Article: 221970 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: About dipoles and current/voltage nodes Date: Tue, 28 Feb 2006 22:03:42 -0600 Message-ID: <7955-44051D1E-1114@storefull-3256.bay.webtv.net> References: Bob, VK2YQA wrote: "The question is this. If one hangs a 1/2-wave dipole in free space I assume it receives such that current maximums are at the centre and voltage maximums at the ends. Is this the case whether a feedline is connected or not?" Yes, but you must have continuity between both halves of the dipole. If you disconnect the feedline leaving an open circuit gap in the dipole at its centre, you no longer have a 1/2-wave dipole of the same frequency. You have (2) lengths of wire and each has its first resonance at about twice the frequency of first resonance of your original dipole. Best rergards, Richard Harrison, KB5WZI Article: 221971 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Wed, 01 Mar 2006 04:25:04 GMT "Roy Lewallen" wrote in message news:12082j8tknvfi05@corp.supernews.com... > dansawyeror wrote: >> Thanks - I will try to figure you how to create a non lumped model for >> the inductors. Right now that is 'undiscovered country'. > > EZNEC v. 4.0 users should use Wires Window/Create/Create Helix. You'll get > many choices, including position, orientation, various ways of specifying > the pitch and number of turns, twist direction, and so forth. (EZNEC demo > users can create any size helix to see how it works, but won't be able to > run a calculation unless the helix is extremely simple.) In NEC, use a GH > 'card'. > > There should be at least a wire diameter of air space between turns, > preferably several. (That is, the center-center distance between the wires > in one turn and the wires in adjacent turns should be at least two wire > diameters, preferably more.) If air spacing is less than 2 or 3 wire > diameters, the calculated loss will be somewhat lower than reality because > NEC (or EZNEC) doesn't account for proximity effect. > > Roy Lewallen, W7EL As I understand NEC; large errors can be introduced by junctions of dissimilar wire diameters, and in particular when the wires are at 90 deg. Therefore, when you have designed your "GH" inductors, the rest of the antenna should by constructed of the same diameter wire. This may be difficult since Dan is using two coils of significantly different Qs. I guess you could overcome this problem by varying the conductivity of the inductor to obtain the desired Q. Also, since segmentation tends to be relatively high in a helix, should segment length tapering be applied to those segments adjacent to the helix? Frank, VE6CB Article: 221972 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1141169364.174650.133280@i39g2000cwa.googlegroups.com> Subject: Re: Help colinear building problems Message-ID: Date: Wed, 01 Mar 2006 04:44:25 GMT wrote in message news:1141169364.174650.133280@i39g2000cwa.googlegroups.com... > Im trying to build a 6dB simple colinear for my 2.4g wireless setup. > Im using a simple setup > from: > > //martybugs.net/wireless/collinear.cgi > > It uses a short piece of 12ga copper house wire with just two one turn > loops at 1/2 wave & 3/4 wave. I have access to a network analyzer @ > work so i tried measuring the antenna'but come up with 1.4 g & 3.4 g. > No matter what i do i cant get the antenna near the 2.4 band. > Over the years Ive build many amateur band antennas of all types but > this ones got the best > of me. Hi Marty Would you be open to trying a different configuration?? This site shows how to build colinear arrays from lengths of coax http://wireless.gumph.org/articles/homemadeomni Jerry > Article: 221973 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Date: Tue, 28 Feb 2006 21:37:57 -0800 Message-ID: <120acppce6jle62@corp.supernews.com> References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> Frank wrote: > > As I understand NEC; large errors can be introduced by junctions of > dissimilar wire diameters, and in particular when the wires are at 90 deg. > Therefore, when you have designed your "GH" inductors, the rest of the > antenna should by constructed of the same diameter wire. This may be > difficult since Dan is using two coils of significantly different Qs. I > guess you could overcome this problem by varying the conductivity of the > inductor to obtain the desired Q. Also, since segmentation tends to be > relatively high in a helix, should segment length tapering be applied to > those segments adjacent to the helix? > > Frank, VE6CB It's difficult to give an absolute answer to these questions, but some general comments and guidelines should help. First, the error introduced by NEC-2 when wires of dissimilar diameter are connected is generally small, unless the wires are grossly different. This error can be minimized by making the segments as *long* as possible adjacent to the junction, which of course is contrary to the general principle that more segments are better. Even a small error can cause major changes in the pattern when the dissimilar diameter wires are in a parasitic element. EZNEC and a number of other programs have a built-in method of avoiding this problem for certain antenna types, but plain NEC-2 doesn't. NEC-4 is relatively free of this problem, but it's quite expensive for hobby use. The Q of an inductor is determined by the inductance and the loss. The loss is a function of the dielectric, wire resistance, and radiation (which isn't really loss, but lowers Q as though it were). NEC type programs automatically account for the radiation, and it's easy to include wire loss. So assuming negligible dielectric loss, the programs should predict Q fairly accurately -- except for proximity affect. Proximity effect could be modeled in NEC by increasing the resistivity of the wires in the coil. EZNEC currently allows only a single wire resistivity for the whole model (although this will probably change in the next version). However, since the overall loss will be dominated by the inductors, the higher resistivity could be specified for the whole model without sacrificing significant accuracy. Alternatively, a number of resistive loads could be inserted in the inductors. Segment length tapering usually isn't necessary with NEC based programs, unless there's a source near a place where the segment length changes. An average gain check should be run to determine if there's a problem. If there is, segment length tapering is one tool which can be tried in improving the average gain. Roy Lewallen, W7EL Article: 221974 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: Message-ID: <44053ca7_4@newsfeed.slurp.net> Date: 1 Mar 2006 01:18:15 -0500 I can't prove this but I suspect there will be very little difference. The wavelength on 80/75 meters is so much longer than the car body that going from a low mount to a high one will be almost unnoticeable. Ground loss will be about the same because the capacitance between the car body and ground is the important factor and does not depend on where the whip is mounted. What will matter greatly is the Q of the coil. Make it inherently as high as you can and keep it away from metal parts of the car body. Resonate it and match it and you will have lots of fun. 80/75 is a great band for mobile and much underused. Bill, W6WRT Article: 221975 of rec.radio.amateur.antenna Date: Wed, 01 Mar 2006 00:59:20 -0700 From: BKR Subject: Re: Help colinear building problems References: <1141169364.174650.133280@i39g2000cwa.googlegroups.com> Message-ID: <44055454$1@nntp.zianet.com> Your link was slightly in error. Here is a corrected version: http://wireless.gumph.org/articles/homemadeomni.html Jerry Martes wrote: > wrote in message > news:1141169364.174650.133280@i39g2000cwa.googlegroups.com... > >>Im trying to build a 6dB simple colinear for my 2.4g wireless setup. >>Im using a simple setup >>from: >> >>//martybugs.net/wireless/collinear.cgi >> >>It uses a short piece of 12ga copper house wire with just two one turn >>loops at 1/2 wave & 3/4 wave. I have access to a network analyzer @ >>work so i tried measuring the antenna'but come up with 1.4 g & 3.4 g. >>No matter what i do i cant get the antenna near the 2.4 band. >>Over the years Ive build many amateur band antennas of all types but >>this ones got the best >>of me. > > > > Hi Marty > > Would you be open to trying a different configuration?? This site shows > how to build colinear arrays from lengths of coax > > http://wireless.gumph.org/articles/homemadeomni > > Jerry > > > > Article: 221976 of rec.radio.amateur.antenna From: condor Subject: pse info balun Message-ID: Date: Wed, 01 Mar 2006 10:55:02 GMT I will made a dipole for 10.1 Mhz v inverted, with total lenght 15 mtrs. What is the appropriate balun ? 1:1 1:2 1:5 or others ? tnx Article: 221977 of rec.radio.amateur.antenna From: Dot Subject: Re: pse info balun Message-ID: References: Date: Wed, 01 Mar 2006 06:40:38 -0500 On Wed, 01 Mar 2006 10:55:02 GMT, condor wrote: >I will made a dipole for 10.1 Mhz v inverted, with total lenght 15 mtrs. >What is the appropriate balun ? 1:1 1:2 1:5 or others ? tnx An inverted V antenna with it's legs pointing downward at about 30 degree angles should present an impedance of about 52 ohms and will not need an impedance matching device. A balun, which is not an impedance matching device, is a good idea. Mount it as close to the antenna's feedpoint as possible to tame feedline radiation that might degrade the performance of the antenna and seriously piss off your neighbors. The easiest one is this... http://www.hamuniverse.com/balun.html Article: 221978 of rec.radio.amateur.antenna From: "Jeff Dieterle" Subject: Coax help Date: Wed, 1 Mar 2006 08:57:51 -0500 Message-ID: Can anyone direct me to a web sight that explains the differences between the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it basically the gauge of the conductor. Article: 221979 of rec.radio.amateur.antenna From: Dot Subject: Re: Coax help Message-ID: References: Date: Wed, 01 Mar 2006 09:16:59 -0500 On Wed, 1 Mar 2006 08:57:51 -0500, "Jeff Dieterle" wrote: >Can anyone direct me to a web sight that explains the differences between >the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it >basically the gauge of the conductor. The key differences are impedence, loss, velocity factor and diameter. An example chart here. http://www.wb8erj.com/coaxloss.htm For detailed information contact your local electronics dealer, find out what he sells, then get the manufacturer's data sheets. Article: 221980 of rec.radio.amateur.antenna From: chuck Subject: Re: Q about balanced feed line References: <1206jvk3rsclp55@corp.supernews.com> Message-ID: Date: Wed, 01 Mar 2006 15:04:23 GMT I keep forgetting some of these principles. Thanks very much for the detailed and helpful explanations, Roy. 73, Chuck Roy Lewallen wrote: > chuck wrote: > >> As a follow-up, is there a practical way to determine how much current >> unbalance will cause a one dB reduction in power delivered to the >> antenna, the "lost power" being that power radiated by the >> transmission line? >> >> It seems like a rather complex modeling problem. >> >> Thanks! >> >> Chuck, NT3G > > > Nope. You can't generally say that one part of an antenna is radiating a > particular amount of the total power. Each part of the antenna creates a > field, and it interacts with the fields from all other parts of the > antenna. The total power radiated has to equal the total power input > less loss, but that's all you can say for sure. An example will help > illustrate the problem. Consider a parasitic element in a Yagi. It has > considerable current and contributes a great deal to the overall > pattern. Yet the total power input to the Yagi element is zero. With > zero power input, it can't, by itself, be radiating any power. What it > does is intercept some of the power radiated by the driven element and > re-radiates it with a different phase and amplitude. So how would you > apportion the power radiated by the driven element and the parasitic > element? > > You might take a look at the current in the driven element and note that > it increases or decreases as you put the parasitic element in place and > remove it. But the current can either increase or decrease, depending on > the length and spacing of the parasitic element. So has the parasitic > element increased or decreased the power radiated by the driven element? > There's no answer. > > You can look at the change in pattern in some idealized cases by > modeling. This can tell you what range of effects you might expect in a > real situation. > > Roy Lewallen, W7EL > Article: 221981 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: About dipoles and current/voltage nodes References: <9th9025nqnmh2h5akisv3v7ll0oo3gn69i@4ax.com> <9vda02phh8315lpi2i6vn40iofv9l1om66@4ax.com> Message-ID: Date: Wed, 01 Mar 2006 09:19:37 -0600 Hi Richard >>I was surprised that the sensor line was so long and so > On the order of 1.5 cM? It is a "U shape". The section parallel to the output stripline is maybe 1cm long (going from memory). The leg length may then put the total size at more like 2cm. --- >>I am thinking also that the 50 ohm output is not being preserved as it >>goes past the sensor stripline. > What does that mean? I am suggesting that given the proximity of the sensor section it presents a significant Z bump. Like I said I dont have a feeling for the track dimensions for stripline etc at microwave. Not that it wouldnt be difficult to look it up mind you! --- >>I think the freq coverage for this model >>is about 10.5 to 11.5GHz. Keep in mind that this really is the frist >>time I have seen microwave TX's up close so my gut feelings about track >>sizes/spacing may be way off. > Check the resistor. One of the first things done. At DC of course. Dont think I ever replaced it. Was considering playing with it last time but since moving the frequency also bought it back to normal operating conditon I couldnt see it as a reason. Cheers Bob VK2YQA Article: 221982 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: Date: Wed, 01 Mar 2006 18:29:49 GMT nm5k@wt.net wrote: > What we found at the CA shootouts is that when the bottom > section runs closely parallel to the vehicle body, as it > does with a trailer hitch mount on an SUV, the field > strength is much lower than if that bottom section is > in the clear, e.g. mounted on the roof of the SUV..... > > I often wonder about this myself, but never get around to trying a > bumper mount. In the past, I've always preferred to have the lower > mast and coil as clear of the body as possible. But on the other > hand, if I mounted the base on the bumper, I could have a longer > mast below the coil. What worked like a charm for me was using the trailer hitch hole on my GMC pickup and removing the tailgate. I looked for a fiberglass aftermarket tailgate but couldn't find one. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221983 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: 80m mobile antenna question Date: Wed, 01 Mar 2006 18:57:39 -0000 Message-ID: <120brl3p0a1rh94@corp.supernews.com> References: <44053ca7_4@newsfeed.slurp.net> In article , Cecil Moore wrote: >What we found at the CA shootouts is that when the bottom >section runs closely parallel to the vehicle body, as it >does with a trailer hitch mount on an SUV, the field >strength is much lower than if that bottom section is >in the clear, e.g. mounted on the roof of the SUV. That seems to match up with various peoples' experiences that I've heard. Close spacing in this way makes the signal weaker, and also seems to make the antenna more difficult to tune/match properly. This also makes sense from an engineering point of view. The closely-parallel spacing of the bottom section and the metal vehicle body would form a transmission line of sorts. This transmission-line section would not radiate much (or efficiently) - its radiation resistance would be quite low. As a result, the antenna's feedpoint impedance would be lower than otherwise (requiring a more aggressive impedance step-up of some sort to match a 50-ohm line). The coil and whip would be above the body, and would still be able to radiate, but you'd be left with something akin to a bottom-loaded whip with no high-current radiating section, rather than a center-loaded radiator with a low-loss high-current radiating section below the coil. In effect, a close/parallel mounting of this sort would seem to sacrifice much of the radiating power of this type of antenna. -- 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: 221984 of rec.radio.amateur.antenna From: "Caveat Lector" References: Subject: Re: Coax help Message-ID: Date: Wed, 1 Mar 2006 13:39:03 -0800 Several URL's to look at http://ac6v.com/techref.htm#coax -- CL -- I doubt, therefore I might be ! "Jeff Dieterle" wrote in message news:afeb0$4405a863$424980aa$9130@COMTECK.COM... > Can anyone direct me to a web sight that explains the differences between > the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it > basically the gauge of the conductor. > Article: 221985 of rec.radio.amateur.antenna From: "Frank's" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> <120acppce6jle62@corp.supernews.com> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: <5JoNf.7747$Ui.2219@edtnps84> Date: Wed, 01 Mar 2006 21:53:05 GMT "Roy Lewallen" wrote in message news:120acppce6jle62@corp.supernews.com... > Frank wrote: >> >> As I understand NEC; large errors can be introduced by junctions of >> dissimilar wire diameters, and in particular when the wires are at 90 >> deg. Therefore, when you have designed your "GH" inductors, the rest of >> the antenna should by constructed of the same diameter wire. This may be >> difficult since Dan is using two coils of significantly different Qs. I >> guess you could overcome this problem by varying the conductivity of the >> inductor to obtain the desired Q. Also, since segmentation tends to be >> relatively high in a helix, should segment length tapering be applied to >> those segments adjacent to the helix? >> >> Frank, VE6CB > > It's difficult to give an absolute answer to these questions, but some > general comments and guidelines should help. > > First, the error introduced by NEC-2 when wires of dissimilar diameter are > connected is generally small, unless the wires are grossly different. This > error can be minimized by making the segments as *long* as possible > adjacent to the junction, which of course is contrary to the general > principle that more segments are better. Even a small error can cause > major changes in the pattern when the dissimilar diameter wires are in a > parasitic element. EZNEC and a number of other programs have a built-in > method of avoiding this problem for certain antenna types, but plain NEC-2 > doesn't. NEC-4 is relatively free of this problem, but it's quite > expensive for hobby use. > > The Q of an inductor is determined by the inductance and the loss. The > loss is a function of the dielectric, wire resistance, and radiation > (which isn't really loss, but lowers Q as though it were). NEC type > programs automatically account for the radiation, and it's easy to include > wire loss. So assuming negligible dielectric loss, the programs should > predict Q fairly accurately -- except for proximity affect. Proximity > effect could be modeled in NEC by increasing the resistivity of the wires > in the coil. EZNEC currently allows only a single wire resistivity for the > whole model (although this will probably change in the next version). > However, since the overall loss will be dominated by the inductors, the > higher resistivity could be specified for the whole model without > sacrificing significant accuracy. Alternatively, a number of resistive > loads could be inserted in the inductors. > > Segment length tapering usually isn't necessary with NEC based programs, > unless there's a source near a place where the segment length changes. An > average gain check should be run to determine if there's a problem. If > there is, segment length tapering is one tool which can be tried in > improving the average gain. > > Roy Lewallen, W7EL Thanks for the information Roy, all remarks noted and saved. Will see what I can do to generate some realistic helical models. Frank VE6CB Article: 221986 of rec.radio.amateur.antenna From: "west" Subject: 3 Monos or a Tribander? Message-ID: Date: Wed, 01 Mar 2006 22:21:10 GMT Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was wondering what I should use for a base antenna that will be over 60ft high (bet I'll get tons of intermod). One thought is to purchase the best tri-bander available or, perhaps there is too much compromise with an all-in-one. Would you use a dual bander and a mono, which band is the dual & which the mono or 3 monos? Of course with anything other than a tri-bander, a triplexer will be needed. Oh what trying decisions a ham must make! Any comments most welcomed. 73s west AF4GC Article: 221987 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Coax help Date: Wed, 1 Mar 2006 16:42:37 -0600 Message-ID: References: Do a Google on : Coax RG8 belden RG58 Loss or variations thereof... There is loss, impedance and size as the primary things that are important. 73, Steve, K9DCI "Jeff Dieterle" wrote in message news:afeb0$4405a863$424980aa$9130@COMTECK.COM... > Can anyone direct me to a web sight that explains the differences between > the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it > basically the gauge of the conductor. > > Article: 221988 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: pse info balun Date: Wed, 1 Mar 2006 23:58:11 +0000 (UTC) Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> "Cecil Moore" wrote > What kind of feedline are you using? In any case, > a good 1:1 choke-balun is preferred. ========================================= How do you select a good choke balun from amongst all the others. --- Reg. Article: 221989 of rec.radio.amateur.antenna From: "Jerry" References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Subject: Re: 80m mobile antenna question Message-ID: <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Date: Wed, 1 Mar 2006 20:26:17 -0500 "Cecil Moore" wrote in message news:xKlNf.36179$Jd.27783@newssvr25.news.prodigy.net... > nm5k@wt.net wrote: >> What we found at the CA shootouts is that when the bottom >> section runs closely parallel to the vehicle body, as it >> does with a trailer hitch mount on an SUV, the field >> strength is much lower than if that bottom section is >> in the clear, e.g. mounted on the roof of the SUV..... >> >> I often wonder about this myself, but never get around to trying a >> bumper mount. In the past, I've always preferred to have the lower >> mast and coil as clear of the body as possible. But on the other >> hand, if I mounted the base on the bumper, I could have a longer >> mast below the coil. > > What worked like a charm for me was using the trailer hitch > hole on my GMC pickup and removing the tailgate. I looked > for a fiberglass aftermarket tailgate but couldn't find one. > -- > 73, Cecil http://www.qsl.net/w5dxp With that in mind, I have a friend who has a Ford Exploder--I mean, EXPLORER :) --- with his DK3 mounted on a homebrew mount level with the rear bumper. The bad part of it (IMHO) is the loading coil is level with the body about where the rear window is and about 8 inches from the body. I mentioned to him that it would be better to get the coil up in the clear above the truck, but he is says he can't get in his carport. Well, what about this: move the coil UP to clear the body and use a shorter whip? IOW, faced with the lesser of two evils, which would be better. Left as is with longer whip and putting up with the loss caused by proximity to body metal, or coil clearing the top of the truck and a shorter whip--even it it has to be 5 feet instead of 6 1/2? I voted for the higher coil and shorter whip. What say ye? :) 73 Jerry K4KWH Article: 221990 of rec.radio.amateur.antenna Date: Wed, 01 Mar 2006 19:28:10 -0600 From: Tom Ring Subject: Re: need help with H antenna References: Message-ID: <44064a2a$0$7335$39cecf19@news.twtelecom.net> Jim wrote: > I need help in building an H type of tracking antenna for use around 166-167 > mhz. This is for wildlife tracking. I have a couple of handheld 3 element > Yagi's that I built using YagiCad to do the math, and they work well, but > they are big and clunky. > > There are times when I am willing to sacrifice the good f/b ratio of the > yagi for convienience, for instance when working in brushy woods. I have > used an H for tracking at 151 mhz, but of course, I can't use that one for > 166. > > My tracking receiver, a King portable, has a BNC connector, so I can > interchange antennas quickly. > > Is there a web page or magazine article that can help me design my H, or can > someone share their experience? > > Thanks > Jim > > I am assuming you mean a 2 element beam with both elements driven. If so, I would recommend trying to make a 2 meter version of Roy W7EL's version of the ZL special. I just messed around with his downloadable program for 15 minutes and got a reasonable version hacked up for your frequency. The impedance wasn't perfect, about 1.5 at best and about 3 to 1 SWR +-1.5 MHz, but you are receive only, so that's not a big deal. Heck, he may notice this response and tell you he's done one and what he came up with for lengths. Tom K0TAR Article: 221991 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: pse info balun Date: Wed, 01 Mar 2006 17:54:20 -0800 Message-ID: <120ck2den5gmhc2@corp.supernews.com> References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Reg Edwards wrote: > > How do you select a good choke balun from amongst all the others. > --- The important characteristic is common mode impedance. Tie the two input conductors together and the two output conductors together, and measure the input-to-output impedance. This can be done in various ways, most easily with an antenna analyzer, or by other means. The higher the impedance, the better. 1000 ohms seems to be a good number to shoot for, with 500 ohms probably being ok for most applications. The angle of the impedance doesn't matter unless you're running high power, in which case it might be necessary to keep the impedance more reactive than resistive to prevent excessive core heating. A good choke balun for multiple band use will have a high common mode impedance on all bands on which it'll be used. Narrower band ones can be connected in series as an alternative. Roy Lewallen, W7EL Article: 221992 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: pse info balun References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Message-ID: Date: Thu, 02 Mar 2006 04:12:03 GMT Reg Edwards wrote: > How do you select a good choke balun from amongst all the others. I roll my own. I have 8 FB-77-5621 cores over a piece of RG-400 in series with an FT-240-61 with ten turns of RG-400. The latter comes in a ~$10 balun kit from Amidon. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221993 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Message-ID: Date: Thu, 02 Mar 2006 04:15:36 GMT Jerry wrote: > I voted for the higher coil and shorter whip. What say ye? :) Within reason, the higher the coil, the better. I only had one foot of antenna above my coil, a one foot section upon which was mounted a large horizontal top hat. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221994 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: <440674bf_3@newsfeed.slurp.net> Date: 1 Mar 2006 23:29:51 -0500 ORIGINAL MESSAGE: nm5k@wt.net wrote: > What we found at the CA shootouts is that when the bottom > section runs closely parallel to the vehicle body, as it > does with a trailer hitch mount on an SUV, the field > strength is much lower than if that bottom section is > in the clear, e.g. mounted on the roof of the SUV..... