Article: 221026 of rec.radio.amateur.antenna From: Antey Subject: [question] current/voltage amplitude inducted in antenna Date: Sat, 14 Jan 2006 00:16:06 +0100 Message-ID: Hello Everyone, There's one thing I need to know for the purpose of my simulation - that is the order of magnitude for currents/voltages inducted in the antenna, or, to be more precise - answer for the question below: can termination of the transmission line be simulated in Spice as voltage generator (VSIN) with 75 Ohm internal impedance and particular frequency AND amplitude ? What amplitude could it be ? Best Regards, Peter Article: 221027 of rec.radio.amateur.antenna From: "news" References: <43C15BA4.3F39@orcon.net.nz> <43c793c4$0$2255$afc38c87@news.optusnet.com.au> <43C80CF5.2B5C@orcon.net.nz> Subject: Re: Dick Smith Radio Direction Finder Date: Sat, 14 Jan 2006 09:55:15 +1000 Message-ID: <43c83db7$0$17190$afc38c87@news.optusnet.com.au> yes thanks glenn. I would like a copy of the circuit. email james_about@hotmail.com with the info please. Any thing you need also. I keep a fairly extensive collection of radio software and circuits. And gidday to Kev ....tanker wanker. private joke. Article: 221028 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Brain Teaser References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> <%kCxf.8393$dW3.92@newssvr21.news.prodigy.com> <3uCdndWcxcMygFXenZ2dnUVZ_tKdnZ2d@crocker.com> Message-ID: Date: Sat, 14 Jan 2006 00:22:38 GMT Dave wrote: > i used the polyroots function in mathcad and it comes up with 4 roots. two > are imaginary and one is less than 5 which is impossible... if you shifted > coordinates to the 5' high crossing level and calculate from there the > equation is a bit simpler i think and the impossible root would come out > negative. the one that fits gives: > A=18.621 > B=6.835 > G=7.299 Exactly what my EXCEL program yielded. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221029 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: [question] current/voltage amplitude inducted in antenna References: Message-ID: Date: Sat, 14 Jan 2006 00:28:17 GMT Antey wrote: > There's one thing I need to know for the purpose of my simulation > - that is the order of magnitude for currents/voltages inducted > in the antenna, or, to be more precise - answer for the question below: > can termination of the transmission line be simulated in Spice as > voltage generator (VSIN) with 75 Ohm internal impedance and particular > frequency AND amplitude ? What amplitude could it be ? Are you simulating a receiving antenna or parasitic elements? The main wave in an ordinary transmitting dipole is conducted, not inducted. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221030 of rec.radio.amateur.antenna From: John - KD5YI Subject: Re: Questions about antennas for 2.4 Ghz References: <1137089669.757781.233540@g44g2000cwa.googlegroups.com> Message-ID: Date: Sat, 14 Jan 2006 03:34:10 GMT johannblake@yahoo.com wrote: > I have a 2.4 Ghz transceiver circuit that is used in a mobile wireless > application. The application runs from a watch battery so power is > crucial. The device will only need to transmit up to 4 or 5 meters to > its receiver. I need to know what kind of antenna to use. I read that a > dipole is typical. My question are: > > 1 - what is the minimum length that this antenna can be? > 2 - what is the minimum diameter that the antenna can be? > 3 - can the antenna be etched on one side of a PCB (to avoid attaching > a physical cable)? > 4 - does the length / diameter of the antenna affect the power output? > 5 - any manufacturers you know of that sell very small antennas for > this application? > > What I need is the smallest antenna possible! > > Thank you for your insight. > Johann Blake > Smallest possible? How about surface mount? http://www.mouser.com 240-4311-115-00245 0 dBi, $4.68 in qty 1 John Article: 221031 of rec.radio.amateur.antenna From: Roger Subject: Re: Questions about antennas for 2.4 Ghz Message-ID: <0nhhs1tf2baee39m9o45uj2dnhkc17esi2@4ax.com> References: <1137089669.757781.233540@g44g2000cwa.googlegroups.com> <1137219803.308238.228690@f14g2000cwb.googlegroups.com> Date: Sat, 14 Jan 2006 04:40:08 -0500 On 13 Jan 2006 22:23:23 -0800, johannblake@yahoo.com wrote: >I came across this as well after my posting. This looks to be a great >solution. > Came across what? Roger (K8RI) >Johann Roger Article: 221032 of rec.radio.amateur.antenna From: Antey