 at 30 deg 1 at -30 deg 1.73 at 0 deg 75 deg 1 at 15 deg 1 at -15 deg 1.93 at 0 deg 90 deg 1 at 0 deg 1 at 0 deg 2.00 at 0 deg Seven points on the standing wave current curve have been produced by superposing the forward current and reflected current. One can observe the phase rotation of the forward and reflected waves. Please note the phase of the standing wave current is fixed at zero degrees. Measuring it in the real world will produce a measurement close to zero degrees. Its phase is already known. Measuring it multiple times over multiple years continues to yield the same close-to-zero value. Except for proving something already known, those measurements were a waste of time. The above magnitudes and phases of the standing wave current are reproduced in a graph by Kraus, "Antennas for All Applications", 3rd edition, Figure 14-2, page 464. > There seems to be a lack of understanding and appreciation for what the > concepts of "linear" and "superposition" really mean. These are not just > mathematical concepts. When they apply it means that the system under > study is fully and completely described by ** either ** the individual > functional subcomponents ** or ** the full superimposed functional > component. It is not necessary to use both formats, and there is no > added information by doing so. No argument there. But the individual doing the superposition needs to understand exactly what he is doing or else he may make some conceptual mental blunders. Trying to measure the phase shift of a quantity that doesn't shift phases is one of those mental blunders. > Take a look at any of your favorite antenna references with an eye > toward the treatment of standing wave antennas. I believe you will find > only passing discussion of traveling waves. There will be some mention > of the equivalence between the two types of waves, but little else. It > is unlikely that you will find anything that says you will get more > information if you take the time and trouble to analyze traveling waves. My only bona fide antenna references are Kraus and Balanis. Quoting: Kraus: "A sinusoidal current distribution may be regarded as the standing wave produced by two uniform (unattenuated) traveling waves of equal amplitude moving in opposite directions along the antenna." Balanis: "The sinusoidal current distribution of long open-ended linear antennas is a standing wave constructed by two waves of equal amplitude and 180 degree phase difference at the open-end traveling in opposite directions along its length." Balanis: "The current and voltage distributions on open-ended wire antennas are similar to the standing wave patterns on open-ended transmission lines." Balanis: "Standing wave antennas, such as the dipole, can be analyzed as traveling wave antennas with waves propagating in opposite directions (forward and backward) and represented by traveling wave currents ..." -- 73, Cecil http://www.qsl.net/w5dxp Article: 222301 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: <0OXRf.56798$Jd.55726@newssvr25.news.prodigy.net> Date: Wed, 15 Mar 2006 17:03:56 GMT Gene Fuller wrote: > OK, the same question. It is a pretty picture, but what extra > information would be gained if somehow the traveling wave components > could be measured? Hopefully, some individuals would gain enough information that they would cease trying to use a quantity that doesn't change phase for the measurement of phase shifts. Maybe iteration would help. The phase shift of standing wave current through 30 degrees of coil or wire is close to zero degrees. The phase shift of standing wave current through 45 degrees of coil or wire is close to zero degrees. The phase shift of standing wave current through 75 degrees of coil or wire is close to zero degrees. Measuring the phase shift of standing wave current through a wire or a coil is pointless. One cannot use a quantity that doesn't change phase for the measurement of phase shifts. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222302 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 17:26:42 GMT Cecil Moore wrote: > Tom Donaly wrote: > >> If >> he applies his reference formulae to one of Tom's coils and it >> doesn't show the correct phase shift, though, his theory is in trouble. > > > His reference formulae are for traveling waves, not standing waves. > We already know that the phase of the standing wave current on a > 1/2WL thin-wire dipole varies not one degree over that entire > 180 degrees. Yet we know the forward wave undergoes a 90 degree > phase shift from feedpoint to tip and the reflected wave undergoes > a 90 degree phase on the trip back to the feedpoint. Standing wave > phase is virtually unchanging and is therefore useless for trying > to determine the electrical length of a wire or a coil. Tell me a couple of things, Cecil: 1. the diameter of your bugcatcher coil, and 2. the turn to turn wire spacing. I'd like to use the information, using the formulae in your reference, to see just how long your bugcatcher coil is electrically. Thanks, Tom Donaly, KA6RUH Article: 222303 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 17:30:10 GMT Richard Clark wrote: > Cecil Moore wrote: >>Your 11.4 meter value assumes a VF of zero. > > A quarter wave tall, two inch diameter coil is not resonant - at least > not at a fundamental in the 80M band. Nobody said it was resonant. The electrical length at 4 MHz can be *estimated* from the self-resonant frequency of 16 MHz. 90 degrees at 16 MHz estimates to be approximately 90(4/16) = ~23 degrees at 4 MHz. Dr. Corum's strongly suggested minimum electrical length for valid application of the lumped- circuit analysis is 15 degrees. Let's do a simple calculation to see how much error would be had by using the lumped-circuit model in the following: X---15 degrees of 450 ohm ladder-line---50 ohm load The lumped-circuit model says the impedance at X is 50 ohms. The impedance at X is really 53.5+j119 According to Dr. Corum, that's the maximum acceptable error when using the lumped-circuit model. His standards apppear to be lower than mine. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222304 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142258081.175752.25110@v46g2000cwv.googlegroups.com> <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 18:01:51 GMT Cecil, Thanks. Your quotes demonstrate my point quite nicely. There is not the slightest hint that there is any special value in treating a standing wave as a pair of traveling waves. The statements say only that it is possible. Indeed, it is clear from the quotes that the two treatments are equivalent. Of course these authors were disadvantaged by a lack of understanding of your "hidden mathematical concepts." 8-) 73, Gene W4SZ Cecil Moore wrote: [large snip] > > My only bona fide antenna references are Kraus and Balanis. Quoting: > > Kraus: "A sinusoidal current distribution may be regarded as the standing > wave produced by two uniform (unattenuated) traveling waves of equal > amplitude moving in opposite directions along the antenna." > > Balanis: "The sinusoidal current distribution of long open-ended linear > antennas is a standing wave constructed by two waves of equal amplitude > and 180 degree phase difference at the open-end traveling in opposite > directions along its length." > > Balanis: "The current and voltage distributions on open-ended wire > antennas are similar to the standing wave patterns on open-ended > transmission lines." > > Balanis: "Standing wave antennas, such as the dipole, can be analyzed > as traveling wave antennas with waves propagating in opposite directions > (forward and backward) and represented by traveling wave currents ..." Article: 222305 of rec.radio.amateur.antenna From: Bob Dixon Subject: Re: Yagi Antenna Question Date: Wed, 15 Mar 2006 13:08:14 -0500 Message-ID: References: <121cdv08ruvo207@corp.supernews.com> <28826-4417187F-1058@storefull-3255.bay.webtv.net> Here's a related question: WHY do parasitic elements work the way they do? Let's consider a two-element yagi with a driven element and a parasitic "reflector", ie a parasitic element longer than a half wavelength. (We could make the same arguments in reverse for a "director".) The driven element radiates an electromagnetic field, some of which impinges on the reflector. This causes a current to flow in the reflector, and a voltage to appear across it. Since it is longer than a half wavelength, it acts inductive, and the current LAGS behind the voltage. The reflector then radiates its own electromagnetic field in all directions, some of which heads back toward the driven element. (For simplicity, we ignore the mutual impedance effects and the new current which is induced in the driven element.) If the fields from the reflector and driven element are to be in phase in the direction from the reflector towards the driven element, then the radiated field from the reflector must be advanced in phase by how much it lost traveling from the driven element to the reflector, plus another same amount as it travels back. So the phase of the field radiated by the reflector LEADS the phase of the driven element significantly. Now the question is (assuming this is all right so far): How do we explain the phase of the field radiated from the reflector, in terms of the phase of the current and voltage in the reflector? Bob W8ERD Article: 222306 of rec.radio.amateur.antenna From: fmmck@aol.com (Fred McKenzie) Subject: Re: FM TRANSCEIVERS @2.4GHz Date: Wed, 15 Mar 2006 13:42:31 -0500 Message-ID: References: <1142433655.827787.26100@i40g2000cwc.googlegroups.com> In article <1142433655.827787.26100@i40g2000cwc.googlegroups.com>, "mazerom" wrote: > does anyone of you knows of fm transceivers at 2.4GHz?if yes,where > could i possibly buy them? > thanks! Mazerom- There is the one watt Kenwood TM-2400, which looks like the TM-642/742/942 Tri-Band Transceivers. I understand it has one double-width 2400-2450 MHz module, leaving room for one more module. As far as I know, it is only available in Japan. Photograph at http://www.rigpix.com/kenwood/tm2400.htm. A discussion is at http://groups-beta.google.com/group/rec.radio.amateur.policy/messages/ 6c91b006cb49575f,9cbc66bf773d1dbf?hl=en&thread_id=a830d56033bfe8f4&mode=thread &noheader=1&q=kenwood+%22tm-2400%22&_done=%2Fgroup%2Frec.radio.amateur.policy %2Fbrowse_frm%2Fthread%2Fa830d56033bfe8f4%2F9cbc66bf773d1dbf%3Fq%3Dkenwood+ %22tm-2400%22%26rnum%3D2%26hl%3Den%26#doc_9cbc66bf773d1dbf You will need to edit this URL to delete line breaks. The news server wouldn't allow the long line to be posted. 73, Fred, K4DII Article: 222307 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142446235.403681.295850@u72g2000cwu.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 19:56:21 GMT w8ji@akorn.net wrote: > Food for thought. > > At this moment in time it seems Cecil is claiming an inductor acts like > so many electrical degrees, but of course at any moment another waffle > might pops out of the Texas toaster and change everything. That's not food for thought. That's emotional gut feelings. I thought we agreed to cease and desist from ad hominem attacks? > Let's assume we have a mobile antenna that is 25 electrical degrees > tall. Now following the logic a loading coil acts like a transmission > line, we have a 65-degree loading coil. *False assumption!* The phase delay through the coil is what it is and we don't know exactly what it is. We do know it is not what has been measured and reported using a signal source (standing wave current) that doesn't ever change phase. Our present choice is between a reported measurement that is 100% flawed, in the absolute sense of the word, and an estimate with unknown accuracy based on the laws of physics. Given those two, and only two, present choices, which choice should one make? Please see the end of this posting for a description of the logical diversion that is taking place here. The phase delay through the coil is what it is and we don't know exactly what it is. We do know it is not zero as the standing wave current phase shift measurement would predict. Let me focus the subject of the argument back upon the actual subject of the argument and try to avoid diversions into the unknown, like the above. How does one measure the phase delay through a coil or wire using a signal with forever unchanging phase? All of the phase delay experiments so far have used the above flawed method. So far, we only have experimental measurements that are flawed except for the self-resonant experiments. Which is preferred? The results from experiments known to be 100% flawed or estimates with unknown accuracy based on the laws of physics? Those are presently our only two choices. > Following the same twisted logic, since the loading inductor is > 65-degrees long, we should be able the move it anywhere in the antenna > without changing antenna tuning. *False assumption!* The superposition of all four of the forward and reflected waves is much more complicated than that. > Our 75 meter antenna should also work on 25 meters as a 3/4 wave > antenna, and on 37.5 meters as a half-wave. It's not as simple as that but I have the EZNEC current distribution patterns that indicate something akin to that indeed does develop. Give me a few hours and I will post those results. > Where are the design equations we can all use? Asked and answered but not sure of the accuracy applied to 75m bugcatcher loading coils. Someone is working on that. Please stand by. The logical diversion that is happening here goes like this: Person A says: "The moon is 10,000 miles from the earth. Person B says: "That can't be true." Person A says: "How far do you say the moon is from the earth?" Person B says: "I don't know, but I do know it is not 10,000 miles." Person A says: "Well, if you don't know and can't give me the correct answer, I am right and you are wrong. The moon is 10,000 miles from the earth." Does an absolutely false answer beat ignorance? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222308 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <16559-4415B1AD-858@storefull-3256.bay.webtv.net> <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 20:00:23 GMT Cecil Moore wrote: > Tom Donaly wrote: > >> Tell me a couple of things, Cecil: 1. the diameter of your bugcatcher >> coil, and 2. the turn to turn wire spacing. I'd like to use the >> information, using the formulae in your reference, to see just how >> long your bugcatcher coil is electrically. > > > Please note that when my 75m bugcatcher coil is mounted > just above my GMC pickup ground plane, it is electrically > almost four times longer than it is laying on a stack of > books in my hamshack. The coil capacitance to ground is > obviously a lot higher when mounted over a ground plane. > The ground plane reduces the VF to approximately 1/4 > the value obtained in isolation. > > 1. The measured self-resonant frequency of the coil > mounted on my pickup is ~6.6 MHz. > > 2. The measured self-resonant frequency of the coil > on a mag mount on my all-metal desk is ~6.6 MHz. > > 3. The measured self-resonant frequency of the coil > isolated from any ground is ~24.5 MHz. > > The self-resonant frequency needs to be measured in > the environment in which it is installed. That means > one needs to model the coil 3 inches above a perfect > ground plane before calculating the self-resonant > frequency, Z0, or VF. I doubt that Dr. Corum's equations > take that into account since it would seem self defeating > to operate a Tesla coil over a physically close ground > plane. But I could be wrong on that point. > > The coil data is: ~6" dia, ~6.7" long, 26.5 T, seems > very close to 4 TPI. Looks to be #14 solid wire. Thanks, Cecil. 73, Tom Donaly, KA6RUH Article: 222309 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121bisltdp0m6ef@corp.supernews.com> <121cb615o4isf77@corp.supernews.com> <1142333732.535039.211850@z34g2000cwc.googlegroups.com> <703e12dnr24fmv2dhvbbuk8qpq03gt7jql@4ax.com> <1142363298.134906.139130@e56g2000cwe.googlegroups.com> <1142371307.650160.117590@j33g2000cwa.googlegroups.com> <32ZRf.60161$dW3.27014@newssvr21.news.prodigy.com> <1142449802.552573.276910@j52g2000cwj.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 20:05:56 GMT w8ji@akorn.net wrote: > There is no "standing wave current". There is only current. > Current can't stand. Addressed and proven to be a false statement. cos(kz)*cos(wt) proves it is standing and not flowing. > Phase difference can be measured in a system that has standing waves, > just as it can in one without standing waves. Addressed and proven to be a false statement. A signal with unchanging phase cannot be used to measure the phase delay through a wire or coil. > Any number of ways, if we disallow the impossible situiation where you > seem to think we can have current "standing still". Please take a look at the equation for standing wave current. It proves that the standing wave current is standing still, just oscillating in place at any point on the wire. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222310 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 20:08:18 GMT Richard Clark wrote: > Provide the Velocity Factor and Characteristic Impedance per the > formulas you offered: Tom Donaly has graciously volunteered to provide those values. Please stand by. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222311 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Balun Question Date: Wed, 15 Mar 2006 12:18:53 -0800 Message-ID: <121gtliq5kegh47@corp.supernews.com> References: <4417658a$0$3760$39cecf19@news.twtelecom.net> <121es3p5el3u5fb@corp.supernews.com> Correction: Roy Lewallen wrote: > . . . > Connect the input terminals together and the output terminals together. > Connect it to your antenna analyzer as a plain series load -- that is, > connect the balun input terminals to the analyzer center conductor and > the balun output terminals to the analyzer connector shell (or reverse > the two -- it doesn't matter). Measure the impedance at frequencies of > interest. You generally need a minimum of around 500 - 1000 ohms for an > effective balun. The angle of the impedance doesn't matter unless you're > running a lot of power, in which case a low angle (that is, a primarily > resistive impedance) might result in objectionable balun heating. > . . . This test works only with a current balun. If done with a voltage balun, the impedance should be very low. Although there are ways to test for the proper functioning of a voltage balun, that is, to test for the voltages at the output terminals being equal and opposite with respect to the "cold" side of the input, they don't tell you how effective it'll be in stopping common mode currents on feedlines. In fact, certain imperfections might improve the performance of a voltage balun in that application. I don't recommend using a voltage balun for feeding antennas for the reasons I gave in http://eznec.com/Amateur/Articles/Baluns.pdf. I apologize for the error. Thanks very much to Owen Duffy for pointing it out to me. Roy Lewallen, W7EL Article: 222312 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Yagi Antenna Question Date: Wed, 15 Mar 2006 12:45:33 -0800 Message-ID: <121gv7dkt7iug78@corp.supernews.com> References: <121cdv08ruvo207@corp.supernews.com> <28826-4417187F-1058@storefull-3255.bay.webtv.net> Bob Dixon wrote: > Here's a related question: > > WHY do parasitic elements work the way they do? > > Let's consider a two-element yagi with a driven element and a parasitic > "reflector", ie a parasitic element longer than a half wavelength. > (We could make the same arguments in reverse for a "director".) > > The driven element radiates an electromagnetic field, some of which > impinges on the reflector. This causes a current to flow in the > reflector, and a voltage to appear across it. Since it is longer than a > half wavelength, it acts inductive, and the current LAGS behind the > voltage. > > The reflector then radiates its own electromagnetic field in all > directions, some of which heads back toward the driven element. > (For simplicity, we ignore the mutual impedance effects and the new > current which is induced in the driven element.) You also need to ignore the fields from all other elements if present. They can have a major impact on the overall field to the rear which the reflector must attempt to cancel. > If the fields from the reflector and driven element are to be in phase > in the direction from the reflector towards the driven element, then the > radiated field from the reflector must be advanced in phase by how much > it lost traveling from the driven element to the reflector, plus another > same amount as it travels back. So the phase of the field radiated by > the reflector LEADS the phase of the driven element significantly. But the purpose of the reflector isn't to make a field which reinforces the driven element's field in the forward direction, but to make a field which cancels it in the reverse direction. For this to happen most effectively, the phase lag of the reflector current (relative to the driven element current) and the distance between reflector and driven element should add to 180 degrees. In practice, both the phase and magnitude of the current induced in the reflector change with element length. And in general, the farther you get from self-resonance, the smaller induced current. So as you adjust the element length, by the time you reach the optimum phase angle of induced current, its magnitude is too small for good cancellation. A compromise is inevitably reached, resulting in an acceptable but far from perfect front/back ratio. > Now the question is (assuming this is all right so far): > How do we explain the phase of the field radiated from the reflector, in > terms of the phase of the current and voltage in the reflector? The magnitude and phase of the field are directly related to the magnitude and phase of the current. The incremental longitudinal voltage in the element can be ignored in calculation of fields. While it's possible to base the field calculation on the longitudinal voltage rather than the current, I don't believe I've ever seen this done. Roy Lewallen, W7EL Article: 222313 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: Message-ID: Date: Wed, 15 Mar 2006 20:57:21 GMT Richard Clark wrote: .> I can do this myself, as certainly Tom can too; but it says nothing > about your well coming up dry when we ask you to carry your own water > in supporting your claims. Pure humor with zero technical content follows: So sue me for being lazy. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222314 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: Message-ID: Date: Wed, 15 Mar 2006 21:29:14 GMT Richard Clark wrote: > Cecil Moore wrote: >>So sue me for being lazy. :-) > > The legacy of Xerox research. Please remind us of the technical content of your posting. Do you think experimental technical results depend upon whom is doing the experiment? If I dropped dead, could Tom's results change from valid to invalid? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222315 of rec.radio.amateur.antenna From: David Subject: Element correction for through beem Yagi elements Message-ID: Date: Wed, 15 Mar 2006 22:17:03 GMT Hi, I am in the process of building a 4-Element Yagi to operate at 915 MHz. The design is as follows... Element Length Distance from REFL REFL 159mm 0mm DE 146mm 40mm D1 139mm 90mm D2 132mm 155mm Boom is 12.8mm OD square aluminium (1.6mm wall thickness) Elements are 6mm solid aluminium rod. The design was assuming that the elements were to be insulated from the boom but I am having trouble making small insulators to hold these in place. It would be simpler for construction if I could simply drill through the beam and weld the rods in place or connect via a screw through the centre of the beam. The correction factor formula I have found seems to be for insulated through-beam elements. Q: Is there a correction factor I can apply to enable me to construct the antenna in this manner ? Q: Does the Driven element need to be in the same plane as the other elements or can it be out of alignment (ie. If I use a small plastic enclosure to house the balun and make connection to the driven elements, the elements will not be in the middle of the beam but rather 5mm or so above the beam). Q: Is there an alternate design I could use that would be simpler to construct. (I am looking for around 7dB gain at low angle of radiation - point to point communications link). Feedline is 50 Ohm coaxial cable, power is less than 1 Watt. Hope I have given enough info to evoke some constructive advice, Thanks in advance for your help Regards David Article: 222316 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> Message-ID: Date: Wed, 15 Mar 2006 22:42:55 GMT Richard Clark wrote: > None of your work appears by your admitted laxity. None of your > testing appears by lack of its accomplishment. My testing results have been reported. Here are the results of the VF calculation for my 75m bugcatcher coil. The test for physical structure is met. The paper asserts that the expression gives acceptable results with errors less than 10%. The VF of my 75m bugcatcher coil calculates out to be VF = 0.0175 at 6.6 MHz where it measured to be self- resonant. That self-resonant measurement included a length of coax and a one foot bottom section so the actual self-resonant frequency will be somewhat higher than I measured. I could probably make a calculation to adjust for the coax and bottom section. The VF calculated directly from the too-low self- resonant frequency was 0.015 which is 14% different >from Dr. Corum's equation. Given the uncertainly in the exact self-resonant frequency in my measurements, that's pretty reasonable. Ballpark is all we need to understand the concepts. Working backward, Dr. Corum's VF would make the coil self-resonant at 7.7 MHz. There's probably enough slop in my measurement configuration to account for the 1.1 MHz difference. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222317 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 15 Mar 2006 16:58:58 -0600 Message-ID: <24187-44189C32-1493@storefull-3251.bay.webtv.net> References: Cecil, W5DXP wrote: "How is it possible to use a signal (standing wave current) that is known not to change phase, to measure the phase delay through a wire or coil?" Ignore it. Lissajous figures result from applying signals to the vertical and horizontal deflection circuits of an oscilloscope simultaneously. Phase difference between signals of the same frequency make a distinctive pattern. One can use coax lines with identical delays to couple the inputs with phase sampling loops. Take samples of the currents at the two points where the phase difference would be known. Amplitudes can be adjusted for a suitable pattern. It will be destinctive. Then take samples from the same source. Add a known delay to one channel until you have reproduced the distinctive pattern you had observed when testing the felay between the points that have the unknown phase difference. With a few elaborations, that`s how a phase monitor works. Best regards, Richard Harrison, KB5WZI Article: 222318 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142460618.098800.8930@p10g2000cwp.googlegroups.com> Message-ID: Date: Wed, 15 Mar 2006 23:17:26 GMT w8ji@akorn.net wrote: > Probably, since it appears you are the only one finding fault with > them. Tom Donaly hasn't even posted any results yet. How could I possibly be finding fault with them? > It appears you have painted yourself into a corner by trying o apply a > paper about Tesla coils that specifically states it applies only to > inductors at self-resonance to inductors operating away from > self-resonance. Quoting from the previously referenced paper: ".. is an approximation ... appropriate for quarterwave resonance and is valid for helices with (5*N*D^2)/lamda < 1. N is the turns/inch, D is the diameter of the coil, and lamda is the self-resonant frequency. That calculation for my 75m bugcatcher coil is ~0.4 so it meets the criteria. The VF calculation of 0.175 is therefore valid. There is no valid reason to suspect that the VF wouldn't hold approximately down to 4 MHz and below. There is no warning of such abrupt shifts in the VF anywhere in the article. And Dr. Corum's VF equation is close enough to my rough earlier estimate of 0.15 to be acceptable. > you'll see time delay is essentially flat except near the 16MHz > self-resonant frequency and a higher-frequency resonance at 26 MHz. But cos(kz)*cos(wt) is what is being measured. That signal has zero phase shift from tip to tip in a 1/2WL thin-wire dipole. It cannot be used to measure phase shift because it is incapable of a phase shift through 180 degrees of wire or 180 degrees of coil. It only changes phase every 180 degrees of a wire or coil. What is happening in the above measurement is that when the coil is more than 1/2WL, the phase of the standing wave current suddenly reverses from close to zero to close to 180 degrees. This is all explained in Kraus', "Antennas for All Applications", 3rd edition, Figure 14-4 and is perfectly understandable. The phase of the standing wave current changes from zero to 180 degrees every 1/2WL. I've seen exactly the same thing in my experiments just as Kraus predicts and it supports my side of the argument. The standing wave current, which has unchanging phase, cannot be used to determine the phase shift in a wire or coil. A signal with a cos(kz)*cos(wt) equation doesn't change phase with variations in 'z'. How can it possibly be used to detect phase changes in the 'z' dimension? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222319 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Wed, 15 Mar 2006 15:38:32 -0800 Message-ID: <121h9bpn0lge16@corp.supernews.com> References: <24187-44189C32-1493@storefull-3251.bay.webtv.net> Richard Harrison wrote: > Cecil, W5DXP wrote: > "How is it possible to use a signal (standing wave current) that is > known not to change phase, to measure the phase delay through a wire or > coil?" > > Ignore it. > > Lissajous figures result from applying signals to the vertical and > horizontal deflection circuits of an oscilloscope simultaneously. Phase > difference between signals of the same frequency make a distinctive > pattern. > > One can use coax lines with identical delays to couple the inputs with > phase sampling loops. Take samples of the currents at the two points > where the phase difference would be known. Amplitudes can be adjusted > for a suitable pattern. It will be destinctive. > > Then take samples from the same source. Add a known delay to one channel > until you have reproduced the distinctive pattern you had observed when > testing the felay between the points that have the unknown phase > difference. > > With a few elaborations, that`s how a phase monitor works. Many analog scopes aren't capable of producing a meaningful Lissajous figure at HF because of the limited bandwidth of the horizontal channel. Significant phase delays occur at frequencies well below the nominal cutoff frequency, which is often much lower than the vertical channel. Before believing in the validity of any figure, you should look at the figure you get when you apply the signal to both axes at the same time. If it deviates significantly from a single diagonal line, you won't be able to trust other patterns. It would be a simple matter for a digital scope to present a good Lissajous figure, since the bandwidth is determined solely by the input samplers rather than a series of amplifiers and the CRT deflection structure as in an analog scope. I haven't looked closely at digital scopes lately, but I'd be surprised if most don't have the capability of making a good Lissajous figure at HF. It would be simply a matter of internal firmware programming. Of course, a dedicated phase monitor would be designed for good phase and amplitude match between channels at the frequencies it's specified to be used at. Roy Lewallen, W7EL Article: 222320 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Current through coils References: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 15 Mar 2006 23:40:26 GMT Cecil Moore wrote: > Richard Clark wrote: > >> Provide the Velocity Factor and Characteristic Impedance per the >> formulas you offered: > > > Tom Donaly has graciously volunteered to provide those values. > Please stand by. Actually, I just wanted to calculate the values for my own personal edification. You'll have to do the arithmetic yourself, Cecil, and then it won't mean much, because, as far as I know, no one has ever done any experimental work to see if these equations have any meaning. If a coil can slow down an electromagnetic wave as much as these equations say it can, though, it qualifies as a very interesting device. 73 Tom Donaly, KA6RUH Article: 222321 of rec.radio.amateur.antenna From: Roger Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Message-ID: References: <121craq3ed95h91@corp.supernews.com> Date: Wed, 15 Mar 2006 19:00:04 -0500 On Mon, 13 Mar 2006 23:14:29 -0800, Roy Lewallen wrote: >The advice to avoid acetic-acid smelling RTV because of corrosion is >passed along from person to person like an urban legend, but like an >urban legend it's just about impossible to find anyone who's actually >seen any corrosion result from its use. (A number of queries I've made >over the years has produced just one, using a very early version of RTV.) OK, here is number 2. Hmmm wait... couldn't we use a different ranking... I retired from the industry and I worked for the original developer of "Silastic RTV (TM)". My address if Midland MI if any one needs another hint. Yes there is an weak acid released from the regular RTVs and it depends on the moisture in the air to aid in curing. Is it, or will it be a problem? That is a Yes and no, or it all depends answer. I use plain old fashion "bathtub calk" on my antenna connections and connectors *outside or outdoors* The acid is not normally a problem *except* where the item is either potted, or enclosed in a container. I would not use it on PC boards where the foil is thin. Outdoors I just "gob it on". As to real corrosion: Some years back we purchased a bunch of remote sensors that were potted in metal boxes for use in harsh environments. They worked very well... for about a year. One failed and who ever removed it brought it into the shop. I decided to perform an autopsy on it. I cut the seal, pried off the cover, and dug out the circuit board, or rather what was left of it. The copper traces were mainly a green powder with bigger chunks of powder around the solder joints where the wires hung loosely. The manufacturer of the sensors had used the wrong potting compound. Had they used the neutral stuff (really stinks) they would have been fine. They replace them all, they were expensive, and we had a bunch. > >I've used the acetic-acid smelling stuff for decades on a variety of >metals including tinned and untinned wire, aluminum, nickel, and copper >circuit boards, and never seen a hint of corrosion. But formulations >vary widely, and my experience certainly isn't exhaustive. I'm not There are two main producers of RTVs and the formulations are pretty much standard. If you analyzed a tube of the stuff I doubt you could tell which manufacturer produced it. However they have slightly different formulations aimed at the specific use. What every you purchase under what ever brand name most likely comes from one of these two producers unless it says Made in China. >entirely convinced, though, that among the many formulations there >aren't others, which don't have that smell, which might be corrosive to >some materials. > >People who worry about this should buy an industrial product and stay >with it, since there's a much better chance the formulation won't change >in the future without notice. The last I knew the only difference was in the packaging. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com > >Roy Lewallen, W7EL Article: 222322 of rec.radio.amateur.antenna From: Roger Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Message-ID: References: <121craq3ed95h91@corp.supernews.com> <67BRf.873$tN3.831@newssvr27.news.prodigy.net> Date: Wed, 15 Mar 2006 19:09:07 -0500 On Tue, 14 Mar 2006 19:04:48 +0000, Ian White GM3SEK wrote: >Mike wrote: >>Roy Lewallen wrote: >>> The advice to avoid acetic-acid smelling RTV because of corrosion is >>>passed along from person to person like an urban legend, but like an >>>urban legend it's just about impossible to find anyone who's actually >>>seen any corrosion result from its use. (A number of queries I've made >>>over the years has produced just one, using a very early version of RTV.) >>> I've used the acetic-acid smelling stuff for decades on a variety of >>>metals including tinned and untinned wire, aluminum, nickel, and >>>copper circuit boards, and never seen a hint of corrosion. But >>>formulations vary widely, and my experience certainly isn't >>>exhaustive. I'm not entirely convinced, though, that among the many >>>formulations there aren't others, which don't have that smell, which >>>might be corrosive to some materials. >>> People who worry about this should buy an industrial product and >>>stay with it, since there's a much better chance the formulation >>>won't change in the future without notice. >>> Roy Lewallen, W7EL > >>I was visiting a local SGC dealer years ago as he was troubleshooting a >>brand new antenna tuner that was not working. When he opened the >>plastic case, that special RTV acidic smell almost knocked us over and >>all the tinned circuit board traces and exposed wiring were corroded >>and black. SGC claimed they used the wrong type of RTV on a batch of >>tuners that was not for electronics use. > >Most likely because they closed the cases before the silicone had cured, That outgasing from a think layer will go on for many days which would make it impractical to use in this case. >not realising they were trapping the acetic acid vapour inside. The same >can happen in balun boxes and the like. > In this case it would also depend on how much RTV, or how thick the layer of RTV. As I said, the outgasing will go on for quite some time and the thicker the longer it outgases. I'd not use the acid smelling version from either producer on PC boards. >It would be interesting to know if there have been *any* cases that >didn't also involve some kind of closed situation, or possibly a layer >that was too thick to let the vapour diffuse out. A thin layer should cause no problem if it is given time to outgas, but a thick layer will most likely eventually ruin the PC board. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Article: 222323 of rec.radio.amateur.antenna Date: Wed, 15 Mar 2006 19:19:55 -0600 From: Tom Ring Subject: Re: Balun Question References: <4417658a$0$3760$39cecf19@news.twtelecom.net> <121es3p5el3u5fb@corp.supernews.com> <121gtliq5kegh47@corp.supernews.com> Message-ID: <4418bd3c$0$7332$39cecf19@news.twtelecom.net> Roy Lewallen wrote: > This test works only with a current balun. If done with a voltage balun, > the impedance should be very low. > > Although there are ways to test for the proper functioning of a voltage > balun, that is, to test for the voltages at the output terminals being > equal and opposite with respect to the "cold" side of the input, they > don't tell you how effective it'll be in stopping common mode currents > on feedlines. In fact, certain imperfections might improve the > performance of a voltage balun in that application. I don't recommend > using a voltage balun for feeding antennas for the reasons I gave in > http://eznec.com/Amateur/Articles/Baluns.pdf. > > I apologize for the error. Thanks very much to Owen Duffy for pointing > it out to me. > > Roy Lewallen, W7EL Thanks for the replies, Roy. They were pretty much what I suspected, but hearing it from you is a nice confirmation. Why don't you make a small white paper on your site covering this subject? As usual, I didn't get my original post, and none of the replies, except for this one. It's nice to have google to pick up what my newsfeed misses. tom K0TAR Article: 222324 of rec.radio.amateur.antenna From: David Subject: To ground or not to ground Message-ID: Date: Thu, 16 Mar 2006 02:02:46 GMT Hi, I followed the links provided by some of you for correction factor calculation and managed to find a folded dipole design that accounts for elements through the boom that are connected to it electrically. I found from another link a construction method for the folded radiator and balun match. The design shows the shield of coax feedline and balun being connected to the boom but the elements in that second design are isolated from the boom. Q: Can I still ground the coax to the boom if the elements are also attached to the boom ? Thanks Regards David Article: 222325 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Wed, 15 Mar 2006 18:12:03 -0800 Message-ID: <121hibknuqlgqb6@corp.supernews.com> References: <24187-44189C32-1493@storefull-3251.bay.webtv.net> <121h9bpn0lge16@corp.supernews.com> Richard Clark wrote: > On Wed, 15 Mar 2006 15:38:32 -0800, Roy Lewallen > wrote: >> Many analog scopes aren't capable of producing a meaningful Lissajous >> figure at HF because of the limited bandwidth of the horizontal channel. > > This is certainly true for poor scopes. If we are limited to HF, then > those with bandwidths above 100MHz might squeak by. . . Either you missed my point, or we differ on what constitutes a "poor" scope. The Tektronix 465, for example, is a 100 MHz scope. Although it's very long in the tooth now, it's not a "poor" scope by most measures. But the specifications for X-Y display are as follows: ------ 5 mV/div to 5 V/div, accurate ± 4%. Bandwidth is dc to at least 4 MHz. Phase difference between amplifiers is 3° or less from dc to 50 kHz. ------ This wouldn't produce a meaningful Lissajous figure at HF. Roy Lewallen, W7EL Article: 222326 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Wed, 15 Mar 2006 18:19:21 -0800 Message-ID: <121hip9t8og871b@corp.supernews.com> References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> Richard Clark wrote: > On Wed, 15 Mar 2006 22:42:55 GMT, Cecil Moore wrote: >> The VF of my 75m bugcatcher coil calculates out to be >> VF = 0.0175 at 6.6 MHz > >> On Fri, 10 Mar 2006 13:35:14 GMT, Cecil Moore wrote: >> >>> I'm willing to bet that my 75m >>> bugcatcher coil has at least a 40 nanosecond delay on 4 MHz >>> which is a 60 degree current phase shift. > >> On Wed, 15 Mar 2006 18:03:28 GMT, Cecil Moore wrote: >> >>> The coil data is: ~6" dia, ~6.7" long, 26.5 T, seems >>> very close to 4 TPI. Looks to be #14 solid wire. > > Total turns 26.5 > Through total turns, total wire appears to be 505" > > With nothing offered in the way of inductance, from calculations it > appears to be 72.9 µH > > With nothing offered in the way of distributed capacitance, from > calculations it appears to be 8pF > > On Tue, 14 Mar 2006 04:09:08 +0000 (UTC), "Reg Edwards" > wrote: >> V = 1 / Sqrt( L * C ) metres per second, >> where L and C are henrys and farads per metre respectively. The >> formula for L and C can be found in your Bibles from coil dimensions, >> numbers of turns, etc. > > V = 1 / Sqrt (5.88 * 72.9* 10^-6 * 8 * 10^-12) meters per second > > where the 5.88 is to correct for per meter computations > > it follows that V must then be 17.1 million meters per second > >> The velocity factor = V / c > Vf = 0.057 >> and Zo = Sqr( L / C ). > Zo = Sqrt (72.9* 10^-6 / 8 * 10^-12) > > 3 KOhms > . . . This is a misapplication of transmission line formulas. The "C" in those formulas is the shunt capacitance per unit length between the conductors, not a series or longitudinal capacitance as used here. In order to use the transmission line formulas, you have to have a second conductor and determine the C per unit length between the two conductors. Otherwise, you (or Cecil) have to come up with some other equations. Some of the more picky of us readers will of course then ask for the source and/or derivation of those other equations. Roy Lewallen, W7EL Article: 222327 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> Message-ID: <%e4Sf.1270$4L1.473@newssvr11.news.prodigy.com> Date: Thu, 16 Mar 2006 02:40:59 GMT Tom Donaly wrote: > Actually, I just wanted to calculate the values for my own personal > edification. You'll have to do the arithmetic yourself, Cecil, and > then it won't mean much, because, as far as I know, no one has ever > done any experimental work to see if these equations have any meaning. There are references for it in the Dr. Corum IEEE paper. Kandoian and Sichak, "Wide Frequency Range Tuned Helical Antennas and Circuits," Electrical Communications, Vol 30, 1953, pp. 294-299. It was published while I was in high school. > If a coil can slow down an electromagnetic wave as much as these > equations say it can, though, it qualifies as a very interesting device. I studied such 50 years ago at Texas A&M from papers such as the above. The parameters for a transmission line or a coil are the same just with different values. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222328 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <1142469410.984882.184550@i40g2000cwc.googlegroups.com> Message-ID: Date: Thu, 16 Mar 2006 02:49:18 GMT w8ji@akorn.net wrote: > If an inductor by itself delayed phase as much as Cecil claims, we > could build a phase or time delay system with only a large inductor. We can build a time delay system with only a large inductor. That's what large inductors do. How does a large inductor cause a large arc on a Smith Chart without shifting the phase of the signal? One cannot use the presuppositions of the lumped-circuit model to prove that there is no time delay through a coil. The lumped-circuit presupposes zero time delay through a coil with propagation times exceeding the speed of light. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222329 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> Message-ID: Date: Thu, 16 Mar 2006 03:20:38 GMT Richard Clark wrote: > A lumped circuit has only one resonance. A transmission line has an > infinite number. It certainly isn't necessary to impose a strict test > of this. Finding second, third, and fourth harmonics for an inductor, > in situ, would certainly be compelling evidence of transmission line > behavior. Using the same coil stock as W8JI's 100uH coil, I just set up a 50 uH coil on a mag mount sitting on my metal desk. Its first solid resonance was 9 MHz (1/4WL), its second solid resonance was 27 MHz (3/4WL), and its third solid resonance was 45 MHz (5/4WL). In addition to those, there other soft spots and double dips along the frequency line. W8JI reported something happening at 24 MHz as well as self- resonance at 16 MHz. He was apparently not testing it over a ground plane like an automobile body. That automobile ground plane drops the VF much lower than an isolated coil's VF. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222330 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> Message-ID: Date: Thu, 16 Mar 2006 03:30:36 GMT Richard Clark wrote: > This is simply proof of an exercise in futility through the > misapplication of the theory of transmission lines to lumped > components. One certainly has to be careful. But Dr. Corum's formulas matched my measurements closer than I expected. One thing is for sure. One cannot use the presuppositions of the lumped-circuit model to prove the validity of the lumped-circuit model and that is what has happened so far. One also cannot use a signal with unchanging phase to measure the phase shift through a wire or coil. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222331 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 15 Mar 2006 21:51:05 -0600 Message-ID: <9127-4418E0A9-1415@storefull-3253.bay.webtv.net> References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> Tom, W8JI wrote: "If an inductor by itself delayed phase as much as Cecil claims, we could build a phase or time delay system with only a large inductor." Recall that another name for the inductor is a "retardation coil", and that the time constant of an inductor having an L in henrys and a resistance in ohms is equal to L/R. Best regards, Richard Harrison, KB5WZI Article: 222332 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Wed, 15 Mar 2006 20:20:23 -0800 Message-ID: <121hps7rrj1ee9e@corp.supernews.com> References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> <9127-4418E0A9-1415@storefull-3253.bay.webtv.net> Richard Harrison wrote: > Tom, W8JI wrote: > "If an inductor by itself delayed phase as much as Cecil claims, we > could build a phase or time delay system with only a large inductor." > > Recall that another name for the inductor is a "retardation coil", and > that the time constant of an inductor having an L in henrys and a > resistance in ohms is equal to L/R. Yes, it's been known for over a century that the phase of the current through an inductor lags the voltage across it, resulting in retardation of the current relative to the voltage. And the time constant you refer to is of course the time constant of the rise or decay of the current through an inductor to which a voltage step is applied. I don't see the connection between these and the contention that the current into and out of an inductor are unequal. If there is one, perhaps you can explain it. My texts all show a single equation relating the voltage across an inductor to the current through it, as follows: v = L * di/dt This holds at all frequencies, i.e., all rates of change of current, and it's from this that the above mentioned characteristics follow. If the currents at the two inductor terminals are to be different, we'll need two equations, one for the input current and one for the output current. That is, v = f1(di1/dt) and v = f2(di2/dt), where f1 and f2 are different functions. Have you come across such a set of equations in your searches through your textbooks, or are the authors unaware of Cecil's theories? Roy Lewallen, W7EL Article: 222333 of rec.radio.amateur.antenna From: "Sal M. Onella" References: <121craq3ed95h91@corp.supernews.com> <67BRf.873$tN3.831@newssvr27.news.prodigy.net> Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? Message-ID: Date: Wed, 15 Mar 2006 20:45:31 -0800 "Roger" wrote in message news:qnah12ljqemhseft6aggm10uu8rsf24e70@4ax.com... > On Tue, 14 Mar 2006 19:04:48 +0000, Ian White GM3SEK > wrote: > > >Mike wrote: > >>Roy Lewallen wrote: > >>> The advice to avoid acetic-acid smelling RTV because of corrosion is > >>>passed along from person to person like an urban legend, but like an > >>>urban legend it's just about impossible to find anyone who's actually > >>>seen any corrosion result from its use. US Navy, fighting corrosion since the Year 1, banned the use of most kinds of silicone sealers and "RTV" in weatherproofing of topside connectors about 20 years ago. It was seen as a boon when it came out and was used extensively, both in the non-hardening varieties as a filler and in the rubberizing kinds as an outer coating. Too bad that many types proved to cause sufficient corrosion to be more of a problem than a solution! Since then, the Navy has gone through Skotchkote and into Pro-seal and other chemicals whose names I forget. Mechanically, we're getting into some exotic Gel-in-the-Middle connector sleeves. (We not only fight on the sea -- we have to fight the sea, itself.) I will see what I can dig out of the files to document this. Keep your fingers crossed, as the archives shrink a little every year and the data might be gone. John Article: 222334 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> <9127-4418E0A9-1415@storefull-3253.bay.webtv.net> <121hps7rrj1ee9e@corp.supernews.com> Message-ID: <1c6Sf.1309$4L1.44@newssvr11.news.prodigy.com> Date: Thu, 16 Mar 2006 04:54:21 GMT Roy Lewallen wrote: > Have you come across such a set of equations in > your searches through your textbooks, or are the authors unaware of > Cecil's theories? I can't take credit for them, Roy, since I studied them at Texas A&M in the 50's. Much of it appears in Ramo and Whinnery's "Fields and Waves" and Johnson's "Transmission Lines and Networks". They are just the rules of the distributed network model of which the lumped-circuit model is a subset. In any situation where the lumped- circuit model yields different results than the distributed-network model, the lumped-circuit model is wrong. The lumped-circuit model presupposes the conclusions that some people are presenting as fact. Obviously, the lumped-circuit cannot be presented as evidence of proof of its presuppositions. But it appears that is exactly what has happened. The lumped-circuit model presupposes faster than light propagation of signals. That alone should be enough to raise a red flag. Can someone prove faster than light speed by quoting the presuppositions of the lumped-circuit model? Quoting Dr. Corum again: "Lumped circuit theory isn't absolute truth, it's only an analytical theory ... The engineer must either use Maxwell's equations or distributed elements to model reality." My 75m bugcatcher meets his criteria for situations where his VF equations work. It yields a VF of 0.0175 for the bugcatcher coil. That VF works just like the 0.66 VF works for RG-213. On a coil physically like the W8JI test coil but with 50 uH inductance, I see coil resonances at 9 MHz, 27 MHz, and 45 MHz, just as if it were 1/4WL of transmission line. It appears that the calculated VF works over a wide frequency range. To prove the presuppositions of the lumped- circuit model, a standing wave current is used to measure phase. We already know the phase of a standing wave current is unchanging all along a 1/2WL dipole, per Kraus, yet some people keep using standing wave current with its unchanging phase to try to measure phase shift as if it were a valid thing to do. One cannot measure a phase shift in 45 degrees of dipole using standing wave current. Why is it surprising that one cannot measure a phase shift in 45 degrees of coil? There's no current phase shift from the top of the coil to the tip of the antenna either. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222335 of rec.radio.amateur.antenna From: David Subject: Where to purchase YO by Brian Beezley Message-ID: Date: Thu, 16 Mar 2006 05:08:47 GMT Would someone mind advising me where I can purchase this software from. I found a email address for him but was returned as invalid when I tried to contact him. Thanks Regards David Article: 222336 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 15 Mar 2006 23:35:25 -0600 Message-ID: <16559-4418F91D-1319@storefull-3256.bay.webtv.net> References: <121hps7rrj1ee9e@corp.supernews.com> Roy, W7EL wrote: "I don`t see the connection between these and the contention that the current into and out of an inductor are unequal." Nor do I. Tom was not making a case for inequality of current in and out of a coil either. He was just making an inaccurate statement. Cecil has a good case. Straight wire and coiled wire have the same properties, only more or less of them. When they are in the path of a traveling wave and a reflection of that wave comes back from the opposite direction, they respond similarly. An interference pattern exists on the coil as it does on straight wire if the distance is comparable to a wavelength. Superpositon makes both volts and amps vary along the route. So, indeed the current at one end of a coil in that situation can be different at from that at the other end, the same as it would along a wire. Distributed network theory is newer than lumped network theory but both have been around plenty long enough to be well established. I don`t think Cecil is breaking any new ground. Best regards, Richard Harrison, KB5WZI Article: 222337 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Where to purchase YO by Brian Beezley Date: Thu, 16 Mar 2006 00:14:14 -0800 Message-ID: <121i7imlr9omt7a@corp.supernews.com> References: For quite a long time, Brian would sell only by mail. But I heard recently from someone that he now won't sell his programs at all. I'd appreciate a correction or update if anyone has contrary or confirming information. Roy Lewallen, W7EL David wrote: > Would someone mind advising me where I can purchase this software from. > I found a email address for him but was returned as invalid when I > tried to contact him. > > Thanks > > Regards > > David Article: 222338 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 00:30:19 -0800 Message-ID: <121i8gsc9itsgaf@corp.supernews.com> References: <121hps7rrj1ee9e@corp.supernews.com> <16559-4418F91D-1319@storefull-3256.bay.webtv.net> Richard Harrison wrote: > Roy, W7EL wrote: > "I don`t see the connection between these and the contention that the > current into and out of an inductor are unequal." > > Nor do I. Tom was not making a case for inequality of current in and out > of a coil either. He was just making an inaccurate statement. What was the inaccurate statement he made? I've found Tom very willing to correct errors, so I'm sure he'll correct it if we point it out to him. > Cecil has a good case. Straight wire and coiled wire have the same > properties, only more or less of them. When they are in the path of a > traveling wave and a reflection of that wave comes back from the > opposite direction, they respond similarly. An interference pattern > exists on the coil as it does on straight wire if the distance is > comparable to a wavelength. Which distance do you mean -- the length of the coil or the length of the wire? Superpositon makes both volts and amps vary > along the route. > > So, indeed the current at one end of a coil in that situation can be > different at from that at the other end, the same as it would along a > wire. Yes, indeed. As I explained in several earlier postings, if you begin with a coil and slowly stretch it out, the current distribution will go >from something resembling that of a lumped inductor (equal currents in and out) to that of a straight wire (sinusoidal distribution). So "a coil" can have any current distribution along that continuum, allowing us to "prove" just about anything we wish as long as we don't say what kind of coil we're talking about. In between the extremes, a third distribution can occur, as King described in his book: when the coil length is much less than a wavelength but the turns are loosely coupled, you get a current that's highest in the middle and lower at both ends. The disagreement regards the currents in what would qualify as a lumped inductor -- one with very good coupling between turns, coil length very short in terms of wavelength, and no significant coupling to other conductors, but regardless of the length of wire it's made of. For that case, it's been theoretically and demonstratively shown to be equal at both ends. > Distributed network theory is newer than lumped network theory but both > have been around plenty long enough to be well established. I don`t > think Cecil is breaking any new ground. His conclusions are sure new and different, and unlike established theory, his theories don't seem to be subject to equations which describe them quantitatively. Roy Lewallen, W7EL Article: 222339 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> Message-ID: Date: Thu, 16 Mar 2006 08:56:19 GMT Richard Clark wrote: > Barring startling results demonstrating how either of the two coils > offered here in evidence reveal multiple resonances, that is enough to > kill the thread without needing tedious computations.¹ Last night I posted 1/4WL, 3/4WL, and 5/4WL measured resonant points using the same coil stock as W8JI but with a shorter 50 uH coil. This coil 2" dia, 8 tpi, 8.5" long. It was sitting on a mag mount on my metal desk. > When the speculation is that the coil presents a 1:1 replacement for > the delay of the "missing" segment of the resonant antenna, then this > premise stumbles at the starting blocks. Nobody said anything about a 1:1 replacement. That was just somebody's strawman. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222340 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> <0osh12lmdqruqjbp9idttnm9mqatsstdlp@4ax.com> Message-ID: Date: Thu, 16 Mar 2006 09:08:37 GMT Richard Clark wrote: > What are they when you raise the assembly (I distinctly note that this > is NOT the resonance of the COIL you are speaking of) two feet higher? Isolating the magmount would be disconnecting the ground plane from a 1/4WL antenna and would contribute nothing of value to the discussion. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222341 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hps7rrj1ee9e@corp.supernews.com> <16559-4418F91D-1319@storefull-3256.bay.webtv.net> Message-ID: Date: Thu, 16 Mar 2006 09:30:52 GMT Richard Harrison wrote: > Distributed network theory is newer than lumped network theory but both > have been around plenty long enough to be well established. Neumann didn't prove that the current through a coil is uniform. He *assumed* it to be true as a simplification, so he could factor out the current term from under the integral sign in one of Maxwell's equations. Now Neumann's mathematical shortcut is being reported here as a fact of physics. That's how well established it is. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222342 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hps7rrj1ee9e@corp.supernews.com> <16559-4418F91D-1319@storefull-3256.bay.webtv.net> <121i8gsc9itsgaf@corp.supernews.com> Message-ID: Date: Thu, 16 Mar 2006 09:54:38 GMT Roy Lewallen wrote: > For that case, it's been theoretically and demonstratively shown to be > equal at both ends. Only one of the reported measurements showed the magnitudes of the currents to be equal and that was a small toroidal coil quite unlike a 75m bugcatcher coil. Wes's web page shows the currents to be unequal at the ends of the coil. Figure 3 shows 1.03 amps at the bottom of the coil and 0.66 amps at the top of the coil. That's not equal. http://www.k6mhe.com/n7ws/Loaded%20antennas.htm -- Here's an example from EZNEC where the currents are not only unequal, but if one considers to standing wave current to be flowing, more current is flowing into the bottom of the coil than out the top. What does the lumped-circuit model have to say about that? This technical question goes unanswered. http://www.qsl.net/w5dxp/qrzgif35.gif -- As for phase shift using standing wave current, consider the following half of a dipole: FP----------x----------y---------- 'x' is at the 30 degree point and 'y' is at the 60 degree point. What is the standing wave phase shift between point 'x' and point 'y'? We can see from Figure 14-4 in Kraus' "Antennas for All Applications", 3rd edition, that the measured phase shift would be zero between 'x' and 'y'. So why is it a surprise that if the wire between 'x' and 'y' is replaced by a coil, the phase shift remains zero? The measured phase shift in the wire and the coil are the same. This technical question goes unanswered. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222343 of rec.radio.amateur.antenna From: "news.viawest.net" References: <1142379642.765519.168180@p10g2000cwp.googlegroups.com> <1142394311.679500.186730@i40g2000cwc.googlegroups.com> Subject: Re: Good coax for WiFi (2.4 & 5 ghz)? Date: Thu, 16 Mar 2006 03:42:58 -0700 Message-ID: <84cfe$44194129$404ee032$27637@VIAWEST.NET> hmmmm, Someone does not know how to read. No where in his post did he stated that he was going to hack the computer system. haha. He did state that he would hack a USB device. Besides, the true definition of wardrivers are only out to log and collect information from the wireless access points (WAPs) they find while driving. The legality of wardriving in the United States is not clearly defined. There has never been any conviction for wardriving, and there is the untested argument that the 802.11 and DHCP protocols operate on behalf of the owner giving consent to use the network, but not if the user has other reason to know that there is no consent. "Bob" wrote in message news:s_NRf.54029$H71.36157@newssvr13.news.prodigy.com... > Did you know the USSS investigates many types of computer fraud and > hacking? Do you think it’s wise to state your intent to maliciously invade > other peoples computer systems and mention a traceable Ebay purchase of > the goods to do so? > USB type adaptors generally do not work with the popular freeware that you > wanna be hackers use to commit your heinous crimes. > Belden RG-174 has about .6dB loss/ft @ 5.6GHz. Your 15ft chunk would have > about 9dB loss, not too impressive. > Bob > > > KG0WX wrote: >> Well, I'm not just building *any* WiFi setup - I researched a bit and >> found >> on eBay what is generally agreed on to be one of the top 5 internal >> 802.11 >> cards. With up to 250mw output and external antenna, I plan on diving >> into >> a new hobby - wardriving. >> >> I could just buy a USB WiFi adapter and crack open the case and hack it >> with an external antenna but from what I've seen, both the low output >> and >> poor rx sensitivity seem to be quite common with these devices and that >> is not what I want. >> >> I did remember a bookmarked site which calculated the info I needed. >> Turns >> out that my coax in question will have about 1.7 db loss at 5ghz. Not >> too bad. >> >> Still, if anyone knows of a coax that is better than RG174 while being >> about >> the same size, please chime in with your comments! >> >> Ken KG0WX >> Article: 222344 of rec.radio.amateur.antenna From: ml Subject: ham ruhmours? Message-ID: Date: Thu, 16 Mar 2006 12:00:32 GMT does anyone know a good web site listing perhaps some soon to be announced 'new' ham rigs? dayton is just around the corner and was hoping to get a heads up on any skuttlebut tnx Article: 222345 of rec.radio.amateur.antenna From: "Frank's" References: <3FIRf.28313$M52.20709@edtnps89> <18qke3-do6.ln1@p400bob.personal.cox.net> <1142499124.542709.89620@e56g2000cwe.googlegroups.com> Subject: Re: Modeling question Message-ID: Date: Thu, 16 Mar 2006 16:19:46 GMT "Arie" <4nec2@gmx.net> wrote in message news:1142499124.542709.89620@e56g2000cwe.googlegroups.com... >> Hi Bob, you are probably right about the different software standards. >> The >> NEC-2 Users Manual, p8, first paragraph, states: "Delta/a must be > >> 'about' >> 8 for errors < 1%". I guess the developers of 4nec2 considered the >> error >> for Delta/a > 6 to be acceptable. > > Yes, and now I am wondering where I got this value of 6 instead of 8... > > However when delta/a (len/radius) < 6 a warning is generated, when > delta/a < 2 an error is generated. When using more thick wires, you can > add the EK card. With this more high delte/a values are possible. > (warning if delta/a < 2, error if delta/a < 0.5). > > Greetings from the 'developer', > > Arie. > > p.s. I can also recommend www.cebik.com Not sure if "EK" will help much here since the "wire" diameter is > lambda/100. Seems to be a borderline case for a wire grid model. It is like building a 20m dipole from 10" diameter pipe. Also noticed the pole touches the ground, which is not allowed in NEC2. Don't understand why it does not produce a warning. Usually when I connect a wire to a non-perfect ground the ground grid turns purple (NEC-Win Pro), and I get crazy results, but not in this case. Not that this is relevant in this model. Frank Article: 222346 of rec.radio.amateur.antenna From: "Snide" References: <441890ae$0$1147$7a628cd7@news.club-internet.fr> Subject: Re: compact antenna for short range direction finding Date: Thu, 16 Mar 2006 18:05:13 +0100 Message-ID: <44199ace$0$1153$7a628cd7@news.club-internet.fr> thank for that. have you more details about all that stuff ? plans, schematics, links ? I'm not an expert... Denis Article: 222347 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Current through coils References: <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142444722.334435.216960@p10g2000cwp.googlegroups.com> Message-ID: <44199e18_1@newsfeed.slurp.net> Date: 16 Mar 2006 12:19:20 -0500 I've been following this mind-numbing discussion for days now and still don't have the answer to the original question: Is the current the same at both ends of a mobile whip's loading coil? Bill, W6WRT Article: 222348 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> Subject: Re: Current through coils Message-ID: <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Date: Thu, 16 Mar 2006 17:34:51 GMT wrote: > OK. I'm not sure what you are trying to say. It sounds like we all know > and agree a reasonable physial size lumped inductor with good flux > coupling between ends and stray C to the outside world that is small > compared to termination impedance works like a lumped inductor below > self-resonance of the inductor. I absolutely agree about the characteristics of an inductor presupposed by the lumped-circuit model. But one cannot use the presuppositions of the model to prove the model is valid for all cases. The dissagreement here is one of degree. I would have stated the assertion above, it behaves "... like a lumped inductor *far* below self-resonance of the inductor." Dr. Corum sets the "far below" range at 15 degrees or 1/6 the self-resonant frequency.I previously showed that 15 degrees of 450 ohm transmission line will change a load of 50+j0 into a load of 54+j100 ohms. That may be accurate enough for Dr. Corum to start using the lumped-circuit model, but not for me. I would be more inclined to set the limit at 5 degrees. > What are you trying to say? Can you give an example in you own words > explaining what you are trying to say and why it is meaningful or > useful to others? What I am trying to say can best be illustrated by an example task that I need to perform. I have a 180 foot dipole that I need to shorten so I am going to install loading coils. I want the length of the loaded antenna to be 90 feet. I'm pretty naive at this, so I am just going to build the coil out of the wire I remove from the antenna. My neighboring ham friend says that will work just fine. And in the process of reducing the size of my antenna, I want to learn something about antennas so I have borrowed two toroidal current pickups to measure the current. Note that at the frequency where the dipole is 1/2WL and resonant, it is 180 feet long and 180 degrees long so the number of feet of wire is also the number of degrees of antenna. Here is my 1/2WL dipole with current pickup coils installed at points 'x' and 'y' and FP is the feedpoint,the impedance of which is 60 ohms. ------------------------------FP-------x---------------y------- Total length is 180 feet. The distance between 'x' and 'y' is 45 feet. Since feet = degrees in this case, the number of degrees between 'x' and 'y' is known to be 45 degrees from antenna theory. Those 45 degrees are what I am going to attempt to replace with a coil. So I adjust the feedpoint current to one amp at a reference phase angle of zero degrees and measure the current at 'x' and the current at 'y'. The current at 'x' is 0.92 amp at 0 deg. The current at 'y' is 0.38 amp at 0 deg. Already I am not understanding my measurements. The electrical length between 'x' and 'y' is obviously 45 deg. Why is there no phase shift at all in the measured current between 'x' and 'y' and the feedpoint current? But I want to complete this task so I will wait until later for an explanation to that apparent paradox. I take the 45 feet of wire from each side of the dipole, wind it into two coils, and install them in each side. Now the 90 foot long dipole looks like this. -------//////-------FP------x-//////-y------ I make some more measurements with the feedpoint current set to one amp at zero degrees. The resonant frequency of the dipole has changed from the earlier resonant frequency. I have to adjust the number of turns on the coil to return to the original frequency. I discover that the feedpoint impedance has dropped to 45 ohms. I measure the current at each end of the coil and at one end it is 1.1 amp at 0 deg and at the other end it is 0.6 amp at 0 deg These are not the results predicted by my neighboring ham friend. I'm confused but here are the things I know for sure. 1. The resonant frequency changed when I installed the coil so the coil is not a perfect replacement for the wire. 2. The feedpoint impedance decreased from 60 ohms to 45 ohms. Since 45 ohms is closer to 50 ohms than is 60 ohms, I'm not too interested in knowing why.. 3. The current at 'x' increased from 0.92 amp at 0 deg in the wire dipole to 1.1 amp at 0 deg in the loaded dipole. The phase didn't change. 4.The current at 'y' increased from 0.38 amps at 0 deg in the wire dipole to 0.6 amp at 0 deg in the loaded dipole. The phase didn't change. 5. No matter where I measure the current in either system, the phase always comes up zero degrees between any two points >from tip to tip anywhere on either dipole no matter how far apart are the measurement points. My neighboring ham friend said the number of degrees in the coil had to be the number of degrees in the wire and indeed, both are measured to be zero degrees, but I wonder if that's really what he had in mind when he said the delay would be equal. Zero equals zero, but what does that mean for me? The change in feedpoint impedance and the different current magnitudes don't much bother me but I am really bothered by those phase measurements. The dipole is 180 degrees long and the current should be changing phase, at least on the wire if not through the coil. I need some expert to explain how those phase measurements on the wire are possible on both antennas. I know my phase measurements are correct but why are they always zero degrees? And since they are always zero degrees, what information are they providing? -- 73, Cecil, W5DXP Article: 222349 of rec.radio.amateur.antenna From: "Cecil Moore" References: <121hps7rrj1ee9e@corp.supernews.com> <16559-4418F91D-1319@storefull-3256.bay.webtv.net> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 18:04:11 GMT "Ian White GM3SEK" wrote: > That was not a "shortcut" or approximation. It really doesn't matter if it is or it isn't. I was quoting another pretty smart guy who seems to know the history of these models. He said Maxwell's equations matured first, then the distributed network model matured as a simplified subset of Maxwell's equations, then the lumped- circuit model matured as a subset of the distributed network model. But a chicken/egg argument is meaningless except for historical accuracy. We are in the present looking at those models. > In that limiting case, the current at the two terminals of a pure > inductance must be the same in both magnitude and phase. There's that catch word, "pure". Pure inductances do not exist in the real world. They are a construct of the lumped-circuit model and are presupposed to have the characteristice that you mention. One cannot prove the validity of that model by quoting the presuppositions. A 75m bugcatcher coil is NOT a pure inductance. > By "current" we > mean the simple, straightforward movement of charge. If you count the > electrons in and out at the two terminals, there can be no difference in > either magnitude or phase because that would require electrons to be > stored or lost from somewhere - which inductance cannot do. Kirchhoff's > current law recognises the logic of this. Standing wave current with its cos(kz)*cos(wt) equation is not constrained by those rules since the phase of the standing wave is everywhere zero deg for a 1/2WL thin-wire dipole. > This is how inductance always works in every type of non-radiating > circuit, both in theory and in real life. A pure inductance cannot work that way in real life because it doesn't exist in real life. If the forward current is in phase with the reflected current at one end of the coil, the current will be a maximum (loop) at that point. If the forward current is 180 degrees out of phase with the reflected current at the other end of the coil, the current will be a minimum (node) at that point. Please take a look at: http://www.qsl.net/w5dxp/3freq.gif How does one explain the current reported by EZNEC at two times the resonant frequency? > When developing a new theory, it is normal, standard required practice > to test it for simplified, limiting cases that we already understand. > The new theory MUST work for all these test cases; it MUST connect > seamlessly with everything we already know. The distributed network model predates my birth by decades and is not new. It is known to work in situations where the lumped-circuit model fails. It has never been known to fail in a situation where the lumped- circuit model works. > At his point, some heckler pipes up: "Ah, but what about Einstein?" > Thank you, sir - the perfect example to prove my point! If Einstein's > equations of relativity are tested for the limiting case where > velocities are very low, they connect seamlessly into Newton's laws of > motion. If they hadn't, Einstein would have thrown them out and gone > back to think again. The distributed network model is to relativity as the lumped-circuit model is to Newtonian physics. Newtonian physics is a subset of relativity. The lumped-circuit model is a subset of the distributed-network model. > When Cecil's theory is tested for the simple limiting case of pure > inductance, it MUST join up seamlessly with conventional circuit theory. It's not my theory and it does indeed join up seamlessly. It is the lumped- circuit model that does not join up seamlessly with Maxwell's equations. How could it since it assumes faster than light speed of current flow? The presuppositions of the lumped-circuit model even violate the theory of relativity. > If it requires anything that "don't fit", such as a phase shift in > current through a pure inductance, or special kinds of "current" that > are different from the simple, straightforward movement of charge > (electrons), then the theory fails. It doesn't require anything of pure inductances since pure inductances don't exist in reality. It requires that real world inductances obey the laws of physics. If one doesn't understand the implications of the equation for standing wave current, one needs to crack open that old dusty math book. -- 73, Cecil, W5DXP Article: 222350 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 18:20:19 GMT Richard Clark" wrote: > On Thu, 09 Mar 2006 21:40:40 GMT, "Cecil Moore" > wrote: > > >Your 100uH coil above exhibits 60 degrees of phase shift > >even for the voltage and that's 1/6 wavelength. That does NOT say the coil replaces 60 degrees of wire in the antenna. One who thinks such is mistaken. The phase shift in the coil is what it is. It usually does NOT correspond to the phase shift of the wire it replaces. The point of that statement was that real world phase shift is never zero. The one-way phase shift is known to be 90 degrees at the self-resonant frequency. > On Thu, 16 Mar 2006 08:56:19 GMT, Cecil Moore wrote: > > >> When the speculation is that the coil presents a 1:1 replacement for > >> the delay of the "missing" segment of the resonant antenna, then this > >> premise stumbles at the starting blocks. > > > >Nobody said anything about a 1:1 replacement. That was just > >somebody's strawman. > > We all know who "somebody" is. [threadbuster #4] > > But if this is news to you, it must have been one of your other > personalities (Hokum's Razor?) at the keyboard who posted the message > at the top. Some people have misunderstood the meaning of that statement. See above. So many jumping to conclusions - so few trying to understand. -- 73, Cecil, W5DXP Article: 222351 of rec.radio.amateur.antenna From: "Cecil Moore" References: <1142469410.984882.184550@i40g2000cwc.googlegroups.com> <0osh12lmdqruqjbp9idttnm9mqatsstdlp@4ax.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 18:23:24 GMT "Richard Clark" wrote in message news:gv6j12dn51fkrd6b5dlfvh1a704b4r6h6n@4ax.com... > Cecil Moore wrote: > >Isolating the magmount would be disconnecting the > >ground plane from a 1/4WL antenna and would contribute > >nothing of value to the discussion. > > Certainly not for you, that is apparent. It would only more closely > conform to your reference material's isolated coils, and that would > jeopardize your "confirmations" n'est pas? On the contrary, Tesla coils are operated over a large ground plane. The sphere at the top functions like a top hat. Everyone really should read the referenced Corum papers to avoid misconceptions like this one. -- 73, Cecil, W5DXP Article: 222352 of rec.radio.amateur.antenna From: "Cecil Moore" References: <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142444722.334435.216960@p10g2000cwp.googlegroups.com> <44199e18_1@newsfeed.slurp.net> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 18:44:45 GMT "Bill Turner" wrote in message news:44199e18_1@newsfeed.slurp.net... > I've been following this mind-numbing discussion for days now and still > don't have the answer to the original question: Bill, I posted an example of me, as a naive ham, reducing the size of my dipole from 180 feet to 90 feet by adding loading coils. Please follow that experimental excursion to find out what the discussion is all about. > Is the current the same at both ends of a mobile whip's loading coil? The mobile antenna is a standing wave antenna. It has a forward current and a reflected current, both traveling waves, flowing through it. 1. The forward current flowing through the coil is close to the same magnitude at both ends of the coil. 2. The forward current phase shift through the coil is difficult to measure but it is NOT zero. It is more in the neighborhood of tens of degrees. 3. The reflected current flowing back through the coil is close to the same magnitude at both ends of the coil. 4. The reflected current phase shift is close to the same as the forward current phase shift, i.e. tens of degrees.. 5. The standing wave current, the only one measured so far, is the phasor sum of the forward current phasor and the reflected current phasor. The magnitude of the standing wave current depends upon the relative phase between the forward current and reflected current. To see some variations please visit: http://www.qsl.net/w5dxp/3freq.gif When one realized that the standing wave current at the bottom of the coil is 0.1 amp while the standing wave current at the top of the coil is 2 amps, one comprehends why he must abandon the concept that standing wave current flows. >From the equation for the standing wave current, cos(kz)*cos(wt), one can be see that the standing wave current is not a normal current. This is explained in terms of light waves in "Optics", by Hecht. 6. Since the forward current phasor and reflected current phasor are rotating in opposite directions, the phase of the standing wave current is fixed and close to zero degrees all up and down the antenna, from feedpoint to tip top. Since the phase of the standing wave is unchanging, it cannot be used to measure the phase delay through a coil. All of the delay measurements, except the self-resonant frequency measurements, have used standing waves which are incapable of phase transitions in the average loaded mobile antenna. The phase of the standing-wave current is fixed close to zero degrees until the antenna gets electrically longer than 90 degrees. Then it shifts abruptly by 180 degrees and remains fixed at that new value for another 90 degrees. This is illustrated in Kraus', "Antennas for All Applications", 3rd edition, Figures 14-4 - 14.6. -- 73, Cecil, W5DXP Article: 222353 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 19:31:04 GMT wrote: > Your measurements are probably wrong. Not much accuracy is needed to measure a constant phase of zero. Anyone is invited to duplicate those phase measurements. > When did you measure that? After we resolve the error in current, we > can move on. I rigged up a 6m dipole yesterday with current pickups driving equal lengths of coax. Remember, we are not discussing the accuracy of my magnitude measurements, only of my phase measurements. After we resolve exactly who made the measurement error, we can move on. My measurements agree with Figure 14-4 in Kraus' "Antennas for All Applications", 3rd edition. Question: would it be legal for me to scan that graphic and post it on my web page if I give Kraus full credit? -- 73, Cecil, W5DXP Article: 222354 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 11:53:22 -0800 Message-ID: <121jghjq49sjiab@corp.supernews.com> References: <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142444722.334435.216960@p10g2000cwp.googlegroups.com> <44199e18_1@newsfeed.slurp.net> Bill Turner wrote: > I've been following this mind-numbing discussion for days now and still > don't have the answer to the original question: > > Is the current the same at both ends of a mobile whip's loading coil? > > Bill, W6WRT No, it isn't, provided it's a solenoidal coil of reasonable length. I don't think anyone disagrees with this. The disagreements are to why, and what would happen to the current if the coil were made very short. Roy Lewallen, W7EL Article: 222355 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Message-ID: Date: Thu, 16 Mar 2006 19:54:17 GMT Cecil, One more time. In a standing wave antenna problem, such as the one you describe, there is no remaining phase information. Any specific phase characteristics of the traveling waves died out when the startup transients died out. Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again. The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. The so-called "phase reversal" in longer antennas is not really about phase either. It is merely a representation of the periodic sign reversal seen in a cosine function. (This is one more definition of phase to add to the confusion.) Of course, all of this depends on an ideal system with no losses, etc. The real world is not ideal, but your posed problem does not appear to contain any of those nasty realities. You have undoubtedly seen small phase offsets reported in EZNEC for this sort of antenna. Those phase offsets represent the impact of real-world effects, such as radiation and ground effects. The applicability of linear superposition and the assumption of steady-state conditions means that the resulting standing wave contains ALL of the possible information about the system in steady-state mode. Yes, you can divide the problem back into two traveling waves, in the manner that Kraus, Balanis, and the entire world understand. But you won't gain any new information by doing so, because any unique traveling wave information is permanently lost. 73, Gene W4SZ Cecil Moore wrote: [snip] > These are not the results predicted by my neighboring ham friend. > I'm confused but here are the things I know for sure. > > 1. The resonant frequency changed when I installed the coil so > the coil is not a perfect replacement for the wire. > > 2. The feedpoint impedance decreased from 60 ohms to 45 > ohms. Since 45 ohms is closer to 50 ohms than is 60 ohms, > I'm not too interested in knowing why.. > > 3. The current at 'x' increased from 0.92 amp at 0 deg in the > wire dipole to 1.1 amp at 0 deg in the loaded dipole. The phase > didn't change. > > 4.The current at 'y' increased from 0.38 amps at 0 deg in the > wire dipole to 0.6 amp at 0 deg in the loaded dipole. The phase > didn't change. > > 5. No matter where I measure the current in either system, the > phase always comes up zero degrees between any two points > from tip to tip anywhere on either dipole no matter how far > apart are the measurement points. My neighboring ham friend said the number > of degrees in the coil had to be the number of degrees in the > wire and indeed, both are measured to be zero degrees, but > I wonder if that's really what he had in mind when he said > the delay would be equal. Zero equals zero, but what does > that mean for me? > > The change in feedpoint impedance and the different current > magnitudes don't much bother me but I am really bothered > by those phase measurements. The dipole is 180 degrees long > and the current should be changing phase, at least on the wire > if not through the coil. I need some expert to explain how those > phase measurements on the wire are possible on both antennas. > I know my phase measurements are correct but why are they > always zero degrees? And since they are always zero degrees, > what information are they providing? > -- > 73, Cecil, W5DXP > > Article: 222356 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 12:00:14 -0800 Message-ID: <121jgugo5argkc3@corp.supernews.com> References: <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142444722.334435.216960@p10g2000cwp.googlegroups.com> <44199e18_1@newsfeed.slurp.net> Richard Clark wrote: > On 16 Mar 2006 12:19:20 -0500, "Bill Turner" wrote: > >> Is the current the same at both ends of a mobile whip's loading coil? > > Sorry Bill, > > Depends.... > > Yes, of course not. The clear and compelling lesson to be learned is > that you CANNOT apply Kirchhoff's laws to networks that are large in > relation to wavelength. This single caveat was drilled into me in > sophomore EE. > > Any variance in current measured, that is larger than errors that may > be attributed to is measurement PROVES that the size in relation to > wavelength necessarily invalidates Kirchhoff solutions. This single > truth has been observed by me at the calibration bench. > > As Roy noted, it demands another set of equations. In the Metrology > field, that is what we were paid to use, or to derive. Suffice it to > say that modeling programs replace the tedium of scribbling out that > math, and just getting on with the next act. > > 73's > Richard Clark, KB7QHC I need to add that the current can be different at both ends even if the coil is quite short in terms of wavelength. All that's required is capacitive coupling that's different from the two ends of the coil, or coupling to a radiating wire. Both are typically the case with an antenna loading coil. Another thing which can cause unequal currents is poor coupling among turns, which can occur in long coils or ones with wide turn spacing. But when the inductor length is short in terms of wavelength, the