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No doubt that is correct. So how about this: I have a '95 Thunderbird which I dearly love and don't want to cut holes in. I've been think of going to a welding shop and having a metal piece made which I could bolt to the frame in the back and which would stick out about six inches or so behind the rear bumper, and installing a ball mount on it. This will keep the lower part of the antenna about a foot away from the body and allow a nice, long whip overall. The loading coil would be in the center, homebrew of course. :-) And not a hole in sight. Comments? Bill, W6WRT Article: 221995 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: <440674ea$1_3@newsfeed.slurp.net> Date: 1 Mar 2006 23:30:34 -0500 ORIGINAL MESSAGE: nm5k@wt.net wrote: > What we found at the CA shootouts ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Speaking of shootouts, are any scheduled for this year anywhere? Bill, W6WRT Article: 221996 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Thu, 02 Mar 2006 05:02:28 GMT Dan, I have been trying to replicate your inductors with NEC. It is a bit tedious, just guessing wire gauge, coil diameter etc., to obtain the desired inductance and Q. What are the physical dimensions of your inductors? Have you had any luck with GH? You may have a problem with 4nec2 since you must have a GM card along with the GH. Frank "dansawyeror" wrote in message news:4403EB86.3020005@comcast.net... > Good question. I will play with that. That said, based on Roy's comment at > minimum the load should appear nearly pure resistive. > > I just tested the Autek with 6.25, 12.5, and 25 Ohm loads. > 25 read 26 > 12.5 read 12 - 13 - 12 etc. > 6.25 read mostly 7 with an occasional 6. > > I would say for non-reactive loads it is pretty close. > > Tomorrow - will be to experiment with non lumped inductors. That will be a > challenge. > > Thanks - Dan > > > Frank wrote: >> "dansawyeror" wrote in message >> news:4403C93F.2040700@comcast.net... >> >>>Frank, >>> >>>The Autek is remarkably close. I have used it to checkout 50 and 25 Ohm >>>loads. For these two values it is very close. (It is battery level >>>sensitive.) >>> >>>The couplers are a pair of M-C ZFDC 20-4's. >>> >>>Dan >> >> >> Thanks Dan, I had forgotten about Mini-Circuits. Their price is hard to >> beat. I may pick up one of the "PDC" series dual directional couplers. >> Incidentally your code indicates resonance occurs at 3.54 MHz. I wonder >> how the Autek behaves when subjected to a reactive load does it actually >> get close to the magnitude? >> >> Frank Article: 221997 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Wed, 01 Mar 2006 21:35:43 -0800 Message-ID: <120d11fn5ontsb0@corp.supernews.com> References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Bill Turner wrote: > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > No doubt that is correct. So how about this: I have a '95 Thunderbird > which I dearly love and don't want to cut holes in. I've been think of > going to a welding shop and having a metal piece made which I could > bolt to the frame in the back and which would stick out about six > inches or so behind the rear bumper, and installing a ball mount on it. > This will keep the lower part of the antenna about a foot away from the > body and allow a nice, long whip overall. The loading coil would be in > the center, homebrew of course. :-) > > And not a hole in sight. > > Comments? > > Bill, W6WRT I'm not sure why, but most amateurs don't seem to realize that the whip isn't an "antenna" and the car "ground", but each is half of a dipole-like antenna. The car part is often much more important with regard to radiation characteristics and efficiency than the whip part. With the arrangement you suggest, the antenna consists of a vertical wire -- the whip -- and a fat, horizontal "wire" -- the car. Whatever current flows into the whip, an equal current flows over the outside of the car, originating at the base of the whip. Any antenna with a low horizontal wire will be quite lossy, because the wire's current will induce a heavy current in the lossy ground beneath the wire, or car. The best arrangement, as others have pointed out, is to mount the antenna right at the center of the top of the car. This makes the car "wire" vertical, a much more efficient arrangement, which the "shootouts" consistently show. You'll also find that larger trucks, which effectively form a longer vertical "wire" for the car part, outdo smaller ones for the same whip. Of course, sometimes you don't have any choice, and you just have to do the best you can. I once had a bumper mounted antenna consisting of a CB whip base loaded with an inductor wound on a powdered iron core to resonate on 40 meters. The car was a VW Squareback, so the antenna had the increased disadvantage of proximity between the square back and the antenna. As others have pointed out, this can reduce efficiency farther. Yet I had a successful QSO with JA while driving down Highway 101, running 8 watts, CW. So you can still communicate and have lots of fun even with a very sub-optimal system. But anyone wanting to improve his system has a much better chance of doing it if he has a basic understanding of how the antenna really works. Roy Lewallen, W7EL Article: 221998 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: need help with H antenna Date: Wed, 01 Mar 2006 21:45:33 -0800 Message-ID: <120d1jtr6triu56@corp.supernews.com> References: <44064a2a$0$7335$39cecf19@news.twtelecom.net> Tom Ring wrote: > I am assuming you mean a 2 element beam with both elements driven. > > If so, I would recommend trying to make a 2 meter version of Roy W7EL's > version of the ZL special. I just messed around with his downloadable > program for 15 minutes and got a reasonable version hacked up for your > frequency. The impedance wasn't perfect, about 1.5 at best and about 3 > to 1 SWR +-1.5 MHz, but you are receive only, so that's not a big deal. For his application, shoot for the best F/B ratio -- that is, for element currents as close to equal and the correct phase -- as possible. The forward lobe of this antenna is broader than a 3 element Yagi. It would work best as a direction finding antenna by determining the direction of the null. Quite a bit of mismatch should be tolerable unless signals are extremely weak, but if an adequate match can't be achieved, it's simple to remedy with a simple matching network. > Heck, he may notice this response and tell you he's done one and what he > came up with for lengths. Nope. I've never had occasion to design an antenna for 166 MHz. One designed for 2 meters (which I haven't done either) won't work satisfactorily at 166. Roy Lewallen, W7EL Article: 221999 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Message-ID: <4406b31d_1@newsfeed.slurp.net> Date: 2 Mar 2006 03:55:57 -0500 Roy Lewallen wrote: > The best arrangement, as others have pointed out, is to mount the > antenna right at the center of the top of the car. This makes the car > "wire" vertical, a much more efficient arrangement, which the > "shootouts" consistently show. You'll also find that larger trucks, > which effectively form a longer vertical "wire" for the car part, > outdo smaller ones for the same whip. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Well, maybe. The problem is, the higher the mounting point, the shorter the whip has to be to be legal to drive down the road. If your car was 13 feet five inches tall, your whip could only be one inch long. How efficient would that be on 80 meters? The point being, everything is a tradeoff of one thing for another. If the shootouts say a rooftop is best, ok, but I have to say I'm surprised. At a relatively low frequency like 80 meters, the car body is more of a coupler to the earth rather than a real "ground" of it's own. Given that, then the longer the whip part, the better. HF mobile antennas are a fascinating subject and one of these days I will set up a "shootout" range on my 2.5 acres here in the desert and do some shooting of my own. Bill, W6WRT Article: 222000 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: pse info balun Date: Thu, 2 Mar 2006 11:53:52 +0000 (UTC) Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> "Cecil Moore" wrote in message news:nguNf.17219$rL5.15156@newssvr27.news.prodigy.net... > Reg Edwards wrote: > > How do you select a good choke balun from amongst all the others. > > I roll my own. I have 8 FB-77-5621 cores over a piece > of RG-400 in series with an FT-240-61 with ten turns of > RG-400. The latter comes in a ~$10 balun kit from Amidon. > -- > 73, Cecil http://www.qsl.net/w5dxp =========================================== Ten or more turns of twin, 18 awg, stranded, speaker cable is even better. Easier to make and has higher choke impedance and lower loss. I don't know why you mess about with coax. ---- Reg. Article: 222001 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Message-ID: Date: Thu, 02 Mar 2006 13:09:54 GMT Bill Turner wrote: > So how about this: I have a '95 Thunderbird > which I dearly love and don't want to cut holes in. I've been think of > going to a welding shop and having a metal piece made which I could > bolt to the frame in the back and which would stick out about six > inches or so behind the rear bumper, and installing a ball mount on it. > This will keep the lower part of the antenna about a foot away from the > body and allow a nice, long whip overall. The loading coil would be in > the center, homebrew of course. :-) The only way to improve on that on 75m would be to mount a piece of sheet metal on fiberglass poles connected at the ends of both bumpers. The piece of horizontal sheet metal, located 13.5 feet from the ground, would have the same footprint as the T-bird and would be used as the top hat. You do want optimum performance don't you? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222002 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Message-ID: Date: Thu, 02 Mar 2006 13:19:27 GMT Roy Lewallen wrote: > I'm not sure why, but most amateurs don't seem to realize that the whip > isn't an "antenna" and the car "ground", but each is half of a > dipole-like antenna. My S10 trailer hitch mounted configuration exhibited considerable directivity toward the front of the pickup on 17m. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222003 of rec.radio.amateur.antenna Message-ID: <4406F37B.1B33CB65@nospam.com> From: jon Subject: Re: Coax help References: Date: Thu, 02 Mar 2006 13:30:35 GMT RG-8 is no longer a military standard RG-213 is a better choice. http://www.thewireman.com he wrote a book ! http://www.belden.com Article: 222004 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: pse info balun References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Message-ID: Date: Thu, 02 Mar 2006 13:34:04 GMT Reg Edwards wrote: > Ten or more turns of twin, 18 awg, stranded, speaker cable is even > better. > > Easier to make and has higher choke impedance and lower loss. > > I don't know why you mess about with coax. The optimum Z0 for the wire that is used is the square root of the product of the input impedance and the output impedance. I vary the length of my ladder-line to accomplish resonance in my antenna system. The impedances seen at the output of my balun averages 50 ohms. Thus, the optimum Z0 for my balun wire is 50 ohms. Magnet wire will do that but speaker cable won't. Ten turns of RG-400 is really convenient. I use RG-400 for everything inside of the shack. All the 1/2" dia. stuff is outside. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222005 of rec.radio.amateur.antenna From: Bob Bob Subject: 2m omnis and radiation takeoff angles - importance Message-ID: <0l8jd3-mag.ln1@p400bob.personal.cox.net> Date: Thu, 02 Mar 2006 07:30:39 -0600 Hi NG About ready to model and build a medium 2m antenna system. Probably run a EDZ with 5/8 elements off one side of the mast for vertical and a three element wide spaced thick element quad for horiz on the other side. The mast mount will form part of the model when I get to it. (Hoping for a cardioid pattern from the EDZ) Main element material for both antennas will probably be 1/2" copper. (That will make the quad interesting to support!) Sticking to the vertical system I am wanting to get a handle on how important the "problem" of desired low angle radiation is and what traps one should avoid. I am aware of the mast/coax decoupling issues. I also believe that the narrower the vertical beamwidth (or rather the less downward radiation) the less the ground reflection problem will be. Also wondering if adjusting phase delay or amplitude variations between the 5/8 elements would be useful in lowering the pattern. (Something I will also be modelling) Feed would probably be a 4:1 coaxial balun. Height will eventually be about 30ft above the house roof. Any thoughts, ideas and debunking most welcome Cheers Bob W5/VK2YQA Article: 222006 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: 3 Monos or a Tribander? Message-ID: <620e025tnbgq20oqd0k9qq3574d967of7r@4ax.com> References: Date: Thu, 02 Mar 2006 14:28:01 GMT In my experience a super antenna for repeater operation is a problem. You bring up enough machines to create your own QRM. Keep it simple. On Wed, 01 Mar 2006 22:21:10 GMT, "west" wrote: >Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was >wondering what I should use for a base antenna that will be over 60ft high >(bet I'll get tons of intermod). One thought is to purchase the best >tri-bander available or, perhaps there is too much compromise with an >all-in-one. Would you use a dual bander and a mono, which band is the dual & >which the mono or 3 monos? Of course with anything other than a tri-bander, >a triplexer will be needed. Oh what trying decisions a ham must make! Any >comments most welcomed. > >73s >west >AF4GC > John Ferrell W8CCW Article: 222007 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Message-ID: <440711e5$1_1@newsfeed.slurp.net> Date: 2 Mar 2006 10:40:21 -0500 Cecil Moore wrote: > The only way to improve on that on 75m would be to mount > a piece of sheet metal on fiberglass poles connected at > the ends of both bumpers. The piece of horizontal sheet > metal, located 13.5 feet from the ground, would have the > same footprint as the T-bird and would be used as the top > hat. You do want optimum performance don't you? :-) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I think my T-Bird might actually fly. :-) 73, Bill W6WRT Article: 222008 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Thu, 2 Mar 2006 10:56:15 -0600 Message-ID: <12478-440723AF-300@storefull-3258.bay.webtv.net> References: <120d11fn5ontsb0@corp.supernews.com> Roy Lewallen, W7EL wrote: "I`m not sure why, but most amateurs don`t seem to realize that a whip isn`t an "antenna" and the car "ground", but each is half of a dipole-like antenna." Not exactly.. In a common balanced dipole, each half has the same current quantity and direction, though in one half the current flows toward the feedpoint while it flows away in the other half. >From such a dipole, both its halves contribute equally to its radiation. Action of a common ground plane is different. When its balanced radials are perpendicular to its whip, radiation from its radials zeros out leaving the whip to do all the radiation. Ideally, a whip mounted on a vehicle or directly on the earth behaves the same. It is the whip which radiates. An antenna is also called an aerial. It is defined as that part of a radio station which radiates or receives radio waves into or from space. An antenna ground system is defined as that portion of an antenna system closely associated with the earth and including an extensive conducting surface which may be the earth itself. Most radio amateurs have it right. Best regards, Richard Harrison, KB5WZI Article: 222009 of rec.radio.amateur.antenna From: "NA" Subject: FS: Heath Marauder Transmitter Message-ID: Date: Thu, 02 Mar 2006 17:50:02 GMT I have checked with the local shipping service. Shipping via FEDX will be between $150 and $200 to most address on the US mainland. I have seen Marauders not meet the reserve on Ebay at over $150 plus shipping. I will sell this one for $100 plus the actual shipping cost charged by the local shipping store. Thanks for reading Jim N6PJQ AT Hotmail Article: 222010 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Thu, 02 Mar 2006 12:16:20 -0800 Message-ID: <120ekkmb2nbrk75@corp.supernews.com> References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> Richard Harrison wrote: > Roy Lewallen, W7EL wrote: > "I`m not sure why, but most amateurs don`t seem to realize that a whip > isn`t an "antenna" and the car "ground", but each is half of a > dipole-like antenna." > > Not exactly.. > > In a common balanced dipole, each half has the same current quantity and > direction, though in one half the current flows toward the feedpoint > while it flows away in the other half. > > From such a dipole, both its halves contribute equally to its radiation. > > Action of a common ground plane is different. When its balanced radials > are perpendicular to its whip, radiation from its radials zeros out > leaving the whip to do all the radiation. Ideally, a whip mounted on a > vehicle or directly on the earth behaves the same. It is the whip which > radiates. A ground plane is a poor model of how currents flow along a car body. Consider an antenna mounted on top of a car. From the base of the antenna, the current flows equally in all directions away from the base of the antenna, like a ground plane. This current doesn't contribute much radiation, for the reasons you state. But then it reaches the edge of the top of the car and flows downward. All the portions of the current are now flowing the same direction, and their fields don't cancel but add in phase. The net result is the same as if it were just flowing down a fat wire the height of the car. If the car is eight feet high, the field from the car will equal the field from an eight foot whip. In fact, unless the whip is top loaded to make the current uniform, the car will radiate more than the whip, because the capacitance of the car to ground will tend to give the car a uniform current distribution, like a top hat does to a whip. This will increase the radiated field strength from the car. Now consider a bumper mounted antenna. The current will spread from the base and proceed around the car. More will probably flow on the bottom than the top and sides due to coupling with the ground, but all portions will be flowing in the same direction and all will radiate. There is no place on the car where the current distribution or flow pattern resembles current on a ground plane. > An antenna is also called an aerial. It is defined as that part of a > radio station which radiates or receives radio waves into or from space. > > An antenna ground system is defined as that portion of an antenna system > closely associated with the earth and including an extensive conducting > surface which may be the earth itself. The problem here is that the currents don't care how you define things. They flow where the physical laws dictate. Defining "ground" doesn't make them behave differently. > Most radio amateurs have it right. If your view represents that of most amateurs, they don't. Roy Lewallen, W7EL Article: 222011 of rec.radio.amateur.antenna From: Jules Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Message-ID: <6qJNf.25805$8d1.12957@read1.cgocable.net> Date: Thu, 02 Mar 2006 16:26:25 -0500 I think if it is too strong it will affect your eyes first, ears then nerves/brain last. There are lots of safety precautions for wx radar on aircraft and they are generally are under 10kw for small planes, x band radar. Large jets, c band. Then there are fighter aircraft whose targeting radar has been know to kill small animals around the runways. But those are out of favour now, low power is in. Thierry wrote: > Hi, > > I received this message from a colleague but I cannot answer him. I d > not know these systems. > Could you help me ? > > My company has installed a Radar Tower for Port survaillence. The tower > is about 50 meter height on top of the of a 3 stories building roof and > my office building just below the tower on the same level, 20 meter away > from the tower. At the same time, the surrounding is my working area ( > Jetty Terminal for ships loading and unloading activities ). I can say > that I'll be around that area 12 hours a day for another 20 years. > > My question: > > Is it safe to work in that area???? > > Thanks in advance > Thierry > http://www.astrosurf.org/lombry > > Article: 222012 of rec.radio.amateur.antenna From: The Visitor Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <1136722082.927929.234700@o13g2000cwo.googlegroups.com> Message-ID: Date: Thu, 02 Mar 2006 16:28:44 -0500 Steve Nosko wrote: > I don't understand being "on the same level" AND being "20 feet below". Yes confusing, but I am sure there are intense lobes to look out for. Article: 222013 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <120ekkmb2nbrk75@corp.supernews.com> Message-ID: Date: Fri, 03 Mar 2006 00:08:42 GMT Roy Lewallen wrote: > A ground plane is a poor model of how currents flow along a car body. If the car body was 1/2WL in the air, would the antenna be more efficient? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222014 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> Message-ID: Date: Fri, 03 Mar 2006 00:12:58 GMT Dan Richardson wrote: > Roy is quite correct in stating that a vehicle's body behaves as one > side of a dipole. A lopsided dipole to be sure, but one half the > antenna just the same. Seems the truth might lie somewhere in between. If the ground plane of a vertical antenna is near the ground, there are losses. If the ground plane of a vertical antenna is located 1/2WL above ground, the losses are a lot less. I'll bet that if the vehicle were located 1/2WL in the air, the efficiency would increase. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222015 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <0YGdnc2vqPncEprZnZ2dnUVZ_t-dnZ2d@comcast.com> Message-ID: Date: Fri, 03 Mar 2006 01:28:06 GMT Amos Keag wrote: > Cecil Moore wrote: >> I'll bet that >> if the vehicle were located 1/2WL in the air, the efficiency >> would increase. > > Kind of tough though going under power lines, bridges and overpasses :-) What if the vehicle is a helicopter? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222016 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: New program CONNECT Date: Fri, 3 Mar 2006 02:03:09 +0000 (UTC) Message-ID: There have been recent discussions about the interchangeability of coaxial plugs and sockets, their dimensions and their impedances. But, as usual, the magnitude of the electrical effects is never mentioned. Without numbers nobody knows what they are talking about. A coaxial connector is a very short length of transmission line but at UHF and microwave frequencies it is an appreciable fraction of a wavelength. When 1/4-wavelength long it has the property of transforming a mismatched termination to another value. When 1/2-wavelength long the input impedance repeats the value of the termination. The SWR on an adjacent line is a function of the input impedance. What is the effect of using a 75-ohm coaxial connector in a 50-ohm system? What is the effect of using a length of transmission line of 50-ohms nominal impedance when it is actually 53 ohms? With mixed values of line Zo at what high frequency does the SWR and reflection loss become excessive? Program CONNECT.exe calculates the effect of inserting a length of line in a system of different Zo. Differences can be large or small. Line length can be physically very short. For a given frequency, mismatched Zo's and a velocity factor, input impedance, SWR, reflection coefficient and reflection loss are calculated. (Reflection loss is sometime known as mismatch loss). The program is worded in terms of a connector mismatch but has other applications. Input data can be varied in small increments from the keyboard while observing the effects on calculated values. Download CONNECT from website below. It has entertainment, educationaal and practical value. Amuse yourselves! ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 222017 of rec.radio.amateur.antenna From: Dot Subject: Re: 80m mobile antenna question Message-ID: <3v7f025mtmbi2cl0iv04g5ffhvoo85iuo7@4ax.com> References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <0YGdnc2vqPncEprZnZ2dnUVZ_t-dnZ2d@comcast.com> Date: Thu, 02 Mar 2006 20:46:56 -0500 On Fri, 03 Mar 2006 01:28:06 GMT, Cecil Moore wrote: >Amos Keag wrote: > >> Cecil Moore wrote: >>> I'll bet that >>> if the vehicle were located 1/2WL in the air, the efficiency >>> would increase. >> >> Kind of tough though going under power lines, bridges and overpasses :-) > >What if the vehicle is a helicopter? :-) Then you should know better than to go flying under power lines, bridges and overpasses. Geesh... Article: 222018 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Thu, 2 Mar 2006 21:35:30 -0600 Message-ID: <4239-4407B982-64@storefull-3253.bay.webtv.net> References: Danny K6MHE wrote: "Boy Richard you sure missed on that one!" A broadcast tower over a perfect ground system is the source of radiated energy even though its image in the ground system produces a pattern which behaves as if there were a dipole, the lower half of which is buried. The earth is not radiating. It is conducting. The tower above the earth is the source of radiation. Every ground radial in the broadcast system (usually all 120 of them), has a twin running in the opposite direction. All radials are tied together at the base of the tower. So the current in the radials all starts out in the same phase and stays roughly in the same phase as it progresses outward. It declines in magnitude away from the feedpoint. That`s the reason ground radials don`t need to be unlimited in length. You don`t need radials after the current plays out. As current travels in opposite directions in the groind radials. the fields they prodoce add to zero. The two halves of a dipole are fed with opposite polarities at their feedpoint. this puts the two halves running in opposite directions in-phase. Their fields thus reinforce. A 1/4-wave ground plane in free space has the same power gain as a center-fed 1/2-wave dipole. The matched power radiated by either ground plane or dipole is the same, but the resistance at the feedpoint of the ground plane is only 50% that of the dipole. Radiation resistance is defined as the resistance at the high current point of the antenna unless otherwise specified. Radiated power is (I) squared times the radiation resistance. Danny did not specify where he thought I erred in my previous posting. I said that a whip mounted on a vehicle is not exactly like a dipole. I meant that the whip did most of the radiating because it carried a concentration of current in the same direction while in the car body the current is dispersed in various directions, some of which canncel in their effects. I still insist that is the case. Best regards, Richard Harrison, KB5WZI Article: 222019 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> <440707DD.1030601@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Fri, 03 Mar 2006 05:39:42 GMT "dansawyeror" wrote in message news:440707DD.1030601@comcast.net... > Frank, > > A 'target' coil is 300mm x 300mm of 5/16 copper tubing. It is about 50 > feet of tubing, a .5 pitch, and should be close to 75 uH. This should be > close. From there simulation should show the best performance between > varying the coils. > > Thanks - Dan Having trouble producing a good model Dan. NEC 2 indicates Qs which are >5000, but no warnings or errors. I can run it in NEC 4.1, single, and double precision, but I get over 400 warnings in the NEC output file; such as: SEGCHK: WARNING - SEGMENTS 1 AND 271 CROSS AT A MIDPOINT WITH SEPARATION LESS THAN THE SUM OF THEIR RADII SEGCHK: WARNING - THE CENTER OF SEGMENT 1 IS WITHIN THE VOLUME OF SEGMENT 271 These warnings are particularly strange since, for example, absolute segments 1 and 271 are almost 12" apart in the model. Will see what I can do to correct the error. 73, Frank The code I am using is as follows: CM Inductor Q Calculation CE GH 1 300 1 12 6 6 6 6 0.3125 GW 2 5 6 0 12 0 0 12 0.3125 GW 3 10 0 0 12 0 0 0 0.3125 GW 4 5 0 0 0 6 0 0 0.3125 GS 0 0 0.025400 GE 0 EX 0 3 5 00 1 0 FR 0 5 0 0 3.7 0.02 LD 5 1 1 320 5.7001E7 RP 0 181 1 1000 -90 90 1.00000 1.00000 EN Article: 222020 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> Message-ID: <4407d7ba$1_1@newsfeed.slurp.net> Date: 3 Mar 2006 00:44:26 -0500 ORIGINAL MESSAGE: Dan Richardson wrote: > That may have some validity in the VHF and higher ranges, but on HF - > particularly on 80 meters - a car body's size is a small fraction of a > wavelength (as is the whip portion). Consequently the vehicle body > acts like the one half of a dipole antenna. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Q. How can a car body which is a "small fraction" of a wavelength act like one half of a dipole? A. It can't. Q. Well, what does it do then? A. It acts like a short piece of wire leading from the bottom of the whip to the actual ground plane, namely the earth itself. Q. Does that help any? A. Probably a little, but remember the piece of wire (the car body) is only a few feet long. Not very much on 80 meters. Q. Thanks, I get it now. A. You're welcome. 73, Bill W6WRT Article: 222021 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 00:24:00 -0600 Message-ID: <120fo85epbaj24d@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> Bill Turner wrote: > ORIGINAL MESSAGE: > > Dan Richardson wrote: > > >>That may have some validity in the VHF and higher ranges, but on HF - >>particularly on 80 meters - a car body's size is a small fraction of a >>wavelength (as is the whip portion). Consequently the vehicle body >>acts like the one half of a dipole antenna. > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Q. How can a car body which is a "small fraction" of a wavelength act > like one half of a dipole? > > A. It can't. > > Q. Well, what does it do then? > > A. It acts like a short piece of wire leading from the bottom of the > whip to the actual ground plane, namely the earth itself. > > Q. Does that help any? > > A. Probably a little, but remember the piece of wire (the car body) is > only a few feet long. Not very much on 80 meters. > > Q. Thanks, I get it now. > > A. You're welcome. > > 73, Bill W6WRT Actually it is acting as one half of a dipole. It is just a non-resonant half of a dipole. Remember "di" means two. Dave WD9BDZ Article: 222022 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Date: Fri, 03 Mar 2006 00:11:27 -0800 Message-ID: <120fuhhaaj786dc@corp.supernews.com> References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> <440707DD.1030601@comcast.net> Frank wrote: > "dansawyeror" wrote in message > news:440707DD.1030601@comcast.net... >> Frank, >> >> A 'target' coil is 300mm x 300mm of 5/16 copper tubing. It is about 50 >> feet of tubing, a .5 pitch, and should be close to 75 uH. This should be >> close. From there simulation should show the best performance between >> varying the coils. >> >> Thanks - Dan > > Having trouble producing a good model Dan. NEC 2 indicates Qs which are > >5000, but no warnings or errors. I can run it in NEC 4.1, single, and > double precision, but I get over 400 warnings in the NEC output file; such > as: > > SEGCHK: WARNING - SEGMENTS 1 AND 271 CROSS AT A MIDPOINT WITH SEPARATION > LESS THAN THE SUM OF THEIR RADII > > SEGCHK: WARNING - THE CENTER OF SEGMENT 1 IS WITHIN THE VOLUME OF SEGMENT > 271 > > These warnings are particularly strange since, for example, absolute > segments 1 and 271 are almost 12" apart in the model. Will see what I can > do to correct the error. > > 73, > > Frank > > The code I am using is as follows: > > CM Inductor Q Calculation > CE > GH 1 300 1 12 6 6 6 6 0.3125 > GW 2 5 6 0 12 0 0 12 0.3125 > GW 3 10 0 0 12 0 0 0 0.3125 > GW 4 5 0 0 0 6 0 0 0.3125 > GS 0 0 0.025400 > GE 0 > EX 0 3 5 00 1 0 > FR 0 5 0 0 3.7 0.02 > LD 5 1 1 320 5.7001E7 > RP 0 181 1 1000 -90 90 1.00000 1.00000 > EN NEC-2 and NEC-4 have different formats for the GH 'card'. This is the NEC-2 format, which will be interpreted differently by NEC-4. See your NEC-4 documentation for the correct NEC-4 format. Roy Lewallen, W7EL Article: 222023 of rec.radio.amateur.antenna From: Big Rich Soprano Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [2/2] Date: Fri, 03 Mar 2006 03:41:15 -0500 Message-ID: References: This scr is a "Backdoor Server Program" according to AntiVir! Article: 222024 of rec.radio.amateur.antenna From: Big Rich Soprano Subject: Re: TEEN SISTER WITH DILDO XXX 7396 [2/2] Date: Fri, 03 Mar 2006 03:41:26 -0500 Message-ID: References: This scr is a "Backdoor Server Program" according to AntiVir! Article: 222025 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 02:07:35 -0800 Message-ID: <120g5ba3toc9oc5@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> I'm afraid people are getting too hung up by trying to squeeze everything into various pigeon holes like "dipole" and "ground". You'll have to think beyond those narrow and poorly defined and understood categories and look at the basics of antenna operation in order to understand what's happening. The field radiated from a conductor is determined by two things: the amount of current on it, and the length of the path the current takes. Theorists have known this for well over a century. The most sophisticated antenna analysis programs break the current paths into very short pieces ("segments"), calculate the current on each piece, and then calculate the resulting field from the product of the current and the segment length. Fields from various parts of the conductors can cancel or reinforce to any degree. (Mathematically, they add vectorally.) If you don't or can't believe this, you needn't bother continuing. For those still reading, let's imagine a 16 foot vertical wire with a tiny 3.5 MHz signal generator at the center. This is known in textbooks as a "dipole", but how things behave aren't dictated by what we call them, so feel free to insist it's a "seagull", "pizza", "xfppftm", or whatever makes you comfortable. The signal generator has two terminals, and any generator must have equal currents in and out of its two terminals. If you don't or can't believe that, brush up on Kirchoff's current law. If that doesn't do it, there's no need to continue further. Let's suppose the generator is producing one amp RMS of RF current. If, say, 0.2 amp is flowing upward out of the top terminal at a given instant, 0.2 amp is flowing upward into the bottom terminal at the same instant. By inspection, one amp RMS is flowing upward in the vertical wire immediately above and below the generator. By a number of techniques, we can show that the current decreases nearly linearly from the center to the ends. That is, four feet from the center, either above or below the source, the current is 1/2 amp. At the antenna tips, the current is zero, which we should expect: there's nowhere for it to go. It should be obvious that the wire above the source is radiating the same field strength as the wire below the source -- for each little piece of the wire above the source there's a piece below the source carrying exactly the same current. And as it turns out, the fields from all parts of both wires add completely in phase directly broadside to the wire, and only partially in phase in other directions. So at least directly broadside, we can say that the contribution from each wire is equal and proportional to its total field strength. Ok, now let's make one of the wires "ground" and the other a "whip", because we like to do that, right? Let's call the top wire a "whip", and bottom load it. We add an inductor (very small, physically, to avoid adding another dimension to this analysis) between the signal generator's top terminal and its connection with the upper wire. We can make the inductor the proper value to make the upper wire/inductor self resonant if it were grounded, or we can make the inductor about twice as large to make the whole dipole resonant. It doesn't matter. Now let's see what happened to the radiation from the "whip" and "ground" wires. There's no change whatsoever! The currents are exactly the same as they were before, on both wires. They still taper from the center to the tips as before. They both radiate equally. All we've done is change the impedance seen by the generator. If you don't believe this, perhaps you can explain why they won't. Next, let's replace the lower wire with a cylinder like a tank, say 10 feet in diameter but still 8 feet high. What happens then? Surely it must now be "ground", and "ground" doesn't radiate, does it? Well, it does radiate. The one amp flowing into the bottom generator terminal spreads out radially over the top of the cylinder. Although the current density decreases as we move out from the center, the total current also decreases. If only the cylinder top was present and the rest of the cylinder missing, the current would drop to nearly zero at the edge. But because of the presence of the rest of the cylinder, the current at the edge drops to about half the value at the center. The half which remains flows down the cylinder sides. This would result in the field from the cylinder being about half the field from the "whip" if the current decreased to zero at the bottom of the cylinder as it does at the top of the whip. But the current along the sides of the cylinder doesn't drop to zero at the bottom of the walls because it can flow onto the bottom of the cylinder. The average current on the whip is 0.5 amp, and on the cylinder (from a model) about 0.35 amp, so the cylinder's field is about 3 dB less than that of the "whip". Not quite what most of envision when we think of a "ground". If we top load the whip with a 10 foot diameter top hat, its average current increases to about 0.9 amp. But its presence also reduces the amount of current drop from the center to the edge of the cylinder top due to mutual coupling. The end result is larger current along the cylinder sides and very nearly the same field strength ratio between the "whip" and cylinder. So far this analysis has taken place in free space. What happens if we put the cylinder bottom just above the ground, say six inches? Now, surely, the cylinder is "ground"! But the current still flows down the sides and radiates just like the old original vertical lower wire did. And putting the bottom close to ground increases the current along the sides! The coupling between the cylinder bottom and ground acts somewhat like a top hat does to a whip, and increases the average current. Instead of 0.35 amp, it increases to about 0.42. Now the cylinder's field is only about 1.5 dB less than that of the "whip". I hope this has encouraged at least a few people to think a little before declaring every conductor to be either an "antenna" or a "ground plane" and assuming that by doing so they'll somehow cause it to behave in some predetermined and only vaguely understood fashion. Roy Lewallen, W7EL Bill Turner wrote: > ORIGINAL MESSAGE: > > Dan Richardson wrote: > >> That may have some validity in the VHF and higher ranges, but on HF - >> particularly on 80 meters - a car body's size is a small fraction of a >> wavelength (as is the whip portion). Consequently the vehicle body >> acts like the one half of a dipole antenna. > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Q. How can a car body which is a "small fraction" of a wavelength act > like one half of a dipole? > > A. It can't. > > Q. Well, what does it do then? > > A. It acts like a short piece of wire leading from the bottom of the > whip to the actual ground plane, namely the earth itself. > > Q. Does that help any? > > A. Probably a little, but remember the piece of wire (the car body) is > only a few feet long. Not very much on 80 meters. > > Q. Thanks, I get it now. > > A. You're welcome. > > 73, Bill W6WRT Article: 222026 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120fo85epbaj24d@corp.supernews.com> Message-ID: <44081617_4@newsfeed.slurp.net> Date: 3 Mar 2006 05:10:31 -0500 David G. Nagel wrote: > Actually it is acting as one half of a dipole. It is just a > non-resonant half of a dipole. Remember "di" means two. > > Dave WD9BDZ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In a strict sense you are correct, but in the context here where one half of the dipole is an eight-foot whip and the other half is four feet of car body, we don't have much of an 80 meter antenna without the coupling from car body to earth ground. Bill, W6WRT Article: 222027 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> Message-ID: <44081a47_1@newsfeed.slurp.net> Date: 3 Mar 2006 05:28:23 -0500 Roy Lewallen wrote: > I hope this has encouraged at least a few people to think a little > before declaring every conductor to be either an "antenna" or a > "ground plane" and assuming that by doing so they'll somehow cause it > to behave in some predetermined and only vaguely understood fashion. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A very good explanation, thank you Roy. However... in your example of the giant tin can in free space, the top of the tin can is acting like a ground plane, the side is acting like an antenna and the bottom is again acting like a ground plane, just as we have been saying. When this model is transferred to a car body, the bottom of the car, in addition to the above, is also acting like one plate of a capacitor coupling the signal to the earth below it, commonly known as "ground". If someone disagrees with this I believe we have a problem with semantics more than physics. In other words, we are arguing over nothing. Bill, W6WRT Article: 222028 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Message-ID: <18XNf.43429$H71.26540@newssvr13.news.prodigy.com> Date: Fri, 03 Mar 2006 13:02:53 GMT Scott wrote: > If I remember correctly, the higher the coil goes, doesn't its value > have to increase as well? If so, might the coil dimensions become a bit > too big to handle? The bigger the top hat, the smaller the required reactance. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222029 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 09:09:34 -0600 Message-ID: <120gn1hpd81lmaa@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120fo85epbaj24d@corp.supernews.com> <44081617_4@newsfeed.slurp.net> Bill Turner wrote: > David G. Nagel wrote: > > >>Actually it is acting as one half of a dipole. It is just a >>non-resonant half of a dipole. Remember "di" means two. >> >>Dave WD9BDZ > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > In a strict sense you are correct, but in the context here where one > half of the dipole is an eight-foot whip and the other half is four > feet of car body, we don't have much of an 80 meter antenna without the > coupling from car body to earth ground. > > Bill, W6WRT No argument here Bill. The point I guess I was trying to make is that a dipole antenna system is two elements no matter what you make them of. I use a Hi Sierra screwdriver antenna on my Honda Element. Even though is is an impressive construct I don't harbor any illusions that it is an efficient radiator. The body of the car is longer than the length of the screwdriver, coil and whip. I have also used an Outbacker. Some say that is a good antenna for it type, I have not had that good of a result with it. Of course I am using my mobile for Civil Air Patrol and the Outbacker does not fit that frequency very well on the precut tuning jacks. I have found this thread to be interesting but I think that is had passed that point. I do not consider myself to be anything other than an interested amateur and always consider your comments with great interest. Thank you for your personal comments. Dave WD9BDZ Article: 222030 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Re: 80m mobile antenna question Date: 3 Mar 2006 09:36:51 -0600 Message-ID: References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Roy Lewallen, W7EL, typed: >I'm not sure why, but most amateurs don't seem to realize that the whip >....[snip].... >The best arrangement, as others have pointed out, is to mount the >antenna right at the center of the top of the car. This makes the car >....[snip].... Although my "evidence" is purely anecdotal, I've sure had good success on 80 meters with a pair of hamsticks mounted horizontally (one pointing forward and one backwards) about two feet above my picup cab (which has a metal "topper" behind the cab at essentially cab-top height). I've always assumed it was acting much like an NVIS dipole.... -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) Article: 222031 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Fri, 3 Mar 2006 11:02:32 -0600 Message-ID: <17919-440876A8-95@storefull-3252.bay.webtv.net> References: Cecil, W5DXP wrote: "The only way to improve on that on 75m would be to mount a piece of sheet metal on fiberglas poles connected at ythe ends of both bumpers." Kraus gives some support to that idea. Cecil has the 3rd edition of "Antennas" In that edition, there is a "Disc antenna" on page 720 with some similarity to cecil`s suggestion. The "flush-disk" antenna, (d) in Figure 21-11 is said to be comparable to a 1/4-wave vertical in performance, but has no projection. It could be covered with a dielectric sheet, make no noise in the wind, and break out no fluorescent tubes in parking garages. But, at 75m, the 0.3 lambda dia. depression to contain it would measure 22.5 meters. That woud require a vehicle that was very large indeed. At VHF and UHF it could be very practical. Best regards, Richard Harrison, KB5WZI Article: 222032 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Fri, 03 Mar 2006 18:56:38 GMT In article <6qJNf.25805$8d1.12957@read1.cgocable.net>, Jules wrote: > I think if it is too strong it will affect your eyes first, ears then > nerves/brain last. There are lots of safety precautions for wx radar on > aircraft and they are generally are under 10kw for small planes, x band > radar. Large jets, c band. Then there are fighter aircraft whose > targeting radar has been know to kill small animals around the runways. > But those are out of favour now, low power is in. > > > > Thierry wrote: > > Hi, > > > > I received this message from a colleague but I cannot answer him. I d > > not know these systems. > > Could you help me ? > > > > My company has installed a Radar Tower for Port survaillence. The tower > > is about 50 meter height on top of the of a 3 stories building roof and > > my office building just below the tower on the same level, 20 meter away > > from the tower. At the same time, the surrounding is my working area ( > > Jetty Terminal for ships loading and unloading activities ). I can say > > that I'll be around that area 12 hours a day for another 20 years. > > > > My question: > > > > Is it safe to work in that area???? > > > > Thanks in advance > > Thierry > > http://www.astrosurf.org/lombry > > > > > The basic facts are: Any commercial civilian Xband Radar will NOT even come close to approching FCC RF Radiation Biologic Health Maximum Radiation Power Densities even if you are right next to the antenna. You are more likely to get hurt by the rotating antenna hiting you in the head than from the RF Energy coming out of the antenna. Wx Radar on Commecrcial Aircraft usually are left in Standby Mode untill the aircraft has taxied onto the tarmac beside the active runway. Eve if they were activated, most xBand versions still don't have the Power Density one foot in front of the antenna to approch the FCC RF Radiation Biologic Health Maximum. Military Radars are a totally different beast altogether, and there are very strict operational rules for when they can be operated inside US Water and Airspace. Me Article: 222033 of rec.radio.amateur.antenna Date: Fri, 03 Mar 2006 14:07:04 -0500 From: jawod Subject: Non-theoretical, practical and probably stupid question Message-ID: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> I'm getting ready to mount a dipole between two trees in my backyard. Both are large sycamores and I plan to have the dipole about 60 feet up (max). In an ARRL publication, there is a description of using a bow and arrow to get over the branch desired. This is the method I guess I'll try (can't climb these trees). Once I have the nylon fishing line over, I'll need to hoist up a nylon rope attached to a pulley attached to the antenna itself (I mean, of course, the support line attached to insulator). I can't figure a way to hoist all this up without, say, 120 feet of nylon rope in an inverted U plus the weighted support line attached to the antenna. Yes, I can use a slip knot but I still end up having 60 feet of rope draped from the tree. Should I find a way to cut the nylon rope near the branch? Just tie up the hanging rope? It seems necessary to "waste" as much as 60 feet of rope in either side. If I support the center insulator, then double that. Is there a better way? John PS, Sorry, I couldn't find a way to insert something with imaginary numbers (hi) Article: 222034 of rec.radio.amateur.antenna From: "Ron H" References: Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [2/2] Message-ID: Date: Fri, 3 Mar 2006 13:23:31 -0600 Now I am not an IT professional mind you but I used test files with the scr extension as "SCRipt" files. The operating system likes to grab them and just do as the text inside instructs it. I use OE and it would reject such files if I set it up to but being a curious fellow, I like to see what I am missing. K3PID "Big Rich Soprano" wrote in message news:j60g02tfv0an71gaspk5k30t2i9vgbitlt@4ax.com... > This scr is a "Backdoor Server Program" according to AntiVir! Article: 222035 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 11:34:00 -0800 Message-ID: <120h6hb13r7b32b@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> Bill Turner wrote: > Roy Lewallen wrote: > >> I hope this has encouraged at least a few people to think a little >> before declaring every conductor to be either an "antenna" or a >> "ground plane" and assuming that by doing so they'll somehow cause it >> to behave in some predetermined and only vaguely understood fashion. > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > A very good explanation, thank you Roy. > > However... in your example of the giant tin can in free space, the top > of the tin can is acting like a ground plane, the side is acting like > an antenna and the bottom is again acting like a ground plane, just as > we have been saying. When this model is transferred to a car body, the > bottom of the car, in addition to the above, is also acting like one > plate of a capacitor coupling the signal to the earth below it, > commonly known as "ground". If someone disagrees with this I believe we > have a problem with semantics more than physics. > > In other words, we are arguing over nothing. > > Bill, W6WRT I interpreted your comments and those by some others as claiming that radiation from the car is insignificant, and that it therefore isn't effectively part of the antenna. I attempted to show that this isn't generally true. I also showed that coupling to the ground actually increases radiation from the car. So either I've convinced you by my illustration, or I misinterpreted your earlier remarks. Roy Lewallen, W7EL Article: 222036 of rec.radio.amateur.antenna From: Dot Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> Date: Fri, 03 Mar 2006 14:21:38 -0500 On Fri, 03 Mar 2006 14:07:04 -0500, jawod wrote: >Is there a better way? Yep... rent a cherry picker for a couple of hours or find someone to climb the tree and affix your pulleys. Article: 222037 of rec.radio.amateur.antenna From: tclay@qmc.ph.msstate.edu Subject: Re: Non-theoretical, practical and probably stupid question Date: 03 Mar 2006 14:20:37 -0600 Message-ID: <87u0afnuui.fsf@qmc.ph.msstate.edu> References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> >It seems necessary to "waste" as much as 60 feet of rope in either >side. If I support the center insulator, then double that. > >Is there a better way? I'm not sure what the problem is, yes, it takes a bunch of rope if you can't climb the tree. I usually don't bother with pulleys as I prefer to get the antenna up as high as possible. You will lose 15-20 feet of height (or more) using a pulley compared to not. Tor N4OGW Article: 222038 of rec.radio.amateur.antenna From: Owen Duffy Subject: Caronlina Windom characterisation Message-ID: Date: Fri, 03 Mar 2006 20:59:01 GMT I am working with some guys on ambient noise measurement in a pre BPL scenario. They are using FSM ( http://www.vk1od.net/fsm/ ) to make field strength measurements using a known comms receiver and a Carolina Windom (CW). We need to form a view on the CW antenna system losses (radiator, ground reflection, isolator, matching unit, feedline, ATU. Has anyone built and calibrated NEC models for the CW, or have they measured reliably feedpoint impedance on the various bands. This is not a troll, and I don't want to excite a war over the claimed performance of the CW, I am not interested in anecdotal evidence or QSO evidence as to whether they "work". I see that there will be significant issues in modelling the "secret" components of the CW unless someone has worked out an RF equivalent circuit of those components (the isolator and matching unit). Thanks... Owen -- Article: 222039 of rec.radio.amateur.antenna From: Jules Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Fri, 03 Mar 2006 16:04:49 -0500 Me wrote: > The basic facts are: Any commercial civilian Xband Radar will NOT even > come close to approching FCC RF Radiation Biologic Health Maximum > Radiation Power Densities even if you are right next to the antenna. > You are more likely to get hurt by the rotating antenna hiting you > in the head than from the RF Energy coming out of the antenna. > Wx Radar on Commecrcial Aircraft usually are left in Standby Mode > untill the aircraft has taxied onto the tarmac beside the active runway. runway > Eve if they were activated, most xBand versions still don't have the > Power Density one foot in front of the antenna to approch the FCC RF > Radiation Biologic Health Maximum. > Military Radars are a totally different beast altogether, and there are > very strict operational rules for when they can be operated inside US > Water and Airspace. On my plane the radar is 7.6 kw (xband). The manual says not to use it on the ground especially around people. Also they have been know to cause some sort of sparking on metal so fuel trucks are to be avoided. Shop people are cautioned to make sure it is not emitting if in stby mode, some do. The display will say STBY, the antenna not panning, but it is emitting. Go figure. Small airplanes have xband not because it is wimpy but because of antenna size constraints. These are 10 ro 12 inch diameter "flat dish" antennas. Lots of waveguide-like openings on it. Extreemly directional. And this is a small 6 seater plane. Large weather radars, ground based are sband. Big antennas. In the late 80's many radars dropped down to under 10 watts. Most under one watt. Mainly due to improved signal processing. Even on large jets with large dishes. With the lower power came more managable attenuation affects in rain too. You do not want your head one foot away from my radar when it is on. And I wouln't let you try it, even if you asked. Article: 222040 of rec.radio.amateur.antenna From: "Frank's" References: Subject: Re: Caronlina Windom characterisation Message-ID: Date: Fri, 03 Mar 2006 21:15:19 GMT "Owen Duffy" wrote in message news:dtah025lldi6hjdk1asg4jcst8mo54oimq@4ax.com... > > I am working with some guys on ambient noise measurement in a pre BPL > scenario. > > They are using FSM ( http://www.vk1od.net/fsm/ ) to make field > strength measurements using a known comms receiver and a Carolina > Windom (CW). > > We need to form a view on the CW antenna system losses (radiator, > ground reflection, isolator, matching unit, feedline, ATU. > > Has anyone built and calibrated NEC models for the CW, or have they > measured reliably feedpoint impedance on the various bands. > > This is not a troll, and I don't want to excite a war over the claimed > performance of the CW, I am not interested in anecdotal evidence or > QSO evidence as to whether they "work". > > I see that there will be significant issues in modelling the "secret" > components of the CW unless someone has worked out an RF equivalent > circuit of those components (the isolator and matching unit). > > Thanks... > > Owen Owen, I have done some tentative modelling of the CW; how valid the model is, I am not sure. I used the "TL" card for the actual coaxial feedline, and ran a single wire from the antenna feed point to one side of the TL source segment. The idea was to replicate the coaxial surface current. I don't think the balun (Isolator) will have any effect on the antenna performance. I may even have the code saved someplace if anybody is interested. Why would you not use a calibrated EMC monopole for HF? Frank Article: 222041 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Caronlina Windom characterisation Message-ID: <6rdh02hso77p0mvmqj92rhnqr5dgv3hevb@4ax.com> References: Date: Fri, 03 Mar 2006 21:49:23 GMT On Fri, 03 Mar 2006 21:15:19 GMT, "Frank's" wrote: > >Owen, I