Subject: Re: [question] current/voltage amplitude inducted in antenna Date: Sat, 14 Jan 2006 11:48:28 +0100 Message-ID: References: > Are you simulating a receiving antenna or parasitic elements? > The main wave in an ordinary transmitting dipole is conducted, > not inducted. I am simulating an amplifier :O) - and I just need a sensible excitation for it; I figured out that described source can do it, but I would like to know if I am right or not. Best Regards, Peter Article: 221033 of rec.radio.amateur.antenna Date: Sat, 14 Jan 2006 22:12:23 +1000 From: Kev Subject: Re: Dick Smith Radio Direction Finder References: <43C15BA4.3F39@orcon.net.nz> <43c793c4$0$2255$afc38c87@news.optusnet.com.au> <43C80CF5.2B5C@orcon.net.nz> <43c83db7$0$17190$afc38c87@news.optusnet.com.au> Message-ID: <43c8eaa8$0$13318$afc38c87@news.optusnet.com.au> news wrote: > yes thanks glenn. I would like a copy of the circuit. > > email james_about@hotmail.com with the info please. > > Any thing you need also. I keep a fairly extensive collection of radio > software and circuits. > > And gidday to Kev ....tanker wanker. private joke. > > :) Kev Article: 221034 of rec.radio.amateur.antenna From: "Wayne P. Muckleroy" References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> Subject: Brain Teaser Practicality Message-ID: Date: Sat, 14 Jan 2006 16:08:00 GMT Question: What is the real world effect on this antenna's performance if the dimensions are calculated to the nearest inch? Suggestion: Use a rough graphical solution to come close to the ideal dimensions. Erect the antenna and then make minor changes in conductor/feed-point dimensions to minimize VSWR and maximize efficiency. "Cecil Moore" wrote in message news:1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com... > Problem: > There's a rather strange antenna with two straight wire elements. > The two elements are supported by two non-conductive poles, Pole > A and Pole B of unequal lengths. The bottoms of the poles are at > ground level and the ground is flat. > > One straight 10 foot wire runs directly from the bottom of Pole > A to the top of Pole B. One straight 20 foot wire runs directly > from the bottom of Pole B to the top of Pole A. The feedpoint of > this strange antenna is where the wires intersect and that point > is exactly five feet above the ground. (The two wires form a > non-symetrical 'X' between the poles and the center of the 'X' > is exactly five feet above the ground.) > > Question: What are the heights of Pole A and Pole B, and > how far apart are the two poles? > > Pole A > |\ > | \ > | \ Pole B > | \ | > | \ / | > | /\ | > | / \ | > |/ \| > -+--------+- > <--d---> > > P.S. None of my math students can solve this problem. > -- > 73, Cecil, http://www.qsl.net/w5dxp Article: 221035 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: [question] current/voltage amplitude inducted in antenna Date: Sat, 14 Jan 2006 10:09:42 -0600 Message-ID: <5543-43C92246-711@storefull-3256.bay.webtv.net> References: Peter wrote: "What amplitude can it be?" A receiving antenna has a radiation resistance. The load which extracts most power is a conjugate match for the antenna. With radiation resistance perfectly matched to receiver input resistance, the radiation resistance becomes the Thevenin equivalent source resistance feeding an identical receiver input resistance. 1/2 the voltage induced into the receiving antenna is used to re-radiate energy received by the antenna. The other 1/2 appears across the receiver`s input resistance. For a professional explanation of this topic, see Kraus` 3rd edition of "Antennas" page 32. "All about antennas at a glance". Best regards, Richard Harrison, KB5WZI Article: 221036 of rec.radio.amateur.antenna From: "Wayne P. Muckleroy" References: Subject: Re: Any Such Coax Switch? Message-ID: <2A9yf.3199$tK4.535@tornado.ohiordc.rr.com> Date: Sat, 14 Jan 2006 16:23:26 GMT Bird Electronic use to carry a manual transfer switch for 50 Ohms. They probably still carry it because they obsolete nothing. You may find one on E-bay. Go to the Bird web-site and get the model number. http://www.bird-electronic.com/products/product.aspx?id=407 Wayne- (KC8UIO) "jimbo" wrote in message news:O9GdnbsyOPa6AVjeRVn-sQ@comcast.com... >I have two, 2 meter radios, one in my basement shack and one in my computer >room on the second floor. I have one 2 meter antenna located in the third >floor attic. I would like a switch that would switch