current imbalance can be explained with simple lumped element models. No distributed or transmission line theory, let alone Cecil's exotic variations, is necessary. Roy Lewallen, W7EL Article: 222357 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 12:07:46 -0800 Message-ID: <121jhck5r955q0f@corp.supernews.com> References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> w8ji@akorn.net wrote: > Cecil Moore wrote: >> Note that at the frequency where the dipole is 1/2WL and resonant, >> it is 180 feet long and 180 degrees long so the number of feet of >> wire is also the number of degrees of antenna. Here is my 1/2WL >> dipole with current pickup coils installed at points 'x' and 'y' and >> FP is the feedpoint,the impedance of which is 60 ohms. >> >> ------------------------------FP-------x---------------y------- >> >> Total length is 180 feet. The distance between 'x' and 'y' is 45 feet. >> Since feet = degrees in this case, the number of degrees between >> 'x' and 'y' is known to be 45 degrees from antenna theory. Those >> 45 degrees are what I am going to attempt to replace with a coil. >> >> So I adjust the feedpoint current to one amp at a reference phase >> angle of zero degrees and measure the current at 'x' and the current >> at 'y'. The current at 'x' is 0.92 amp at 0 deg. The current at 'y' is >> 0.38 amp at 0 deg. Already I am not understanding my measurements. > > Your measurements are probably wrong. > > When did you measure that? After we resolve the error in current, we > can move on. The measurement looks good to me. The phase is exactly what EZNEC predicts -- constant along the wire. The ratio in magnitudes we'd expect depends on the positions along the wire, not just the spacing. Roy Lewallen, W7EL Article: 222358 of rec.radio.amateur.antenna Subject: Re: Element correction for through beem Yagi elements References: From: Glen Overby Message-ID: Date: Thu, 16 Mar 2006 13:21:56 -0600 David wrote: >The design was assuming that the elements were to be insulated from the >boom but I am having trouble making small insulators to hold these in >place. >It would be simpler for construction if I could simply drill through the >beam and weld the rods in place or connect via a screw through the >centre of the beam. > >The correction factor formula I have found seems to be for insulated >through-beam elements. > >Q: Is there a correction factor I can apply to enable me to construct >the antenna in this manner ? The ARRL Antenna Book has a graph showing the correction needed for thru-the-beam elements. I can't recall if it is for insulated elements or not. It's in the chapter on Yagis -- the chapter with all the K1FO yagi designs. >Q: Is there an alternate design I could use that would be simpler to >construct. (I am looking for around 7dB gain at low angle of radiation - >point to point communications link). Feedline is 50 Ohm coaxial cable, >power is less than 1 Watt. WA5VJB has some cheap yagi designs, and also sells PC board-based antennas on his web site. http://www.clarc.org/Articles/uhf.htm I built a 902mhz WA5VJB design using a piece of square moulding. If you paint the boom with primer or polyurethene, it should last some time. Glen, kc0iyt Article: 222359 of rec.radio.amateur.antenna From: "Cecil Moore" References: <07mdnQ9xiNzNX4jZ4p2dnA@adelphia.com> <3mrRf.744$tN3.23@newssvr27.news.prodigy.net> <36GRf.53899$H71.37105@newssvr13.news.prodigy.com> <33kf121j2i9kjcodd345o8ahdijq7ibuua@4ax.com> <30WRf.738$4L1.193@newssvr11.news.prodigy.com> <1142444722.334435.216960@p10g2000cwp.googlegroups.com> <44199e18_1@newsfeed.slurp.net> <121jghjq49sjiab@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 20:14:14 GMT "Roy Lewallen" wrote : > No, it isn't, provided it's a solenoidal coil of reasonable length. I > don't think anyone disagrees with this. The disagreements are to why, > and what would happen to the current if the coil were made very short. The phase shift measurements are being made using a signal with unchanging phase and thus incapable of providing a phase shift. The disagreement is what would valid phase measurements actually look like if a signal capable of changing phase was used to make the phase measurements. -- 73, Cecil, W5DXP . Article: 222360 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Thu, 16 Mar 2006 12:30:18 -0800 Message-ID: <121jimsb3if6v7a@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> art wrote: > Most hams have an awareness of what skin depth is all about > but I am stumbling over the fact that the formulae show it > as a 2 dimensional thing which raises a question to me. Skin depth is a scalar quantity, not two dimensional. Perhaps you're referring to the fact that concentration of the current in a thin layer affects both the resistance and inductance of a conductor? > Can one compensate for radiation purposes element width > for lack of the required skin depth I've never seen an application that requires a particular skin depth. Can you give an example? and also what role > does skin depth play with homogenous or > non-homogenous capacitive ( capacitor) fields.? Skin depth is a property of conductors, not fields -- although of course it comes about because of interaction of fields with the conductors. If a capacitor is made from conductors, those conductors will exhibit skin effect like any others. > Both of these items contain inductance and resistance > but apparently volume which is three dimensional does not > play a role. Skin effect causes current to be concentrated near the surface of a conductor. Its density exponentially decays as you go deeper. Consequently, the fraction of the total current flowing below a few skin depths is insignificant, so the depth and makeup of the conductor below that depth makes no real difference to the resistivity of the material. That's why a hollow tube conducts just as well as a solid wire at radio frequencies. > Can somebody explain this personal puzzle of mine or > point to a book that points to the lacking volume aspect ? > The above questions I suppose could come into play > if one thought about aluminised mylar for antenna use > which has about the thinnest conductor depth around. I hope the brief description above explains why volume isn't important -- it's just that at RF there's no current in most of the volume of a wire or plate, so that volume which carries no current can be ignored. As for your metalized Mylar, the first thing to do is to determine whether the aluminum is at least several skin depths thick. If it is, then any greater thickness makes no difference, and you can treat it as though that's all the thicker it is. If it's one skin depth or thinner, you can ignore skin effect and treat it as though the current is evenly distributed throughout the thickness. If it's in between those limits, the R and internal L can be calculated, but it involves Bessel functions. An estimate is usually adequate in those situations. There's a great deal of information about skin effect on the web, although like most topics found there, you should read with caution. The subject is covered thoroughly in virtually every text involving electromagnetics, and most texts on transmission lines. I'd expect to find it covered in the ARRL Handbook as well. I should add one final note. Due to a fortunate quirk of mathematics, the resistivity of an infinitely thick material at RF is the same as that of a material which is exactly one skin depth thick in which current is uniformly flowing. That is, if we know the skin depth we can easily calculate the RF resistivity by calculating the DC resistivity of a one skin depth thick layer of the material. It's important to realize that's not really how the current is distributed, but the method gives the correct answer. For this method to work with reasonable accuracy, the material has to be thick enough for the current to follow the exponentially dropping density characteristic down to a depth where it's insignificant. This is on the order of 3 - 5 skin depths, depending on the accuracy you require. Roy Lewallen, W7EL Article: 222361 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 20:47:20 GMT "Gene Fuller" wrote: > Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen > again. So how can a signal, devoid of phase, be used to measure the phase shift through a loading coil? > The only "phase" remaining is the cos (kz) term, which is really an > amplitude description, not a phase. How can one make a phase measurement using only the amplitude of a signal? -- 73, Cecil, W5DXP Article: 222362 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <121jhck5r955q0f@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 20:55:46 GMT "Roy Lewallen" wrote: > The measurement looks good to me. The phase is exactly what EZNEC > predicts -- constant along the wire. The ratio in magnitudes we'd expect > depends on the positions along the wire, not just the spacing. We are not talking about the magnitude measurements right now. We are talking about the phase measurements. What good does it do to use a signal, whose phase is fixed, to measure the phase shift through a coil or through a wire. The phase is constant along the wire with or without the presence of a coil. Why then is a phase shift of zero on both sides of the coil surprising? And of what importance is that measurement? -- 73, Cecil, W5DXP Article: 222363 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Modeling question References: <3FIRf.28313$M52.20709@edtnps89> <18qke3-do6.ln1@p400bob.personal.cox.net> <1142499124.542709.89620@e56g2000cwe.googlegroups.com> Message-ID: <0ntoe3-dab.ln1@p400bob.personal.cox.net> Date: Thu, 16 Mar 2006 14:17:04 -0600 Hi Frank/Arie Not really knowing what I was doing I tried EK and got the same bad average gain figure.. I also removed most of the lower part of the mast since its effect will be fairly minimal. No help there either. Tnxs for your comments gents. There is still the two questions though; - Does one bother to model in a "curved" wire for copper pipe joiners? I note Mr Cebik didnt mention it when he was talking about J poles on 2m. - Is the diameter of the source wire important? Thinking now about reducing the copper pipe diameter simply so I can model it properly. Then again its a pretty broad design and tuning would be easy... Cheers Bob VK2YQA Frank's wrote: > Not sure if "EK" will help much here since the "wire" diameter is > > lambda/100. Seems to be a borderline case for a wire grid model. It is > like building a 20m dipole from 10" diameter pipe. > > Also noticed the pole touches the ground, which is not allowed in NEC2. > Don't understand why it does not produce a warning. Usually when I connect > a wire to a non-perfect ground the ground grid turns purple (NEC-Win Pro), > and I get crazy results, but not in this case. Not that this is relevant in > this model. Article: 222364 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 21:14:50 GMT wrote > > Cecil Moore wrote: > > I rigged up a 6m dipole yesterday with current pickups driving equal > > lengths of coax. Remember, we are not discussing the accuracy of > > my magnitude measurements, only of my phase measurements. > > What was the indicator? What was the coupling device? I have an assortment of toroids of various materials from Amidon. I'm at work right now and I don't remember if I used 43 or F material. > On six meters, it would take a darned small probe and indicator to not > greatly perturb the system. They are small toroids. I chose 6m because the dipole area was physically small. > If I was going to test something like this, I'd use a small indicator > hanging from the antenna and do it on a low frequency. Please feel free to make that measurement. W7EL just reported that EZNEC agrees with my phase measurements. So does Kraus. > So, tell us about the probe and indicator. Similar to the ones W7EL used. They were calibrated within one turn of each other. The signals at the ends of the coax lines were calibrated for equality in magnitude and phase. Magnitudes are a relative measurement but phase was not. I ran the experiment two ways. One was Lissajous figures on my 100 MHz Leader. The other was putting the two samples in opposite phase to each other, i.e. phasor subtraction. For small angles, the angle is equal to the sine of the angle so the addition of two coherent sine waves yields an amplitude proportional to the phase difference when the phase difference is small. The phase difference was so small it was virtually undetectable. -- 73, Cecil, W5DXP Article: 222365 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Message-ID: Date: Thu, 16 Mar 2006 22:00:42 GMT Cecil Moore wrote: > "Gene Fuller" wrote: > >>Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen >>again. > > > So how can a signal, devoid of phase, be used to measure the phase > shift through a loading coil? > > >>The only "phase" remaining is the cos (kz) term, which is really an >>amplitude description, not a phase. > > > How can one make a phase measurement using only the amplitude > of a signal? > -- > 73, Cecil, W5DXP > > Cecil, The phase is uniformly zero, so the phase shift is also zero. Your messages seem to imply that there is some sort of characteristic "phase shift" in a loading coil. Ain't so. In the example of a standing wave antenna the phase shift is zero, both experimentally and theoretically. (Approximate. Real world conditions might cause small non-zero shifts.) If you place this same loading coil in a traveling wave antenna you can undoubtedly measure some sort of phase shift. (Exact amount left as an exercise for the student.) Bottom line: Any characteristic, such as phase, that explicitly depends on the wave nature of a signal needs to be referenced to that condition, not some arbitrary setup. 73, Gene W4SZ Article: 222366 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 14:13:04 -0800 Message-ID: <121jonhqbrpjea9@corp.supernews.com> References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Gene Fuller wrote: > > Cecil, > > The phase is uniformly zero, so the phase shift is also zero. > > Your messages seem to imply that there is some sort of characteristic > "phase shift" in a loading coil. Ain't so. > > In the example of a standing wave antenna the phase shift is zero, both > experimentally and theoretically. (Approximate. Real world conditions > might cause small non-zero shifts.) > > If you place this same loading coil in a traveling wave antenna you can > undoubtedly measure some sort of phase shift. (Exact amount left as an > exercise for the student.) > > Bottom line: Any characteristic, such as phase, that explicitly depends > on the wave nature of a signal needs to be referenced to that condition, > not some arbitrary setup. > It's likely that quite a number of people don't realize that there's no phase shift of current or voltage along a short or open circuited lossless transmission line -- except for, like on an antenna, periodic polarity reversals. Roy Lewallen, W7EL Article: 222367 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 22:23:35 GMT "Gene Fuller" wrote:.. > Your messages seem to imply that there is some sort of characteristic > "phase shift" in a loading coil. Ain't so. Thanks, Gene. What was implied is what has been reported as fact by others - that the zero phase shift on both ends of a loading coil measures the delay through the coil to be close to zero. > In the example of a standing wave antenna the phase shift is zero, both > experimentally and theoretically. (Approximate. Real world conditions > might cause small non-zero shifts.) Please note that the phase shift in the wire is also zero. That the phase shift is measured to be zero in a coil or a wire in a standing wave environment is not of any practical importance whatsoever. > If you place this same loading coil in a traveling wave antenna you can > undoubtedly measure some sort of phase shift. (Exact amount left as an > exercise for the student.) That was the discussion involving Dr. Corum's papers and the VF of large RF inductors, like a 75m bugcatcher coil. -- 73, Cecil, W5DXP Article: 222368 of rec.radio.amateur.antenna From: "Cecil Moore" References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <121jonhqbrpjea9@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Thu, 16 Mar 2006 22:27:47 GMT "Roy Lewallen" wrote: > It's likely that quite a number of people don't realize that there's no > phase shift of current or voltage along a short or open circuited > lossless transmission line -- except for, like on an antenna, periodic > polarity reversals. If we have 45 degrees of transmission line and measure no phase shift at each end of that 45 degrees, does that mean the transmission line is really zero degrees long? If we have an unknown number of degrees of coil and measure no phase on each side of the coil, does that mean the coil is really zero degrees long? -- 73, Cecil, W5DXP Article: 222369 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> Message-ID: <5_lSf.571648$qk4.401354@bgtnsc05-news.ops.worldnet.att.net> Date: Thu, 16 Mar 2006 22:51:45 GMT Cecil, You're a sly one, but not quite sly enough. 8-) 8-) What is the meaning of "delay" in a standing wave antenna? Delay, like phase, depends on the environment. The measurement results reported by W8JI a few days ago stand on their own. He described the setup and measurements adequately. If you choose to make extrapolations to another environment, have at it. Just don't expect anyone else to automatically agree with your extrapolations. As I recall, this three-year saga started with consideration of a loaded mobile antenna, which I believe would be considered a standing wave antenna. Have you since equipped your steed with a Beverage or rhombic? Are phase shifts and delays now important? 73, Gene W4SZ Cecil Moore wrote: > "Gene Fuller" wrote:.. > >>Your messages seem to imply that there is some sort of characteristic >>"phase shift" in a loading coil. Ain't so. > > > Thanks, Gene. What was implied is what has been reported as fact > by others - that the zero phase shift on both ends of a loading coil > measures the delay through the coil to be close to zero. > > >>In the example of a standing wave antenna the phase shift is zero, both >>experimentally and theoretically. (Approximate. Real world conditions >>might cause small non-zero shifts.) > > > Please note that the phase shift in the wire is also zero. That the phase > shift is measured to be zero in a coil or a wire in a standing wave > environment is not of any practical importance whatsoever. > > >>If you place this same loading coil in a traveling wave antenna you can >>undoubtedly measure some sort of phase shift. (Exact amount left as an >>exercise for the student.) > > > That was the discussion involving Dr. Corum's papers and the VF of > large RF inductors, like a 75m bugcatcher coil. > -- > 73, Cecil, W5DXP > > Article: 222370 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Coils are transmission lines Date: Thu, 16 Mar 2006 23:06:10 +0000 (UTC) Message-ID: ALL coils are distributed in space. They have a conductor. Therefore they can be analysed in the same manner as transmission lines. They ARE transmission lines, no matter what length. They can't help it! Program COILINE demonstrates how a simple coil-loaded vertical antenna can be designed by using classical transmission line mathematics. Enter length, diameter and number of turns on the coil, the length of the top rod or whip or wire, and you can examine how the thing behaves at any frequency. You can design anything from a bottom loaded long wire to a helical for 160 metres. Coils can vary between a few turns on an empty toilet roll tube to a 4 feet long, 1 inch diameter, plastic pipe wound with 1000 turns. You can prune the whip to obtain resonance at a given frequency without having to go out in the freezing cold back yard. Discover the velocity factor, nano-seconds per meter, and other numbers for your particular coil. All will be of interest to the participants in the interminable civil war still raging on another thread. Ammunition galore! Download program COILINE from website below and run immediately. Only 47 kilo-bytes. Its quite entertaining. By the way, it has just occurred to me, I forgot to include coil Q in the results. But it hardly matters - there's little to be done with the number even if you know it. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 222371 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <5_lSf.571648$qk4.401354@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Thu, 16 Mar 2006 23:39:13 GMT Gene Fuller wrote: > What is the meaning of "delay" in a standing wave antenna? Same as in a traveling wave antenna - the length of time it takes a traveling wave signal to make it through a coil or a wire. The lumped-circuit model assumes that delay is equal to zero even for traveling wave antennas. > Delay, like phase, depends on the environment. I defined what I meant by "delay" through a coil a few days ago. It was the delay experienced by a traveling wave flowing through a coil or 1/2 the delay experienced by a traveling wave making a round trip to the end of a coil and back based on the self-resonant frequency. That's what the velocity factor calculations were all about. Does the 0.66 velocity factor disappear when RG-8 is used as a stub? Then neither does the 0.0175 coil velocity factor disappear when it is used in a standing wave environment. The cos(kz)*cos(wt) nature of the standing wave current prohibits that standing wave current from being used to determine the velocity factor of a coil or of a wire. The lumped-circuit model assumes the velocity factor through any and every coil to be *greater than unity*. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222372 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 00:01:10 GMT w8ji@akorn.net wrote: > Just because EZnec agrees with the phase measurements it > doesn't mean the current measurement was even remotely > close to being correct. I officially withdraw my measurements as evidence in this debate and instead substitute the EZNEC results, provided by W7EL, as evidence. What does it mean that EZNEC agrees with my possibly flawed phase measurements? What does it mean that EZNEC agrees with my argument and disagrees with yours? How does one use a signal with unchanging phase to measure the phase shift through a coil or wire? Forgive me if I'm wrong, but seems to me, you have claimed to have done exactly that. Please explain how you did that so we can judge whether your measurements were also flawed. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222373 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: Message-ID: Date: Fri, 17 Mar 2006 00:02:45 GMT Reg Edwards wrote: > Discover the velocity factor, nano-seconds per meter, and other > numbers for your particular coil. Reg, would you care to share your formula for velocity factor? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222374 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Coils are transmission lines Date: Fri, 17 Mar 2006 00:21:53 +0000 (UTC) Message-ID: References: > But what about comparing different ways of obtaining the same > inductance to find those with higher or lower Q? ====================================== To double Q, whatever it is, just double length and diameter of the coil, wind on a number of turns of much thicker wire for the same inductance, and Bingo, Q is doubled. The value of Q is unecessary. Efficiency and bandwidth can be deduced by calculating from the known values of wire and radiation resistances. But I suppose Q, once available, would be a short cut to crudely estimating bandwidth. Additional information is needed. The loss in the coil may not be the dominating factor. What matters is the System Q. It can be considerably worse than coil Q. ---- Reg. Article: 222375 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Coils are transmission lines Date: Fri, 17 Mar 2006 01:12:38 +0000 (UTC) Message-ID: References: > > Reg, would you care to share your formula for velocity factor? ========================================== Cec, can't you find it in your bibles? Velocity = 1 / Sqrt( L * C) metres per second where L and C are henrys and farads per metre. What you really want to know is how to calculate L and C from coil dimensions. But you won't find that from any bible. As a special favour, I'll attach the source code for the program to an e-mail. Read it with a non-proportional text editor such as Notepad. In your discussions on the other thread you have mentioned a coil's self-resonant frequency. In the source code you will also find a formula for Fself. Which, again, cannot be found in any bible. It is a fairly straightforward 2 or 3-line formula. Fself is not used anywhere in the program. It is available solely out of interest. It is fairly accurate. I have measured it on many coils of all proportions and numbers of turns from 1 inch to 6 feet long with 1500 turns. ---- Reg, G4FGQ Article: 222376 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 01:24:36 GMT w8ji@akorn.net wrote: > I took the time to carefully outline what Roy's measurements and mine > would be significantly more reliable, and I see you disregarded that > also. You demanded that I defend my measurements so I removed them as evidence. Now I am requesting that you defend the use of a signal without phase to measure phase through a coil. That's a very simple request. If one refuses such a simple request to defend one's methods, what is one to think? I gave up on my measurements rather than defend them. If you don't defend yours, are you automatically giving up on them? If no, one might then wonder why you require me to defend my measurements while you refuse to defend yours. Gene says standing wave current doesn't carry any phase information. I concur. Roy says EZNEC agrees with my possibly flawed measurements. I concur. Since EZNEC disagrees with your conclusions about your measurements, and agrees with my conclusion about your measurements, could your conclusions possibly be flawed? I'm sure many readers would be interested in a detailed explanation of exactly how to use a signal with unchanging phase to measure the phase shift through a coil. I certainly would be more interested in that explanation than a boring tutorial on measurement techniques. Heck, even the IEEE would be interested in such a unique technique and it might even be patentable. You could start by explaining the center graphic in the following: http://www.qsl.net/w5dxp/3freq.gif One can't help but notice your absolute silence on that subject. > I'm very disappointed in your reaction to the effort I made to help you > understand measurement techniques. Reminds me of a T-shirt I saw. It read, "I'm from the government. I'm here 'to help you'." Logical diversions are very transparent - they even have names. That one is called "diverting the issue". The issue is not my measurements since I have withdrawn them as evidence. Seems that automatically makes your measurements the subject of the discussion. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222377 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: Message-ID: Date: Fri, 17 Mar 2006 01:34:45 GMT Reg Edwards wrote: > Velocity = 1 / Sqrt( L * C) metres per second Well now, W7EL, a pretty smart fellow questioned that equation, as I remember before a bottle of CA Sutter Home Cabernet Sauvignon, circa 2001. (Not bad for a 5 year old red.) Dr. Corum's equation is a mite more complicated involving fractional powers of diameter, turns per inch, and wavelength and it closely agreed with my self-resonant measurements. If we work backwards from Dr. Corum's fairly accurate VF, can we calculate the L and C of the coil? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222378 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Thu, 16 Mar 2006 17:48:30 -0800 Message-ID: <121k5bftea4vl3f@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> <1142558012.295624.174830@e56g2000cwe.googlegroups.com> art wrote: >. . . > A follow up qurestion would now be if an element was > made of a skin fashioned from aluminised mylar using a comparitive > aluminum volume aproach would any changes in radiation efficiency > weould occur? I can't answer that one because it makes no sense to me. Maybe someone else can give it a shot. > As a side note the contra current flow that I refferred to > was what it appears various straas of current flow that one sees > illustrated in text books would change radiation > as one aproaches a sigle strata where their is no contra flow, but let > us put that aside for another day. Guess I missed that posting. Current isn't stratified in a homogeneous conductor. But it sounds like some good stuff to use in explaining why some antenna or other has magical properties that have defied all the conventional thinkers for generations. > As another aside I have made an apparatus where I have placed to > parallel wires inside a glass tube ( flourescnt > lamp tube where I can draw a vacuum with some dust inside the tube so > the point of static flow can be observed > and then observe the cross over point when using thin > aluminised strip in the hope that for the same frequency > the same cross over point will be seen as the same. That makes no sense to me either. Time to pass the baton to someone who can understand what you're saying. Roy Lewallen, W7EL Article: 222379 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 02:20:13 GMT Cecil, I have to admit I am mostly lost about the meaning in your post below. However, nothing in my comments was intended in any way as support or denial of the measurements presented by Tom, W8JI. They look proper to me, but I am not an expert on such measurements. This entire thread is quite bizarre in that all sorts of special cases are being debated (Tesla coils????) while the simplest basic level of standing wave behavior is overlooked and even challenged. I suppose that's typical for RRAA. 73, Gene W4SZ Cecil Moore wrote: > w8ji@akorn.net wrote: > >> I took the time to carefully outline what Roy's measurements and mine >> would be significantly more reliable, and I see you disregarded that >> also. > > > You demanded that I defend my measurements so I removed them > as evidence. Now I am requesting that you defend the use of a > signal without phase to measure phase through a coil. That's > a very simple request. If one refuses such a simple request > to defend one's methods, what is one to think? > > I gave up on my measurements rather than defend them. If you > don't defend yours, are you automatically giving up on them? > If no, one might then wonder why you require me to defend my > measurements while you refuse to defend yours. > > Gene says standing wave current doesn't carry any phase > information. I concur. Roy says EZNEC agrees with my possibly > flawed measurements. I concur. Since EZNEC disagrees with your > conclusions about your measurements, and agrees with my conclusion > about your measurements, could your conclusions possibly be > flawed? I'm sure many readers would be interested in a > detailed explanation of exactly how to use a signal with > unchanging phase to measure the phase shift through a coil. > I certainly would be more interested in that explanation > than a boring tutorial on measurement techniques. Heck, even > the IEEE would be interested in such a unique technique and > it might even be patentable. > > You could start by explaining the center graphic in the following: > > http://www.qsl.net/w5dxp/3freq.gif > > One can't help but notice your absolute silence on that subject. > >> I'm very disappointed in your reaction to the effort I made to help you >> understand measurement techniques. > > > Reminds me of a T-shirt I saw. It read, "I'm from the > government. I'm here 'to help you'." > > Logical diversions are very transparent - they even have names. > That one is called "diverting the issue". The issue is not my > measurements since I have withdrawn them as evidence. Seems > that automatically makes your measurements the subject of the > discussion. Article: 222380 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 02:41:45 GMT w8ji@akorn.net wrote: > I'm suprised you wouldn't want to learn more about measurements. I'm surprised you wouldn't want to share your engineering knowledge, e.g. is it really possible to use a phaseless signal to measure phase shift? If so, please enlighten us. I can't figure out how to do it. Since you apparently have figured it out, please share your knowledge with us. > I don't see anything Roy said that disagrees with what I measured, so > that's a non-issue. Roy and I have previously agreed with your measurements. It's your conclusions about those measurements that he apparently doesn't seem to understand and neither do I. I'm certainly not speaking for Roy, but when he points out to you that my measurements agree with EZNEC, one wonders what that means in reality. > I take it you don't want to discuss how to make better measurements? I take it you don't want to share you knowledge of how to measure phase using a phaseless signal? Such a feat is extremely more important than any measurement discussion. Please just explain from a technical standpoint how a signal without phase can be used to measure a phase shift through a coil. That's an extremely simple request and would be extremely useful to the entire group. While you are at it, please explain the EZNEC results in the middle graphic at: http://www.qsl.net/w5dxp/3freq.gif. the request for which you seem to have forgotten about. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222381 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560863.044161.15920@u72g2000cwu.googlegroups.com> Message-ID: <0tpSf.1521$4L1.395@newssvr11.news.prodigy.com> Date: Fri, 17 Mar 2006 02:49:32 GMT w8ji@akorn.net wrote: > Cecil Moore wrote: >>You could start by explaining the center graphic in the following: >>http://www.qsl.net/w5dxp/3freq.gif > > I don't understand what it is and how you "constructed" it. Maybe you > can explain. I simulated a typical vertical base-loaded coil system using the helical coil feature of EZNEC. I found the resonant frequency and displayed the results in the left graphic. I then left everything else alone while I multiplied the resonant frequency by 2 and displayed the results in the middle graphic. I then multiplied the resonant frequency 3 and displayed the results in the right graphic. It's a no-brainer. Have you never done such with EZNEC? Would someone, somewhere, please explain the ~0.2 amps at the bottom of the coil in the middle configuration Vs the ~2.0 amps at the top of the coil? Is EZNEC reporting bogus results? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222382 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Coils are transmission lines Date: Fri, 17 Mar 2006 02:52:56 +0000 (UTC) Message-ID: References: <121k5168d8svq85@corp.supernews.com> L and C are neither in series or in parallel with each other. They are both DISTRIBUTED as in a transmission line. To calculate the self-resonant frequency what we are looking for is an equivalent shunt capacitance across the ends of the inductance. Turn to turn capacitance is is a very small fraction of the total capacitance. If there are 10 turns then there are 10 turn-to-turn capacitances all in series. After a few turns there is very little capacitance which can be considered to be across the coil. Consider two halves of the coil. We have two large cylinders each of half the length of the coil. Diameter of the cylinders is the same as coil diameter. Nearly all the capacitance across the coil is that due to the capacitance between the two touching cylinders (excluding their facing surfaces). The formula for VF is true for any transmission line with distributed L and C. And a coil has distributed L and C. Agreed, L and C are approximations for very short fat coils. But any approximation is far better than none at all. All antennas have to be pruned at their ends. ---- Reg. "Roy Lewallen" wrote > Velocity = 1 / Sqrt( L * C) metres per second > > > > where L and C are henrys and farads per metre. > > > What seems to be getting lost in the discussion is that L is *series* L > per meter and C is *shunt* C per meter -- that is, the C to another > conductor(*). C is not the self-capacitance of the inductor. > > (*) Conductors also have capacitance to free space, but I'm not at all > sure the transmission line equations for such things as velocity are > valid if this is used for C. The equation for the resonant length of a > wire in space is very complex and can't be solved in closed form, and > even approximate formulas are much more complex than those for > transmission lines. So while transmission lines and antennas -- or > radiating inductors -- share some characteristics, you can't blindly > apply the equations for one to the other and expect valid results. > > Roy Lewallen, W7EL Article: 222383 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 02:54:25 GMT John Popelish wrote: > It seems > that this is nearly what you are demonstrating with your EZNEC > examples. Electrical length (propagation distance) is collapsing into > the inductor. Please explain how that could be possible with constant magnitude and phase of the currents through the coil. The magnitude and phase is absolutely constant according to the presuppositions of the lumped-circuit model. How could it possibly collapse? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222384 of rec.radio.amateur.antenna Date: Thu, 16 Mar 2006 20:58:16 -0600 From: Tom Ring Subject: Re: Current through coils References: <1211ig3hafcm451@corp.supernews.com> <1142003771.861185.56110@e56g2000cwe.googlegroups.com> <1142040868.926875.4670@j33g2000cwa.googlegroups.com> <1142078065.701187.54500@i40g2000cwc.googlegroups.com> <0NzQf.132$tN3.62@newssvr27.news.prodigy.net> Message-ID: <441a25ca$0$7322$39cecf19@news.twtelecom.net> Cecil Moore wrote: > Reg Edwards wrote: > >> A 100 turn coil, 10 inches long, 2 inches in diameter, has an >> inductance of 102 microhenrys, a Q of aproximately 380 at F = 1.9 MHz, >> and the self-resonant frequency is 12.0 MHz. > > > I'll bet the measured self-resonant frequency would be lower > if mounted as a base-loading coil on my pickup. > > Seems the VF of the coil is 0.041 based on 10" being 1/4WL > at 12 MHz. Assuming that VF holds down to 1.9 MHz we > can calculate the electrical length of the coil on 1.9 MHz > which will be the same as the phase shift through the coil. > > So I get about ~14 degrees of phase shift through that coil > at 1.9 MHz assuming the self-resonant frequency really > is 12 MHz at the spot where the coil is mounted. > > If the coil were used on 3.8 MHz, the phase shift would > be ~28 degrees. > > But my 75m bugcatcher coil shows to be self-resonant at > 6.6 MHz while sitting there on my pickup being driven > by an MFJ-259B. It is 6.5" long. When 6.5" is 1/4WL > at 6.6 MHz, the VF = 0.0145, considerably lower than > the coil above and operating much closer to its self- > resonant frequency. > > A length of 6.5" coil with a VF of 0.145 on 4 MHz is > ~55 degrees of phase shift. And indeed the net current > at the top of the coil drops to about 2/3 of what it > is at the bottom. Ok, I have had a thought. And I had to go back to where everyone, starting with Cecil, was talking about or responding to a constant delay through the coil. Picking a nice round number, say 55 degrees, I would then need 35 degrees of whip above that coil to make a quarter wave resonant antenna, correct? So, it should work just as well, using Cecil's reasoning, if I displace that coil to another position. He did measure the coil as a standalone device which causes a fixed delay, correct? Ok, so now I move that coil up the antenna, not much, say 2 degrees. Now I have 2 degrees below the coil, and 33 above it. It will still be resonant, right? Now I move it another 2, and another and another, until it it at the top, with no stinger. With the reasoning I have heard from Cecil, it will always be resonant. tom K0TAR Article: 222385 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <713h125fsterthf8j8gq5bsq53fs1ijcar@4ax.com> <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> Message-ID: <9BpSf.1524$4L1.426@newssvr11.news.prodigy.com> Date: Fri, 17 Mar 2006 02:58:13 GMT Gene Fuller wrote: > However, nothing in my comments was intended in any way as support or > denial of the measurements presented by Tom, W8JI. They look proper to > me, but I am not an expert on such measurements. How about his conclusions about those measurements? Maybe you can help him out. How does one measure the phase shift through a coil using a signal that doesn't support phase? If there is a way, I and others would certainly like to know about it. So far, I confess that I haven't been able to figure it out. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222386 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142003771.861185.56110@e56g2000cwe.googlegroups.com> <1142040868.926875.4670@j33g2000cwa.googlegroups.com> <1142078065.701187.54500@i40g2000cwc.googlegroups.com> <0NzQf.132$tN3.62@newssvr27.news.prodigy.net> <441a25ca$0$7322$39cecf19@news.twtelecom.net> Message-ID: Date: Fri, 17 Mar 2006 03:19:59 GMT Tom Ring wrote: > Picking a nice round number, say 55 degrees, I would then need 35 > degrees of whip above that coil to make a quarter wave resonant antenna, > correct? No, that is a myth spread by some people as a strawman argument. Please don't support that strawman. The requirement for resonance at the feedpoint is that the phasor sum of the forward and reflected voltages be in phase with the phasor sum of the forward and reflected currents. Therefore, 90 degrees is *NOT* required in the round trip. Indeed, the round trip for the voltage doesn't have to be the same number of degrees as the round trip for the current. That is a misconception spawned by the lumped-circuit model where everything is perfect and waves travel faster than the speed of light. The real world is not so perfect. Given that the resonant feedpoint impedance equals (Vfor+Vref)/(Ifor+Iref) isn't it obvious that the individual components are not required to have the same phase? For instance, Vfor could be at +50 degrees, Vref could be at -40 degrees, Ifor could be at +20 degrees, Iref could be at -10 degrees, and the feedpoint impedance would still be resistive. The coil distorts the heck out of the phase relationships between the voltages and the currents. Why is it surprising that the result is unpredictable and needs an antenna analyzer to find the resonant frequency? Factor in that the lowest 50 ohm SWR may not be at the purely resistive point and what do you have? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222387 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560863.044161.15920@u72g2000cwu.googlegroups.com> <0tpSf.1521$4L1.395@newssvr11.news.prodigy.com> Message-ID: Date: Fri, 17 Mar 2006 03:24:34 GMT John Popelish wrote: > It looks like various magnitudes that you would find at 2 points along a > standing wave, with various fractions of the wave in the inductor as > frequency changes. In spite of hitting these various magnitude values, > there are still only two phases, 0 or 180 anywhere outside the coil. In > some cases, the standing wave goes through a node, inside the coil and > reverses phase from one end of the coil to the other. Exactly! Now please explain how the nS delay through a coil could possibly be measured using a signal that abruptly shifts fixed phase by 180 degrees every 180 degrees. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222388 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Coils are transmission lines Date: Thu, 16 Mar 2006 19:25:57 -0800 Message-ID: <121kb283v4krv87@corp.supernews.com> References: <121k5168d8svq85@corp.supernews.com> Of course I understand that both L and C are distributed. But the C in the transmission line formula isn't a longitudinal C like the C across an inductor; it's the (distributed, of course) shunt C between the two conductors of the transmission line. I don't believe you can justify claiming that the C across an inductor is even an approximation for the C from the inductor to whatever you consider to be the other transmission line conductor. Roy Lewallen, W7EL Reg Edwards wrote: > L and C are neither in series or in parallel with each other. > > They are both DISTRIBUTED as in a transmission line. > > To calculate the self-resonant frequency what we are looking for is an > equivalent shunt capacitance across the ends of the inductance. > > Turn to turn capacitance is is a very small fraction of the total > capacitance. If there are 10 turns then there are 10 turn-to-turn > capacitances all in series. After a few turns there is very little > capacitance which can be considered to be across the coil. > > Consider two halves of the coil. We have two large cylinders each of > half the length of the coil. Diameter of the cylinders is the same as > coil diameter. Nearly all the capacitance across the coil is that due > to the capacitance between the two touching cylinders (excluding their > facing surfaces). > > The formula for VF is true for any transmission line with distributed > L and C. And a coil has distributed L and C. > > Agreed, L and C are approximations for very short fat coils. But any > approximation is far better than none at all. All antennas have to be > pruned at their ends. > ---- > Reg. > "Roy Lewallen" wrote > >> Velocity = 1 / Sqrt( L * C) metres per second >>> where L and C are henrys and farads per metre. >>> >> What seems to be getting lost in the discussion is that L is > *series* L >> per meter and C is *shunt* C per meter -- that is, the C to another >> conductor(*). C is not the self-capacitance of the inductor. >> >> (*) Conductors also have capacitance to free space, but I'm not at > all >> sure the transmission line equations for such things as velocity are >> valid if this is used for C. The equation for the resonant length of > a >> wire in space is very complex and can't be solved in closed form, > and >> even approximate formulas are much more complex than those for >> transmission lines. So while transmission lines and antennas -- or >> radiating inductors -- share some characteristics, you can't blindly >> apply the equations for one to the other and expect valid results. >> >> Roy Lewallen, W7EL > > Article: 222389 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 03:26:12 GMT John Popelish wrote: > Cecil Moore wrote: >> Please explain how that could be possible with constant >> magnitude and phase of the currents through the coil. >> The magnitude and phase is absolutely constant according >> to the presuppositions of the lumped-circuit model. How >> could it possibly collapse? > > Have I claimed that the lumped model strictly applies? ;-) No, but someone else has. ;-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222390 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Thu, 16 Mar 2006 19:30:44 -0800 Message-ID: <121kbb65cj0om31@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> John Popelish wrote: > Roy Lewallen wrote: > (snip) >> You can compensate for the loss, yes, by increasing the surface area. >> The way you reduce loss is to provide a large cross-sectional area for >> the current to flow through. > > The problems I have with this approach is that the larger conductor > (only the outside of which is contributing to conductivity) is blocking > the path of more and more flux, crowding it into the space that is > left. It is a matter of gaining some and losing some (hopefully less). I'm sorry, I don't understand this. Can you elaborate? In what way does increasing a wire's diameter block the path of existing current and cause crowding? When a wire's diameter is at least many times the skin depth, the RF conductivity of the wire is directly proportional to the surface area of the wire, hence to its circumference or diameter. So in what way does this blocking and crowding manifest itself, and what would be the relationship between area and conductivity if it didn't occur? Roy Lewallen, W7EL Article: 222391 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Fri, 17 Mar 2006 03:38:34 +0000 (UTC) Message-ID: References: <1142003771.861185.56110@e56g2000cwe.googlegroups.com> <1142040868.926875.4670@j33g2000cwa.googlegroups.com> <1142078065.701187.54500@i40g2000cwc.googlegroups.com> <0NzQf.132$tN3.62@newssvr27.news.prodigy.net> <441a25ca$0$7322$39cecf19@news.twtelecom.net> Wanna bet? The phase shift along the coil plus the phase shift along antenna conductors does NOT add up 90 degrees when the antenna is 1/4-wave resonant. It is not anywhere near to it. Article: 222392 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 19:53:52 -0800 Message-ID: <121kcmhiqfk2r47@corp.supernews.com> References: <1142003771.861185.56110@e56g2000cwe.googlegroups.com> <1142040868.926875.4670@j33g2000cwa.googlegroups.com> <1142078065.701187.54500@i40g2000cwc.googlegroups.com> <0NzQf.132$tN3.62@newssvr27.news.prodigy.net> <441a25ca$0$7322$39cecf19@news.twtelecom.net> Reg Edwards wrote: > Wanna bet? > > The phase shift along the coil plus the phase shift along antenna > conductors does NOT add up 90 degrees when the antenna is 1/4-wave > resonant. It is not anywhere near to it. The first problem is that the phase shift along the antenna is about zero. Having the phase shift along the antenna and coil add to 90 degrees would require a 90 degree shift of current phase across the coil, regardless of the size of the coil or the antenna. Only the inductor in an EH antenna drive system has that magical property. I assume you have to empty the internal coulomb bucket periodically, but I'm sure that's proprietary. Pluck a guitar string and watch it oscillate. Notice that all parts of the string reach their maximum and minimum excursions at the same time. There's no delay from one point to another. Same thing happens on a (standing wave) antenna or a shorted or open transmission line, and for the same reason. Roy Lewallen, W7EL Article: 222393 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Thu, 16 Mar 2006 20:07:27 -0800 Message-ID: <121kdg17arvj08a@corp.supernews.com> References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> w8ji@akorn.net wrote: > Cecil Moore wrote: >> w8ji@akorn.net wrote: >>> I'm suprised you wouldn't want to learn more about measurements. >> I'm surprised you wouldn't want to share your engineering >> knowledge, e.g. is it really possible to use a phaseless >> signal to measure phase shift? If so, please enlighten us. >> I can't figure out how to do it. Since you apparently have >> figured it out, please share your knowledge with us. > > I think you are the one with a problem, not me. I don't know what a > "phaseless" signal is. Does it come from a phaseless signal generator > through phaseless transmission lines?? > >>> I don't see anything Roy said that disagrees with what I measured, so >>> that's a non-issue. > >> Roy and I have previously agreed with your measurements. It's >> your conclusions about those measurements that he apparently >> doesn't seem to understand and neither do I. I'm certainly not >> speaking for Roy, but when he points out to you that my >> measurements agree with EZNEC, one wonders what that means >> in reality. > > I haven't seen Roy question anything and he hasn't told me he doesn't > understand anything. > > Can you requote his post where he said that, or should I take your word > for that along with the phaseless signal?? "Phaseless signals". What an imaginative creation. If you measure zero phase angle between two points, you *have* measured the phase shift between them, and it's zero. Sounds like what Cecil is looking for is a way to measure a non-zero phase shift when the phase shift is in fact zero, to make it fit his theory. Sorry, it's zero. Period. If that doesn't fit the theory, then the theory is faulty. I said that Cecil's phase measurements agree with EZNEC (and generally accepted theory) -- there should be almost no phase shift in the current along the wire. I also said that I couldn't say whether his amplitude measurements are correct, since Cecil didn't say (at least in the quoted posting I saw) what the positions along the wire were, just their distance from each other. But it's a trivial thing to model with EZNEC, so anyone can easily see and judge for himself. With an antenna that simple, any disagreement between EZNEC and measurements is almost certain to be due to either measurement error or failure to make the antenna like the model, e.g., prevent common mode feedline currents. Roy Lewallen, W7EL Article: 222394 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Thu, 16 Mar 2006 20:16:03 -0800 Message-ID: <121ke06ev9jep86@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> <121kbb65cj0om31@corp.supernews.com> John Popelish wrote: > > Take it to the extreme case. make the conductor diameter the average > coil diameter. Then there is little space for the total coil flux to > pass through. > >> In what way does increasing a wire's diameter block the path of >> existing current and cause crowding? > (snip) > > It doesn't block current, it blocks flux from other turns of the same > coil, reducing the inductance and lowering the Q. > > I am thinking that there must be a better conductor cross section than a > big fat round cross section, a ribbon, perhaps, aligned edgewise to the > local flux, to increase the conductivity while not blocking much, the > coil flux. Thanks for the elaboration. I didn't realize you were talking about the wire used to make a coil, but thought you (and Art) were talking about skin depth in conductors in general. The discussion gets much more complex when talking about an inductor with its linked flux. Even when there's no flux coupled from other turns, current bunches at the edges of a flat conductor, giving it a higher resistivity than a round conductor of the same surface area. So that's a point against using a flat conductor, although other factors might -- or might not -- still tilt the balance in its favor. Proximity effect is another factor which alters current distribution and therefore resistivity and Q in an inductor, so there are a number of trades to be made. Roy Lewallen, W7EL Article: 222395 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Coils are transmission lines Date: Fri, 17 Mar 2006 04:21:38 +0000 (UTC) Message-ID: References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <7P6dnXiIS9NSsofZRVn-pw@adelphia.com> I don't understand what you are trying to say. Express yourself, less ambiguously, in fewer words. Or perhaps you are nit-picking. I can't tell. I have just explained that the resulting capacitance between adjacent conductors in a coil is very small in comparison with the capacitance of a large solid cylinder (of the same diameter as the coil) to the rest of the world. The capacitance to the rest of the world includes electric lines of force from one half of the cylinder to the other, especially from one end to the other. The capacitance of the coil we are dealing with has very little to do with coil turns. ---- Reg. "John Popelish" wrote in message news:7P6dnXiIS9NSsofZRVn-pw@adelphia.com... > Roy Lewallen wrote: > > Of course I understand that both L and C are distributed. But the C in > > the transmission line formula isn't a longitudinal C like the C across > > an inductor; it's the (distributed, of course) shunt C between the two > > conductors of the transmission line. I don't believe you can justify > > claiming that the C across an inductor is even an approximation for the > > C from the inductor to whatever you consider to be the other > > transmission line conductor. > > Agreed. They are as different as a shunt element and a series element > in a pi filter. Article: 222396 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 04:27:00 GMT w8ji@akorn.net wrote: > I think you are the one with a problem, not me. I don't know what a > "phaseless" signal is. Does it come from a phaseless signal generator > through phaseless transmission lines?? I apologize, but I actually have to plead complete ignorance on this subject. You seem to be the expert on using phaseless signals to measure phase. But I'm willing to learn and it is certainly considerably more interesting than a tutorial on measurements. > I haven't seen Roy question anything and he hasn't told me he doesn't > understand anything. > > Can you requote his post where he said that, or should I take your word > for that along with the phaseless signal?? Please stop asking me to do your research for you. I'm a very busy person anchoring the bass section in my Methodist Choir's Easter music and performing a very demanding solo. Have you any idea how difficult it is for a Homo Sapien to hit low-low C? Roy said about my measurements: "The measurement looks good to me. The phase is exactly what EZNEC predicts -- constant along the wire. The ratio in magnitudes we'd expect depends on the positions along the wire, not just the spacing. Roy Lewallen, W7EL" That's why I withdrew my "flawed" measurements and offered Roy's "exactly" observation instead. I'm thinking back and it seems to me that Roy reported his measurements without drawing strange conclusions about them. But you can lay all the objections to waste simply by explaining how to measure phase using a source signal that doesn't change phase. You have asserted that you have done it. Please tell us how. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222397 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560863.044161.15920@u72g2000cwu.googlegroups.com> <0tpSf.1521$4L1.395@newssvr11.news.prodigy.com> <7P6dnXuIS9N8rYfZRVn-pw@adelphia.com> Message-ID: Date: Fri, 17 Mar 2006 04:29:20 GMT John Popelish wrote: > The only way I can see to do it is to go outside the coil and look at > how the standing current nodes move. Standing wave phase is with > respect to position, not time. Well John, you are obviously not up on the latest techniques. (But neither am I.) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222398 of rec.radio.amateur.antenna From: David Subject: Looking to contract someone to design antenna Message-ID: <%YqSf.8491$dy4.6755@news-server.bigpond.net.au> Date: Fri, 17 Mar 2006 04:31:55 GMT Hi, I am looking for someone who would be interested in designing a Yagi antenna under contract. (Paper design is fine, I can construct and test the unit). The frequency band required is 915 - 928 MHz I prefer a design that is simple to make such as elements though beam, welded in place. The design needs to be reasonably short (Beam length less than 300mm). The material I have freely available is 6mm solid aluminium rod (and larger if needed), 12.8mm square aluminium tube (or larger if required) but have difficulty obtaining smaller than this. Power handling is not critical as max. power is 1 Watt. Units will be used in vertical orientation and beam width is not critical. Required gain is at least 6dB (4 or 5 element should suffice). Feed line is 50 Ohms coaxial cable. SWR across band target < 1.4 : 1 Maybe folded element would be the simplest to match to with a balun even though I have to create the bends. I expect the dipole can be held in place by small plastic enclosure that isolates the radiator from the beam and enables connections to balun and feed line via cable glands ? Please email me direct if you are interested. Thanks regards David Article: 222399 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121hip9t8og871b@corp.supernews.com> <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <7P6dnXqIS9OUrIfZRVn-pw@adelphia.com> Message-ID: Date: Fri, 17 Mar 2006 04:31:50 GMT John Popelish wrote: > "Did you hear what he said about your wife?" Whatever he said is probably true. My ex-wife made off with $3 mil of my hard-earned dollars in 1984. I've never trusted a female since. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222400 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> <121kdg17arvj08a@corp.supernews.com> Message-ID: Date: Fri, 17 Mar 2006 04:37:40 GMT Roy Lewallen wrote: > "Phaseless signals". What an imaginative creation. Well not really, if you think about it, the phase of a DC signal can be considered to be zero everywhere. The phase of a standing wave current *is* zero everywhere on a 1/2WL thin-wire dipole. Seems to me, a standing- wave current indeed does have a lot in common with a DC current. But that might just be a coincidence. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222401 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <7P6dnXqIS9OUrIfZRVn-pw@adelphia.com> Message-ID: Date: Fri, 17 Mar 2006 05:31:35 GMT John Popelish wrote: > Cecil Moore wrote: >> Whatever he said is probably true. My ex-wife made >> off with $3 mil of my hard-earned dollars in 1984. >> I've never trusted a female since. > > This factoid brings several apparently unrelated things into focus for me. Remember the Koala Pad? I was VP of Engineering and a couple of those patents are in my name. Koala Technologies could not survive the president's divorce and my divorce at the same time. The venture capitalists pulled the plug. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222403 of rec.radio.amateur.antenna Date: Fri, 17 Mar 2006 01:22:01 -0700 From: BKR Subject: Re: Phase shift circuits References: Message-ID: <441a71b6@nntp.zianet.com> Look up the Turnstile antenna on the web and you should see the radiation pattern of a 90 degree phase shift. There is also a small amount of gain over a single dipole. Most examples are for VHS, but they can be scaled up. KD5RPO Harry Gross wrote: > Thanks for all the input. I'll be playing with the idea for the next > few weeks/months, and I'll let you all know how it works out. Article: 222404 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Fri, 17 Mar 2006 02:05:58 -0800 Message-ID: <121l2g8gk2ep0e4@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> <121kbb65cj0om31@corp.supernews.com> <121ke06ev9jep86@corp.supernews.com> John Popelish wrote: > . . . > Is proximity effect essentially the effect of the local flux (that falls > off at 1/r) that wraps around the neighboring conductor in a coil that > causes conductivity distortions in its neighbors that are in addition to > the crowding caused by the flux around the current through the conductor > segment in question? Or is it another effect, entirely? I believe what you're describing is the cause of skin effect. Proximity effect is a redistribution of current around a conductor due to the flux >from one turn interacting with the current in the adjacent turn. One of the simpler explanations I've seen is in Johnson & Graham, _High-Speed Signal Propagation: Advanced Black Magic_, and their quantitative and non-mathematical explanation requires seven paragraphs and two figures. Roy Lewallen, W7EL Article: 222405 of rec.radio.amateur.antenna From: "Cecil Moore" References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> Subject: Re: Coils are transmission lines Message-ID: <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Date: Fri, 17 Mar 2006 14:54:50 GMT wrote: > Any answer, even if just an educated guess, is better than giving no > answer at all. No matter how far off. An answer that is completely wrong is better than no answer at all? Speaking of answers, here is a question to which you have, so far, avoided giving an answer. In the graphic at: http://www.qsl.net/w5dxp/3freq.gif , the currents in the center graphic reported by EZNEC are: The current at the bottom of the coil is 0.17 amps with a phase angle of -1.72 degrees. The current at the top of the coil is 2.0 amps with a phase angle of -179.6 degrees. The current at the top of the coil is about 12 times the magnitude of the current at the bottom of the coil. The phase shift through the coil is about 178 degrees. Once again, please explain those results. Thanks in advance. -- 73, Cecil, W5DXP Article: 222406 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Fri, 17 Mar 2006 09:19:16 -0600 Message-ID: <18781-441AD374-1466@storefull-3252.bay.webtv.net> References: Reg wrote: "Wanna bet?" Don`t bet against Reg. Phase shift aling the coil plus the phase shift along the conductors DOES add up to 90 degrees when the antenna is 1/4-wave resonant. Recall the purpose of the coil is electrically to make the too-short whip appear full-sized. The assembly is resonant when worked against the earth. Its plus and minus 90-degree reactances are equal in magnitude to each other. Best regards, Richard Harrison, KB5WZI Article: 222407 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> <121kdg17arvj08a@corp.supernews.com> <1142596786.484861.188720@i39g2000cwa.googlegroups.com> Message-ID: <4SASf.2253$bn3.2076@bgtnsc04-news.ops.worldnet.att.net> Date: Fri, 17 Mar 2006 15:47:12 GMT Cecil, I never in my wildest dreams said anything about Tom's measurements. (Perhaps in your dreams.) I don't believe that Tom set up a simple standing wave antenna and then tried to measure the phase of the standing wave. You seem to have forgotten, but a few days ago you were vehemently arguing that the bugcatcher coil in your mobile antenna must have X amount of phase shift. My comments, which may have proven too successful, dealt only with the basic fundamental properties of waves. That's the sort of thing that everyone should have learned in elementary school, but such knowledge seems to be fleeting for some people. 73, Gene W4SZ Cecil Moore wrote: > w8ji@akorn.net wrote: > >> It sounds like Cecil is trying to find a way to make his theory fit >> despite the fact that models and measurements show the phase shift is >> zero, and demanding I agree with his unusual theories like current >> that doesn't flow, phaseless signals, and in his latest post antennas >> behaving like dc circuits. > > > Again, it is not my theory. It is the distributed network model > known to succeed when the lumped-circuit model fails in the presence > of standing waves. There is no useful phase information left in > a standing wave current. DC current and standing wave current are > equally 100% ineffective at measuring the delay through a coil. > > I have asked this technical question multiply times: How does one > use a signal with unchanging phase to measure the delay through a > coil? The answer is that one cannot. > >> All that aside, it appears the main argument is Cecil's theory requires >> measuring current that doesn't flow ... > > > No, using a signal with unchanging phase to try to measure delay > is your main argument, not mine. I know it is foolish to measure > a current with unchanging phase. Any phase measurement is > meaningless. > > cos(kz)*cos(wt) doesn't possess phase information. One can > tell that from the formula. Unlike you, Gene Fuller understands > the meaning of those standing wave equation terms. > > > Gene Fuller wrote: > >>> In a standing wave antenna problem, such as the one you describe, > > >> there is no remaining phase information. Any specific phase > >> characteristics of the traveling waves died out when the startup > >> transients died out. > >>> >>> Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be > > >> seen again. > >>> >>> The only "phase" remaining is the cos (kz) term, which is really > > >> an amplitude description, not a phase. > > Do you disagree with what Gene had to say? > > "PHASE IS GONE. KAPUT. VANISHED. CANNOT BE RECOVERED. NEVER TO BE > SEEN AGAIN." In other words, one cannot use standing wave current > to measure the delay through a coil. Delay doesn't exist in a standing > wave current, i.e. "PHASE IS GONE." > >> The worse part of that is he is >> demanding I answer something I cannot answer ... > > > There's nothing wrong with admitting ignorance. Just please cease > trying to disguise your ignorance as some technical fact. When > are you going to correct the technical errors on your web page? > > 75m mobile bugcatcher loading coils possess a velocity factor > of approximately 0.0175. They are about 6.6 inches long. The > delay through that coil is ~0.128 wavelength at 4 MHz. That's > a delay of 32 degrees. That's how much electrical length the > coil is occupying when it is used on 4 MHz. Article: 222408 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Fri, 17 Mar 2006 16:03:32 GMT Cecil, 1. I have looked at that figure, and I suspect many others have as well. There is no information given about dimensions or any other modeling conditions, so it is difficult to say anything more than, "Yep, there's a bunch of lines and numbers on that figure." 2. As I pointed out recently, a phase shift of 178 degrees is really a phase shift of 2 degrees. It is a common, but unfortunate, convention that the ordinary sign reversal of a sinusoidal function is deemed a "phase shift" or "phase reversal". The only "phase" worth discussing is the one that occurs inside the argument for the sinusoidal function. That phase does not typically undergo sudden jumps or reversals. 73, Gene W4SZ Cecil Moore wrote: > > Speaking of answers, here is a question to which you have, so far, > avoided giving an answer. > > In the graphic at: http://www.qsl.net/w5dxp/3freq.gif , the currents > in the center graphic reported by EZNEC are: > > The current at the bottom of the coil is 0.17 amps with a phase angle > of -1.72 degrees. > > The current at the top of the coil is 2.0 amps with a phase angle of > -179.6 degrees. > > The current at the top of the coil is about 12 times the magnitude of > the current at the bottom of the coil. > > The phase shift through the coil is about 178 degrees. > > Once again, please explain those results. Thanks in advance. > -- > 73, Cecil, W5DXP > > Article: 222409 of rec.radio.amateur.antenna From: "Cecil Moore" References: <1142503649.315716.97920@j52g2000cwj.googlegroups.com> <1142514625.406329.65530@u72g2000cwu.googlegroups.com> <%khSf.56996$Jd.29555@newssvr25.news.prodigy.net> <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> <121kdg17arvj08a@corp.supernews.com> <1142596786.484861.188720@i39g2000cwa.googlegroups.com> <4SASf.2253$bn3.2076@bgtnsc04-news.ops.worldnet.att.net> Subject: Re: Current through coils Message-ID: Date: Fri, 17 Mar 2006 16:40:05 GMT "Gene Fuller" wrote: > I never in my wildest dreams said anything about Tom's measurements. Of course not and I certainly didn't mean to imply otherwise. What you said was *objective and impersonal*, applicapable to anyone's measurements and also applies directly to Tom's earlier measurements. > I don't believe that Tom set up a simple standing wave antenna and then > tried to measure the phase of the standing wave. Maybe we should ask him. As I understand it, both Tom and Roy set up a simple loaded 1/4WL resonant *standing wave* monopole and measured the standing wave current at the bottom and top of the coil. EZNEC could have told them that they wouldn't measure any phase shift around the coil or anywhere else around along the antenna.. It's an easy mistake to make to look at the current displayed by EZNEC and picture that current flowing from the feedpoint to the tip while being 100% radiated in the process so the current falls to zero at the tip of the antenna. As we know, those are not the technical facts. The reflected wave is a large percentage of the forward wave. As seen from the graphic at: http://www.qsl.net/w5dxp/3freq.gif that standing wave current can have virtually any magnitude but has a phase that comes only in near-zero or near-180 degrees increments. I've been asking how to obtain phase information from a standing wave current. Nobody has answered. -- 73, Cecil, W5DXP Article: 222410 of rec.radio.amateur.antenna From: "Cecil Moore" References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Subject: Re: Coils are transmission lines Message-ID: Date: Fri, 17 Mar 2006 16:48:27 GMT "Gene Fuller" wrote: > 1. I have looked at that figure, and I suspect many others have as well. > There is no information given about dimensions or any other modeling > conditions, so it is difficult to say anything more than, "Yep, there's > a bunch of lines and numbers on that figure." The EZNEC file is available for the asking. Do you want a copy? I will add the antenna specs to the bottom of the graphic. -- 73, Cecil, W5DXP Article: 222411 of rec.radio.amateur.antenna From: "Cecil Moore" References: Subject: Re: Coil Current Summary Message-ID: Date: Fri, 17 Mar 2006 17:03:33 GMT "John Popelish" wrote: > Cecil Moore wrote: > > There is no useful phase information in standing wave > > current. Therefore, standing wave current cannot be used > > to determine the percentage of a wavelength that is > > occupied by the coil. > > I think I disagree with this. A standing wave has one of two phases > with respect to time, but the two waves traveling through both the > antenna elements and any loading coils do have phase shifts, both with > respect to time and with respect to position. But when the two waves > are superposed, all that is left of this phase information is phase > with respect to position. The phase shift of both the single > direction waves can be inferred by the shift in position of where they > combine to form a node (if you make the (reasonable?) assumption that > the delay in both directions is equal. I don't disagree with you so I need to rephrase my apparently poorly worded statement above to make it more understandable. > There is information about this in the amplitude versus position of > the standing wave. But the only very definite points in this > variation are the nodes, so is the length is less than a half > wavelength, you have only the node at the end to work with, so you > have to use the sinusoidal amplitude curve to work with. > Or the velocity factor of the traveling waves can be measured by the > interference pattern they produce as a standing wave. One cycle of > the standing amplitude wave has to occupy the length that carries one > cycle of the traveling wave. I agree, one can use knowledge and indirect methods. That's exactly what I do and have been recommending. You and I seem to be in agreement. -- 73, Cecil, W5DXP Article: 222412 of rec.radio.amateur.antenna Message-ID: <441AEC80.263F33@scotchtapes.com> From: Scotty Subject: Re: RTV Silicone And Coax Outer Jacket: Safe ? References: Date: Fri, 17 Mar 2006 17:06:09 GMT Scotch® Self-Fusing Silicone Rubber Electrical Tape 70 1 in x 30 ft This is a high-temperature, arc-and track-resistant tape composed of self-fusing, inorganic silicone rubber with an easy-tear and easy-strip liner. Packed 1 per box, 10 per carton with 50 per case. Article: 222413 of rec.radio.amateur.antenna From: "Snide" References: <441890ae$0$1147$7a628cd7@news.club-internet.fr> <1142552477.603813.237860@i39g2000cwa.googlegroups.com> Subject: Re: compact antenna for short range direction finding Date: Fri, 17 Mar 2006 18:27:17 +0100 Message-ID: <441af17c$0$1146$7a628cd7@news.club-internet.fr> the problem is that the finder will be mounted in a vehicle, and can't be rotated, unless with a motor. I would avoid such a mecanic system, and I'm rather interested in an circular antenna or array of antennas. Denis Article: 222414 of rec.radio.amateur.antenna From: "Cecil Moore" References: Subject: Re: Coil Current Summary Message-ID: Date: Fri, 17 Mar 2006 18:01:14 GMT "John Popelish" wrote: > The real revelation for me, from this discussion is how the concept of > "phase" takes a dimensional jump (from time to position) when you > change from taking about a traveling wave to the standing wave that > results from the superposition of a pair of oppositely traveling waves > of the same frequency. Yet some people continue to argue that standing wave current is the same in form and function as traveling wave current. There certainly is quite a difference between cos(kz)*cos(wt) and cos(kz+wt) -- 73, Cecil, W5DXP Article: 222415 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: ANTENNA SHARING Date: Fri, 17 Mar 2006 11:40:09 -0600 Message-ID: References: <1142271577.733440.280370@p10g2000cwp.googlegroups.com> I don't think its quite that simple (circulator) and I'm not sure how the circulator solves the problem particularly if it has only two ports. In addition a circulator for 30-512 probably isn't in existence. Perhaps more explanation is needed on this, Dan. This depends on the actual frequencies. A diplexer must have two non-overlapping frequency ranges to "split" in two. Like one is 30 - 90 and the other is 100-512. Each can be quite wide. What your post has is OVERLAPPING frequencies and that is a problem. If one was 30-90 and the other 120-512 that would be easier. There are units that are quite inexpensive that will do 2-150 and 200-512. You seem to have the correct idea about the impedance "seen" at one, but at the frequency of the other, but this applies when using some methods, not all. If the two radios will be operated at the same time, then the problem is more strict in the requirements of the method used. When one transmitter is transmitting, it puts considerable power into the system at the transmit frequency, and harmonics as you well know, however, a transmitter also puts out considerable NOISE all over the place. There is typically more noise nearer to the transmit frequency. This noise must be reduced to prevent it >from desensing the other receiver and this may require additional filtering. I know this makes things more difficult, but from your post, it looks that way. 73, Steve, K,9.D;C'I "Dan Andersson" wrote in message news:SSKdnUw3lvL2fYjZSa8jmw@karoo.co.uk... > Big Nose wrote: > > > Currently I am looking into the problem of using a common antenna for > > two VHF transceivers. One operates 30 - 90 MHz and the other from 30 - > > 512 MHz. They would both be tuned into seperate frequencies and need > > to share a common broadband, omni directional, vertical monopole. > > > > I think I am getting myself a bit confused (or should I say more > > confused), do I need to used a diplexer? Would a T piece not suffice > > as both sets would be tuned to different frequencies and seperation and > > harmonics would be considered? Would these factors not mean that the > > input impedance to the set tuned into the different frequency would > > remain high thus not effect matching? > > > Simple... > > Get a two port circulator. That'll solve your problem ( but at a price. Try > E-Bay ). At your low frequencies, try build one yourself. > > Regarding the impedance, that is not that problematic. You can basically > transform any impedance to your taste. You will incur signal loss tho'. > > Also, as you unfortunately are looking at the lower end of the RF spectra, > all these parts will be bulky but it's still possible. > > > Cheers > > > Dan / M0DFI Article: 222416 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coil Current Summary References: Message-ID: Date: Fri, 17 Mar 2006 18:50:50 GMT Cecil Moore wrote: > There is no useful phase information in standing wave > current. Therefore, standing wave current cannot be used > to determine the percentage of a wavelength that is > occupied by the coil. Please replace the above with: There is no useful phase information contained in the standing wave current phase measurement. Therefore, the standing wave current phase measurement alone cannot be used to determine the percentage of a wavelength that is occupied by the coil. The standing wave current amplitude measurement does contain some implied information about the underlying forward and reflected waves, e.g. they are equal and out of phase at a point where the standing wave amplitude is zero. How's that, John? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222417 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coil Current Summary References: <1142623343.222039.185800@e56g2000cwe.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 19:58:09 GMT w8ji@akorn.net wrote: > This reminds me of the famous Fractenna Threads of years ago, where > Fractenna argued and argued, couldn't convine most people of anything, > and then declared himself correct. What is really strange is that you believe what it "reminds you of" is of technical importance. How about a technical rebuttal? Guilt by association is an easily recognized diversion of the issue. For the record, I argued with Chip as much as you did. In fact, Tom, I always take your side when you are right. Gene appears to me to be incredulous that you could possibly believe there is any information at all in the standing wave current phase measurement. Hint: There is none, just as Gene asserts. I suspect that Roy, W7EL, has discovered that same thing and realizes that his standing wave current measurements, though perfectly accurate, didn't provide any information that wasn't already available from EZNEC or Kraus. What I suspect is that neither you nor Roy realized that the standing wave current phase is virtually constant from the feedpoint to the tip of the antenna in a mobile antenna, *whether a coil is present or not*. (When I reported the same results as EZNEC, you implied my measurements were wrong.) Roy said my measurements agreed with EZNEC. Is EZNEC wrong? So when is one going to correct the errors on one's web page? (Please note the use of the objective, third-person, impersonal pronoun, "one".) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222418 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> <121kdg17arvj08a@corp.supernews.com> <1142596786.484861.188720@i39g2000cwa.googlegroups.com> <4SASf.2253$bn3.2076@bgtnsc04-news.ops.worldnet.att.net> <1142623541.576408.96120@j52g2000cwj.googlegroups.com> Message-ID: Date: Fri, 17 Mar 2006 19:59:42 GMT w8ji@akorn.net wrote: > Roy measured a real antenna for phase, I measured a moblile antenna for > current. Not sure what this means. Are you distancing yourself from Roy's phase measurements? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222419 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Coil Current Summary References: <1142623343.222039.185800@e56g2000cwe.googlegroups.com> Message-ID: <10FSf.577003$qk4.144048@bgtnsc05-news.ops.worldnet.att.net> Date: Fri, 17 Mar 2006 20:30:53 GMT Cecil, It is often entertaining to see someone switch positions and then claim that's what he meant all along. (Yes, I am talking about you.) However, I assure you that I am not "incredulous" about anything to do with this topic. 73, Gene W4SZ Cecil Moore wrote: > w8ji@akorn.net wrote: > >> This reminds me of the famous Fractenna Threads of years ago, where >> Fractenna argued and argued, couldn't convine most people of anything, >> and then declared himself correct. > > > What is really strange is that you believe what it "reminds you > of" is of technical importance. How about a technical rebuttal? > Guilt by association is an easily recognized diversion of the > issue. For the record, I argued with Chip as much as you did. > In fact, Tom, I always take your side when you are right. > > Gene appears to me to be incredulous that you could possibly > believe there is any information at all in the standing wave > current phase measurement. Hint: There is none, just as Gene > asserts. > > I suspect that Roy, W7EL, has discovered that same thing and > realizes that his standing wave current measurements, though > perfectly accurate, didn't provide any information that wasn't > already available from EZNEC or Kraus. > > What I suspect is that neither you nor Roy realized that the > standing wave current phase is virtually constant from the > feedpoint to the tip of the antenna in a mobile antenna, > *whether a coil is present or not*. (When I reported the same > results as EZNEC, you implied my measurements were wrong.) > Roy said my measurements agreed with EZNEC. Is EZNEC wrong? > > So when is one going to correct the errors on one's web page? > (Please note the use of the objective, third-person, impersonal > pronoun, "one".) Article: 222420 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Coil Current Summary Date: Fri, 17 Mar 2006 12:30:37 -0800 Message-ID: <121m73f340pt49c@corp.supernews.com> References: John Popelish wrote: > . . . > The real revelation for me, from this discussion is how the concept of > "phase" takes a dimensional jump (from time to position) when you change > from taking about a traveling wave to the standing wave that results > from the superposition of a pair of oppositely traveling waves of the > same frequency. Of course, we can speak of the phase (temporal or spacial) of any periodic waveform. But it might be important to keep in mind that the spacial amplitude distribution of a standing wave isn't generally sinusoidal. When the forward and reverse traveling waves are equal in magnitude, the amplitude distribution -- that is, the "waveform" if you plot magnitude versus position -- is the absolute value of a sine function. For all other cases, it's described by hyperbolic trig functions. So the "jump" from time to position involves more than phase; it also involves a change in waveshape. Roy Lewallen, W7EL Article: 222421 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coil Current Summary References: <121m73f340pt49c@corp.supernews.com> Message-ID: Date: Fri, 17 Mar 2006 20:53:12 GMT Roy Lewallen wrote: > When the forward and reverse traveling waves are equal in > magnitude, the amplitude distribution -- that is, the "waveform" if you > plot magnitude versus position -- is the absolute value of a sine > function. For all other cases, it's described by hyperbolic trig > functions. So the "jump" from time to position involves more than phase; > it also involves a change in waveshape. Exactly! That's why the current waveforms through the coils are not perfect cosine waves. To maintain the same forward and reflected power, when the phase between the voltage and current changes, their amplitudes must change accordingly. Conservation of energy dictates that V*I*cos(A) must remain constant (assuming no storage) so if the (A) angle changes, voltage and current magnitudes must change accordingly. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222422 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coil Current Summary References: <1142623343.222039.185800@e56g2000cwe.googlegroups.com> <10FSf.577003$qk4.144048@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Fri, 17 Mar 2006 21:05:41 GMT Gene Fuller wrote: > It is often entertaining to see someone switch positions and then claim > that's what he meant all along. My basic position has been consistant for years and so has Tom's. If you google the newsgroup from a couple of years ago, I asserted to Roy that his standing wave phase measurements were meaningless. I asserted that he had measured the wrong parameter. Where were you? Years ago, I indeed thought it was a simple problem. I no longer think it is a simple problem. If that's defined as "switching positions", then I am guilty. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222423 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Skin depth question Date: Fri, 17 Mar 2006 14:11:40 -0800 Message-ID: <121md0ur9gdg973@corp.supernews.com> References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> <121kbb65cj0om31@corp.supernews.com> <121ke06ev9jep86@corp.supernews.com> <121l2g8gk2ep0e4@corp.supernews.com> <1142629987.383332.301360@e56g2000cwe.googlegroups.com> When the material is thin relative to a skin depth, the current isn't completely uniform at any frequency above DC. However, it's close enough that the resistivity is essentially the same as if it were uniformly distributed. That's why I said you could treat the problem as though it were. I'm surprised that you couldn't find this on the web, but I'll provide a number of textual references if you're truly interested in learning more about it. Some include the necessary equations with which you can do the calculations yourself, if you've got access to tables of modified Bessel functions or a software math library which includes them. Roy Lewallen, W7EL art wrote: > You know that is exactly how I see it which is contrary to what Roy is > saying. I cannot find any corroberation of his statement that for thin > material relative to skin depth current density is constant. Perhaps he > has read something that forces the current flow to follow D,C. > properties. As the current surface moves away > from the interactive field/s the conditions on the surface certainly > must differ. > Hopefully, Tom with his superior knoweledge on this subject will > intercede and share his knoweledge. > Regards > Art > Article: 222424 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Fri, 17 Mar 2006 15:23:15 -0800 Message-ID: <121mh75g3ekkme9@corp.supernews.com> References: <1142535716.514573.157360@p10g2000cwp.googlegroups.com> <1142540530.873073.195590@e56g2000cwe.googlegroups.com> <1142549862.793446.236090@v46g2000cwv.googlegroups.com> <1142556063.774604.35640@v46g2000cwv.googlegroups.com> <1142560398.111011.181380@i39g2000cwa.googlegroups.com> <1142566723.768430.196020@p10g2000cwp.googlegroups.com> <121kdg17arvj08a@corp.supernews.com> <1142596786.484861.188720@i39g2000cwa.googlegroups.com> <4SASf.2253$bn3.2076@bgtnsc04-news.ops.worldnet.att.net> <1142623541.576408.96120@j52g2000cwj.googlegroups.com> w8ji@akorn.net wrote: > > Roy measured a real antenna for phase, I measured a moblile antenna for > current. > > http://www.w8ji.com/agreeing_measurements.htm Actually, I measured both phase and amplitude of the current at both ends of a toroidal inductor. It was measured at the base of a shortened vertical antenna, and also on the bench with the antenna replaced by lumped components having the same impedance as the antenna. The results were published in the October 2003 thread on this newsgroup. Roy Lewallen, W7EL Article: 222425 of rec.radio.amateur.antenna Date: Fri, 17 Mar 2006 19:34:32 -0600 From: Tom Ring Subject: Re: Skin depth question References: <1142550534.599921.43100@j33g2000cwa.googlegroups.com> <121jsuqafmpqgfb@corp.supernews.com> <121kbb65cj0om31@corp.supernews.com> <121ke06ev9jep86@corp.supernews.com> <121l2g8gk2ep0e4@corp.supernews.com> <1142629987.383332.301360@e56g2000cwe.googlegroups.com> <12bm12pnnuuqv8lpe0qogu6cc81oouei5i@4ax.com> Message-ID: <441b63a9$0$7325$39cecf19@news.twtelecom.net> Richard Clark wrote: > On 17 Mar 2006 13:13:07 -0800, "art" wrote: > >>I cannot find any corroberation of his statement that for thin >>material relative to skin depth current density is constant. > > > It's simple math. > > For instance, you go to the store to buy penny candy. You plunk down > the penny. The grocer says there's 5% tax on sales. 