have done some tentative modelling of the CW; how valid the model >is, I am not sure. I used the "TL" card for the actual coaxial feedline, >and ran a single wire from the antenna feed point to one side of the TL >source segment. The idea was to replicate the coaxial surface current. I >don't think the balun (Isolator) will have any effect on the antenna >performance. I may even have the code saved someplace if anybody is >interested. Why would you not use a calibrated EMC monopole for HF? Thanks Frank. Some thoughts... I think they call the thing at the top a matching unit, and it seems to be a 4:1 transformer, but I have no idea of its common mode impedance that is relevant to the model. Similarly the common mode impedance of the lower unit (Isolator) is relevant to the model, and of course the treatment of the main feedline (routing, where it is earthed). The loss in the vertical coax is probably relevant, and not adequately modelled in NEC. The loss in the main feedline and ATU are also relevant, and can be calculated from the feedpoint Z. If I were building a model, I would be thinking of the assymetric dipole with the generator at the "upper" feedpoint, a vertical wire to ground loaded where the matching unit and isolator are located, and loaded for an underground coax feed (as is the case in this installation). But, the model will depend heavily on the common mode impedance of the two proprietary boxes. Unless someone has measured these, or calibrated a model, the model results will be of limited value. Perhaps Roy will comment on the above. Owen -- Article: 222042 of rec.radio.amateur.antenna From: ml Subject: ftp 2m rig? Message-ID: Date: Sat, 04 Mar 2006 01:43:43 GMT hi I was wondering if anyone knew of any fairly current 2m or 2/440 rigs that allow programming access to the memories via means OTHER THAN 'cloaning' method? for example here are a few that i already know of tm700 tmv7 i am not sure about the most current rigs seems the web sites of the manuf don't really say any help is appreciated m Article: 222043 of rec.radio.amateur.antenna From: "Hal Rosser" References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: Date: Fri, 3 Mar 2006 21:14:07 -0500 "jawod" wrote in message news:54f81$440893e2$42a1bfc2$25389@FUSE.NET... > I'm getting ready to mount a dipole between two trees in my backyard. > Both are large sycamores and I plan to have the dipole about 60 feet up > (max). > > In an ARRL publication, there is a description of using a bow and arrow > to get over the branch desired. > > This is the method I guess I'll try (can't climb these trees). > Once I have the nylon fishing line over, I'll need to hoist up a nylon > rope attached to a pulley attached to the antenna itself (I mean, of > course, the support line attached to insulator). > > I can't figure a way to hoist all this up without, say, 120 feet of > nylon rope in an inverted U plus the weighted support line attached to > the antenna. Yes, I can use a slip knot but I still end up having 60 > feet of rope draped from the tree. Should I find a way to cut the nylon > rope near the branch? Just tie up the hanging rope? > > It seems necessary to "waste" as much as 60 feet of rope in either side. > If I support the center insulator, then double that. > Wasting 60 ft of line is cheaper than a cherry picker rental, or broken leg. I will usually tie the rope off by putting a couple of large nails within step-ladder distance from the ground - but higher than a kid can normally reach. Then if you need to lower it again, it may be possible. Article: 222044 of rec.radio.amateur.antenna From: Butch Magee Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [1/2] Date: Fri, 03 Mar 2006 21:02:32 -0600 Message-ID: <120i0qb41ith58e@corp.supernews.com> References: Ron H wrote: > I certainly hope everyone in this list is smart enough to NEVER open a file > with the .scr extension! > > > Carry On! > K3PID > Ron H. > > I don't mind my ignorance showing,...what is an .scr ext? KF5DE Article: 222045 of rec.radio.amateur.antenna From: jc Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: Date: Fri, 03 Mar 2006 21:51:12 -0800 sananda@hotmail.com wrote: > Concord Police Department Officer Ron Turner is a fucken dirty black > pig cop > he stoped me because i had 820lbs. in a 1 ton pu truck > First the cop called for chp portable scale to get the > wt of my truck he could not get one then he had me > go to the chp truck scale on the hwy to get the wt of > my truck no one was there then he had me go to moving co. > and had me drive on there scale to get wt of my truck with > me in it . the scale said i was under 6000lbs. but he gave > me a ticket for overloaded tire load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the > boxes was cardboard. just before he let me go he had me go > into the restroom at the moving co. and told me to strip with 2 > back up cops 1 male cop and 1 girl cop. and then he let me > go after 8 hours. got to court i showed him how to do the > math on the tire load range and he walks up to the judge and > says ALL CHARGES DROPPED. > > Ron tuner who is 300lb black dirty pig cop needs to go > hunting with dick cheney . > > > Toilets > Police employees in Concord, California, filed a $30 million > lawsuit against the Concord Police Department after they found > a hidden in the restroom. > You should see this problem from the prof truckdrivers point this crap has been going on for years. and people in CA wonder why stuff cost soo much in CA? try a $3000.00 ticket for a 10 minute infraction on a logbook want to see more than afew bad cop's go and see KERN county this seems to be the sweet spot where the a$$hole's hang.I mean serve and protect FWIW OTR trucker.......20 years + J.C. Article: 222046 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Caronlina Windom characterisation Message-ID: References: Date: Sat, 04 Mar 2006 04:11:07 GMT On Fri, 03 Mar 2006 20:59:01 GMT, Owen Duffy wrote: > >I am working with some guys on ambient noise measurement in a pre BPL >scenario. > >They are using FSM ( http://www.vk1od.net/fsm/ ) to make field >strength measurements using a known comms receiver and a Carolina >Windom (CW). > >We need to form a view on the CW antenna system losses (radiator, >ground reflection, isolator, matching unit, feedline, ATU. > >Has anyone built and calibrated NEC models for the CW, or have they >measured reliably feedpoint impedance on the various bands. > >This is not a troll, and I don't want to excite a war over the claimed >performance of the CW, I am not interested in anecdotal evidence or >QSO evidence as to whether they "work". > >I see that there will be significant issues in modelling the "secret" >components of the CW unless someone has worked out an RF equivalent >circuit of those components (the isolator and matching unit). > >Thanks... > >Owen Their catalog shows modelled patterns. Might be some NEC models available at the Radio Works web site. bob k5qwg Article: 222047 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <120i0qb41ith58e@corp.supernews.com> Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [1/2] Message-ID: Date: Sat, 04 Mar 2006 04:28:29 GMT "Butch Magee" wrote in message news:120i0qb41ith58e@corp.supernews.com... > Ron H wrote: > > I certainly hope everyone in this list is smart enough to NEVER open a file > > with the .scr extension! > > > > > > Carry On! > > K3PID > > Ron H. > > > > > I don't mind my ignorance showing,...what is an .scr ext? > > KF5DE The .scr is usually the screen saver program extentions. They are exicutable programs just like the .exe programs. They can take over the computer and do almost anything. Good way to pass on a virus or worm or anything if the programmer does not want to really use them as a screen saver. Article: 222048 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> <120acppce6jle62@corp.supernews.com> <5JoNf.7747$Ui.2219@edtnps84> <440675EC.9070204@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Sat, 04 Mar 2006 05:11:20 GMT > Frank, > > I observed by playing with the relative inductor values on the vertical > segment and the radial elements that it was possible to move the relative > feedpoint. This supports tuning the antenna by either inductor. > > Reg's c_poise program predicts a 75 uH loading coil. > > I am excited with prospect of coil models. > > Thanks - Dan Dan, I have done some minor approximations with your coil. I took the length and diameter to be 12", rather than 300 mm (11.8"). The coil copper pipe diameter is, as specified, 5/16" (0.3125"). I was a little confused with your use of the term "Pitch" as 0.5". In the sense of a screw thread pitch is the distance between adjacent thread peaks, but I took it to mean the actual distance between the outer walls of the pipe; in which case the actual pitch is 0.8125". If this is the case the total pipe length is just over 47 ft. The inductance calculates to 54.2uH, and the Q = 2990. I have not yet run the program in NEC 4, for greater accuracy, since I would like to get the model as close as possible in NEC 2. If I have gotten the pitch definition wrong then the model dimensions will violate the NEC criteria of the minimum distance between adjacent turns. The code for this preliminary run is shown below. Some of the odd-ball dimensions are just to approximately equalize segment lengths. Despite some of the weirdness of 4nec2, concerning "GH" cards, you should be able to run it. Frank CM Inductor Q Calculation CE GH 1 300 0.8125 12 6 6 6 6 0.15625 GW 2 3 0.72322 -5.95625 12 .35542 0 12 0.15625 GW 3 6 .35542 0 12 .35542 0 0 0.15625 GW 4 3 .35542 0 0 6 0 0 0.15625 GS 0 0 0.025400 GE 0 EX 0 3 3 00 1 0 FR 0 5 0 0 3.7 0.02 LD 5 1 1 312 5.7001E7 RP 0 181 1 1000 -90 90 1.00000 1.00000 EN Article: 222049 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Caronlina Windom characterisation Message-ID: References: Date: Sat, 04 Mar 2006 05:20:36 GMT On Sat, 04 Mar 2006 04:11:07 GMT, Bob Miller wrote: >Their catalog shows modelled patterns. Might be some NEC models >available at the Radio Works web site. Bob, I saw that, but did not find links to model files. Owen -- Article: 222050 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Question for Roy (was Re: 80m mobile antenna question) References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> Message-ID: <4409280f_2@newsfeed.slurp.net> Date: 4 Mar 2006 00:39:27 -0500 Roy, your analogy of the car body as a tin can really got me to thinking. With the whip mounted dead center on the top of the car, I can see how the roof acts like a ground plane (a very short one) but I'm puzzled about the radiation from the lower part of the car body. If one visualizes RF flowing through the sides, hood and trunk of the car, the currents will all be in phase with each other (roughly, of course) but the currents are displaced in space by several feet. How does this affect the net radiation from the car body as a whole? Is there some addition or subtraction due to having the same current, same phase but at a different location in space, and arranged in a more or less 360 degree pattern? An interesting thought. 73, Bill W6WRT Article: 222051 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: <44092970$1_2@newsfeed.slurp.net> Date: 4 Mar 2006 00:45:20 -0500 ORIGINAL MESSAGE: Anonymous wrote: > Contact a lawyer. And then see a psychiatrist. > > On second thought, see a psychiatrist and THEN contact a lawyer. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ On third thought, just see the psychiatrist. After you're cured, he might even explain what the "antenna" in this group's name is all about. Bill T. Article: 222052 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: <44092a6d$1_1@newsfeed.slurp.net> Date: 4 Mar 2006 00:49:33 -0500 ORIGINAL MESSAGE: jc wrote: > try a $3000.00 ticket for a 10 minute infraction on a logbook ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Try a million dollar lawsuit over permanent disability because some dumb trucker kept on driving and fell alseep. Serves you right. Bill T. Article: 222053 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Question for Roy (was Re: 80m mobile antenna question) Date: Fri, 03 Mar 2006 22:31:49 -0800 Message-ID: <120id2o6n2b1od9@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> <4409280f_2@newsfeed.slurp.net> Think for a moment about a wire carrying RF current. RF current in any good conductor stays very close to the surface, so it's valid to imagine it flowing right on the surface. On a wire, the current spreads uniformly around the wire (unless it's very close to some other conductor), and each little part radiates. But at any distant point, the fields from the currents at various places around the wire (at a single location along the wire) are virtually the same, so it acts like a single current filament flowing on an infinitesimally thin wire. This is, in fact, how NEC and similar programs model conductor currents. The same even spreading happens as the wire gets fatter and fatter, but only up to a point. The model of a single current filament begins breaking down when the fields from different places around the wire are noticeably different at a distant point. This happens when the wire diameter becomes an appreciable fraction of a wavelength. Other things happen, then, too -- circumferential currents -- ones flowing around the wire -- develop, resulting in (or being caused by, depending on your point of view) non-uniform current distribution around the wire. And the wire itself affects the field. That is, the current on the side away >from a distant point can't directly radiate to the distant point because the wire is in the way. Because the various current contributions around the wire won't all add together at a distant point any longer, the pattern changes. I can't give any more specific answer to the question, really, than that the pattern will become more complex. In the case of the example I gave earlier with the cylindrical "car", if you raise the frequency, you'll reach a point where these effects happen. One result will be that the horizontal pattern will no longer be omnidirectional, but develop lobes. The height of the cylinder or car might affect the way current is distributed around it -- I haven't thought about it enough to hazard a guess. The good news is that today's modeling programs do a good job of showing these effects. The general technique is to represent flat surfaces such as a car top or side as a wire grid, to stay within the program's requirements that wire diameter must be no more than a very small fraction of a wavelength. As long as the holes in the grid are kept to a tenth of a wavelength or less, results are quite good. Roy Lewallen, W7EL Bill Turner wrote: > Roy, your analogy of the car body as a tin can really got me to > thinking. > > With the whip mounted dead center on the top of the car, I can see how > the roof acts like a ground plane (a very short one) but I'm puzzled > about the radiation from the lower part of the car body. If one > visualizes RF flowing through the sides, hood and trunk of the car, the > currents will all be in phase with each other (roughly, of course) but > the currents are displaced in space by several feet. > > How does this affect the net radiation from the car body as a whole? Is > there some addition or subtraction due to having the same current, same > phase but at a different location in space, and arranged in a more or > less 360 degree pattern? > > An interesting thought. > > 73, Bill W6WRT Article: 222054 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Question for Roy (was Re: 80m mobile antenna question) References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> <4409280f_2@newsfeed.slurp.net> <120id2o6n2b1od9@corp.supernews.com> Message-ID: <44097625_3@newsfeed.slurp.net> Date: 4 Mar 2006 06:12:37 -0500 Thanks, Roy. Interesting. 73, Bill W6WRT Article: 222055 of rec.radio.amateur.antenna From: subdude Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop Message-ID: References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Date: Sat, 04 Mar 2006 14:54:29 GMT On Fri, 03 Mar 2006 21:51:12 -0800, jc graced us with: >sananda@hotmail.com wrote: >> Concord Police Department Officer Ron Turner is a fucken dirty black >> pig cop >> he stoped me because i had 820lbs. in a 1 ton pu truck >> First the cop called for chp portable scale to get the >> wt of my truck he could not get one then he had me >> go to the chp truck scale on the hwy to get the wt of >> my truck no one was there then he had me go to moving co. >> and had me drive on there scale to get wt of my truck with >> me in it . the scale said i was under 6000lbs. but he gave >> me a ticket for overloaded tire load range . he added the >> gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs >> is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs >> over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the >> boxes was cardboard. just before he let me go he had me go >> into the restroom at the moving co. and told me to strip with 2 >> back up cops 1 male cop and 1 girl cop. and then he let me >> go after 8 hours. got to court i showed him how to do the >> math on the tire load range and he walks up to the judge and >> says ALL CHARGES DROPPED. >> >> Ron tuner who is 300lb black dirty pig cop needs to go >> hunting with dick cheney . >> >> >> Toilets >> Police employees in Concord, California, filed a $30 million >> lawsuit against the Concord Police Department after they found >> a hidden in the restroom. >> > >You should see this problem from the prof truckdrivers point >this crap has been going on for years. >and people in CA wonder why stuff cost soo much in CA? >try a $3000.00 ticket for a 10 minute infraction on a logbook >want to see more than afew bad cop's go and see KERN county this seems >to be the sweet spot where the a$$hole's hang.I mean serve and protect >FWIW >OTR trucker.......20 years + >J.C. Worked in the industry for 15 years, as a consultant then as a General Manager of a freight forwarding firm in DTW. Not only did I do the occaisional ride along for QA, but also had to discipline a number of truckers for log infractions. Most truckers are required only to do 2 things - drive and follow the rules. Maintaining logs is a small part of the latter - and necessary to protect other drivers on the road. Christ, in my day you had to load and unload the trucks on LTL deals, now they don't even do that. And BTW, I'd *STILL* rather pay more than risk more. So stop whining; if the job is too difficult go work for Mc D's... Article: 222056 of rec.radio.amateur.antenna From: "Allan W. Bart, Jr." Subject: Errors in Wilfred Caron Smith Chart Book Message-ID: <2RjOf.253$eJ1.142@trndny05> Date: Sat, 04 Mar 2006 17:09:18 GMT Hello, I have owned the book for about 15 years and now I am hearing aout errors. does anyone have a list of them? AB Article: 222057 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Sat, 04 Mar 2006 18:18:55 GMT In article , Jules wrote: > Me wrote: > > > The basic facts are: Any commercial civilian Xband Radar will NOT even > > come close to approching FCC RF Radiation Biologic Health Maximum > > Radiation Power Densities even if you are right next to the antenna. > > You are more likely to get hurt by the rotating antenna hiting you > > in the head than from the RF Energy coming out of the antenna. > > Wx Radar on Commecrcial Aircraft usually are left in Standby Mode > > untill the aircraft has taxied onto the tarmac beside the active runway. > runway > > Eve if they were activated, most xBand versions still don't have the > > Power Density one foot in front of the antenna to approch the FCC RF > > Radiation Biologic Health Maximum. > > Military Radars are a totally different beast altogether, and there are > > very strict operational rules for when they can be operated inside US > > Water and Airspace. > > On my plane the radar is 7.6 kw (xband). The manual says not to use it > on the ground especially around people. Also they have been know to > cause some sort of sparking on metal so fuel trucks are to be avoided. > Shop people are cautioned to make sure it is not emitting if in stby > mode, some do. The display will say STBY, the antenna not panning, but > it is emitting. Go figure. Small airplanes have xband not because it is > wimpy but because of antenna size constraints. These are 10 ro 12 inch > diameter "flat dish" antennas. Lots of waveguide-like openings on it. > Extreemly directional. And this is a small 6 seater plane. > > Large weather radars, ground based are sband. Big antennas. > > In the late 80's many radars dropped down to under 10 watts. Most under > one watt. Mainly due to improved signal processing. Even on large jets > with large dishes. With the lower power came more managable attenuation > affects in rain too. > > You do not want your head one foot away from my radar when it is on. And > I wouln't let you try it, even if you asked. > > > Jules, you really need to go back to Radar School and try and understand the technology that your using. 7.6Kw Pulsed Xband Radars have an AVERAGE Power of less than 20 watts. It isn't the Peak Pulse Power that fries you, or causes the sparks, it is the AVERAGE Power, and less than 20 watts one foot in front of ANY antenna is considerably less than that, due to RF Radiation being subject to the Inverse Square Law. Most of the old Decca 20Kw Commercial Marine Radars in xBand had Average Powers less that 35 watts, and were well below maximum Radiation Power Densities directly in from of the 6ft Slotline Antennas. Your socalled Flat Dish antennas at nothing more than a tuned Phase Array, and again, one foot out in front, Power Densities are well below maximum permissable Power Densities. Third Generation Commercial xBand Radar Technology, that came in the 80's, introduced Solid State LNA's, Ring Circulating Isolators, and Logrythemic IF ampilfiers, which improved the receivers Noise Figures, and Dynamic Gain by an Order of Magnitude. This is all in the RF Path, and had nothing to do with signal processing of baseband signals which didn't come into play untill DSP Processors were intoduced in the mid 90's and the Fourth Generation of Commercial Radars. Manuals are written by folks who understand the technology, about as much as the lawyers, that approve them before they are published. Yes, there are safety concerns with radar operations around FBO Fueling Operations, but the incidents of actual causal problems, are rare to the extreme. Again, all the above is TRUE only for commercial radars, and may, or may not be TRUE, and likely NOT TRUE for Military Radars, as these are more often than not CW operating, and, or doppler type radars that are NOT Pulsed. Me Article: 222058 of rec.radio.amateur.antenna From: Jim Chandler Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: Date: Sat, 04 Mar 2006 18:38:44 GMT sananda@hotmail.com wrote: > Concord Police Department Officer Ron Turner is a fucken dirty black > pig cop > he stoped me because i had 820lbs. in a 1 ton pu truck > First the cop called for chp portable scale to get the > wt of my truck he could not get one then he had me > go to the chp truck scale on the hwy to get the wt of > my truck no one was there then he had me go to moving co. > and had me drive on there scale to get wt of my truck with > me in it . the scale said i was under 6000lbs. but he gave > me a ticket for overloaded tire load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the > boxes was cardboard. just before he let me go he had me go > into the restroom at the moving co. and told me to strip with 2 > back up cops 1 male cop and 1 girl cop. and then he let me > go after 8 hours. got to court i showed him how to do the > math on the tire load range and he walks up to the judge and > says ALL CHARGES DROPPED. > > Ron tuner who is 300lb black dirty pig cop needs to go > hunting with dick cheney . > > > Toilets > Police employees in Concord, California, filed a $30 million > lawsuit against the Concord Police Department after they found > a hidden in the restroom. > Well, for your information, Moron, you DO NOT add the tire load range to the gross weight. The gross weight is the absolute maximum that the vehicle is designed for. The tire load range is the weight that the tire is designed to carry and have a margin for safety. The one ton pickup's maximum gross weight would be the EMPTY weight of the vehicle plus the 2000 pound weight of the cargo. face it, you screwed up. It's YOUR fault that you got a ticket, not the cops. YOU are the fat dumbass that earned it. Grow up, whiner. JimC Article: 222059 of rec.radio.amateur.antenna From: The Visitor Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Sat, 04 Mar 2006 14:01:30 -0500 Me wrote: 7.6Kw Pulsed Xband Radars have an AVERAGE > Power of less than 20 watts. I know it works in pulses and it is the pulse you should look out for. Like a microwave oven , it can induce voltages in pieces of metal, high enough to cause sparks. What would that do to a person with a pacemaker? I only know the power rating. I am not sure arcing incidents are that rare as I have met a couple of people who claim to have seen it happen. If a hammer drops on your foot and then rests there for 20 minutes, is it the pulse or the average force to look out for. My radar... Peak Power Output: 7.5 KW nominal, 6.0 KW minimum Output Frequency: 9375 Mhz (X-Band) I think it does 160 pulses per second. You would be willing to take the full brunt of that one foot away? I will be back at the airport this afternoon and ask for someone to hold thier head up to the radome. I never went to radar school. I'll take your word for it, but I won't volunteer! Article: 222060 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: radar and health ? Date: Sat, 4 Mar 2006 19:31:01 +0000 (UTC) Message-ID: References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> As an ex-RAF radar technician, during WW2 I have stood in the radar beam, on many occasions, on the airfield runway and in the maintenance workshop, just a few feet from the parabolic dish, of a 50 KW, 3 Gigahertz, airborne radar. It was the radar which guided death-dealing machines to their targets, the many incinerated German cities culminating in the innocent city of Dresden - entirely destroyed just to educate the Russians whose tanks were only a few hours away. I was not warned of the possible dangers of such exposure. The powers that be were not aware of them either in those days. I am now in my 81st year. Still alive. I have fathered 5 healthy children and have grandchildren. Draw your own conclusions about the real dangers of electromagnetic radiation. ---- Reg. Article: 222061 of rec.radio.amateur.antenna From: "Al \"Sparks\" Heere" Subject: Re: pse info balun Date: Sat, 4 Mar 2006 22:28:12 +0100 Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Ok sofar.... I want to receive low frequencies < 500 Khz. Planning to build long wire for it inside the house. How to connect this longwire to coax? Only for receiving, do I need balun then also ? "Cecil Moore" schreef in bericht news:gvCNf.17312$rL5.8757@newssvr27.news.prodigy.net... > Reg Edwards wrote: >> Ten or more turns of twin, 18 awg, stranded, speaker cable is even >> better. >> >> Easier to make and has higher choke impedance and lower loss. >> >> I don't know why you mess about with coax. > > The optimum Z0 for the wire that is used is the square root > of the product of the input impedance and the output impedance. > I vary the length of my ladder-line to accomplish resonance > in my antenna system. The impedances seen at the output of > my balun averages 50 ohms. Thus, the optimum Z0 for my > balun wire is 50 ohms. Magnet wire will do that but speaker > cable won't. Ten turns of RG-400 is really convenient. I use > RG-400 for everything inside of the shack. All the 1/2" dia. > stuff is outside. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 222062 of rec.radio.amateur.antenna From: Dot Subject: Re: radar and health ? Message-ID: <0d4k025qor7l2u6ne3k6jdjql6en5ajdko@4ax.com> References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Date: Sat, 04 Mar 2006 17:17:47 -0500 On Sat, 4 Mar 2006 19:31:01 +0000 (UTC), "Reg Edwards" wrote: >I am now in my 81st year. Still alive. I have fathered 5 healthy >children and have grandchildren. Draw your own conclusions about the >real dangers of electromagnetic radiation. In the interests of caution and safety... I would congratulate you on becoming an octogenarian, having a fine brood of kids and grandkids, and I'd wish to be so lucky... but then I'd remind you just how darned lucky you are. Article: 222063 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Errors in Wilfred Caron Smith Chart Book Date: Sat, 4 Mar 2006 22:59:52 +0000 (UTC) Message-ID: References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> Nobody's books or publications are bibles. Not even Terman's or B.L & E's. ---- Reg Article: 222064 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: radar and health ? Date: Sat, 4 Mar 2006 22:59:53 +0000 (UTC) Message-ID: References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> <0d4k025qor7l2u6ne3k6jdjql6en5ajdko@4ax.com> "Dot" wrote in message news:0d4k025qor7l2u6ne3k6jdjql6en5ajdko@4ax.com... > On Sat, 4 Mar 2006 19:31:01 +0000 (UTC), "Reg Edwards" > wrote: > > >I am now in my 81st year. Still alive. I have fathered 5 healthy > >children and have grandchildren. Draw your own conclusions about the > >real dangers of electromagnetic radiation. > > In the interests of caution and safety... I would congratulate you on > becoming an octogenarian, having a fine brood of kids and grandkids, and I'd > wish to be so lucky... but then I'd remind you just how darned lucky you > are. ======================================== I'm not lucky. I'm just an ordinary person. My genetic history remains unaffected by high-power electromagnetic radiation. On the contrary, it seems to have done me good! But if I should eventually die with a brain tumour no doubt my electromagnetic history will unjustly be blamed. ;o) ---- Reg. Article: 222065 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: pse info balun Date: Sat, 4 Mar 2006 22:59:52 +0000 (UTC) Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> You don't need a balun or coax. A feedline at low frequencies is very much short of a wavelength. Just extend your antenna wire direct to the receiver. Perhaps use a tuned preselector. And away you go! ---- Reg. Article: 222066 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: radar and health ? Date: Sat, 4 Mar 2006 23:42:07 +0000 (UTC) Message-ID: References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> <0d4k025qor7l2u6ne3k6jdjql6en5ajdko@4ax.com> Incidentally, in 1945, I was an unsuspecting guinea pig sent to the radioactive aftermath of Hiroshima for a week or so. Again, my genetic history appears to have remained unaffected. Perhaps, as you say, I am lucky. I am just another very minor statistic, like everybody else, in the field of statistics and probability. See the widespread works of Sir Ronald Arthur Fisher, the greatest statistician of all time who died in the 1960's. Just imagine what he could have done with just a modern pocket calculator, never mind a personal computer. ---- Reg. > Article: 222067 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Errors in Wilfred Caron Smith Chart Book Date: Sun, 5 Mar 2006 00:36:14 +0000 (UTC) Message-ID: References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> <1141515299.293793.105240@z34g2000cwc.googlegroups.com> wrote in message news:1141515299.293793.105240@z34g2000cwc.googlegroups.com... > > Reg Edwards wrote: > > Nobody's books or publications are bibles. > > > > Not even Terman's or B.L & E's. > > ---- > > Reg > Nobody's books or publications are bibles.\ > What are we supposed to believe? It would take many years to verify > all that has been printed over the last 100 years. If I am a ham and I > wish to put up an antenna, what should I do? Surely not refer to to > the Bibles. > Gary N4AST ========================================== Nobody understands the bibles without a great deal of study. They are full of mistakes anyway. Most of them were written just to make a living. Its easy to understand what THAT leads to. Just put up some wire and you will learn more in a few hours of listening and transmitting than a lifetime of reading about it. ---- Reg. Article: 222068 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Errors in Wilfred Caron Smith Chart Book Date: Sun, 5 Mar 2006 01:06:20 +0000 (UTC) Message-ID: References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> I fully admit my antenna programs are not bibles. They are merely my idea of how things can be modelled. In general they are well inside the ball park. They serve their intended purpose. What better quality can you ask for? I am a Fellow of the British Institute of Quality Asurance but I don't brag about it. ---- Reg. Article: 222069 of rec.radio.amateur.antenna From: "oh well" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirtyblack pig cop Date: Sat, 4 Mar 2006 19:09:04 -0600 Message-ID: <120keieq746nh56@corp.supernews.com> References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Jim Chandler wrote in message news:U8lOf.3533$CT.658@trnddc04... > sananda@hotmail.com wrote: > > > Concord Police Department Officer Ron Turner is a fucken dirty black > > pig cop > > he stoped me because i had 820lbs. in a 1 ton pu truck > > First the cop called for chp portable scale to get the > > wt of my truck he could not get one then he had me > > go to the chp truck scale on the hwy to get the wt of > > my truck no one was there then he had me go to moving co. > > and had me drive on there scale to get wt of my truck with > > me in it . the scale said i was under 6000lbs. but he gave > > me a ticket for overloaded tire load range . he added the > > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > > over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the > > boxes was cardboard. just before he let me go he had me go > > into the restroom at the moving co. and told me to strip with 2 > > back up cops 1 male cop and 1 girl cop. and then he let me > > go after 8 hours. got to court i showed him how to do the > > math on the tire load range and he walks up to the judge and > > says ALL CHARGES DROPPED. > > > > Ron tuner who is 300lb black dirty pig cop needs to go > > hunting with dick cheney . > > > > > > Toilets > > Police employees in Concord, California, filed a $30 million > > lawsuit against the Concord Police Department after they found > > a hidden in the restroom. > > > > Well, for your information, Moron, you DO NOT add the tire load range to > the gross weight. The gross weight is the absolute maximum that the > vehicle is designed for. The tire load range is the weight that the > tire is designed to carry and have a margin for safety. The one ton > pickup's maximum gross weight would be the EMPTY weight of the vehicle > plus the 2000 pound weight of the cargo. face it, you screwed up. It's > YOUR fault that you got a ticket, not the cops. YOU are the fat dumbass > that earned it. Grow up, whiner. > > JimC I think somebody is getting their leg pulled. http://www.dot.ca.gov/hq/traffops/trucks/trucksize/weight.htm oh well........... Article: 222070 of rec.radio.amateur.antenna From: Jim Chandler Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> <1141513915.382206.86290@i39g2000cwa.googlegroups.com> Message-ID: <3WqOf.20323$W42.6686@trnddc02> Date: Sun, 05 Mar 2006 01:12:31 GMT sananda@hotmail.com wrote: > Jim Chandler wrote: > >>sananda@hotmail.com wrote: >> >> >>>Concord Police Department Officer Ron Turner is a fucken dirty black >>>pig cop >>>he stoped me because i had 820lbs. in a 1 ton pu truck >>>First the cop called for chp portable scale to get the >>>wt of my truck he could not get one then he had me >>>go to the chp truck scale on the hwy to get the wt of >>>my truck no one was there then he had me go to moving co. >>>and had me drive on there scale to get wt of my truck with >>>me in it . the scale said i was under 6000lbs. but he gave >>>me a ticket for overloaded tire load range . he added the >>>gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs >>>is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs >>>over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the >>>boxes was cardboard. just before he let me go he had me go >>>into the restroom at the moving co. and told me to strip with 2 >>> back up cops 1 male cop and 1 girl cop. and then he let me >>>go after 8 hours. got to court i showed him how to do the >>>math on the tire load range and he walks up to the judge and >>>says ALL CHARGES DROPPED. >>> >>>Ron tuner who is 300lb black dirty pig cop needs to go >>>hunting with dick cheney . >>> >>> >>>Toilets >>>Police employees in Concord, California, filed a $30 million >>>lawsuit against the Concord Police Department after they found >>>a hidden in the restroom. >>> >> >>Well, for your information, Moron, you DO NOT add the tire load range to >>the gross weight. The gross weight is the absolute maximum that the >>vehicle is designed for. The tire load range is the weight that the >>tire is designed to carry and have a margin for safety. The one ton >>pickup's maximum gross weight would be the EMPTY weight of the vehicle >>plus the 2000 pound weight of the cargo. face it, you screwed up. It's >>YOUR fault that you got a ticket, not the cops. > > > YOU are the fat dumbass > > YOU are the fat dumbass you ass go back and read it you ass > but he gave cop > me a ticket for this is what is said on the ticket: overloaded tire > load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. > > if you can't read don't post a reply you ass - > Well, your whiney blathering is rather difficult to read. You haven't figured out where the Shift key is or what it's for and your writing is atrocious. If he had you weighed the scales would have told him that you were not overloaded, if you were loaded as you claim. Personally I think you are just a whiney moron who got a ticket and can't deal with it. Now please stop cross posting to AFPF. Cross posting is not welcome there. JimC Article: 222071 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Errors in Wilfred Caron Smith Chart Book Message-ID: <6sfk025u6mpqmccm9cvlvdt2pcr4rubvor@4ax.com> References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> Date: Sun, 05 Mar 2006 01:44:17 GMT An interesting point of view. I have been participating in a Bible Study program for the last three years based on the Old Testament and the New Testament. One of the more important things I have learned is that there are many inconsistencies and cases of ambiguity. We are fortunate in all cases that someone was willing to sit down and put the documents together so that we could enjoy the benefits of their studies! If Terman made an error, I can forgive him. My copy is older than I am... Sometimes a published error is what it takes to get the right answer. BTW, thanks for all the programs Reg. I am learning a lot from them! On Sat, 4 Mar 2006 22:59:52 +0000 (UTC), "Reg Edwards" wrote: >Nobody's books or publications are bibles. > >Not even Terman's or B.L & E's. >---- >Reg > > John Ferrell W8CCW Article: 222072 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> <1141513915.382206.86290@i39g2000cwa.googlegroups.com> Message-ID: <440a41ff_3@newsfeed.slurp.net> Date: 4 Mar 2006 20:42:23 -0500 ORIGINAL MESSAGE: sananda@hotmail.com wrote: > YOU are the fat dumbass > > YOU are the fat dumbass you ass go back and read it you ass > but he gave cop > me a ticket for this is what is said on the ticket: overloaded tire > load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. > > if you can't read don't post a reply you ass - ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ By noting the quality of grammar, the disorganized sentenced structure and observing the level of adrenaline flowing in sanandan's system, I wouldn't believe a word he says. Bill T. Article: 222073 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Reflection Loss Date: Sun, 5 Mar 2006 03:29:51 +0000 (UTC) Message-ID: I have just had several glasses of Australian Zonte's Footstep wine. I can recommend it. Its name can be traced back to a marsupial which replaced the dinosaurs. Transmission lines, which even the dinosaurs knew nothing about, are associated with losses of one sort and another. But there is one sort of loss which is never mentioned in discussions on this newsgroup. It is reflection loss. Reflection loss is sometimes known as mismatch loss. It is that loss which occurs in the load impedance because it is not matched to the line impedance Zo. When the line is not matched there is a reflection of amps and volts back towards the generator. The reflected volts and amps, in conjunction with the existing volts and amps, present to the generator an impedance which causes it to deliver to the line exactly the power in the load plus the power lost in the line. That this occurs is quite obvious. When calculated, the power lost in the line automatically takes into account the increase in loss due to SWR which occurs on the line due to the mismatch of the load. But the most important parameter is not the SWR but the reflection coefficient, Gamma. Gamma = ( Zt - Zo ) / ( Zt + Zo ). The loss in the load due to reflection is given by Reflection Loss = 4.343 * Ln( 1 - Square( G ) ) decibels. where G is the magnitude of the reflection coefficient which is easy to measure. ---- Reg. Article: 222074 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Reflection Loss References: Message-ID: Date: Sun, 05 Mar 2006 03:59:34 GMT Reg Edwards wrote: > The reflected volts and amps, in conjunction with the existing volts > and amps, present to the generator an impedance which causes it to > deliver to the line exactly the power in the load plus the power lost > in the line. That this occurs is quite obvious. A tuner will present the designed-for impedance to the generator and thus develops reflection gain that neutralizes, to varying degrees, the reflection loss at the load. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222075 of rec.radio.amateur.antenna From: "Sal M. Onella" References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> <120keieq746nh56@corp.supernews.com> Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirtyblack pig cop Message-ID: Date: Sat, 4 Mar 2006 21:02:53 -0800 "oh well" wrote in message news:120keieq746nh56@corp.supernews.com... > > I think somebody is getting their leg pulled. Ah, yes! I have been a Californian most of my life (now 63+). Our cops rarely seem to care what you have in the back of a pickup. It would have to be a cage full of naked, screaming children to get their attention. They want the speeders, the weavers, the red-light runners -- all genuine hazards. In fact, overloaded pickups are quite common -- with tall sideboards to contain all the junk -- yet I can't remember the last time I saw one pulled over. Article: 222076 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: NBFM transceiver @2.4GHz References: <1141528860.979067.156700@i40g2000cwc.googlegroups.com> Message-ID: <1l5qd3-1jp.ln1@p400bob.personal.cox.net> Date: Sat, 04 Mar 2006 22:22:25 -0600 Maxim make a range of chips you may be interested in. Start with; http://www.maxim-ic.com/Wireless.cfm I have been looking with interest at one of there 900MHz products. It takes a single IF I/O (eg 10.7MHz) and can produce QPSK/QAM etc at around 2dBm. I have been looking at a transceiver chip at; http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1773 Havent looked at their 2.4GHz offerings (if any) Cheers Bob VK2YQA mazerom wrote: > > hello guys, > > im into designing a base station that needs a transceiver with FM as > well as digital modulation ability(or Spread spectrum) at 2.4ghz.i > found 3 products;winceiver(we2408),numa technologies(nt2924) and > toshiba(tb2301m) > any information for additional chipsets that i may venture with? > thanks a lot! > > mazerom > Article: 222077 of rec.radio.amateur.antenna From: "Paul R. Stoetzer" Subject: Twinlead antenna Date: Sun, 05 Mar 2006 00:13:57 -0500 Message-ID: I needed an indoor HF antenna recently and had a 40 ft roll of Radio Shack twinlead. I cut down the middle about 16.5 feet, hung one end at one side of the room and the other end at the other side of the room and fed it into the balanced line input on my tuner. It tunes easily. I have no ground set up, so I ran another 16.5 foot wire from the ground port. Making contacts is a bit of a struggle, from my QTH in Michigan I've worked Nevada and Arizona on PSK and during the DX contest today in limited operation near sunset I worked Barbados and the Dominican Republic with about 50W (probably a bit of a high level of RF radiation, I know). The question I have is what the downside of this is. I have seen many websites that show various antennas fed with twinlead, but I've never seen my approach (the twinlead used for both the antenna and feedline). Since I got this roll of twinlead on clearance from Radio Shack for 38 cents, this is a cheap antenna indeed. 73, Paul, N8HM Article: 222078 of rec.radio.amateur.antenna From: "Sal M. Onella" References: Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [2/2] Message-ID: Date: Sat, 4 Mar 2006 21:29:14 -0800 "Ron H" wrote in message news:WI0Of.29940$5r5.20323@newsfe17.lga... > Now I am not an IT professional mind you but I used test files with the scr > extension as "SCRipt" files. The operating system likes to grab them and > just do as the text inside instructs it. I use OE and it would reject such > files if I set it up to but being a curious fellow, I like to see what I am > missing. > > K3PID Following quote is lifted from Symantec [Norton Antivirus], edited only for brevity: < quote> Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices": * Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files. If you wonder what you're missing in scr files, you could be a mite too curious. Article: 222079 of rec.radio.amateur.antenna From: "Sal M. Onella" References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: <8WvOf.430$wp.130@fed1read12> Date: Sat, 4 Mar 2006 22:53:02 -0800 "jawod" wrote in message news:54f81$440893e2$42a1bfc2$25389@FUSE.NET... > I'm getting ready to mount a dipole between two trees in my backyard. > Both are large sycamores and I plan to have the dipole about 60 feet up > (max). > > In an ARRL publication, there is a description of using a bow and arrow > to get over the branch desired. > > This is the method I guess I'll try (can't climb these trees). > Once I have the nylon fishing line over, I'll need to hoist up a nylon > rope attached to a pulley attached to the antenna itself (I mean, of > course, the support line attached to insulator). > > I can't figure a way to hoist all this up without, say, 120 feet of > nylon rope in an inverted U plus the weighted support line attached to > the antenna. Yes, I can use a slip knot but I still end up having 60 > feet of rope draped from the tree. Should I find a way to cut the nylon > rope near the branch? Just tie up the hanging rope? > > It seems necessary to "waste" as much as 60 feet of rope in either side. > If I support the center insulator, then double that. > > Is there a better way? > > John > > PS, Sorry, I couldn't find a way to insert something with imaginary > numbers (hi) I'm going to suggest you "waste" not only the sixty feet of rope at each end, but an additional sixty feet at each end. (But, not being acquainted with sycamore trees, I don't know how dense their branches are, so this idea may not always work.) Create a closed loop of rope, so you can raise and lower the thing at will with total, personal control. You will someday need to lower the antenna and growth in the tree may snag the insulator or the antenna, so you could tug down on a rope, and not have to tug down on your antenna. I am curious about the pulley. Hereabouts (Southern California) we do almost nothing with trees. John (Ah, two Johns -- no waiting.) Article: 222080 of rec.radio.amateur.antenna From: Your@email.adr Subject: Please read - nothing nasty Message-ID: Date: Sun, 05 Mar 2006 10:52:34 GMT I want start a trend, this is make ppl to think carefully about where they live and how we are screwing it up, and the cures. goto my site and look i am a disabled ex-truck driver, and i have to find a new career, so this it, i want to plant a few trees, My site url :-) http://www.global-airconditioning.com/index.html its on a candian server my name and address is fully available I want help, and thats very hard for me to say. i don't lie it costs too much, truth hurts but it costs nothing, phishers beware, balderdash is binned Article: 222081 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Non-theoretical, practical and probably stupid question References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> <8WvOf.430$wp.130@fed1read12> Message-ID: Date: Sun, 05 Mar 2006 12:25:21 GMT Sal M. Onella wrote: > Hereabouts (Southern California) we do almost nothing with trees. > John I hear y'all give 'em lots of hugs. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222082 of rec.radio.amateur.antenna From: Dot Subject: Re: Twinlead antenna Message-ID: <06ll029ph9vhd9aabc7vtisla70rd90pj4@4ax.com> References: Date: Sun, 05 Mar 2006 07:17:16 -0500 On Sun, 05 Mar 2006 00:13:57 -0500, "Paul R. Stoetzer" wrote: >The question I have is what the downside of this is. I have >seen many websites that show various antennas fed with twinlead, but >I've never seen my approach (the twinlead used for both the antenna and >feedline). Since I got this roll of twinlead on clearance from Radio >Shack for 38 cents, this is a cheap antenna indeed. Just because there's no fancy feedpoint device and no mechanical delimiter between the end of the feedline and the beginning of the antenna doesn't mean it's not a viable method of radiating RF. I have a dipole antenna I regularly make by folding the shield back over the outside of the coax leaving 1/4 wave of the center lead exposed... The folded back braid can also be seen as a bazooka balun. It is wholly unclear where the antenna ends and the balun begins but it does an enviable job of radiating RF. It seems likely the first parallel wire feedline was nothing more than the excess wire length from a dipole gathered up and run neatly along spacers down to the transmitter. The thing I'd be more worried about is the levels of RF you are pumping into yourself and your neighbors... 50 or 60 watts produces a very tangible electromagnetic field that could well cause problems down the road. Article: 222083 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Twinlead antenna References: Message-ID: Date: Sun, 05 Mar 2006 14:34:22 GMT Paul R. Stoetzer wrote: > I have > seen many websites that show various antennas fed with twinlead, but > I've never seen my approach (the twinlead used for both the antenna and > feedline). Balanis illustrates exactly that idea on page 18 of "Antenna Theory, Analysis and Design", 2nd edition. It is a very old idea. 50+ years ago, when I was a Novice, it was standard practice to tie a knot in zip cord 1/4WL from the end, unzip the cord down to the knot, use the unzipped part for the 1/2WL antenna, and use the rest for balanced feedline. It worked like a charm in spite of the feedline losses. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222084 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Errors in Wilfred Caron Smith Chart Book References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> Message-ID: Date: Sun, 05 Mar 2006 14:35:27 GMT Dan Richardson adelphia wrote: > Including Reg's factoids. Hey Danny, I think you need to reset your clock. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222085 of rec.radio.amateur.antenna From: Cecil Moore Subject: Current in Loading Coils Message-ID: <%2DOf.39694$F_3.36050@newssvr29.news.prodigy.net> Date: Sun, 05 Mar 2006 15:01:15 GMT A loading coil thread is climaxing over on qrz.com. I have used EZNEC to generate a graphic which shows a 3/4WL vertical and a similar 1/2WL vertical with a ~1/4WL loading coil. The loading coil is a wire helical coil containing (surprise) roughly 1/4WL of wire. The coil does a good (not perfect) job of replacing 1/4WL of wire. Many things can be gathered >from observation of the current reported by EZNEC for the two antennas. The coil occupies roughly the same number of degrees of the antenna as the wire it replaces. The current at the top and bottom of the coil is roughly the same as the current at the two ends of the wire it replaces. Is the coil an exact replacement? Of course not. EZNEC says the current flowing into the bottom of the coil is 0.1168 amps and the current flowing out of the top of the coil is 0.748 amps. Say what? How can more current flow out of a coil than is flowing in? Aren't those two currents supposed to be equal? What gives? Some gurus have mistakenly treated the net current on a standing wave antenna as a lumped circuit current. The lumped circuit analysis falls apart in the presence of standing waves and the myth of equal net current in and out of a coil has been created as a result. Hint: A typical mobile antenna is a standing wave antenna and the net standing wave current reported by EZNEC doesn't much flow at all. It just, well, stands there like good little standing waves are supposed to. That standing wave pattern is illustrated in the graphic at: http://www.qsl.net/w5dxp/qrzgif35.gif The two EZNEC files used to generate that graphic are available >from me upon request. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222086 of rec.radio.amateur.antenna From: Paul Burridge Subject: Re: Errors in Wilfred Caron Smith Chart Book Date: Sun, 05 Mar 2006 15:41:57 +0100 Message-ID: References: <2RjOf.253$eJ1.142@trndny05> <1141507275.315496.201100@z34g2000cwc.googlegroups.com> On Sat, 4 Mar 2006 22:59:52 +0000 (UTC), "Reg Edwards" wrote: >Nobody's books or publications are bibles. > >Not even Terman's or B.L & E's. Indeed, Reg. It's always struck me as rather annoying that there are more errors in books on electronics than in any other published subject _bar none_ to my knowledge. I can think of no text book that is entirely error-free with the _possible_ exception of Art of Electronics. Most of the errors in radio & electronics tomes are related to ambiguous authoring, but there is a regrettably large number of outright errors (examples calculations or fundamental misunderstanding on the part of the writer) that are utterly poisonous snake oil to the unwitting and unguided student. Chris Bowick's 'RF Circuit Design' springs to mind here! Article: 222087 of rec.radio.amateur.antenna From: Paul Burridge Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop Date: Sun, 05 Mar 2006 15:44:11 +0100 Message-ID: <98ul021kc15f5fgk3uheuc2q350rcfnsg4@4ax.com> References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> On 3 Mar 2006 17:00:57 -0800, "sananda@hotmail.com" wrote: >Concord Police Department Officer Ron Turner is a fucken dirty black >pig cop [...] Maybe. But I dare say his English is a darn sight better than yours! Article: 222088 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Where can I get a new telescoping Antenna for a Grundig FR-200 References: <120m3dj1dc9eh8e@corp.supernews.com> Message-ID: Date: Sun, 05 Mar 2006 16:20:03 GMT R Black wrote: > Does anyone know where I can purchase a new antenna? I did a web search > and found no references to spare parts. Some Rat Shack stores carry an assortment of replacements. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222089 of rec.radio.amateur.antenna From: "west" Subject: SMA Cables Message-ID: Date: Sun, 05 Mar 2006 17:58:14 GMT Anybody know where I can purchase custom cables (3', 6', 12', 25' ) with a male SMA on 1 end to plug into a HT and a PL-259 on the other end? Thanks in advance. Cordially, west Article: 222090 of rec.radio.amateur.antenna From: "RST Engineering" References: <120m3dj1dc9eh8e@corp.supernews.com> Subject: Re: Where can I get a new telescoping Antenna for a Grundig FR-200 Date: Sun, 5 Mar 2006 10:43:20 -0800 Message-ID: Mouser Electronics (www.mouser.com) has half a dozen or so generic replacement telescopers. Jim "R Black" wrote in message news:120m3dj1dc9eh8e@corp.supernews.com... >I have a Grundig FR-200 and it works great. My kids, however broke the > telescoping antenna, and I would like to get a new one. > > Does anyone know where I can purchase a new antenna? I did a web search > and found no references to spare parts. > > > Thanks > > Chip > kf4wbk Article: 222091 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current in Loading Coils References: <%2DOf.39694$F_3.36050@newssvr29.news.prodigy.net> Message-ID: Date: Sun, 05 Mar 2006 18:45:35 GMT Cecil Moore wrote: > Is the coil an exact replacement? Of course not. Just got an email that prompted me to expand this statement. The worst thing about replacing a piece of wire antenna with a coil is of course, the wire radiates well and the coil radiates hardly at all. But that's a compromise we are forced to live with for 75m mobile antennas. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222092 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Sun, 05 Mar 2006 19:13:41 GMT In article , The Visitor wrote: > Me wrote: > 7.6Kw Pulsed Xband Radars have an AVERAGE > > Power of less than 20 watts. > > I know it works in pulses and it is the pulse you should look out for. > Like a microwave oven , it can induce voltages in pieces of metal, high > enough to cause sparks. What would that do to a person with a pacemaker? No, absolutly NOT, Microwave Ovens are NOT pusled, they are CW, and continious. It is AVERAGE Power that fries you, not Peak Pulse Power. See, this is what you seem not to understand, about the technology that is being discussed. You don't seem to have a grasp of how the technolgy works. > > I only know the power rating. > I am not sure arcing incidents are that rare as I have met a couple of > people who claim to have seen it happen. > and I have meet a lot of people that claim to have seen and been kidnapped by aliens, too...... > If a hammer drops on your foot and then rests there for 20 minutes, is > it the pulse or the average force to look out for. not analogous, at all, and just shows that yoiu don't undertand the technology that you talking about. > > My radar... > > Peak Power Output: 7.5 KW nominal, 6.0 KW minimum > > Output Frequency: 9375 Mhz (X-Band) Most likely using a 2J42 Magnitron or equivilent.... > > I think it does 160 pulses per second. that seems a bit low, should be in the 500 to 750 range, but ok.. and the Pulse Width, which you don't cite, is the determining factor in calculating the Average Power of the RF Energy emitted from the device. Typical Pulse Widths would be in the .1 to 1 microsecond range for this type of radar. So lets take 1 microsecond. 1 * 160 = 160 microseconds total ON time out of 1000000 microsends/second 160.0/1000000 *7500 Watts Peak Pulse Power = 1.2 Watts Average Power Now understand that RF Energy is nonIonizing radiation and therefore interacts with biologics as HEAT. Now just how much heat will be transfered to you from a 1.2 Watt light bulb held in your hand, assuming that you get 100% capture of that power into your hand, and considering that if your standing out in front of the antenna even at one foot, the Inverse Square Law still applies? > > > > You would be willing to take the full brunt of that one foot away? I > will be back at the airport this afternoon and ask for someone to hold > thier head up to the radome. I never went to radar school. that is obvious.... > > I'll take your word for it, but I won't volunteer! Me Article: 222093 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: SMA Cables Message-ID: Date: Sun, 05 Mar 2006 19:26:43 GMT Try: http://www.pasternack.com. Regards, Frank "west" wrote in message news:WEFOf.57210$Fw6.24840@tornado.tampabay.rr.com... > Anybody know where I can purchase custom cables (3', 6', 12', 25' ) with > a > male SMA on 1 end to plug into a HT and a PL-259 on the other end? Thanks > in > advance. > > Cordially, > west > > Article: 222094 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Current through coils Date: Sun, 5 Mar 2006 19:47:28 +0000 (UTC) Message-ID: Different currents at each end of a coil are easily explained. A coil has capacitance to its surroundings distributed along its length. And current flows from it radially. Every coil has length. Both L and C are distributed. Therefore the coil behaves as a transmission line. There are standing waves. Current and voltage both vary with length. The longer the line the greater the variation. The line has phase-shift, Zo and attenuation resulting from wire loss resistance and radiation resistance. The line can have a resonant length. It then becomes a short antenna. The whole business can be mathematically modelled. ---- Reg, G4FGQ. Article: 222095 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: Message-ID: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Date: Sun, 05 Mar 2006 20:03:14 GMT Reg Edwards wrote: > The whole business can be mathematically modelled. The point is that it cannot successfully be modeled with the lumped circuit model where the current is constant everywhere in the circuit. What would Kirchhoff have thought about a coil with 0.1 amp at the bottom and 0.7 amps at the top? It certainly doesn't mean that 0.6 amps is flowing sideways. All it means is that the relative phase of the forward current and reflected current changes through the coil and therefore the distributed network model needs to be used. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222096 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: measuring impedance through a balun ? References: Message-ID: Date: Sun, 05 Mar 2006 20:25:18 GMT dansawyeror wrote: > I am trying to measure impedance through a balun, or more accurately a > 1:1 in line "transformer". For test purposes the transformer is two > windings of 10 turns each on a toroid. The winding are tightly wound on > opposite sides. The material is #43, the toroid is 3/4 inch OD. For 4 MHz, I would use #61 material and bifilar windings. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222097 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Current in Loading Coils Message-ID: <1uhm02pe8vpko9rsab5tnaoblesp4prnub@4ax.com> References: <%2DOf.39694$F_3.36050@newssvr29.news.prodigy.net> Date: Sun, 05 Mar 2006 20:26:57 GMT Okay, I will take the bait and demonstrate my ignorance: RE: EZNEC says the current flowing into the bottom of the coil >is 0.1168 amps and the current flowing out of the top of >the coil is 0.748 amps. Say what? How can more current >flow out of a coil than is flowing in? Aren't those two >currents supposed to be equal? What gives? I thought the power was constant, not the current. If that is the case, then IE must be constant and therefore the current must go up where the volts go down. I would appreciate the EZNEC copies because I learn easiest by examples and I am interested in how you put the comparison together. John Ferrell W8CCW Article: 222098 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: 1n21 diode housing References: Message-ID: <9yJOf.29654$2c4.29425@dukeread11> Date: Sun, 05 Mar 2006 16:23:37 -0600 Richard Clark wrote: >On Sun, 05 Mar 2006 09:20:20 -0600, Chris W <1qazse4@cox.net> wrote: > > > >>Can someone tell me where I can find the housings for a 1n21 crystal >>detector diode so I can hook it to some coax and a directional coupler? >>I can't seem to fine one anywhere >> >> > >Try googling with: > 1n21 crystal mount > > A google search for that is giving me some links but still no luck finding a place I can buy one -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 222099 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: measuring impedance through a balun ? Message-ID: Date: Sun, 05 Mar 2006 22:31:05 GMT Dan, I think #43 is powdered iron, which is fine for high Q inductors, but not very good for broadband transformers. As has been mentioned by others; a ferrite core with bifilar windings should do it. Check out: http://www.oselectronics.com/downloads/Broadband%20Transformers.pdf for more info. Frank "dansawyeror" wrote in message news:hLedncOeu6382ZbZnZ2dnUVZ_sOdnZ2d@comcast.com... > All, > > I am trying to measure impedance through a balun, or more accurately a 1:1 > in line "transformer". For test purposes the transformer is two windings > of 10 turns each on a toroid. The winding are tightly wound on opposite > sides. The material is #43, the toroid is 3/4 inch OD. > > If I drive one side of the transformer with one milliwatt at 4 MHz and > terminate the other side into 50 Ohms, and then measure the input voltage > and the output voltage. The output voltage significantly less then the > input voltage, about 1/3. > > The second measurement that does not support my understanding is: If I > connect the transformer up to an 8450A through appropriate couplers, and > then short the output the 8405A does not show a 180 degree phase shift > between 'open' and 'shorted'. If this measurement is made without the > transformer then the results are as expected. > > This is obviously something with the transformer. I would like to > construct a simple 1:1 in line transformer good from 3 to 30 MHz and 100 > watts. What core size, material, and windings are a good starting point > for this? > > Thanks - Dan - kb0qil > Article: 222100 of rec.radio.amateur.antenna From: "John, N9JG" Subject: Compact loop question Message-ID: Date: Sun, 05 Mar 2006 22:41:54 GMT I am in the process of constructing a compact loop for 80 meters. The loop is constructed from 3/4 inch copper pipe in the shape of an octagon with a perimeter of 72 feet, and the plane of the loop is vertical. According to the literature, a loop of this type usually has a remotely tuned capacitor in series with the top side of the loop, and the loop is feed at the bottom with a gamma match. For mechanical stability reasons, I would like to have the tuning capacitor at the bottom of the loop, and feed the loop at the top of the loop. The coax would be constrained to lie in the plane of the loop and would drop vertically from the top of the loop to the ground. What disadvantages, if any, are there to this second method of loop construction? For more details of my project, see http://tinyurl.com/bwobb Article: 222101 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: measuring impedance through a balun ? Message-ID: <2tqm029ua0ev89mfr3knmpe876hkp98j83@4ax.com> References: Date: Sun, 05 Mar 2006 23:02:38 GMT On Sun, 05 Mar 2006 22:31:05 GMT, "Frank" wrote: >Dan, I think #43 is powdered iron, which is fine for high Q inductors, but Type 43 is a nickel zinc ferrite. Spec sheets indicate it is principally a suppression material, but usable for broadband transformers up to 10MHz. Bifilar winding, and possibly better material are probably the key to improving the transformer, or alternatively making a common mode choke. Owen -- Article: 222102 of rec.radio.amateur.antenna From: "John, N9JG" References: Subject: Re: Compact loop question Message-ID: Date: Mon, 06 Mar 2006 00:15:21 GMT I am not sure what you are recommending - Are you suggesting I make the plane of the loop horizontal? -- John "Richard Clark" wrote in message news:qerm02hrs2duqvbhlmrla4gkg571ccbdr4@4ax.com... [snip] > > Hi John, > > What advantage is there in climbing a ladder to place the loop? Put > it at the bottom too. > > 73's > Richard Clark, KB7QHC Article: 222103 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Vertical vs Horizontal shootout part one Message-ID: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> References: Date: Mon, 06 Mar 2006 00:57:02 GMT On Sun, 05 Mar 2006 19:29:12 -0500, Mike Coslo wrote: >Based on another thread a few weeks back in which Horizontal dipoles >were being compared to Vertical antennas, and from a little chiding from >Roy, W7EL, I decided to do some testing on my own personal versions of >the two. > Mike, this sounds interesting. > >My setup is: > >Icom IC-761 >Antenna 1 - Homebrew OCF dipole at ~ 50 feet. >Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. > Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? Another, are the antennas coupled significantly, eg is one within the near field zone of the other? It is pretty hard to avoid in a residential block on the low bands, and it will confuse the results somewhat. > >Part one of this experiment is to calibrate the S-meter. I found that >trying to calibrate the thing with on-air signals was a nuisance, and >probably wouldn't be as accurate, so I used a signal generator. > >I started out with a +20 signal, then worked my way down. > >+20 start >S9 -18 db >S8 -23 db >S7 -26 db >S6 -29 db >S5 -32 db >S4 -35 db >S3 -37 db >S2 -39 db >S1 -41 db Not only is the shape of the scale an issue, but the granularity or resolution, especially with LCD meters, or any meter where there are discrete steps in the meter current (such as where a D/A converter drives the meter movement). If you want to move beyond S meters, you could try FSM (www.vk1od.net/fsm) and organise some constant carriers at known distances / radiation angles that you could make a series of measurements of and produce summary statistics (median and inter quartile range) for each antenna type. > >All in all, I would have to say that the meter tracks very well from S8 >to S4, and the only place that wasn't that great was from S9 to S8. But >considering the transient nature of the signals we are receiving, I >would have to day that the S-meter is of reasonably close accuracy. > >With my newly calibrated S-meter I am ready to start looking at what the >two different antennas are doing for me. I have a coaxial switch to jump >back and forth between the two. My initial impressions are that there >are some surprises. The difference in noise levels varies by antenna by >band. On some bands the vertical is noisier, and on others it is the OCF >dipole. Especially intriguing is that on PSK mode, where I can see >several signals at one time, switching between antennas will attenuate >some signals, while other signals increase in strength. I think that my >vertical works better than I gave it credit for, but If I definitely >want *both* antennas. I described a technique for assessing the relative performance of mobile stations by having them transmit known constant carrier, each station space about 200Hz and turning circles in a carpark near each other, and to observe them at typical propagation distances with an audio spectrum analyser, watching the relative strength of the carriers. Your PSK setup is affording you the same type of comparison, and provides a ready (and recordable) assessment of the relative strength of the stations under the two antenna scenarios. Be great if you could orchestrate stations at known distances as part of an organised test. Owen > >Next installment will be the band to band comparison of the two antennas >with some numbers. > >Installment three will be an investigation of that PSK signal strength >business. > > - 73 de Mike KB3EIA - -- Article: 222104 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: Date: Mon, 06 Mar 2006 01:05:25 GMT Cecil, Interesting. I am quite familiar with Kirchoff's equation in regard to voltages around a loop and his equation about currents at a node. Did I miss a third equation regarding currents around a loop? Hint: Kirchoff would not be the slightest bit bothered by this problem. Reg, as usual, has it completely correct. 73, Gene W4SZ Cecil Moore wrote: > Reg Edwards wrote: > >> The whole business can be mathematically modelled. > > > The point is that it cannot successfully be modeled > with the lumped circuit model where the current is > constant everywhere in the circuit. What would > Kirchhoff have thought about a coil with 0.1 amp > at the bottom and 0.7 amps at the top? It certainly > doesn't mean that 0.6 amps is flowing sideways. All > it means is that the relative phase of the forward > current and reflected current changes through the > coil and therefore the distributed network model > needs to be used. Article: 222105 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: Date: Mon, 06 Mar 2006 02:16:47 GMT Gene Fuller wrote: > I am quite familiar with Kirchoff's equation in regard to voltages > around a loop and his equation about currents at a node. Did I miss a > third equation regarding currents around a loop? Nope, you missed an implication of Kirchhoff's current law. Unequal currents into and out of a passive black box implies the existence of a node inside the box. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222106 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: Message-ID: Date: Mon, 06 Mar 2006 02:26:26 GMT Reg Edwards wrote: > The whole business can be mathematically modelled. IF one uses the correct model. Here's an email I received today. > Walter Maxwell, W2DU wrote: >> Hi Cecil, I just today found the (QRZ.com) discussion. I agree >> with your position 100%. It's as simple as this: >> >> If an inductance is in series with a line that has no reflections, >> the current will be the same at both ends of the inductor. >> >> If an inductance is in series with a line that has reflections, >> the current will NOT be the same at both ends of the inductor. >> >> Consequently, circuit analysis will not work when both forward >> and reflected currents are present in a lumped circuit. > >> When reflections are present, a current node and a current loop >> can appear at separate points on an inductor simultaneously. >> >> Walt -- 73, Cecil http://www.qsl.net/w5dxp Article: 222107 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: Date: Mon, 06 Mar 2006 03:07:31 GMT Cecil, Your response makes no sense at all. Unequal currents into and out of a passive black box implies charge storage, which generally means capacitance. You cannot have it any other way, with or without waves or reflections. Conservation of charge is one of the most fundamental laws in nature. Reg was correct. 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> I am quite familiar with Kirchoff's equation in regard to voltages >> around a loop and his equation about currents at a node. Did I miss a >> third equation regarding currents around a loop? > > > Nope, you missed an implication of Kirchhoff's current law. > Unequal currents into and out of a passive black box implies > the existence of a node inside the box. Article: 222108 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Reflection Loss References: Message-ID: <440bb5da_3@newsfeed.slurp.net> Date: 5 Mar 2006 23:08:58 -0500 ORIGINAL MESSAGE: Reg Edwards wrote: > I have just had several glasses of Australian Zonte's Footstep wine. > I can recommend it. Its name can be traced back to a marsupial which > replaced the dinosaurs. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I love the Aussie sense of humor. Who else would name a marsupial "Footstep"? Bill, W6WRT Article: 222109 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Sun, 05 Mar 2006 21:08:01 -0800 Message-ID: <120ngtl3drs574@corp.supernews.com> References: I'm glad to see that my chiding has had a positive result. Be sure you calibrate your S-meter on each band you'll be using it on, and that the RF gain control and any preamplifier and input attenuator settings are the same as they are when making measurements. Especially when comparing horizontal and vertical antennas, you'll likely have to make several measurements over a period of time. I've seen many cases where one antenna is a good 20 dB stronger than the other, then over the next minute or so their relative strengths reverse. This is due to polarization rotation of the received signal. On 40 and 80 meters at least, this is common and often has a period of around a minute or more. Really makes me chuckle when I hear "Ok, this is antenna 1. Now this is antenna 2. Which is stronger?" If neither antenna is consistently stronger than the other, you can put a fixed attenuator is line with one of the antennas and the step attenuator in line with the other to make comparison easier. People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. Roy Lewallen, W7EL Mike Coslo wrote: > Based on another thread a few weeks back in which Horizontal dipoles > were being compared to Vertical antennas, and from a little chiding from > Roy, W7EL, I decided to do some testing on my own personal versions of > the two. > > > My setup is: > > Icom IC-761 > Antenna 1 - Homebrew OCF dipole at ~ 50 feet. > Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. > > > Part one of this experiment is to calibrate the S-meter. I found that > trying to calibrate the thing with on-air signals was a nuisance, and > probably wouldn't be as accurate, so I used a signal generator. > > I started out with a +20 signal, then worked my way down. > > +20 start > S9 -18 db > S8 -23 db > S7 -26 db > S6 -29 db > S5 -32 db > S4 -35 db > S3 -37 db > S2 -39 db > S1 -41 db > > All in all, I would have to say that the meter tracks very well from S8 > to S4, and the only place that wasn't that great was from S9 to S8. But > considering the transient nature of the signals we are receiving, I > would have to day that the S-meter is of reasonably close accuracy. > > With my newly calibrated S-meter I am ready to start looking at what the > two different antennas are doing for me. I have a coaxial switch to jump > back and forth between the two. My initial impressions are that there > are some surprises. The difference in noise levels varies by antenna by > band. On some bands the vertical is noisier, and on others it is the OCF > dipole. Especially intriguing is that on PSK mode, where I can see > several signals at one time, switching between antennas will attenuate > some signals, while other signals increase in strength. I think that my > vertical works better than I gave it credit for, but If I definitely > want *both* antennas. > > Next installment will be the band to band comparison of the two antennas > with some numbers. > > Installment three will be an investigation of that PSK signal strength > business. > > - 73 de Mike KB3EIA - Article: 222110 of rec.radio.amateur.antenna From: "Sal M. Onella" References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> <8WvOf.430$wp.130@fed1read12> Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: Date: Sun, 5 Mar 2006 21:33:34 -0800 "Cecil Moore" wrote in message news:RMAOf.65891$PL5.47402@newssvr11.news.prodigy.com... > Sal M. Onella wrote: > > Hereabouts (Southern California) we do almost nothing with trees. > > John > > I hear y'all give 'em lots of hugs. :-) > -- > 73, Cecil http://www.qsl.net/w5dxp Hey, good one! Nice laugh, here. I'm not one of "Them," however. I believe that trees are a crop, like so many useful plants. I mean, you never hear protesters wailing, "Save the lima beans." Now, I think I'll go put an antenna up in a tree -- just to do it. 73, John KD6VKW Article: 222111 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Mon, 6 Mar 2006 01:28:51 -0600 Message-ID: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> References: Gene Fuller weote: "Conservation of charge is one of the most fundamental laws of nature." Unequal currents into and out of a passive black box are very simple to produce. Suppose the black box contains a simple transformer with a ratio other than one to one? The power can be constant but the voltage and current must be different on input and output. R-F is a-c, not d-c. Best regards, Richard Harrison, KB5WZI Article: 222112 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 02:34:06 -0600 Message-ID: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "The most important parameter is not SWR but the reflection coefficient, Gamma." My age is about the same as Reg`s. I have 4 children and 6 grandchildren, and am a veteran of WW-2, but doubt that adds to my credibility. Neither does the beer I had with dinner add authority to what I write. I have a degree in Electrical Engineering, but Americans and probably Brits too view this credential with suspicion. It did open the door to good jobs. Reg expresses disdain for "bibles" such as Terman or Kraus but their writings have endured the test of time and are proved by countless experiments. On page 99 of Terman`s 1955 edition of "Electronic and Radio Engineering" (my textbook was an earlier edition) is found the formula to convert the reflection coefficient into SWR or vice versa. These two parameters are innexorably locked together by formulas (4-22a) and (4-22b). There really is no need to rename the ubiquituos SWR meter as Reg has recommended. This really requires no comment as it isn`t about to happen. Best regards, Richard Harrison, KB5WZI Article: 222113 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Mon, 06 Mar 2006 01:10:05 -0800 Message-ID: <120nv3gt1f8gi3a@corp.supernews.com> References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> Richard Harrison wrote: > Gene Fuller weote: > "Conservation of charge is one of the most fundamental laws of nature." > > Unequal currents into and out of a passive black box are very simple to > produce. Suppose the black box contains a simple transformer with a > ratio other than one to one? The power can be constant but the voltage > and current must be different on input and output. R-F is a-c, not d-c. > > Best regards, Richard Harrison, KB5WZI Now explain how you'd do it with a box having only two terminals -- and assuming the box is very small compared to a wavelength. Roy Lew Article: 222114 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Reflection Loss Message-ID: References: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> Date: Mon, 06 Mar 2006 09:13:21 GMT On Mon, 6 Mar 2006 02:34:06 -0600, richardharrison@webtv.net (Richard Harrison) wrote: >On page 99 of Terman`s 1955 edition of "Electronic and Radio >Engineering" (my textbook was an earlier edition) is found the formula >to convert the reflection coefficient into SWR or vice versa. These two >parameters are innexorably locked together by formulas (4-22a) and >(4-22b). Richard, formula 4-22b calculates the magnitude of the reflection coefficient from SWR. It is not possible to calculate the reflection coefficient (as you say) in the general sense since you lack the phase information. Owen -- Article: 222115 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 04:49:53 -0600 Message-ID: <16154-440C13D1-846@storefull-3256.bay.webtv.net> References: Owen Duffy wrote: "Richard, formula 4-22b calculates the magnitude of the reflection coefficient from SWR, it is not possible to calculate the reflection coefficient (as you say) in the general case since you lack phase information." Phase information is not needed. It is true that the reflection coefficient is a vector ratio of the reflected voltage to the incident voltage at the load but this does not affect conversion of the reflection coefficient to the SWR. Reactance at the load has the same effect as adding a same-impedance line (of particular length) between the generator and load. This only shifts the SWR pattern on the line, but in a practical line has no effect on the minima and maxima on the line. SWR is simply the ratio of the maximmum amplitude to the minimum amplitude of voltage (or current) on the line in a particular region of the line. A maximum is displaced by 1/4-wave from a minimum. Phase information is irrelevant to conversion between reflection coefficient and SWR. That`s why Terman didn`t include it. Best regards, Richard Harrison, KB5WZI Article: 222116 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Mon, 6 Mar 2006 05:45:28 -0600 Message-ID: <16154-440C20D8-847@storefull-3256.bay.webtv.net> References: <120nv3gt1f8gi3a@corp.supernews.com> Roy Lewallen, W7EL wrote: "Now explain how you`d do it with a box having only two terminals--" I`ll give the mathematician`s answer: "It`s of no interest. It`s already been solved." Cecil said he would put a coil in the box. I agree. Retardation between incident and reflected waves in each direction would in most cases cause a current difference between the two ends of the coil. Unlike the usual transmission line, the wire is coiled to get reactance into a small space. The effect is the same in that phase shift is distributed along the length of the wire. There is just more of it and and the intervals between maxima and minima are short. Impedance and therefore voltage along the vire is a function of site along the wire. There will be a standing wave pattern throughout the coil. Best regards, Richard Harrison, KB5WZI Article: 222117 of rec.radio.amateur.antenna From: "John, N9JG" References: Subject: Re: Compact loop question Message-ID: Date: Mon, 06 Mar 2006 13:25:39 GMT Well, my problem is in deterring the antecedent for the "it" in your suggestion. Are you recommending that both the tuning capacitor and the feedpoint should be at the bottom of the loop? Please enlighten me. Thanks, John "Richard Clark" wrote in message news:oh8n02ltmh1ioj74tl0jiqhibrve55cn87@4ax.com... > On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG" > wrote: > >>I am not sure what you are recommending - Are you suggesting I make the >>plane of the loop horizontal? > > no > >>> What advantage is there in climbing a ladder to place the loop? Put >>> it at the bottom too. >>> >>> 73's >>> Richard Clark, KB7QHC >> Article: 222118 of rec.radio.amateur.antenna From: "John, N9JG" References: Subject: Re: Compact loop question Message-ID: Date: Mon, 06 Mar 2006 13:27:19 GMT Now I understand your suggestion. Reg also recommends this method of feeding, but the mechanics of mounting the second loop concerns me. "Richard Clark" wrote in message news:bmhn021d9ln2gfbl85l32p9v81mn7li9f2@4ax.com... > On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG" > wrote: > >>I am not sure what you are recommending - Are you suggesting I make the >>plane of the loop horizontal? > > Hi John, > > A second loop driven by the coax placed in the same plane as your > larger one - and at the bottom. No reason to be fooling around at the > top of the arc of the big loop. No reason to break the big loop to > drive it. > > 73's > Richard Clark, KB7QHC Article: 222119 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 13:39:33 +0000 (UTC) Message-ID: References: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> "Richard Harrison" wrote > On page 99 of Terman`s 1955 edition of "Electronic and Radio > Engineering" (my textbook was an earlier edition) is found the formula > to convert the reflection coefficient into SWR or vice versa. These two > parameters are innexorably locked together by formulas (4-22a) and > (4-22b). ============================================= Richard, I'm afraid your worship of Terman has let you down. The two parameters are NOT inexorably locked together. SWR can be calculated from the Reflection Coefficient. But half of the information is then lost and gone for ever. And so, NOT vice-versa! --- Reg. Article: 222120 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> Message-ID: Date: Mon, 06 Mar 2006 14:17:42 GMT Richard, After that response all I can say is, this newsgroup is sure good for entertainment. 