the antenna between >the two radios and I want the radio that is not connected to the antenna to >be connected to a dummy load. > > Maybe I haven't looked hard enough, but all of the switches I have found > so far, switch multiple antennas to one radio and ground the unused > antenna(s). > > Thanks for any help, jimbo Article: 221037 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Brain Teaser Practicality References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> Message-ID: <9P9yf.2822$nT6.247@newssvr27.news.prodigy.net> Date: Sat, 14 Jan 2006 16:39:33 GMT Wayne P. Muckleroy wrote: > Question: > What is the real world effect on this antenna's performance if the > dimensions are calculated to the nearest inch? > > Suggestion: > Use a rough graphical solution to come close to the ideal dimensions. Erect > the antenna and then make minor changes in conductor/feed-point dimensions > to minimize VSWR and maximize efficiency. Actually, it's a classical mathematics problem involving ladders. Since Kurt N. Sterba uses ladders for antennas, it occurred to me too post the problem as an antenna problem. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221038 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Brain Teaser Practicality Date: Sat, 14 Jan 2006 18:34:15 +0000 (UTC) Message-ID: References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> <9P9yf.2822$nT6.247@newssvr27.news.prodigy.net> "Cecil Moore" wrote > Actually, it's a classical mathematics problem involving ladders. > Since Kurt N. Sterba uses ladders for antennas, it occurred to > me too post the problem as an antenna problem. ======================================= I first heard of the problem about 50 years back. It involved ladders in a passage-way leaning on two enclosing brick walls. The solution involved a pair of simultaneous equations and Pythagorus' "sum of the squares on the hypotenuse, etc." Pythagorus would have had little difficulty with it. He probably cribbed his ideas from the ancient Egyptians who built the perfect triangular pyramids using only copper tools several thousand years before. We can do nothing but admire the ancient peoples who lifted themselves up with their own boot-straps. The Greeks, Egyptians, Babylonians, Sumerians, Persians, the peoples of North and South India, and, not the least, the Chinese. Their descendents can teach us ill-educated westerners a lot. Instead of using guided weapons and threats of much worse, perhaps we should listen and take careful note. The first essential is to get rid of Bush and his puppy-dog Blair. Then severely regulate the oil, gas and energy corporations. ---- Reg. Article: 221039 of rec.radio.amateur.antenna From: Richard Reese Subject: FS: Heathkit Manuals Message-ID: <9clis15i74n2k362ccco25fomq0nkr55h8@4ax.com> Date: Sat, 14 Jan 2006 19:48:55 GMT If you need any Heathkit Manuals please visit my website at www.gemair.com/~reeser 73 Dick WA4PLL Article: 221040 of rec.radio.amateur.antenna From: "Ken Taylor" References: <43C15BA4.3F39@orcon.net.nz> <43C98DF6.2958@orcon.net.nz> Subject: Re: Dick Smith Radio Direction Finder Message-ID: Date: Sun, 15 Jan 2006 14:08:48 +1300 "Glenn McAllister" <"(my_callsign)"@orcon.net.nz> wrote in message news:43C98DF6.2958@orcon.net.nz... > Glenn McAllister wrote: > > (snip) > > > > If/when I find the dox, I'll get back to you. Let me know how you > > progress. > > > > Glenn ZL2TLD > > Dox found, photographed (no scanner) and emailed to James, Al and Gary. > > If anyone else would like it, email me with a VALID email address and > I'll send. ( that's pointed at you, al! :-) ) > It's about 2.5MB zipped. Anyone got some space to host it? > > I'll scan it properly when I find someone locally with a flatbed > scanner. > > My email address is my callsign at orcon dot net dot enn zed > > > de Glenn ZL2TLD Whereabouts are you Glenn? I'm in Auckland - have scanner. Ken Article: 221041 of rec.radio.amateur.antenna From: "John Hancock" References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> <0NOxf.465$Jd.220@newssvr25.news.prodigy.net> <1137181409.423923.271590@f14g2000cwb.googlegroups.com> Subject: Re: Brain Teaser Message-ID: Date: Sun, 15 Jan 2006 07:27:04 GMT test "Reg Edwards" wrote in message news:dq954j$g73$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com... > The trouble with pure maths programs is worrying about whether the > answer is the right one from amongst the great variety of