5% of 1 penny > ultimately reduces his options. He takes the penny and gives it to > the government. You get nothing. The grocer sells nothing. The > government gives the penny to a billionare as a tax refund. Deprived > of your penny candy, you get to drive through pot holes as the > billionare helicopters over you. To show his charitable feelings, he > scatters messages of cheer and thanks to those below. You are pulled > over for littering, fined $1000 and put on a trash pick-up team. I missed the part about why the billionaire gets a refund.\ It never works that way in the real world, Richard. How it works, and I'm from a retail family, is that you will get charged 2 cents for the penny candy. Except nothing costs a penny anymore, penny candy is at least 10 to 20 cents, so that is a moot argument. And when you deal with all the combinations of price and tax, and how the retailer has to handle it, by law, the retailer loses money on average handling the tax for the state/local govt. In other words, the tax is 7%, but because of how the govt. makes the tax tables work, the retailer collects less than 7%, but is required to give the govt. exactly 7% plus a penny. The business is almost always screwed, and the consumer is usually, not always like the seller, required to pick up the extra cost the govt. added. tom K0TAR Article: 222426 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sat, 18 Mar 2006 02:30:08 GMT Gene Fuller wrote: > 1. I have looked at that figure, and I suspect many others have as well. > There is no information given about dimensions or any other modeling > conditions, so it is difficult to say anything more than, "Yep, there's > a bunch of lines and numbers on that figure." Information has been added to the graphic at: http://www.qsl.net/w5dxp/test316.GIF The associated EZNEC file can be downloaded from: http://www.qsl.net/w5dxp/test316.EZ -- 73, Cecil http://www.qsl.net/w5dxp Article: 222427 of rec.radio.amateur.antenna From: "Frank" References: <3FIRf.28313$M52.20709@edtnps89> <18qke3-do6.ln1@p400bob.personal.cox.net> <1142499124.542709.89620@e56g2000cwe.googlegroups.com> <0ntoe3-dab.ln1@p400bob.personal.cox.net> Subject: Re: Modeling question Message-ID: Date: Sat, 18 Mar 2006 02:59:24 GMT "Bob Bob" wrote in message news:0ntoe3-dab.ln1@p400bob.personal.cox.net... > Hi Frank/Arie > > Not really knowing what I was doing I tried EK and got the same bad > average gain figure.. I also removed most of the lower part of the mast > since its effect will be fairly minimal. No help there either. > > Tnxs for your comments gents. There is still the two questions though; > > - Does one bother to model in a "curved" wire for copper pipe joiners? I > note Mr Cebik didnt mention it when he was talking about J poles on 2m. > > - Is the diameter of the source wire important? > > Thinking now about reducing the copper pipe diameter simply so I can model > it properly. Then again its a pretty broad design and tuning would be > easy... > > Cheers Bob VK2YQA Hi Bob, attempting to model a curved wire will possibly lead to over-segmentation. It is also important to avoid junctions of dissimilar wire diameters as it can lead to errors. The source wire should therefore be the same diameter as the rest of the structure. 73, Frank Article: 222428 of rec.radio.amateur.antenna From: "Richard Miller" Subject: Need help Date: Sat, 18 Mar 2006 16:37:48 +1100 Message-ID: <441b9cb7$0$20113$afc38c87@news.optusnet.com.au> Hi I was just digging around the garage and I found my old multi band trap vertical antenna LOL.. Anyway it covered 80m to 10m and I got it from Dick Smith back in the 80's that's a long time ago.. Dos anyone have a diagram for one of them I can not find mine but still looking for it.. Can any one help.. -- 73's Regards, Richard Miller E-mail: wizzard6@optusnet.com.au Article: 222429 of rec.radio.amateur.antenna From: "Basil Burgess" Subject: First Attempt Date: Sat, 18 Mar 2006 10:21:27 -0500 Message-ID: Hello all I've made a first attempt at installing an antenna. It's a 2 Slinky dipole strung across my roof. I chose the Slinky dipole because it promised to give good (if not excellent) results in a relatively short antenna. I strung it between two 2' wood standards at the top of the roof. The roof is about 25-30' from the ground. I used the twin feedline, which is about 18', and the insulators from a GSRV Mini antenna I bought. The twinline is connected with a balun to a 50' RG-8X cable that runs across the roof and down to my window. I've temporarily led it in through the window. The excess cable, probably about 20 feet or so, is loosely coiled between the inner and outer window. The reception is great. I was picking up DX from Europe. However, I got no answers to any attempt to call out. I wasn't expecting DX for my very first QSO, but I was hoping for someone. I think it may be because the feedline runs along the roof rather than hanging in free space. Could this be the case? The SWR was terrible; it took my automatic tuner a lot of work to get a match, but I was getting 1.5 or less on 80 and 40. Thank you for any advice you can offer. 73 Basil Burgess, VE3JEB My email is basilb which is through hotmail Article: 222430 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: First Attempt References: Message-ID: Date: Sat, 18 Mar 2006 15:38:50 GMT Basil Burgess wrote: > Hello all > > I've made a first attempt at installing an antenna. It's a 2 Slinky dipole > strung across my roof. I chose the Slinky dipole because it promised to give > good (if not excellent) results in a relatively short antenna. I strung it > between two 2' wood standards at the top of the roof. The roof is about > 25-30' from the ground. I used the twin feedline, which is about 18', and > the insulators from a GSRV Mini antenna I bought. The twinline is connected > with a balun to a 50' RG-8X cable that runs across the roof and down to my > window. I've temporarily led it in through the window. The excess cable, > probably about 20 feet or so, is loosely coiled between the inner and outer > window. > I think it may be because the feedline runs along the roof rather than > hanging in free space. Could this be the case? The SWR was terrible; it took > my automatic tuner a lot of work to get a match, but I was getting 1.5 or > less on 80 and 40. Actually, the entire antenna design is terrible. What is the SWR on the coax at the balun? Steel is not a good conductor to use in an antenna at RF frequencies. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222431 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sat, 18 Mar 2006 15:42:07 GMT Gene Fuller wrote: > 1. I have looked at that figure, and I suspect many others have as well. > There is no information given about dimensions or any other modeling > conditions, so it is difficult to say anything more than, "Yep, there's > a bunch of lines and numbers on that figure." I have added the information gathered in this thread and others to my web page. Please click on my web page below and scroll down to the bottom of the page. -- 73, Cecil http://www.qsl.net/w5dxp/current.htm Article: 222432 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Sat, 18 Mar 2006 11:17:13 -0600 Message-ID: <28826-441C4099-1651@storefull-3255.bay.webtv.net> References: <121mh75g3ekkme9@corp.supernews.com> This thread ran almost as long as "47KW CB mobile, was Re: CW = Engineer?" Not sure which holds the duration record. Cheers, Richard Harrison, KB5WZI Article: 222433 of rec.radio.amateur.antenna From: "Basil Burgess" Subject: Re: First Attempt Date: Sat, 18 Mar 2006 13:10:11 -0500 Message-ID: References: Thank you for your response I'm afraid I don't have a way of measuring the SWR at the coax. Should I consider connecting the balun directly to the slinkys rather than at the end of the twinline? Should the twinline be supported so that it is not lying on the roof? Or should I just dismantle it and go back to positioning the GSRV Mini. That, at least, is a copper dipole. Thanks again Basil, VE3JEB "Cecil Moore" wrote in message news:eQVSf.54852$H71.31027@newssvr13.news.prodigy.com... > > Actually, the entire antenna design is terrible. What is the SWR > on the coax at the balun? Steel is not a good conductor to use in > an antenna at RF frequencies. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 222434 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Current through coils Date: Sat, 18 Mar 2006 12:15:41 -0600 Message-ID: <121ojih732ucf6f@corp.supernews.com> References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> Richard Harrison wrote: > This thread ran almost as long as "47KW CB mobile, was Re: CW = > Engineer?" > > Not sure which holds the duration record. > > Cheers, Richard Harrison, KB5WZI > I counted almost 500 entries. Cecil had almost 25% of them. Dave N Article: 222435 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: First Attempt References: Message-ID: Date: Sat, 18 Mar 2006 18:31:12 GMT Basil Burgess wrote: > Or should I just dismantle it and go back to positioning the GSRV Mini. > That, at least, is a copper dipole. I won't presume to tell you what you "should" do. There are too many unknowns in your system. You may need to spring for an antenna analyzer, like the MFJ-259B. If it were me, I would junk the slinky antenna. At least the half-sized G5RV is known to work relatively well on 40m, 20m, 10m, and 6m. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222436 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 18:41:24 GMT David G. Nagel wrote: > I counted almost 500 entries. Cecil had almost 25% of them. I kicked it off with "Current in loading coils". Reg then responded with "Current through coils" and the rest is history. When one is up against most of the r.r.a.a gurus, all at the same time, one needs to make a lot of postings. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222437 of rec.radio.amateur.antenna From: Kba Subject: aluminium element segment corrosion & weather proofing... ? Message-ID: Date: Sat, 18 Mar 2006 19:04:19 GMT Hi all just have some plans for yagi construction, but yagi tapering segments may need some corrosion & weather protection... Any recommendations ? Aluminum powder or grease ? or without ?? rgds Kari Article: 222438 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: aluminium element segment corrosion & weather proofing... ? References: Message-ID: Date: Sat, 18 Mar 2006 19:16:51 GMT Kba wrote: > just have some plans for yagi construction, but yagi tapering > segments may need some corrosion & weather protection... > Any recommendations ? > Aluminum powder or grease ? or without ?? There's a conductive compound that reduces oxidation. It's sold under various brand names. Oxiguard comes to mind but that may be a toothpaste compound or some such. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222439 of rec.radio.amateur.antenna From: "Ralph Mowery" References: Subject: Re: First Attempt Message-ID: Date: Sat, 18 Mar 2006 19:23:57 GMT "Basil Burgess" wrote in message news:dvhier$g48$1@emma.aioe.org... > Thank you for your response > > I'm afraid I don't have a way of measuring the SWR at the coax. > > Should I consider connecting the balun directly to the slinkys rather than > at the end of the twinline? Should the twinline be supported so that it is > not lying on the roof? > > Or should I just dismantle it and go back to positioning the GSRV Mini. > That, at least, is a copper dipole. > As Cecil said , it is hard to tell you what to do with the limiated information you have given. Nothing simple beats the good old dipole antenna. Problem is it is mostly a one band antenna. I have up an off center fed antenna and it seems to work fair for all the harmonic bands. The swr is a bit high on the WARC bands. It is about 130 feet long with a 4:1 balun in the center and fed with rg-8x coax. Even with the antenna you have up you should be able to work something if the rig will load it. It may be that the internal tuner to the rig is not able to match the antenna and most of the power is not getting out of the rig. The inernal tuners are only good for about a 3:1 or less swr to the antenna on most rigs. Cecil mentioned an expensive MFJ device. It is probably way too much over kill for most hams. One of the least expensive SWR meters will tell you if the antenna is anywhere in the ball park and which way you need to trim the antenna if you take several readings across the band. Article: 222440 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Sat, 18 Mar 2006 19:23:54 +0000 (UTC) Message-ID: References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> > I counted almost 500 entries. Cecil had almost 25% of them. > > Dave N =================================== - - - and I get the impression nobody learned anything! Problems should be handed over to the sewer rats in Rio de Janerio to sort out, rather than culling them. ---- Reg. Article: 222441 of rec.radio.amateur.antenna From: "Basil Burgess" Subject: Re: First Attempt Date: Sat, 18 Mar 2006 14:54:25 -0500 Message-ID: References: Thank you, Ralph I'm sorry if I am giving inadequate information. Besides the basic description of the antenna, I'm not sure what else to offer. I doubt it took anyone long to realize that I am a novice and have as much info on antennas as one learns for the Canadian basic exam, and and can glean from a borrowed copy of the ARRL Antenna Book. The only additions I have are that on closer inspection, the balun is Van Gorden's (the manufacturer of the original antenna) Hi-Q Center Insulator. Also, I am using an external automatic tuner, a Z-11 Pro by LDG. It apparently tunes the antenna down to an SWR of <1.5, but doesn't have the means to give a more accurate figure. My FT-875 displays SWR, as a bar display, but when the tuner has done its job, the rig seems to display no SWR bars, which I take to mean the rig sees a 1:1 or close to it. Still, I guess that's no guarantee that the power is being used efficiently. Anyway, thanks again for your help 73 Basil Burgess, VE3JEB Article: 222442 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 19:57:32 GMT Reg Edwards wrote: > - - - and I get the impression nobody learned anything! You think nobody learned anything from the fact that measuring standing wave current phase is meaningless? If nobody learned anything, they would no doubt still be contributing to the technical discussion. Here's what I think happened. Person A and Person B engage in an argument and both are wrong. Person A believes he cannot possibly be wrong so he digs in and argues his rigid position. Person B realizes that he may be wrong and uses the scientific method to fine tune his argument thus correcting any errors along the way. Which person has the advantage and is likely to win the argument? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222443 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: First Attempt References: Message-ID: Date: Sat, 18 Mar 2006 20:03:20 GMT Basil Burgess wrote: > It apparently tunes the antenna down to an SWR of <1.5, ... An antenna tuner doesn't change the SWR between the tuner and the antenna. If it's 100:1 before the tuner does its thing, it is still 100:1 after the tuner does its thing. The extra feedline losses are caused by that unchanging SWR. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222444 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: First Attempt Date: Sat, 18 Mar 2006 20:03:12 +0000 (UTC) Message-ID: References: The best, all round, all band, antenna is a high centre-fed dipole of no particular length, fed with an open-wire feedline of no particular length or impedance, all the way to the shack, used with a choke-balun and an unbalanced tuner. It is good down to the frequency at which the dipole is about 1/3-wavelength long. Simplicity = efficiency. Once tried you will never return to anything else. ---- Reg. Article: 222445 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: First Attempt Message-ID: References: Date: Sat, 18 Mar 2006 20:14:18 GMT On Sat, 18 Mar 2006 14:54:25 -0500, "Basil Burgess" wrote: >Thank you, Ralph > >I'm sorry if I am giving inadequate information. Besides the basic >description of the antenna, I'm not sure what else to offer. I doubt it took >anyone long to realize that I am a novice and have as much info on antennas >as one learns for the Canadian basic exam, and and can glean from a borrowed >copy of the ARRL Antenna Book. > >The only additions I have are that on closer inspection, the balun is Van >Gorden's (the manufacturer of the original antenna) Hi-Q Center Insulator. >Also, I am using an external automatic tuner, a Z-11 Pro by LDG. It >apparently tunes the antenna down to an SWR of <1.5, but doesn't have the >means to give a more accurate figure. My FT-875 displays SWR, as a bar >display, but when the tuner has done its job, the rig seems to display no >SWR bars, which I take to mean the rig sees a 1:1 or close to it. Still, I >guess that's no guarantee that the power is being used efficiently. > >Anyway, thanks again for your help > >73 >Basil Burgess, VE3JEB For a first attempt, it sounds like you've built a complicated affair: slinkies, twinlead, balun, coax, tuner, etc. You might try the other extreme, simple. A dipole of two straight wires cut to frequency, and a length of coax to the rig. Make the antenna a little long, and use your rig's swr meter to adjust the length down to resonance. bob k5qwg > Article: 222446 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: First Attempt Message-ID: <7spo12di64otinqkj0eanefcufnrl46dpv@4ax.com> References: Date: Sat, 18 Mar 2006 20:21:31 GMT On Sat, 18 Mar 2006 10:21:27 -0500, "Basil Burgess" wrote: >Hello all > >I've made a first attempt at installing an antenna. It's a 2 Slinky dipole >strung across my roof. I chose the Slinky dipole because it promised to give >good (if not excellent) results in a relatively short antenna. I strung it There is nothing in your post to indicate how long or short your antenna is. Perhaps it is a well known design and I just haven't heard of it in my limited experience. You say how difficult the coax was to match with an ATU, that is a big hint that the coax is operating at high VSWR. You say the SWR was terrible, what does that mean, do you have the numbers? Coax operated at high VSWR for significant length is quite lossy. If the impedance presented to the tuner is extreme, you can expect excessive losses there too. The ambient noise on low HF bands is very high compared to the noise floor in your receiver. An antenna system could be seriously lossy, and yet still allow you to hear all signals above the noise (though at reduced S meter deflection). Beware of depending on a simplified receiver test to infer transmit performance. Owen -- Article: 222447 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Skin depth question Date: Sat, 18 Mar 2006 20:33:56 +0000 (UTC) Message-ID: References: <1142535306.321916.198140@j52g2000cwj.googlegroups.com> <1142542035.975885.202000@z34g2000cwc.googlegroups.com> <1142654608.872051.303460@g10g2000cwb.googlegroups.com> <1142712771.878378.237860@e56g2000cwe.googlegroups.com> Art, it's very unlike you, but your message sounds like a load of gobble-de-gook to me. What is your point? Are you asking a question? Can you summarise in one sentence of few words of plain English. ---- Reg. Article: 222448 of rec.radio.amateur.antenna From: "Jerry Martes" References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Subject: Re: Current through coils Message-ID: Date: Sat, 18 Mar 2006 20:44:15 GMT "Cecil Moore" wrote in message news:MCZSf.57481$Jd.28122@newssvr25.news.prodigy.net... > Reg Edwards wrote: >> - - - and I get the impression nobody learned anything! > > You think nobody learned anything from the fact that > measuring standing wave current phase is meaningless? > If nobody learned anything, they would no doubt still > be contributing to the technical discussion. > > Here's what I think happened. Person A and Person B > engage in an argument and both are wrong. Person A > believes he cannot possibly be wrong so he digs in and > argues his rigid position. Person B realizes that he may > be wrong and uses the scientific method to fine tune his > argument thus correcting any errors along the way. > > Which person has the advantage and is likely to win > the argument? > -- > 73, Cecil http://www.qsl.net/w5dxp Hi Cecil I've read more than 80% of the posts in this thread. I still dont understand the objective. BUT, I sure have learned a few things, thanks to you guys who do what is being soughtafter. Jerry Article: 222449 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: First Attempt Date: Sat, 18 Mar 2006 20:45:38 +0000 (UTC) Message-ID: References: <7spo12di64otinqkj0eanefcufnrl46dpv@4ax.com> Owen, you know as well as I do his SWR meter does not indicate SWR on the feedline where it might matter. So some of your comments don't make much sense. ---- Reg. Article: 222450 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Sat, 18 Mar 2006 21:07:28 +0000 (UTC) Message-ID: References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> > Hi Cecil > > I've read more than 80% of the posts in this thread. I still dont > understand the objective. BUT, I sure have learned a few things, thanks to > you guys who do what is being soughtafter. > > Jerry ======================================= Ah, but how do you know you learned the RIGHT things? Or what you learned was true and correct? The participants in the argument NEVER agreed on ANYTHING. So what can bystanders do? I learned far more about people than I did about current through coils. Quite interesting nevertheless. ---- Reg, G4FGQ. Article: 222451 of rec.radio.amateur.antenna From: Ian Jackson Subject: Re: Coax To Coax Noise transfer ? Date: Sat, 18 Mar 2006 21:16:19 +0000 Message-ID: <2e+jB+QjiHHEFwkT@g3ohx.demon.co.uk> References: In message <121bjjll54og800@corp.supernews.com>, Dave Platt writes >In article , >Robert11 wrote: > >>Hello: >> >>Am about to start stringing some coax from an outside Receive-Only antenna's >>Balun up to >>my study where the receiver is. (30 MHz on down listening) >> >>The easiest thing for me is to run it alongside an existing (looks like >>coax, but am not sure) wire >>that Comcast has strung for my broadband service to the PC. Actually to >>their always-on modem which is then >>connected to the PC. >> >>Was wondering about coax to coax noise transfer into the receiving antennas >>coax from being right alongside >>this Comcast stuff. >> >>Think there's any reason for concern ? > >If the Comcast cable was installed properly, there shouldn't be a >problem. Coax cable with high-quality shielding leaks very little >signal, and the cable companies have to use well-shielded cable in >their plants in order to avoid leakage of channels whose fall into the >airband, amateur, and public-safety allocations. > >Also, I don't think that Comcast's plant is likely to carry much, if >any content below 30 MHz. > You're forgetting about the UPSTREAM data and interactive signals (QPSK and/or QAM, from the cable modem or the set-top TV box). These will be in the range of (probably) 15MHz to 42MHz. The max transmit level will be typically 40dBmV (max around 56dBmV). The actual frequency used will depend on the local area (segment). The upstream levels are higher than the downstream (typically 10dBmV analogue, 0dBmV QAM). However, where possible, the cable operator may be avoiding the HF amateur frequencies, in order to minimise any problems of ingress. >There's some possibility, I suppose, of some leakage of noise from the >cable modem itself back up along the outside of the Comcast coax. You >might want to consider buying a few snap-on interference-suppression >ferrites, and snap 'em onto the outside of both cables (e.g. where the >Comcast cable leaves the building, where your receiver coax enters the >building, and maybe a few more scattered along one or both coaxes). >This would help block or dissipate any RF currents flowing on the >outsides of the coaxes. > This is certainly a good idea 'just in case', and won't hurt any. Ian. -- Article: 222452 of rec.radio.amateur.antenna From: "Basil Burgess" Subject: Re: First Attempt Date: Sat, 18 Mar 2006 16:29:55 -0500 Message-ID: References: Thank you all for your help. The consensus seems to be that the overall antenna is ill-conceived. I will revert the design to the original antenna and work out how to rig it. Thanks again for the information and education. I guess when one of you hears me, you'll know I worked it all out :-) 73 to all Basil Burgess, VE3JEB Article: 222453 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: First Attempt Message-ID: References: <7spo12di64otinqkj0eanefcufnrl46dpv@4ax.com> Date: Sat, 18 Mar 2006 21:33:32 GMT On Sat, 18 Mar 2006 20:45:38 +0000 (UTC), "Reg Edwards" wrote: >Owen, you know as well as I do his SWR meter does not indicate SWR on >the feedline where it might matter. So some of your comments don't >make much sense. Reg, If Basil measured the SWR at the ATU end of the RG8/X (either directly or effectively with the ATU in bypass configuration if that is possible), that would provide information that could be used to estimate whether losses in the RG8/X were reasonable, and if reasonable, how reasonable. The RG8/X is probably the highest risk of serious loss in the antenna system. For clarity, I am not at all interested in the VSWR indicated looking into the ATU unless the ATU is in the bypass configuration, in which case the measurement is a valid indicator of the VSWR on the RG8/X. The line loss of 50' of RG8/X at 3.6MHz with a source end VSWR of 8:1 is around 1dB, and probably quite acceptable. Beyond a source end VSWR of 20:1, losses increase quickly to infinite loss at source end VSWR around 28:1. If the indicated reflected *power* at the ATU end of the coax is less than about 80%, or VSWR less than about 20, coax loss is probably manageable. Owen -- Article: 222454 of rec.radio.amateur.antenna Date: Sat, 18 Mar 2006 15:33:56 -0600 From: Terry Sellick Subject: Diamond antenna repair parts Message-ID: <50c3e$441c7cc3$4087da85$19612@FOXVALLEY.NET> Does anyone know if Diamond offers replacement repair parts for their antennas? I had an X510MA 2m/70cm vertical blow down in a recent storm. The lower fiberglass section broke. Thanks & 73 Terry WA9TTY Article: 222455 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 22:00:50 GMT Jerry Martes wrote: > I've read more than 80% of the posts in this thread. > I still dont understand the objective. Since the foundation of other's measurements was the use of standing wave current phase to prove the percentage of a wavelength occupied by a loading coil is zero, my objective was simple: To prove that the standing wave current, with its unchanging phase, cannot be used to make a valid measurement of the percentage of a wavelength occupied by a loading coil. I proved that using the standing wave current phase to measure the percentage of a wavelength occupied by a wire or a whip also yields an answer of zero. If the coil plus the whip both occupy a percentage of a wavelength equal to zero, all sorts of laws of physics are violated. Not to mention a full length 1/2WL wire dipole occupying a percentage of a wavelength equal to zero. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222456 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sat, 18 Mar 2006 22:04:38 GMT Cecil, I downloaded your EZNEC file, and I played around for a while with both the original and several variations. There were no surprises for the fundamental frequency case. When I modeled a real bugcatcher coil, or at least as real as those on the GLA web site, the current at the top of the coil was 85% to 90% of the base current. I think it is more typical that a bugcatcher coil is at least 4 turns per inch rather than the 2 turns per inch in your example. I also attempted to model the coil tested by Tom, W8JI, and reported earlier in this thread. This coil pushes EZNEC both in terms of the number of segments and the short length of the segments, but in any case it appears that his coil when placed in your antenna model has higher current at the top than you reported. I ignored the harmonic examples. Who ever said that a coil would be a lumped inductor when it is operated above its self resonant frequency? Even your new guru from Mount Olympus, Dr. Teslacoil, does not discuss such things. In summary, the world of RF electrical phenomena is still intact. I don't believe I have anything more to add, and I plan to back to sleep. 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> 1. I have looked at that figure, and I suspect many others have as >> well. There is no information given about dimensions or any other >> modeling conditions, so it is difficult to say anything more than, >> "Yep, there's a bunch of lines and numbers on that figure." > > > Information has been added to the graphic at: > > http://www.qsl.net/w5dxp/test316.GIF > > The associated EZNEC file can be downloaded from: > > http://www.qsl.net/w5dxp/test316.EZ Article: 222457 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 22:09:26 GMT Cecil, I could have sworn that you were insisting the phase still had meaning in a standing wave environment. It only required the correct measurement technique. I am glad to see that you have now adopted the truth, even if the history appears a bit shaky. 