73, Gene W4SZ Richard Harrison wrote: > Roy Lewallen, W7EL wrote: > "Now explain how you`d do it with a box having only two terminals--" > > I`ll give the mathematician`s answer: "It`s of no interest. It`s already > been solved." Cecil said he would put a coil in the box. I agree. > Retardation between incident and reflected waves in each direction would > in most cases cause a current difference between the two ends of the > coil. Unlike the usual transmission line, the wire is coiled to get > reactance into a small space. The effect is the same in that phase shift > is distributed along the length of the wire. There is just more of it > and and the intervals between maxima and minima are short. Impedance and > therefore voltage along the vire is a function of site along the wire. > There will be a standing wave pattern throughout the coil. > > Best regards, Richard Harrison, KB5WZI > Article: 222121 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: Date: Mon, 06 Mar 2006 14:29:54 GMT Cecil, This is getting more interesting by the moment. Have you now removed some of the well-known physical attributes of wire and transmission lines? Specifically, what happened to the L and C of the wire? I have no issue with the use of network theory, reflection coefficients, standing waves, or any other commonly used descriptions. However, none of these mathematical conveniences change the fundamental physical laws. If current, and therefore charge, appears to be unbalanced, then there must be charge storage somewhere. As Reg pointed out, the charge is stored in the capacitance of the coil. No need to invoke any magic incantations about networks and standing waves. In principle any of these problems can be solved with very basic equations found in any E&M text. In practice it is extremely cumbersome to do so, and that is why all of the network formulations have been developed. Just don't fall into the trap of thinking that any new physical behavior is created by the reflections and standing waves. I believe in previous messages you have referred to that thinking as "seduced by the math models." 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> Your response makes no sense at all. Unequal currents into and out of >> a passive black box implies charge storage, which generally means >> capacitance. > > > Boundary condition: There's nothing but wire inside the black box. Article: 222122 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: does doppler systems work only for unmodulated continous wave References: <1141647965.814664.310580@i39g2000cwa.googlegroups.com> Message-ID: <2mvtd3-4kv.ln1@p400bob.personal.cox.net> Date: Mon, 06 Mar 2006 09:05:04 -0600 Yes. Dunno if I'd call it reliable though . If you had this kind of system on a moving vehicle for example the RX would have to be able to follow the TX. You'll get about +-200Hz shift with a speed of 100kph. (ie 400Hz as a vehicle goes past you) I have been intending for ages setting up a 2m beacon on my car and seeing if I can yield any driving location/speed etc info from the shift and phase noise. (11Hz at 100kph) Cheers Bob VK2YQA mazerom wrote: > > the doppler shift is fundamentally a tone frequency brought about by a > continuous wave source moving in and out. is it possible to have > reliable doppler shift when our source is spread spectrum or say some > form of digital modulation? > Article: 222123 of rec.radio.amateur.antenna From: R Black Subject: Re: Where can I get a new telescoping Antenna for a Grundig FR-200 Date: Mon, 06 Mar 2006 11:21:12 -0500 Message-ID: <120onvc73aopp9c@corp.supernews.com> References: <120m3dj1dc9eh8e@corp.supernews.com> Well, I finally discovered that the radio is made an serviced by eaton and they have a website with replacemet parts. To bad grundig does not tell one this on there website. Chip R Black wrote: > I have a Grundig FR-200 and it works great. My kids, however broke the > telescoping antenna, and I would like to get a new one. > > Does anyone know where I can purchase a new antenna? I did a web search > and found no references to spare parts. > > > Thanks > > Chip > kf4wbk Article: 222124 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> <120nv3gt1f8gi3a@corp.supernews.com> Message-ID: Date: Mon, 06 Mar 2006 16:36:40 GMT Roy Lewallen wrote: > Now explain how you'd do it with a box having only two terminals -- and > assuming the box is very small compared to a wavelength. Assume a one-wavelength dipole off-center fed 1/4WL from one end. Using EZNEC with 60 segments, feeding at segment number 15 is 24.2% from one end and that's close enough for this example. This is actually done in EZNEC with a 130 ft. dipole on 7.2 MHz and I'll email out that file upon request. I'm going to describe the current distribution in the following diagram with 60 segments running from left to right in *fixed font*. Eash dash corresponds to a segment in EZNEC and F is the feedpoint. seg L L seg 1 v v 60 --------------F--------------------------------------------- ^ ^ ^ N N N The current distribution is sinusoidal. N stands for 'node' which is a current minimum point. L stands for 'loop' which is a current maximum point. Since I'm limited to ASCII, the reader will need to imagine a current envelope drawn from seg 1 up to 'L', down to seg 30, back up to 'L', and back down to seg 60. I'll follow this posting up with actual EZNEC graphics posted to my web page. Now we are going to replace part of that wire with a 6" long coil. A 6" long coil on 7.2 MHz is about 1/3 of one percent of a wavelength so that should qualify as 'very small'. And, to illustrate another fact, I'm going to make the coil from 1/4 wavelength of wire, 33' on 40m, and try to model that using the helical coil feature of EZNEC. That may or may not violate an EZNEC design rule - I just don't know yet. But it doesn't change the concepts being presented here. Let me say this is a very rough approximation to what happens in the real world. The concepts are accurate. The values may be off by a relatively large percentage. The coil certainly distorts the current away from that near-perfect sinusoid and certainly doesn't radiate like the wire it replaces. But roughly, here will be the results of placing the bottom of the coil at seg 30: seg L L seg 1 v v 46 --------------F---------------////---------------- ^ ^ ^ N N N The current at the left end of the coil will be low because that is roughly the location of a current node (minimum). The current at the right end of the coil will be high because that is roughly the location of a current loop (maximum). If one considers the current flowing from left to right, more current will be flowing into the coil than is flowing out of it, like the current at: http://www.qsl.net/w5dxp/qrzgif35.gif This is a standing-wave antenna so the standing-wave current displayed by EZNEC is flowing hardly at all. That standing- wave current consists of two component phasors, rotating in opposite directions. That's why the phase of the standing-wave current is relatively constant. The standing-wave phasor, the superposition of the forward and reflected current phasors, rotates hardly at all, usually by just a few degrees from end to end in a 1/2WL dipole. If the dipole is made of 'thin wire', the phase of the standing-wave current is fixed at zero degrees. (Can a phasor that doesn't rotate be called a phasor?) Taking 1/4WL of the antenna wire and winding it into a high-Q coil above replaces *roughly* 90 degrees of the antenna. The radiation pattern certainly changes because the coil doesn't radiate much. But we are not concerned about radiation patterns in this discussion. We are concerned about the current at each end of the coil, the same current that we measure and the same current reported by EZNEC. That current is certainly not constant through the coil and THE DIFFERENCE IN THE MAGNITUDE OF THE CURRENT AT EACH END OF THE COIL DEPENDS UPON WHERE IT IS PLACED IN THE STANDING-WAVE SYSTEM. The traveling-wave current through a coil is close to equal at each end. The standing-wave current at each end of a coil is NOT equal unless we locate the center of the coil at a current node or at a current loop. In a bottom-loaded mobile antenna, the coil is located very near a current loop where the slope of the current is near zero. In fact, the net current peaks inside the bottom-loading coil. So the concept that net current at each end of a coil installed in a standing-wave environment is equal is just a myth, an old wives' tale that needs to be banned from ham radio. The coil does indeed cause considerable distortion away from the perfect cosine current wave exhibited by a thin wire. But the macro effects of that cosine wave still exist when a coil is installed. The current at each end of a coil installed in a standing-wave antenna depends upon its location in the system. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222125 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> Message-ID: Date: Mon, 06 Mar 2006 16:55:20 GMT Richard Harrison wrote: > Unlike the usual transmission line, the wire is coiled to get > reactance into a small space. The effect is the same in that phase shift > is distributed along the length of the wire. W8JI measured a 60 degree phase shift through a 100uH coil at 1 MHz. Consider that at one end of that coil the forward and reflected currents may be: Ifor = 0.55 amps at zero deg, Iref = 0.45 amps at zero deg. Inet = Ifor + Iref = 1 amp at zero degrees. At the other end of the coil, the forward and reflected currents may be: Ifor = 0.55 amps at +60 deg, Iref = 0.45 amps at -60 deg Inet = Ifor*cos(60) + Iref*cos(-60) Inet = 0.275 + 0.225 = 0.5 amps at zero deg Some items of note: 1. The forward current magnitude is the same at both ends 2. The forward current phase is shifted by 60 degrees 3. The reflected current magnitude is the same at both ends 4. The reflected current magnitude is shifted by -60 deg 5. The forward and reflected current phasors rotate in opposite directions 6. The net current phase is unchanged through the coil 7. The net current magnitude is changed by 100% from 0.5 amps to 1.0 amps. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222126 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 16:58:03 +0000 (UTC) Message-ID: References: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> Dear Richard, You must have a very extensive library. By the way, it is NOT Terman or his books which I disdain. It is the TREATMENT, by his readers, of his books as Bibles which I disdain. The situation is on a par with the more modern, unjustifyable, absolute confidence placed in computer programs and pocket calculators by their users. Computer programs have authors. How much confidence can be placed in THEM is what matters. Amongst my exceedingly small collection of books is one of Terman's. It was printed during WW2. I bought it, second hand, just after the war. 60 years back I learned, critically, a lot from it. Nowadays I refer to it every few months when searching for something about which to write another computer program. So the book is still quite valuable as a comprehensible collection of topics. I have nothing from Kraus. I know of him only from the frequency at which he is referred to by bible worshippers on this newsgroup. I have read about B,L & E. They are the famous trio who left the site without bothering to measure ground resistivity. Their boss should have sent them back. Who was HE? He must have known what they were up to less than THEY did. Being a WW2 veteran I'm pleased to meet you. The experience, like mine, was educational. And I'm sure you have a sense of humour similar to mine. ;o) ---- Regards, Reg, G4FGQ. Article: 222127 of rec.radio.amateur.antenna From: "west" References: <120ngtl3drs574@corp.supernews.com> Subject: Re: Vertical vs Horizontal shootout part one Message-ID: <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> Date: Mon, 06 Mar 2006 16:45:48 GMT "Roy Lewallen" wrote in message news:120ngtl3drs574@corp.supernews.com... > I'm glad to see that my chiding has had a positive result. > > Be sure you calibrate your S-meter on each band you'll be using it on, > and that the RF gain control and any preamplifier and input attenuator > settings are the same as they are when making measurements. > > Especially when comparing horizontal and vertical antennas, you'll > likely have to make several measurements over a period of time. I've > seen many cases where one antenna is a good 20 dB stronger than the > other, then over the next minute or so their relative strengths reverse. > This is due to polarization rotation of the received signal. On 40 and > 80 meters at least, this is common and often has a period of around a > minute or more. Really makes me chuckle when I hear "Ok, this is antenna > 1. Now this is antenna 2. Which is stronger?" > > If neither antenna is consistently stronger than the other, you can put > a fixed attenuator is line with one of the antennas and the step > attenuator in line with the other to make comparison easier. > > People who blindly assume the marks on their S-meters are 6 dB apart > should take a good look at your calibration results. > > Roy Lewallen, W7EL > > Mike Coslo wrote: > > Based on another thread a few weeks back in which Horizontal dipoles > > were being compared to Vertical antennas, and from a little chiding from > > Roy, W7EL, I decided to do some testing on my own personal versions of > > the two. > > > > > > My setup is: > > > > Icom IC-761 > > Antenna 1 - Homebrew OCF dipole at ~ 50 feet. > > Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. > > > > > > Part one of this experiment is to calibrate the S-meter. I found that > > trying to calibrate the thing with on-air signals was a nuisance, and > > probably wouldn't be as accurate, so I used a signal generator. > > > > I started out with a +20 signal, then worked my way down. > > > > +20 start > > S9 -18 db > > S8 -23 db > > S7 -26 db > > S6 -29 db > > S5 -32 db > > S4 -35 db > > S3 -37 db > > S2 -39 db > > S1 -41 db > > > > All in all, I would have to say that the meter tracks very well from S8 > > to S4, and the only place that wasn't that great was from S9 to S8. But > > considering the transient nature of the signals we are receiving, I > > would have to day that the S-meter is of reasonably close accuracy. > > > > With my newly calibrated S-meter I am ready to start looking at what the > > two different antennas are doing for me. I have a coaxial switch to jump > > back and forth between the two. My initial impressions are that there > > are some surprises. The difference in noise levels varies by antenna by > > band. On some bands the vertical is noisier, and on others it is the OCF > > dipole. Especially intriguing is that on PSK mode, where I can see > > several signals at one time, switching between antennas will attenuate > > some signals, while other signals increase in strength. I think that my > > vertical works better than I gave it credit for, but If I definitely > > want *both* antennas. > > > > Next installment will be the band to band comparison of the two antennas > > with some numbers. > > > > Installment three will be an investigation of that PSK signal strength > > business. > > > > - 73 de Mike KB3EIA - Man, this is Ham Radio at its best! west AF4GC Article: 222128 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: Date: Mon, 06 Mar 2006 17:33:15 GMT Gene Fuller wrote: > I have no issue with the use of network theory, reflection coefficients, > standing waves, or any other commonly used descriptions. However, none > of these mathematical conveniences change the fundamental physical laws. > If current, and therefore charge, appears to be unbalanced, then there > must be charge storage somewhere. Gene, the flaw is in your misunderstanding of the fundamental physical laws, not in those laws. We measure the net current at one end of a coil at 0.1 amp and we measure net current at the other end of the coil at 0.7 amps (my web page example). The net current *APPEARS* to be unbalanced, but appearances can be deceiving. THERE IS NO STEADY-STATE CHARGE STORAGE ANYWHERE IN THE SYSTEM. Does this violate any fundamental physical laws? Of course not. Here's why (neglecting losses): V*I*cos(theta) equals the same power at both ends of the coil. That proves there is no steady-state energy storage. V1*(0.7)*cos(theta1) = V2*(0.1)*cos(theta2) This is a distributed network. A lumped circuit analysis fails miserably when you try to use it in a standing- wave environment and you have just proved it. That is also the same mistake that W8JI and W7EL have been making. The forward current at the 0.7 amp point is 0.4 amps at zero deg. The reflected current at the 0.7 amp point is 0.3 amps at zero degrees. The net current is the phasor sum of those two component currents. Inet = (0.4 amps at zero deg) + (0.3 amps at zero deg) Inet = 0.7 amps at zero deg The forward current at the 0.1 amp point is 0.4 amps at 82 degrees. The reflected current at the 0.1 amp point is 0.3 amps at -82 degrees. The coil causes an 82 degree phase shift in both forward and reflected currents and since their phasors are rotating in opposite directions, the sign of their phase shifts are opposite. The net current at this end of the coil is: Inet = Ifor + Iref Inet = (0.4 amp at 82 deg) + (0.3 amp at -82 deg) Inet = 0.057 amps + 0.043 amps = 0.1 amp at zero deg The fundamental physical laws are perfectly valid as has been demonstrated here. It is your understanding of them that seems to be the problem. You seem to have been fooled by appearances and as a result, you chose the wrong model with which to try to solve the problem. The distributed network analysis was developed because the lumped circuit analysis falls apart under certain circumstances. One of those circumstances is the presence of standing waves like the ones that exist in a 75m mobile antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222129 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 17:42:41 +0000 (UTC) Message-ID: References: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> "Richard Harrison" wrote > There really is no need to rename the ubiquituos SWR meter as Reg has > recommended. This really requires no comment as it isn`t about to > happen. ========================================= Richard, Maybe you are right about no need to rename the SWR meter. It does indeed indicate SWR when located at the correct place in the system, it is correctly calibrated impedance-wise, and there is a line on which it can be assumed an SWR exists. But where the thing is located in 99.9 percent of occasions it indicates nonsense. Where SWR on the antenna's feedline is concerned it is totally misleading to novices, CB-ers, amateurs and professionals alike. Hardly educational! I have noticed a few references to TLI are beginning to appear. All that's needed is a sensible Japanese, Chinese or Korean transceiver manufacturer to face the facts and refer to TLI in an operating or maintenance manual. I know its sometimes difficult to learn a new word in a new way of thinking but force yourself to comply with the obvious! It's much easier than having to change to the Metric System. The same economies apply. ---- Reg, G4FGQ. Article: 222130 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Reflection Loss References: <27174-440BF3FE-883@storefull-3257.bay.webtv.net> Message-ID: Date: Mon, 06 Mar 2006 17:50:16 GMT Reg Edwards wrote: > I have nothing from Kraus. I know of him only from the frequency at > which he is referred to by bible worshippers on this newsgroup. Reg, for anyone who is interested, "Antennas for All Applications", 3rd edition, by Kraus and Marhefka, ISBN 0-07-232103-2, is available "new" or "as new" from the following source for $30. It would be nice if everyone on this newsgroup would spring for one. It comes close to being the best $30 that I ever spent on a book. http://www.abebooks.com/ http://dogbert.abebooks.com/servlet/SearchResults?sts=t&y=12&isbn=0072321032&x=54 -- 73, Cecil http://www.qsl.net/w5dxp Article: 222131 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Mon, 6 Mar 2006 11:47:45 -0600 Message-ID: <12478-440C75C1-945@storefull-3258.bay.webtv.net> References: Gene Fuller, W4SZ wrote: "This is getting more interesting by the moment." There are plenty of coils in boxes which have different currents into and out of their two ends. A coil in a box used to be a common way to resonate a too-short 1/4-wave (90-degree) whip. A company I worked for had many Land Rovers, trucks, boats, and ships on and around the Argentine side of the island of Tierra del Fuego.These were equipped with H-F SSB tranceivers. Mobile amntenna was a stainless whip mounted atop a substantial fiberglass box. The box contained the loading coil which was accessible for preselecting the right coil tap to resonate the whip with the vehicle for a particular operating frequency. The box also contained a motor-driven band-switch to automatically change taps on the coil when the frequency was changed on the radio. I am well aware of the ability to resonate a 90-degree whip with no more than the proper coil in series with the short whip on a base insulator. I tuned every one of those coils for each of the frequencies we used in Argentina with my own hands. ON4UN has a graph, Fig 9-22 on page 9-15 of "Low-Band DX-ing" which shows current distribution of a base-loaded whip, In his example, the whip is 45-degrees long.. The loading coil provides the extra 45-degrees required for resonance. Current at the base of ON4UN`s whip is one amp times the cosine of 45-degrees, or 0.707 amp. The loading coil has an input of one amp. With 1 amp into the loading coil and 0.707 amp out of the loading coil, the coil definitely does not have the same current at both ends. Best regards, Richard Harrison, KB5WZI Article: 222132 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 6 Mar 2006 18:21:44 +0000 (UTC) Message-ID: References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> Roy says, > > People who blindly assume the marks on their S-meters are 6 dB apart > > should take a good look at your calibration results. ======================================= The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do with which antenna produces the stronger received signal. It is purely a comparison. Just use the same meter throughout the tests. Roy, you must be still be using that ancient receiver. No doubt it is working fine. But you still refer, quite arbitraliry, to your personal S-meter as the North American Calibration Standard. Must everybody else fall into line? Not me! ---- Reg. Article: 222133 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Mon, 06 Mar 2006 18:37:15 GMT Richard Harrison wrote: > ON4UN has a graph, Fig 9-22 on page 9-15 of "Low-Band DX-ing" which > shows current distribution of a base-loaded whip, In his example, the > whip is 45-degrees long.. The loading coil provides the extra 45-degrees > required for resonance. > > Current at the base of ON4UN`s whip is one amp times the cosine of > 45-degrees, or 0.707 amp. The loading coil has an input of one amp. > > With 1 amp into the loading coil and 0.707 amp out of the loading coil, > the coil definitely does not have the same current at both ends. It's not that perfect in the real world but the basic concept still applies. The actual current at the top of the coil is somewhat higher than 0.707 amp because the current inside the coil is greater than 1 amp. EZNEC says the current about 1/3 of the way up from the bottom of the coil is about 1.15 amp. The inductance of the coil forces the phase between the voltage and current to increase. To maintain the same V*I*cos(theta) power, the current must also increase. The high flux fields developed inside the coil somewhat distort the perfect current cosine wave found in a thin wire dipole so it is not quite as black and white as ON4UN indicates. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222134 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> <120nv3gt1f8gi3a@corp.supernews.com> Message-ID: Date: Mon, 06 Mar 2006 19:00:40 GMT Cecil Moore wrote: > If one > considers the current flowing from left to right, more current > will be flowing into the coil than is flowing out of it, ... Correction! Should say: If one considers the current flowing from left to right, more current will be flowing out of the coil than is flowing into it, ... -- 73, Cecil http://www.qsl.net/w5dxp Article: 222135 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 06 Mar 2006 11:03:16 -0800 Message-ID: <120p1rocfoni584@corp.supernews.com> References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> Reg Edwards wrote: > Roy says, >>> People who blindly assume the marks on their S-meters are 6 dB > apart >>> should take a good look at your calibration results. > > ======================================= > > The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do > with which antenna produces the stronger received signal. It is purely > a comparison. Just use the same meter throughout the tests. > > Roy, you must be still be using that ancient receiver. No doubt it is > working fine. But you still refer, quite arbitraliry, to your personal > S-meter as the North American Calibration Standard. Must everybody > else fall into line? Not me! > ---- > Reg. I hate to call a liar a liar, but sometimes it's hard to take. You're lying again, Reg. I've never referred to my rig's meter as a calibration standard. I've used it as an example many times of a meter whose response is far from the 6 dB per S unit many people assume. It's my argument that any S-Unit "standard" at all is of no use, except by misleading people into thinking that it has some relation to the markings on their S meters. Mike's measurements serve the same purpose. And you've claimed your rig has an adjustment allowing calibration of its S-meter to 6 dB per unit, but have never been willing to share the type of rig or what the adjustment control designation is. Frankly, I believe you're fabricating that, also. It's sad -- you have a lot to offer, but somehow feel compelled to come up with pure fabrications from time to time. It makes some of us view everything else you say with some skepticism. Roy Lewallen, W7EL Article: 222136 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Current through coils Date: Mon, 06 Mar 2006 11:16:12 -0800 Message-ID: <120p2jvqiuees27@corp.supernews.com> References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> Gene Fuller wrote: > Richard, > > After that response all I can say is, this newsgroup is sure good for > entertainment. > And you don't even need to read the present postings. This topic was beat to death in rather nauseating detail in November of 2003 -- see the "Current in antenna loading coils controversy (long)" thread in groups.google.com. It disgusted me because I spent a day setting up a test to make some careful measurements. Before reporting them, I asked Cecil, Yuri, and other proponents of various theories to use their theory to predict what the results would be. As you can see by reviewing the record, after being pushed, Cecil made a couple of different guesses but retracted them. Yuri didn't make any. I made the measurements, and Cecil immediately claimed that I had just proved exactly what he had predicted! Then there was "More W8JI "wisdom" in August 2005. And now things must be getting boring again out in the Texas prairie, so here it comes again. Have fun, folks. Roy Lewallen, W7EL Article: 222137 of rec.radio.amateur.antenna From: "John, N9JG" References: Subject: Re: Compact loop question Message-ID: Date: Mon, 06 Mar 2006 19:26:14 GMT As you describe it, it does seem to be simple. But, the inner loop is made >from coax and is flexible. Now I do plan to have a fiberglass pole, in the plane of the loop, which will connect the top and the bottom of the loop so as to give some rigidity to the outer loop. Perhaps this pole can also partially support the inner loop. In any case I do appreciate your advice and comments. -- John "Richard Clark" wrote in message news:ut0p02tglqqhhg50l137k8lrg686lobkd9@4ax.com... > On Mon, 06 Mar 2006 13:27:19 GMT, "John, N9JG" > wrote: > >>the mechanics of mounting the second loop concerns me. > > Very simple. Build a loop out of coax 1/5 the size of the main loop. > Make it out of the drive line by attaching the center conductor to the > shield at the point of full circumference. Put the loop inside the > main loop, co-planar, anywhere that conveniently suits you (I cannot > imagine a reason to climb a ladder to the top of the arc to do this, > though). Reggie's correspondence is more complete than this if you > can find it among his leavings in the archive. > > 73's > Richard Clark, KB7QHC Article: 222138 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> <120p2jvqiuees27@corp.supernews.com> Message-ID: Date: Mon, 06 Mar 2006 19:30:52 GMT Roy Lewallen wrote: > And now things must > be getting boring again out in the Texas prairie, so here it comes > again. Have fun, folks. Roy, you are like the novice who uses a DC ohm-meter to measure the feedpoint impedance of an antenna. You are using a lumped circuit analysis in the presence of standing waves, not realizing what an extreme technical blunder that really is. Worse yet, you belittle people who point out your blunder. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222139 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> Message-ID: <4j0Pf.514311$qk4.668@bgtnsc05-news.ops.worldnet.att.net> Date: Mon, 06 Mar 2006 19:45:04 GMT Cecil, I have lots of flaws, most of them unrelated to RRAA. But a lack of understanding of fundamental physical laws is not one of them. Two points, and I won't carry on further. * Who said anything about "steady state"? * Current is generally accepted as the flow of charge. (If you know some other definition perhaps that is part of our disagreement.) When the current is different at the ends of a simple two terminal device then the charge flow is different as well. Since charge cannot be created or destroyed (I hope you have no argument with that) then it must be stored or depleted somewhere in that two terminal device. We most likely don't have chemical reactions going on in that device so the charge storage is facilitated through capacitance. That is what Reg said. You disagreed. Reg is correct. (No one is discussing power, phasors, degrees, distributed models or anything else you expounded on. Save it for another day.) 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> I have no issue with the use of network theory, reflection >> coefficients, standing waves, or any other commonly used descriptions. >> However, none of these mathematical conveniences change the >> fundamental physical laws. If current, and therefore charge, appears >> to be unbalanced, then there must be charge storage somewhere. > > > Gene, the flaw is in your misunderstanding of the > fundamental physical laws, not in those laws. > > We measure the net current at one end of a coil at 0.1 > amp and we measure net current at the other end of the > coil at 0.7 amps (my web page example). The net current > *APPEARS* to be unbalanced, but appearances can be > deceiving. THERE IS NO STEADY-STATE CHARGE STORAGE > ANYWHERE IN THE SYSTEM. Does this violate any fundamental > physical laws? Of course not. Here's why (neglecting losses): > > V*I*cos(theta) equals the same power at both ends of the > coil. That proves there is no steady-state energy storage. > > V1*(0.7)*cos(theta1) = V2*(0.1)*cos(theta2) > > This is a distributed network. A lumped circuit analysis > fails miserably when you try to use it in a standing- > wave environment and you have just proved it. That is > also the same mistake that W8JI and W7EL have been > making. > > The forward current at the 0.7 amp point is 0.4 amps at > zero deg. The reflected current at the 0.7 amp point is > 0.3 amps at zero degrees. The net current is the phasor > sum of those two component currents. > > Inet = (0.4 amps at zero deg) + (0.3 amps at zero deg) > Inet = 0.7 amps at zero deg > > The forward current at the 0.1 amp point is 0.4 amps at > 82 degrees. The reflected current at the 0.1 amp point is > 0.3 amps at -82 degrees. The coil causes an 82 degree > phase shift in both forward and reflected currents and > since their phasors are rotating in opposite directions, > the sign of their phase shifts are opposite. > > The net current at this end of the coil is: > > Inet = Ifor + Iref > Inet = (0.4 amp at 82 deg) + (0.3 amp at -82 deg) > Inet = 0.057 amps + 0.043 amps = 0.1 amp at zero deg > > The fundamental physical laws are perfectly valid as has > been demonstrated here. It is your understanding of them > that seems to be the problem. You seem to have been fooled > by appearances and as a result, you chose the wrong model > with which to try to solve the problem. The distributed > network analysis was developed because the lumped circuit > analysis falls apart under certain circumstances. One of > those circumstances is the presence of standing waves like > the ones that exist in a 75m mobile antenna. Article: 222140 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Reflection Loss Message-ID: References: <16154-440C13D1-846@storefull-3256.bay.webtv.net> Date: Mon, 06 Mar 2006 20:23:35 GMT On Mon, 6 Mar 2006 04:49:53 -0600, richardharrison@webtv.net (Richard Harrison) wrote: Richard, You originally stated: On page 99 of Terman`s 1955 edition of "Electronic and Radio Engineering" (my textbook was an earlier edition) is found the formula to convert the reflection coefficient into SWR or vice versa. These two parameters are innexorably locked together by formulas (4-22a) and (4-22b). You are squirming away from the accuracy of your assertion that Terman calculates reflection coefficient from SWR, ie the "or vice versa" in your statement. The reflection coefficient is a complex number with magnitude and phase, as you acknowledge when you later say "It is true that the reflection coefficient is a vector ratio of the reflected voltage to the incident voltage at the load". In formula 4-22b of my copy of Terman, the term on the lhs is |rho|, which is the magnitude of the reflection coefficient. No, you cannot calculate the reflection coefficient from SWR alone, but you can calculate the magnitude alone, but that is less information than the reflection coefficient. To illustrate, and as you know, the reflection coefficient at a point can be used with the line propagation constants to calculate the impedance at another point on the line. You cannot do that with the magnitude of the reflection coefficient. You have misrepresented Terman, he does not calculate the reflection coefficient from SWR (at least not in my copy). Owen -- Article: 222141 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> <4j0Pf.514311$qk4.668@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Mon, 06 Mar 2006 20:21:37 GMT Gene Fuller wrote: > I have lots of flaws, most of them unrelated to RRAA. But a lack of > understanding of fundamental physical laws is not one of them. Gene, you proved beyond any doubt, during the rest of your posting, that you even though may quote the fundamental laws, you are misunderstanding those fundamental laws. I think Richard Harrison does understand. If you refuse to listen to me, then please listen to him. > Current is generally accepted as the flow of charge. 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. Please read, understand, and respond to the following simple example and questionaire: Lossless Transmission Line, SWR is infinite ------------------------------------------------- Ifor--> 1 amp <--Iref 1 amp 1. Is there any net flow of charge? ______ 2. Is the current at a current maximum point equal to 2 amps? ______ 3. Is the current at a current minimum point equal to 0 amps? ______ 4. Is there any net flow of charge between the 2 amp point and the zero amp point? ________ 5. If I replace the 1/4WL section of wire with a 90 degree phase shifting coil, have I changed very much? _________ 6. If the current at one end of that coil is 0 amps and the current at the other end of that coil is 2 amps, is there any net flow of charge through the coil? ________ > When the current is different at the ends of a simple two terminal > device then the charge flow is different as well. That is definitely NOT true for standing wave current. There is ZERO net charge flow for standing wave current. And standing wave current is exactly what you are measuring in a standing wave antenna like a 75m mobile antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222142 of rec.radio.amateur.antenna From: Ed Subject: Re: Vertical vs Horizontal shootout part one Date: 6 Mar 2006 20:11:35 GMT Message-ID: References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> > > And you've claimed your rig has an adjustment allowing calibration of > its S-meter to 6 dB per unit, but have never been willing to share the > type of rig or what the adjustment control designation is. Frankly, I > believe you're fabricating that, also. This thread raises a possible marketing opportunity for someone. Yes, it is quite unlikely, due to their non-linear construction, that an analog meter would properly display S units in 6dB increments. So..... someone ought to design a nice little digital unit that could somewhat easily be hooked up to most radio Rx circuits, and be capable of displaying S units or microvolts (selected at push of a button) and also have a fully adjustable means to calibrate the S unit readings so that they would, in fact, display in linear 6dB increments, and actual microvolts at Rx input, too. Probably wouldn't sell cheap, but there would be those hams who'd love to have such a device. I suppose just a display for microvolts would suffice, though, and that isn't hard to do at all. or just calibrate and re-paint the S meter face to match... Ed K7AAT Article: 222143 of rec.radio.amateur.antenna From: "Richard Fry" References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 6 Mar 2006 14:51:26 -0600 Message-ID: <440ca00e_5@newsfeed.slurp.net> "Ed" wrote: > I suppose just a display for microvolts would suffice, though, and > that isn't hard to do at all. or just calibrate and re-paint the S meter > face to match... ________________ Just don't expect that the S-meter so "calibrated" is reading the real value of the incident field arriving at the rx antenna. It won't be, unless that calibration includes (exactly) the real-world performance of the receiving antenna system at each frequency, including line loss, local reflections, and other factors. Otherwise the reading still will be given in fairly meaningless, relative terms -- the same as S-units. RF Article: 222144 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Mon, 06 Mar 2006 21:19:20 GMT Ian White GM3SEK wrote: > 1. The magnitude and phase of the current flowing into the loading > inductance are both the same as that of the current flowing out (this is > a fundamental property of pure inductANCE). That is a fundamental property of a pure inductance in a lumped circuit analysis which assumes a DC current or a pure traveling- wave current. It is NOT a fundamental property of a pure inductance if the current you are talking about is a net standing wave current. Your stated principle is simply false for a standing wave environment. In a transmission line, it is easy to install a coil that has zero current at one end and an amp of current at the other end. It simply doesn't apply in a standing wave environment - and a 75m bugcatcher loaded mobile antenna is a standing wave antenna. Please take a look at my example and questionaire to understand what is wrong with your above statement. The measured current at the bottom of a loading coil is primarily standing wave current. IT IS NOT FLOWING. The measured current at the top of a loading coil is primarily standing wave current. IT IS NOT FLOWING. Since neither of these two currents are flowing, they don't have to be equal. They just stand there. If I present to you a black box with zero amps at one terminal and one amp at the other terminal, what can we conclude? One possibility is 1/4 wavelength of coiled up coax with an infinite SWR. Please ponder that and apply it to your coil assertion above. 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. Take the transmission line example. ---------------------------X---------------------------- Ifor=1.0amp --> <--Iref=1.0amp There's a black box at 'X'. Inside the black box is 1/4WL of coiled up transmission line. The current measured at left of the black box is zero amps. The current measured at the right of the black box is 2 amps. That doesn't violate any laws of physics. That obeys the laws of physics for a transmission line with reflections. You are measuring the currents at a current node and at a current loop. It's absolutely no big deal. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222145 of rec.radio.amateur.antenna Subject: Re: Vertical vs Horizontal shootout part one From: Ed References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> Message-ID: Date: 06 Mar 2006 21:25:48 GMT > > Just don't expect that the S-meter so "calibrated" is reading the real > value of the incident field arriving at the rx antenna. It won't be, > unless that calibration includes (exactly) the real-world performance > of the receiving antenna system at each frequency, including line > loss, local reflections, and other factors. > > Otherwise the reading still will be given in fairly meaningless, > relative terms -- the same as S-units. The bottom line for the Rx, all it cares about since it doesn't know what kind of antenna is feeding it, is the signal strength at the input.... so I'd say a calibrated microvolt reading reflecting that strength is not very meaningless at all. Any changes in the antenna system will of course change that, but the whole point of any antenna work is to maximize the signal voltage to that rx input, so I'd think a calibrated reading would be extremely useful over an S meter alone. Ed K7AAT Article: 222146 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 06 Mar 2006 13:47:04 -0800 Message-ID: <120pbesgie9bdd3@corp.supernews.com> References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> Ed wrote: > > The bottom line for the Rx, all it cares about since it doesn't know > what kind of antenna is feeding it, is the signal strength at the > input.... so I'd say a calibrated microvolt reading reflecting that > strength is not very meaningless at all. Any changes in the antenna > system will of course change that, but the whole point of any antenna > work is to maximize the signal voltage to that rx input, so I'd think a > calibrated reading would be extremely useful over an S meter alone. I'm afraid it might require more than simple calibration. The S-meter typically just shows the AGC voltage. The AGC response is only approximately logarithmic, and depends on the gain characteristics of the various stages being controlled. Gain characteristics are commonly very temperature sensitive, so any calibration scheme would have to take that into account, as well as the common deviation from true logarithmic response of the various stages. Calibration would also be different on different bands, with and without preamplifier or attenuators, etc. Of course, you could make a receiver with very nearly true logarithmic response, by use of one of the excellent, wide dynamic range log amps which are available these days. But however much you or I might like one, the vast majority of amateurs couldn't care less about what their S meter is really indicating, so they wouldn't pay the added cost for it. On top of that, most amateurs would consider a 6dB-per-S-unit meter to be "dead", and would rather have it wiggle more. Roy Lewallen, W7EL Article: 222147 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 06 Mar 2006 14:42:26 -0800 Message-ID: <120pemmnd5voi9f@corp.supernews.com> References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> <120pbesgie9bdd3@corp.supernews.com> <1141684037.607691.234800@p10g2000cwp.googlegroups.com> K7ITM wrote: > I fully agree with Roy's comment about the AGC-derived S-meter output. > As he says, the AGC characteristics are temperature dependent, and they > are also dependent on the particular set of active devices (and to some > extent the passives too) in the signal path. > > If you have access to a spectrum analyzer, chances are decent that it > will have a well-calibrated amplitude readout. The one I use is > accurate in a relative sense to a fraction of a dB over more than an > 80dB range, and would certainly be sensitive enough for antenna > comparisons. I suppose both those would be true of most modern > spectrum analyzers. In addition, some are quite good at determining > the total power in a specified frequency range, and if you can find > such a range with no signals, you can get a better reading on noise > than you're likely able to do with an S meter, or even a narrow band > spectral measurement. One of the most complex and difficult parts of a spectrum analyzer to design is the log amp which provides this stable and precisely logarithmic response over a wide dynamic range. There's an incredible amount of really ingenious work on the part of some extremely talented engineers in those circuits. In relatively recent times, Barrie Gilbert and his folks at Analog Devices have done some equally clever work in the design of IC log amps. It's not a trivial task by any means. Roy Lewallen, W7EL Article: 222148 of rec.radio.amateur.antenna Subject: Re: Vertical vs Horizontal shootout part one From: Ed References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> <120pbesgie9bdd3@corp.supernews.com> Message-ID: Date: 06 Mar 2006 22:44:19 GMT > Of course, you could make a receiver with very nearly true logarithmic > response, by use of one of the excellent, wide dynamic range log amps > which are available these days. But however much you or I might like > one, the vast majority of amateurs couldn't care less about what their > S meter is really indicating, so they wouldn't pay the added cost for > it. > > On top of that, most amateurs would consider a 6dB-per-S-unit meter to > be "dead", and would rather have it wiggle more. > > Roy Lewallen, W7EL So true, that last part! Well, I certainly understand the non- linearity of the RX when comparing gain accross the entire HF spectrum. I tend to limit my operations to top band and 75, so I hadn't considered changes in Rx gain when moving down the band (or up, as some would have it). Currently, when I do an Rx calibration, I just take some readings on my "S" meter when injecting a signal in the bands of my concern. A "list" of these readings for each band suffices, although I agree with you that that is far more than most hams would bother with. Ed , K7AAT Article: 222149 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <6uHOf.37270$Jd.36960@newssvr25.news.prodigy.net> <4j0Pf.514311$qk4.668@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Mon, 06 Mar 2006 23:22:49 GMT Cecil, A few questions. Do you have a reference that explains this "net standing wave current that does not flow"? Does this magical current have any other interesting properties besides the lack of charge flow? Do ordinary properties such as inductance and capacitance cease to function when dealing with "net standing wave current"? Do you really think it is a good idea to base detailed numerical analysis on these "conceptual constructs" as you call them? Do you have a convenient listing of your "conceptual contructs" so that we can avoid these battles in the future? 8-) 8-) 73, Gene W4SZ Article: 222150 of rec.radio.amateur.antenna From: "Richard Fry" References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 6 Mar 2006 17:45:01 -0600 Message-ID: <440cc8ba_5@newsfeed.slurp.net> "Ed" wrote: > The bottom line for the Rx, all it cares about since it doesn't know > what kind of antenna is feeding it, is the signal strength at the > input.... so I'd say a calibrated microvolt reading reflecting that > strength is not very meaningless at all. ___________ Received signal strength, whether in terms of relative S-units or the measure of real incident fields, is at least as much the result of local conditions as of the ERP of the transmission source on the path toward the receiver, the frequency, and propagation conditions. So the received signal strength indication, whether relative or "real," isn't a hugely significant indicator of any of these parameters. RF Article: 222151 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Tue, 07 Mar 2006 01:03:45 GMT Ian White GM3SEK wrote: > Be very careful here. We're talking about the effect of cutting the > physically shortened wire antenna, and inserting a loading device. This > therefore has to be a TWO-terminal device. Yes, I realize that. Do you realize that the characteristic impedance of a single #14 wire 30 feet above ground is 600 ohms? That pesky ground return path raises its ugly head once again. It's impossible to install a two-terminal system 30 feet above *ground* and have it remain a two-terminal system. It's only a two-terminal system in your mind. > Electrical current is defined as a net rate of transfer of electrons, so > by the very definition of the term there is literally no such thing as a > non-flowing current (except when the current is exactly zero and the > definition becomes moot). You have hit the nail squarely on the head without realizing it. A non-flowing current doesn't exist in reality but that is exactly what you are measuring when you measure standing-wave current. The only things that exist in reality are the forward and reflected current. So you guys are basing your high and mighty concepts on something that doesn't even exist in reality. No wonder you are confused. You are measuring two currents flowing in opposite directions at the same time and don't realize it. > I seriously wonder if you understand what a standing wave is. It is > simply a pattern of variation in current along the length of a > transmission line, which is stable in time. Nope, that's not what it is. For example, a current standing wave on a particular transmission line is the sum of one amp flowing in one direction and one amp flowing in the opposite direction. Exactly what is the net charge flow when identical currents are flowing in opposite directions? Let's see now, this is a really tough one. One amp flowing in one direction minus one amp flowing in the opposite direction. What could the result possibly be? :-) Hint: think DC to see what the net charge flow would be. > If you pick any point along the transmission line or antenna wire, there > is a simple net current characterized by one amplitude and one phase, > relative to some other reference point. (In this whole discussion we > discount the normal cyclic sinusoidal variation of instantaneous RF > current which is happening everywhere in the system.) I suggest you review traveling wave phasors which rotate at omega (2*pi*f). A standing wave 'phasor' doesn't rotate at all so a standing wave current is not moving. I'm not even sure it is technically valid to call a standing wave current a "phasor" since it doesn't even possess a frequency characteristic. Please think about a perfectly stationary, non-revolving 'phasor' and then comment. Wouldn't a non-revolving phasor be DC? > To be valid, your concept must do nothing more than explain > what's seen to be happening; it cannot seek to affect it. The same thing applies to your concepts. So what do your concepts say about a phasor with an omega(2*pi*f) equal to zero as is the case for standing waves? Are standing waves really DC? Do they exist at all anywhere besides the human mind? > At the point where you have to say that a measured (and therefore > measurable) current does not flow, your concept is in trouble. Sorry, I have absolutely no idea what that means. Surely you have measured zero current at a standing wave current minimum where the forward current equals one amp and the reflected current equals one amp. Is that zero amps in the act of flowing? > Your length of coiled up coax is a FOUR-terminal device, like Richard's > transformer was. It isn't an applicable solution for this problem. If you include that pesky ground under antennas, it is. My electronics equation book contains a formula for the characteristic impedance of a single wire transmission line over ground. Is that invalid? Doesn't that sound very much like a dipole wire in the air? > The laws it violates are those of logic. Your black box is not allowed > to sometimes have two terminals and sometimes need four. An antenna system installed on this earth is always a four terminal system whether you like it or not. Haven't you ever seen those diagrams of the current return to ground from an antenna system? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222152 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Tue, 07 Mar 2006 01:29:00 GMT Ian White GM3SEK wrote: > Electrical current is defined as a net rate of transfer of electrons, so > by the very definition of the term there is literally no such thing as a > non-flowing current ... I'm sorry, I forgot to provide a reference for your non-existant non-flowing current. On page 464 of "Antennas for All Applications", by Kraus and Marhefka, 3rd edition, it shows the current on a 1/2WL dipole along with its phase. The phase is *fixed* at zero degrees over the entire 1/2 wavelength. So what does an RF current with a fixed phase of zero degrees really mean? It means that the 'phasor', if it is indeed a phasor, doesn't flow. How could an RF current with a fixed phase of zero degrees manage to flow? e^wt would be zero. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222153 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Reflection Loss Date: Mon, 6 Mar 2006 20:20:14 -0600 Message-ID: <27174-440CEDDE-994@storefull-3257.bay.webtv.net> References: Owen Duffy wrote: "In formula 4-22b of my copy of Terman, the term on the lhs is Irhol which is the magnitude of the reflection coefficient." In my copy, 4-22b gives the "absolute value" of the reflection coefficient (it is embraced with bars) which I believe means the "absolute value" of a number or a symbol without reference to its algebraic sign. (4-22b): +or- reflection coefficient= SWR-1 / SWR+1 These formulas, (4-22a) and 4-22b) aren`t just theory. They are constantly put to use. A derivation which uses the sq rt of the ratio of refllected power to forward power for the reflection coefficient appears on page 23 of my Bird Model 43 Directional Thruline Wattmeter Manual.: SWR = 1+reflection coefficient / 1-reflection coefficient (Same as 4-22a) Transmission lines are special because they enforce Zo. That is, in either direction of travel, when you apply a voltage to the low-loss line, the current which results is locked in-phase with the applied voltage. In other words, Zo is a resistance. Best regards, Richard Harrison, KB5WZI