other > possible "equally correct" answers. > > For confidence in results, it is necessary to know EXACTLY how a > program deals with the problem it is presented with. Generally this > is unknown. Users are seldom mathematicians. Otherwise they would > not be using the program. > .... > Reg. > > > Article: 221042 of rec.radio.amateur.antenna Date: Sun, 15 Jan 2006 11:26:08 +0100 From: Zoli Pitman HA1AG Subject: Re: Homemade Antenna Tower References: <1137304876.730884.173780@o13g2000cwo.googlegroups.com> Message-ID: <43ca2341$0$71443$dbd43001@news.wanadoo.nl> tekmanx@gmail.com wrote: > Hey guys, I don' t have a design ready to post yet, but my question > is.. How high should my tower be for my vertical sector wifi antenna? What you see is what you cover > I'm currently still undecided on which antenna to get It depends on lot of factors. As a (over) simplistic method use LoS equation, add some margin for fading and calculate link balance to get ERP figures. From ERP you can find out the antenna you need for your feeder losses. GL, zoli ha1ag Article: 221043 of rec.radio.amateur.antenna Date: Sun, 15 Jan 2006 11:34:01 +0100 From: Zoli Pitman HA1AG Subject: Re: FS: Heathkit Manuals References: <9clis15i74n2k362ccco25fomq0nkr55h8@4ax.com> Message-ID: <43ca251a$0$36837$dbd43001@news.wanadoo.nl> > > If you need any Heathkit Manuals please visit my website at xxx.xxx.com/~reeser > > 73 Dick WA4PLL what a cheap advertiser... good that these stuff is available from half a dozen sites for free... Zoli HA1AG Article: 221044 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Homemade Antenna Tower References: <1137304876.730884.173780@o13g2000cwo.googlegroups.com> Message-ID: Date: Sun, 15 Jan 2006 08:35:39 -0600 Generally speaking you should have an unobstructed line of site to the other end of the link. Think of WiFi as being a light beam. Work out the path loss based on the basic distance formula and plug your power, losses and RX sensitivity in to determine your margin and thus max range. Radiomobile and/or UKWtools can be used for this and some allowance for terrain as well. Cheers Bob VK2YQA tekmanx@gmail.com wrote: > is.. How high should my tower be for my vertical sector wifi antenna? Article: 221045 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Homemade Antenna Tower References: <1137304876.730884.173780@o13g2000cwo.googlegroups.com> <1137343121.779638.21450@z14g2000cwz.googlegroups.com> Message-ID: Date: Sun, 15 Jan 2006 12:52:14 -0600 In addition to Richards comments As a guide I use to run two spread spectrum links. One on 2.4GHz over about 10km and another on 5.6Ghz over 8km. The 5.6GHz link was one of those Cisco patch panel things with 30dBm EIRP. The RF power was about 8dBm. We had 56MB/sec about 90% of the time. (Including the BER) (keeping in mind that this is aggregate) The 2.4GHz link was initially setup wrongly. There is a parameter one has to set that defines the max distance of the link I think to reduce packet retries and collisions. When it wasnt set the rate was a real bad and flakey 1MB/sec but when fixed 11Mb/sec was good about 80% of the time (incl BER) What eventually killed the 2.4GHz link was mainly other users on the same freq. The radio design didnt seem to allow it to hop away from interfering signals. A cold power boot often resolved the issue as it chose another clearer freq. We eventually dropped it to 2MB/sec with about 50% reliability. We didnt really have any major multipath problems that were noted in the design phase. We did however have a building go up in the path and for a while were firing between two concrete floors! (We moved one end later) We used a 2 metre gridpack horiz polarization at each end (to avoid some user interference). One end had a 16m run of LMR400, the other about a 12m run. I dont remember the calcs/margin we did off hand, sorry. We didnt however exceed the 30dBm EIRP legal limit. (The company had a very good standing with the ACA/ACMA so we were kind of pedantic about doing it right) Both links were kind of high point to high point accross Sydney. ie There was a large series of valleys between each site. Hope you find this helpful Cheers Bob Tekmanx wrote: > > Also, I heard 802.11g sucks outdoors. This true? And would you guys say > my 400mw radio is overkill for 4-10mile shot? > Article: 221046 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Homemade Antenna Tower Date: Sun, 15 Jan 2006 21:05:08 -0000 Message-ID: <11sle84r4si5g96@corp.supernews.com> References: <1137304876.730884.173780@o13g2000cwo.googlegroups.com> <1137352853.746254.69170@f14g2000cwb.googlegroups.com> <3i9ls1h10h0l2v0k33fe4qase7ts1hjhnn@4ax.com> <1137354972.920090.147520@g44g2000cwa.googlegroups.com> >So what is it you would say determines wither or not my signal will be >received on the other end? I mean with just a regular soho wifi access >point in open space you can only communicate within a couple hundred >feet (That's open space). If gain/wattage isn't so important when we're >talking distance.. what is? Line of site? Are you saying that that I >can shoot my 30mw signal from my soho access point couple of miles? I've spoken with a guy who has set up a number of reliable point-to-point links in the Sacramento valley, using standard unamplified off-the-shelf SOHO-type access points and/or PCI cards or USB dongles. He said he achieves reliable performance, with a good margin of signal strength to handle rain fade, etc., with no amplifiers, over distances of as much as 5 miles. The key to doing this are a clear line of sight, an antenna with high directional gain at each end of the link, and careful aiming. Getting the radio right up at the antenna (rather than at the end of a length of coax) is also beneficial. The carefully-aimed highly-directional antennas give you several advantages, over a standard SOHO omni antennas. The directionality increases the effective radiated power of the transmitter (50 milliwatts through a 20 dBi antenna is equivalent to 5 watts isotropic), it increases the receiver's effective sensitivity by the same degree, and it makes the receiver _less_ sensitive to interference arriving from other angles (e.g. competing transmitters). Also, with proper choice of antenna, you can select the signal's polarization angle. Since most home and business access points seem to use vertically-oriented antennas (and thus a vertically polarized signal) you can reduce interference problems by using point-to- point antennas which are horizontally polarized. The guy I spoke with was not complementary about the idea of trying to "blast" signals through by using high-power transmitters or amplifiers, and blanketing a large area with the signal. You can buy wire-dish parabolic antennas for the 2.4-gig ISM radio band quite easily. I think I've seen 'em advertised as having 15 to 19 dBi of gain. One of these at each end of the link would be a good place to start. -- 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: 221047 of rec.radio.amateur.antenna From: "DJboutit" Subject: RadioPirates Forum Check It out Message-ID: <2ezyf.16077$SD1.2376@tornado.texas.rr.com> Date: Sun, 15 Jan 2006 21:34:54 GMT A community for Pirate Radio enthusiasts to discuse this great hobby and too meet other people interested in Pirate Radio http://radiopirates.ny-cp.net/index.php Article: 221048 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: Homemade Antenna Tower Date: Sun, 15 Jan 2006 21:51:04 +0000 (UTC) Message-ID: References: <1137304876.730884.173780@o13g2000cwo.googlegroups.com> <1137352853.746254.69170@f14g2000cwb.googlegroups.com> <3i9ls1h10h0l2v0k33fe4qase7ts1hjhnn@4ax.com> <1137354972.920090.147520@g44g2000cwa.googlegroups.com> <11sle84r4si5g96@corp.supernews.com> Dave Platt wrote: > I've spoken with a guy who has set up a number of reliable > point-to-point links in the Sacramento valley, using standard > unamplified off-the-shelf SOHO-type access points and/or PCI cards or > USB dongles. He said he achieves reliable performance, with a good > margin of signal strength to handle rain fade, etc., with no > amplifiers, over distances of as much as 5 miles. It's important to point out that using these extreme high gain antennas with out a license is illegal in the U.S. The guy that invented the "pringles can" antenna was an FBI agent so he was not prosecuted, but if he had been an average citizen the FCC would have come after him. Then the question becomes which if any of the 14 WiFi channels is actually in the 2.4gHz ham band. Here in Israel it's even worse. WiFi and terrestrial 2.4gHz ham activity is limited to 100mw EIRP. If you use a gain antenna, you must reduce the transmitter power proportionaly. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 The trouble with being a futurist is that when people get around to believing you, it's too late. We lost. Google 2,000,000:Hams 0. Article: 221075 of rec.radio.amateur.antenna Date: Tue, 17 Jan 2006 08:39:02 -0500 From: jawod Subject: noise bridge Message-ID: <678ea$43ccf378$42a1bfc2$9536@FUSE.NET> As I read through the various opinions regarding antenna load, impedance, etc., most of the arguments seem to be mathematically oriented. Does anyone use a noise bridge (as mentioned in ARRL pubs) to determine the feedpoint impedance? Is there a source for these bridges? This came up as I am studying for general exam. Thanks john Article: 221076 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: noise bridge Date: Tue, 17 Jan 2006 14:41:02 +0000 (UTC) Message-ID: References: <678ea$43ccf378$42a1bfc2$9536@FUSE.NET> jawod wrote: > Does anyone use a noise bridge (as mentioned in ARRL pubs) to determine > the feedpoint impedance? I used to until MFJ came out with their antenna analyizers. I bought a model 249 which read directly in SWR which is what I was interested in. The newer ones read impedance also. > Is there a source for these bridges? They can be had used, made fairly easily and I've seen kits. I had a Palomar which I sold when I bought the MFJ unit. > This came up as I am studying for general exam. Good luck! 73, Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 The trouble with being a futurist is that when people get around to believing you, it's too late. We lost. Google 2,000,000:Hams 0. Article: 221077 of rec.radio.amateur.antenna From: "Bill Ogden" References: <11soo7c2j8qbc0b@corp.supernews.com> Subject: Re: Near Field Calculations Message-ID: Date: Tue, 17 Jan 2006 10:38:05 -0500 > I'll run about 250Wpep. This leaves me below 1/10 the uncontrolled > limit (ignoring duty cycle) except directly underneath and in-line > with the doublet (which by chance is difficult to get near). Do not ignore duty cycle. It is one of the most important factors involved. For someone like myself, who listens a lot on CW and does not transmit much, the duty cycle is something like 1% and this makes a huge difference in the exposure results. 250 watts PEP (with reasonable compression) and a talk time of perhaps 25% probably yields a duty cycle less than 10%. (Someone else will probably have a real formula for PEP x compression x average voice.) The averaging time is not always clear in the exposure formulas, and this could make a large difference. What is your duty cycle averaged over 24 hours? Bill W2WO Article: 221078 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: [question] current/voltage amplitude inducted in antenna Date: Tue, 17 Jan 2006 10:53:59 -0800 Message-ID: References: Cecil Moore wrote: > The main wave in an ordinary transmitting dipole is conducted, > not inducted. That's right. To be inducted requires a vote of the academy. :-) jk Article: 221079 of rec.radio.amateur.antenna From: "F4DRH" References: <9ccos1ha7533l6e1cuhu8gtpi61s9cs3el@4ax.com> Subject: Re: Dipole and Ladder Line Matching Date: Tue, 17 Jan 2006 21:05:43 +0100 Message-ID: <43cd4e16$0$29195$8fcfb975@news.wanadoo.fr> Hi Jimg, Do not bother about the antenna impedance if you want to use it as a multi-band antenna because it will change a lot with the frequency band. 1) First, install a dipole 2 x D, D being the higher length that can afford your backyard. (2 x 20 m is good for 80m band operation) http://www.barbaxoops.com/modules/xcgal/displayimage.php?album=7&pos=4&pid=4 2) Then you install the ladder (in the middle of the dipole). The ladder should go straight from the center of the dipole to the antenna tuner (in the shack). The ladder can be made of electric wires and PVC pipes as spacers (do not forget to glue them) http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=5&album=7&pos=5 http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=57&album=7&pos=2 3) Finally, you built an balanced antenna tuner. The F3LG type is the easiest to built. The MacCoy (see the following pictures) is the most popular http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=46&album=7&pos=0 http://www.barbaxoops.com/modules/xcgal/displayimage.php?album=7&pos=1&pid=47 ... as you know, that antenna is called a "Center Feeded Dipole" .... but french people say "Antenne Levy" Contact me if you want more details about it. Best regards Jean-Marc F4DRH www.barbaxoops.com > Hi. I've heard and read some about ladder line and dipoles. > So what is the basic configuration look like? My impression is > the set-up starts with either a balanced tuner with 400 ohm output > or a 50 