73, Gene W4SZ Cecil Moore wrote: > Jerry Martes wrote: > >> I've read more than 80% of the posts in this thread. > > > I still dont understand the objective. > > Since the foundation of other's measurements was > the use of standing wave current phase to prove the > percentage of a wavelength occupied by a loading > coil is zero, my objective was simple: To prove > that the standing wave current, with its unchanging > phase, cannot be used to make a valid measurement > of the percentage of a wavelength occupied by a loading > coil. > > I proved that using the standing wave current phase to > measure the percentage of a wavelength occupied by a > wire or a whip also yields an answer of zero. If the > coil plus the whip both occupy a percentage of a > wavelength equal to zero, all sorts of laws of physics > are violated. Not to mention a full length 1/2WL wire > dipole occupying a percentage of a wavelength equal > to zero. Article: 222458 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 22:11:25 GMT Gary Schafer wrote: > Rather than a 50 ohm load how about if a load was placed at the end of > the coil to simulate the antenna, a resistor and capacitor to take the > place of the antenna impedance and reactance. Then measure the current > in and out and the phase shift. The measurement problem is harder than it looks. Here's a quote from "Field and Waves in Modern Radio", Ramo and Whinnery, 2nd edition, page 227. "Difficulties in applying these equations arise since the current and charge distributions are not known, but are determined by the field distributions which are calculated from the retarded potentials which depend upon current and charge distribution - a vicious circle! The exact solution of this problem is usually of prohibitive difficulty." -- 73, Cecil http://www.qsl.net/w5dxp Article: 222459 of rec.radio.amateur.antenna From: "Richard Miller" Subject: OLD 5 BAND TRP ANTENNA Date: Sun, 19 Mar 2006 09:22:01 +1100 Message-ID: <441c880a$0$7604$afc38c87@news.optusnet.com.au> Hi I was just digging around the garage and I found my old multi band trap vertical antenna LOL.. Anyway it covered 80m to 10m and I got it from Dick Smith back in the 80's that's a long time ago.. Dos anyone have a diagram for one of them I can not find mine but still looking for it.. Can any one help.. 73's Regards, Richard Miller E-mail: wizzard6@optusnet.com.au Article: 222460 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: Date: Sat, 18 Mar 2006 22:43:46 GMT Gene Fuller wrote: > I could have sworn that you were insisting the phase still had meaning > in a standing wave environment. I know that's what you thought, but you were mistaken. By thinking that, you accidentally posted some support for my side of the argument. Thanks very much. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222461 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sat, 18 Mar 2006 23:26:29 GMT Gene Fuller wrote: > I think it is more typical that a bugcatcher coil is at least 4 > turns per inch rather than the 2 turns per inch in your example. I tried 4 turns per inch. EZNEC didn't like it. > I ignored the harmonic examples. Who ever said that a coil would be a > lumped inductor when it is operated above its self resonant frequency? Whoever said that a coil would be a lumped inductor at 60% of its self resonant frequency? Did you say that? Used at 5.89 MHz, self-resonant at 9.75 MHz, phase-reversing at 11.78 MHz. Sounds a lot like a slow wave transmission line to me. 5.89 is 60% of the self-resonant frequency. Dr. Corum says that the lumped-circuit fails above a 15% value. 60% is far above 15%. > In summary, the world of RF electrical phenomena is still intact. Of course, and more than that, I took its side in the argument. When I reported measuring no phase shift up and down a dipole, Tom, W8JI, said my measurements were wrong. But EZNEC says the same thing as I. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222462 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sat, 18 Mar 2006 23:48:38 GMT Gene Fuller wrote: > I ignored the harmonic examples. Who ever said that a coil would be a > lumped inductor when it is operated above its self resonant frequency? Oh, I forgot to ask you a technical question, Gene. Given that at 11.78 MHz, the current at the bottom of the coil is 0.17 amps and the current at the top is 2.0 amps, how do you explain those values if the current is flowing up through the coil? The details are at the bottom of the following web page. -- 73, Cecil http://www.qsl.net/w5dxp/current.htm Article: 222463 of rec.radio.amateur.antenna From: "Jerry Martes" References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Subject: Re: Current through coils Message-ID: <6B1Tf.1266$hC.712@trnddc08> Date: Sun, 19 Mar 2006 00:28:50 GMT "Reg Edwards" wrote in message news:dvhsqg$klf$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > >> Hi Cecil >> >> I've read more than 80% of the posts in this thread. I still > dont >> understand the objective. BUT, I sure have learned a few things, > thanks to >> you guys who do what is being soughtafter. >> >> Jerry > ======================================= > > Ah, but how do you know you learned the RIGHT things? Or what you > learned was true and correct? > > The participants in the argument NEVER agreed on ANYTHING. So what can > bystanders do? > > I learned far more about people than I did about current through > coils. Quite interesting nevertheless. > ---- > Reg, G4FGQ. Hi Reg I note that you question my ability to know if I learned the Right Things. How do we ever know?? I wrote that I learned a FEW things. Let me be the judge about whats right for me. I dont know if you wrote the question about my learning the Right thing to impune my ability to sort out the Right from the NotRight, or you wrote to imply that were some statements made in the thread that werent right. I submit to you that if you find the need to show where any statement made in the antenna group that isnt True and Correct, you can correct them directly. By my standards, all the posts in this thread were worthy of being read. It is even possible that you learn something from these guys on the antenna group when you take time to read and think. Please dont stop trying to learn Reg, you are a great source of good information and you can improve if you try. Jerry Article: 222464 of rec.radio.amateur.antenna From: David Subject: Reducing number of elements in this design Message-ID: <0e3Tf.9944$dy4.8651@news-server.bigpond.net.au> Date: Sun, 19 Mar 2006 02:20:44 GMT Hi, Would someone be able to advise me how I would calculate new dimensions to scale the 9-Element Yagi (described at http://www.qsl.net/ve3cvg/antennas/900b/index.html) down to say a 4 or 5 element version. (ie. I would like the same physical construction method and frequency but shorter boom length - around 350mm), around 7dBi gain would be fine Thanks in advance Regards David Article: 222465 of rec.radio.amateur.antenna From: "Lisa Simpson" Subject: antenna theory for idiots? Message-ID: Date: Sun, 19 Mar 2006 02:23:07 GMT Can anyone point me at a good book or website that can teach me about antenna theory from a beginner's standpoint? I'm getting into SWL & feel I really need to understand this subject well . . . Article: 222466 of rec.radio.amateur.antenna Message-ID: <441CC42A.B4B544F9@jake.net> From: jake Subject: Re: antenna theory for idiots? References: Date: Sun, 19 Mar 2006 02:38:34 GMT hi lisa, check you local library, the arrl antenna books are very good, also http://www.cebik.com jake Lisa Simpson wrote: > Can anyone point me at a good book or website that can teach me about > antenna theory from a beginner's standpoint? I'm getting into SWL & feel I > really need to understand this subject well . . . Article: 222467 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna theory for idiots? Date: Sat, 18 Mar 2006 18:45:25 -0800 Message-ID: <121phe846j8pdd1@corp.supernews.com> References: The ARRL Antenna Book is very good, and it's a good deal more accurate than many other beginners' books. There's very likely to be a copy at your local library. Roy Lewallen, W7EL Lisa Simpson wrote: > Can anyone point me at a good book or website that can teach me about > antenna theory from a beginner's standpoint? I'm getting into SWL & feel I > really need to understand this subject well . . . > > Article: 222468 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> <1142734010.632531.71060@v46g2000cwv.googlegroups.com> Message-ID: Date: Sun, 19 Mar 2006 02:45:39 GMT w8ji@akorn.net wrote: **************************************************************** Please turn your technical expertise on this example which I have asked you about many times with no response from you: http://www.qsl.net/w5dxp/current.htm At the bottom of the page, the coil is seen to have 0.17 amps at the bottom and 2.0 amps at the top. With your lumped inductor way of thinking, how is that possible? ***************************************************************** > A bench test is fine. An inductor is an inductor. But the chosen valid model varies depending upon which inductor it is. Dr. Corum says the model must be changed over at 15 degrees of the self-resonant frequency. These are velocity inhibited slow- wave helical coils that we are talking about. And standing wave current is certainly not traveling wave current. Remember what Gene Fuller said? Please read it again. > Gene said about standing wave current: >> Phase is gone. Kaput. Vanished. Cannot be recovered. >> Never to be seen again. The only "phase" remaining is the >> cos (kz) term, which is really an amplitude description, >> not a phase. How can one use a signal where the phase is gone to measure phase? > However, inductors were measured in an actual antenna. I measured > current, and Roy Lewallen measured phase and current. You and Roy measured standing wave current the phase of which is unchanging over the coil and whip and entire antenna. You should have realized over the past week that those measurements were meaningless. EZNEC shows the same thing. Kraus reports the same thing. ONE CANNOT USE THE PHASE OF STANDING WAVE CURRENT TO MEASURE THE PART OF AN ANTENNA THAT A LOADING COIL REPLACES. > ... and that for a > reasonable sized inductor the taper is very small. The present argument is not about taper, it is about how much of a wavelength a loading coil occupies. One cannot measure that value using standing wave current as you and Roy did. Roy reported accurate phase measurements but standing wave current phase is meaningless since it has unchanging phase. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222469 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> Message-ID: <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> Date: Sun, 19 Mar 2006 03:10:51 GMT Cecil Moore wrote: > Gene Fuller wrote: > >> I could have sworn that you were insisting the phase still had meaning >> in a standing wave environment. > > > I know that's what you thought, but you were mistaken. > By thinking that, you accidentally posted some support > for my side of the argument. Thanks very much. Cecil, I am attaching a few of your quotes in this thread. Sorry to hear about your total loss of short term memory. [Direct quotes from March 5-7] Standing wave current is a net charge flow of zero. Standing wave current is DIFFERENT from traveling wave current. At any and every point, the standing wave current is NOT moving. Since it is not moving, there is NO net charge flow. ****** To tell the truth, standing waves are a product of the human mind. The forward and reflected waves couldn't care less about standing waves Surely you understand that standing waves in a transmission line don't flow - they just stand there, which is why they are called "standing waves". Exactly the same principle applies to standing wave antennas. The two traveling waves have to be analyzed separately and then superposed to obtain valid results. If you analyze net current without superposition, you are doing the same thing as superposing powers, which is a known no-no. ****** The currents that are doing the flowing are the underlying current components, the forward current and the reflected current and they are close to equal. Everything you say about a coil is true for the forward current and the reflected current. It is simply not true for the standing wave current which is just a conceptual construct and not a flowing phasor at all. If you really want to accurately apply the principles you are asserting, you must treat the forward current and reflected current separately and then superpose the results. Applying your above principle to standing wave current is akin to superposing power and that's a no-no. I have never seen such a wide-spread blind spot. [end quotes] 73, Gene W4SZ Article: 222470 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sun, 19 Mar 2006 03:18:51 GMT Cecil Moore wrote: > Gene Fuller wrote: > >> I ignored the harmonic examples. Who ever said that a coil would be a >> lumped inductor when it is operated above its self resonant frequency? > > > Oh, I forgot to ask you a technical question, Gene. Given that > at 11.78 MHz, the current at the bottom of the coil is 0.17 amps > and the current at the top is 2.0 amps, how do you explain those > values if the current is flowing up through the coil? The details > are at the bottom of the following web page. Cecil, Why is this an issue? Is there someone other than your strawman who has a problem with this concept? I don't recall anyone ever questioning such matters. Only in your imagination does anyone deny the existence of distributed, non-lumped components. If there really is such a person, it might be better to address your query to him or to her. 73, Gene W4SZ Article: 222471 of rec.radio.amateur.antenna From: "Lisa Simpson" References: <121phe846j8pdd1@corp.supernews.com> Subject: Re: antenna theory for idiots? Message-ID: <784Tf.33151$UZ5.20552@tornado.ohiordc.rr.com> Date: Sun, 19 Mar 2006 03:22:43 GMT Thanx all - I'll check this book out! "Roy Lewallen" wrote in message news:121phe846j8pdd1@corp.supernews.com... > The ARRL Antenna Book is very good, and it's a good deal more accurate > than many other beginners' books. There's very likely to be a copy at > your local library. > > Roy Lewallen, W7EL > > Lisa Simpson wrote: > > Can anyone point me at a good book or website that can teach me about > > antenna theory from a beginner's standpoint? I'm getting into SWL & feel I > > really need to understand this subject well . . . > > > > Article: 222472 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Sun, 19 Mar 2006 03:32:28 GMT Gene Fuller wrote: > I am attaching a few of your quotes in this thread. Sorry to hear about > your total loss of short term memory. I'm in a learning process here and using the scientific method to correct my mistakes. Isn't that what rational people do? > [Direct quotes from March 5-7] > Standing wave current is a net charge flow of zero. I was corrected on that one and already admitted my mistake. The charges obviously migrate from end to end in the antenna. > Surely you understand that standing waves in a transmission line don't > flow - they just stand there, which is why they are called "standing > waves". Exactly the same principle applies to standing wave antennas. This means the same thing as your posting that phase is gone. A phasor requires a rotating phasor to exhibit flow in the real sense of the word. Standing wave current doesn't possess a rotating phasor so it is not flowing in the normal sense of current flow. If you think standing wave current is flowing, how do you explain 0.17 amps at the bottom of the coil and 2.0 amps at the top? http://www.qsl.net/w5dxp/current.htm bottom of page > The two traveling waves have to be analyzed separately and then > superposed to obtain valid results. Don't see anything wrong with that. If one uses the standing wave current phase to try to measure phase shift through a coil, one is making a mistake as has been demonstrated here. > The currents that are doing the flowing are the underlying current > components, the forward current and the reflected current and they are > close to equal. Everything you say about a coil is true for the forward > current and the reflected current. It is simply not true for the > standing wave current which is just a conceptual construct and not a > flowing phasor at all. You said it yourself, Gene, phase has disappeared from standing wave current. Do you understand the implications of your statements? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222473 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Coils are transmission lines References: <121k5168d8svq85@corp.supernews.com> <121kb283v4krv87@corp.supernews.com> <1142594713.076548.91360@v46g2000cwv.googlegroups.com> <_4ASf.54676$H71.48530@newssvr13.news.prodigy.com> Message-ID: Date: Sun, 19 Mar 2006 03:38:59 GMT Gene Fuller wrote: > Cecil Moore wrote: >> Oh, I forgot to ask you a technical question, Gene. Given that >> at 11.78 MHz, the current at the bottom of the coil is 0.17 amps >> and the current at the top is 2.0 amps, how do you explain those >> values if the current is flowing up through the coil? The details >> are at the bottom of the following web page. > > I don't recall anyone ever questioning such matters. You seem to be trying to have it both ways. 0.17 amps is not equal to 2.0 amps. 0 degrees is not equal to 180 degrees. How are those values possible in a lumped inductor? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222474 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Current through coils Message-ID: <8kqp12h5hs3bmrn2vn34i96m5fr0osv90s@4ax.com> References: <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> Date: Sun, 19 Mar 2006 06:01:29 GMT On Sun, 19 Mar 2006 04:57:54 GMT, Cecil Moore wrote: >Please see http://www.qsl.net/w5dxp/current.htm I refer to the diagram in the section entitled "What EZNEC Says About Current Distribution Using Inductive Loading Stubs" You use the diagram to assert that there is "not a lot of difference between inductive loading stubs and loading coils" by comparing the current distribution with another case. You show graphically the current on each side of the stub. You do not show the current in each wire of the stub or the sum of the currents in the stub. EZNEC calculates the currents in each wire of the stub? Aren't those currents a relevant detail that you have omitted from the diagram. Owen -- Article: 222475 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Sun, 19 Mar 2006 00:10:16 -0800 Message-ID: <121q4fbgb89gb1a@corp.supernews.com> References: <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> <8kqp12h5hs3bmrn2vn34i96m5fr0osv90s@4ax.com> Owen Duffy wrote: > On Sun, 19 Mar 2006 04:57:54 GMT, Cecil Moore > wrote: > >> Please see http://www.qsl.net/w5dxp/current.htm > > I refer to the diagram in the section entitled "What EZNEC Says About > Current Distribution Using Inductive Loading Stubs" > > You use the diagram to assert that there is "not a lot of difference > between inductive loading stubs and loading coils" by comparing the > current distribution with another case. > > You show graphically the current on each side of the stub. You do not > show the current in each wire of the stub or the sum of the currents > in the stub. > > EZNEC calculates the currents in each wire of the stub? Aren't those > currents a relevant detail that you have omitted from the diagram. I don't quite follow the theory on the web page, but what does it predict should happen if there were no antenna at all, and the inductor were connected to a simple series RC circuit instead of the whip? I've taken the EZNEC model available there and modified it by replacing the whip with a wire to ground from the top of the coil (http://eznec.com/misc/test316_modified.EZ). I added a lumped impedance in that wire to represent the impedance of the vertical wire I deleted(*). The feedpoint impedance is the same as for the original model, and the currents at the top and bottom of the inductor are almost exactly the same as for the original model. Can the traveling wave analysis be used to explain the inductor currents in this model? Is traveling wave analysis necessary to explain them? (*) The impedance inserted in the new wire isn't equal to the impedance of the top wire driven against ground. The reason is that the new wire to ground does radiate some, does have significant impedance itself, and does interact with the inductor. The modified system, however, is quite obviously very different in radiating properties from the original, and isn't too different from a lumped RC load. Roy Lewallen, W7EL Article: 222476 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Sun, 19 Mar 2006 03:46:18 -0800 Message-ID: <121qh4dm7om8j13@corp.supernews.com> References: <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> <8kqp12h5hs3bmrn2vn34i96m5fr0osv90s@4ax.com> <121q4fbgb89gb1a@corp.supernews.com> Roy Lewallen wrote: > . . . > I've taken the EZNEC model available there and modified it by replacing > the whip with a wire to ground from the top of the coil > (http://eznec.com/misc/test316_modified.EZ). I added a lumped impedance > in that wire to represent the impedance of the vertical wire I > deleted(*). The feedpoint impedance is the same as for the original > model, and the currents at the top and bottom of the inductor are almost > exactly the same as for the original model. Can the traveling wave > analysis be used to explain the inductor currents in this model? Is > traveling wave analysis necessary to explain them? > > (*) The impedance inserted in the new wire isn't equal to the impedance > of the top wire driven against ground. The reason is that the new wire > to ground does radiate some, does have significant impedance itself, and > does interact with the inductor. The modified system, however, is quite > obviously very different in radiating properties from the original, and > isn't too different from a lumped RC load. Notice that the current into the grounded wire at the bottom of the coil is about 1 amp, and the current going into ground at the grounded end of the added wire is about 0.56 amp. So where is the extra current for the coil bottom wire coming from? The answer is displacement current from the coil. That is, the coil is capacitively coupled to ground, and this causes displacement current from the coil to ground. The effect is greatest at the end of the coil which is farthest from the source. A decent model of the coil is an L network, with a series L, and a shunt C to ground from the far end. This is all that's necessary to explain the drop in current from the bottom to the top; no current waves, standing or traveling, no transmission line analysis are required. If you're not convinced, try this. Change the ground type to free space. Then connect the bottoms of the two formerly grounded wires together with another wire. You'll see that the current at the top of the coil is now very nearly the same as at the bottom. We haven't changed any waves, antenna lengths, or anything else related to antennas or waves. All we've done is to eliminate the other side of the capacitor -- we've removed the C in the equivalent lumped L network. A simple lumped component model explains the difference between grounded and free space models just fine. How well does the traveling wave theory do at it? Roy Lewallen, W7EL Article: 222477 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Sun, 19 Mar 2006 03:48:06 -0800 Message-ID: <121qh7p34ed2a7d@corp.supernews.com> References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> <1142734010.632531.71060@v46g2000cwv.googlegroups.com> <1142764908.270955.105010@i40g2000cwc.googlegroups.com> w8ji@akorn.net wrote: > . . . > This entire thread reminds me of the Fractenna threads of years ago. Don't be so harsh, Tom. Cecil hasn't threatened to sue anybody or called anyone a pirate. But I have to say that the logic does have a familiar ring. Roy Lewallen, W7EL Article: 222478 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> <8kqp12h5hs3bmrn2vn34i96m5fr0osv90s@4ax.com> Message-ID: Date: Sun, 19 Mar 2006 12:41:43 GMT Owen Duffy wrote: > Cecil Moore wrote: >>Please see http://www.qsl.net/w5dxp/current.htm > > I refer to the diagram in the section entitled "What EZNEC Says About > Current Distribution Using Inductive Loading Stubs" > > You use the diagram to assert that there is "not a lot of difference > between inductive loading stubs and loading coils" by comparing the > current distribution with another case. > > You show graphically the current on each side of the stub. You do not > show the current in each wire of the stub or the sum of the currents > in the stub. The currents in stubs cannot be displayed very well at full size in EZNEC just as the currents in coils cannot be displayed very well. Maybe an enlarged view would show it. I will try to do that. > EZNEC calculates the currents in each wire of the stub? Aren't those > currents a relevant detail that you have omitted from the diagram. Remember the present discussion is about the ability to use standing wave current phase to measure the electrical length of a wire or a coil. I have run the currents that you mention. The phase of the current is almost constant through the stubs. The phase of the current is almost constant through the coils. Would you like to see a list of the current at points through the stub Vs the current at points through the coil? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222479 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> <8kqp12h5hs3bmrn2vn34i96m5fr0osv90s@4ax.com> <121q4fbgb89gb1a@corp.supernews.com> Message-ID: Date: Sun, 19 Mar 2006 13:02:14 GMT Roy Lewallen wrote: > Can the traveling wave > analysis be used to explain the inductor currents in this model? In this new configuration, the traveling wave current encounters a short-circuit to ground instead of the open-circuit in a normal antenna. And that forward current is reflected by that short circuit. In the shorted case its phase doesn't change so the forward and reflected currents add instead of subtrace. But their phasors are still rotating in opposite directions. Please note that the phase shift in the standing wave current is almost zero throughout the system, i.e. standing wave phase information has still been lost. We still don't know the electrical length of the coil for the same reasons we didn't know it before. Below 'func' stands for 'function of'. The standing wave current reported by EZNEC is of the form: func(kz)*func(wt) = fun(kz+wt) + func(kz-wt) Is there any way in EZNEC to subtract out the func(kz-wt) reflected term and leave just the forward term? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222480 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> <1142734010.632531.71060@v46g2000cwv.googlegroups.com> <1142764908.270955.105010@i40g2000cwc.googlegroups.com> Message-ID: Date: Sun, 19 Mar 2006 13:04:45 GMT w8ji@akorn.net wrote: > Cecil Moore wrote: >>At the bottom of the page, the coil is seen to have 0.17 amps >>at the bottom and 2.0 amps at the top. With your lumped inductor >>way of thinking, how is that possible? > > Yes it is possible. There is no difference between doing things as > lumped components or standing wave models. Please explain how 0.17 amps can be on the source side of a lumped inductor while 2.0 amps exists at the top of the inductor. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222481 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <121mh75g3ekkme9@corp.supernews.com> <28826-441C4099-1651@storefull-3255.bay.webtv.net> <121ojih732ucf6f@corp.supernews.com> <%Y3Tf.584343$qk4.104946@bgtnsc05-news.ops.worldnet.att.net> <121pmm3758jm4f4@corp.supernews.com> Message-ID: Date: Sun, 19 Mar 2006 13:16:41 GMT Roy Lewallen wrote: > In a linear system like an antenna or transmission line, superposition > applies. ... We must get exactly the same result, ... > If Cecil's analysis shows, or his theory requires, that the result be > different when adding the responses to traveling current waves than it > is by calculating the response directly from the total current, then the > analysis or theory is wrong. Superposition requires that the two results > be identical. Superposition does not require that all information be preserved through the superposition process. Here's an example: Two people are across the room from each other with a coax cable running between them. They each have two identical PSK modems but only one coax. When they use one modem pair, any information one sends is received 100% by the other. When they use the other modem pair, any information one sends is received 100% by the other. When they superpose the signals over the single coax line, all phase information is lost. The superposition results are the same but all phase information is lost in the process. The rules of superposition do not apply to the phase information content. The phase information is lost in the process of superposition. In like manner, the rules of superposition do not apply to the ability of a standing wave to detect phase shift. The phase information is lost in the process of superposition. One cannot use standing wave current phase to measure the electrical length of a wire or a coil. A 75m wire dipole is known to be close to 90 degrees long from the feedpoint to the tip. EZNEC says the current changes phase by 2.5 degrees. How can current change phase by only 2.5 degrees in an antenna wire known to be 90 degrees long? Since EZNEC's standing wave current cannot detect a phase shift in 90 degrees of wire, why should it detect a phase shift in a coil? If standing wave current measurements cannot detect a phase shift in 90 degrees of wire, why should anyone's measurements detect a phase shift in a coil? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222482 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: antenna theory for idiots? Message-ID: References: Date: Sun, 19 Mar 2006 14:11:10 GMT The ARRL Radio Amateur's Handbook (ANY year) is a little less intimidating than the Antenna Handbook. The Antenna Handbook is enough for most of us for many years. On Sun, 19 Mar 2006 02:23:07 GMT, "Lisa Simpson" wrote: >Can anyone point me at a good book or website that can teach me about >antenna theory from a beginner's standpoint? I'm getting into SWL & feel I >really need to understand this subject well . . . > John Ferrell W8CCW