ohm tuner with a 4:1 balun to the 440ohm ladder line. The > ladder line then runs to the dipole and that's pretty much about it. > > So my EZNEC on my future backyard Vee shows about 60ohm which is about > a 12:1 mismatch at the antenna feedpoint! So do I have something wrong > in the basic config? Or do you all put a balanced impedance > transformer up at the antenna feedpoint? > > Just a little confuzed? > > > jimg > Oregon > USA Article: 221080 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Larger size HF antenna's References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Message-ID: <52fzf.2827$Yu.423@newssvr27.news.prodigy.net> Date: Tue, 17 Jan 2006 23:25:53 GMT Maarten wrote: > Do you have suggestions for HF antenna's I should check out? Let me > know in this forum or pm me. Thanx in advance. 73 Here's information on a 130 ft. dipole, good for 80m-10m. -- 73, Cecil http://www.qsl.net/w5dxp/notuner.htm Article: 221081 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Larger size HF antenna's Message-ID: References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Date: Tue, 17 Jan 2006 23:37:29 GMT On 17 Jan 2006 15:14:16 -0800, "Maarten" wrote: >Hi, > >I seek some help, advise or suggestions on HF antenna's. I've bought a >house with a plot of approx 330 x 80 ft / 100 x 23 mtr available for HF >antenna's. >But when I research HAM HF antenna's, home build or commercially >available, I only find a lot of small, smaller and smallest HF >antenna's (eg. wire antenna's, inverted V, T2DF) that don't take full >advantage of the size of my land available. On the other end of the >spectrum there are plans for very, VERY large antenna's like Rhombic >and Beverage. For this size of antenna's my plot is to small. > >Do you have suggestions for HF antenna's I should check out? Let me >know in this forum or pm me. Thanx in advance. 73 Marteen, the reason for the gap from small to very large antennas is mainly that the longer ones are developments of long wires and need to be several wavelengths long at the lowest operating frequency. However, it sounds like you block is large enough to accomodate a half wave dipole on 160m... it all depends on the bands that are of interest to you. Similarly, you migh be able to accomodate an Extended Double Zepp for 80m, depending on orientation requirements, or an array of verticals. Don't forget that guyed structures consume space for the back guys. The space might allow you to erect several towers / antennas without them all being tightly coupled as is the case with smaller blocks. Whilst you are working at how to fill the space now, I am guessing that it won't be too long before the space won't seem large enough! Owen> >Maarten >maartenkoning2002 (at) yahoo.com -- Article: 221082 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Larger size HF antenna's References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 18 Jan 2006 00:06:04 GMT Owen Duffy wrote: > Don't forget that guyed structures consume space for the back guys. A friend of mine in AZ solved that problem like this. +---------------Antenna wire----- G |\ U | \ Y | \ | \ Pole W | \ I | \ R | \ E | \ +--------+--------Ground--------- -- 73, Cecil http://www.qsl.net/w5dxp Article: 221083 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Larger size HF antenna's References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 18 Jan 2006 00:07:19 GMT Maarten, How about a loop. Something like 320 x 120, or whatever you can manage. Tuner and ladder line fed. 'Doc Article: 221084 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Larger size HF antenna's Date: Tue, 17 Jan 2006 16:22:18 -0800 Message-ID: <11sr2hvf93pt27f@corp.supernews.com> References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> What exactly do you mean by an antenna that "takes advantage" of your lot size? The main advantage of a larger antenna over a simple one is higher gain. But you only get gain in one or a few directions, at the expense of gain in other directions. So unless you can rotate the large antenna, you'll have an antenna that works great in a very few directions but typically much worse than a dipole in most others. Is that what you want? One of the few ways to get both gain and some control over pattern direction is with a phased array of verticals, symmetrically constructed so you can switch directions. Among the sources for information are ON4UN's _Low-Band DXing_ and Chapter 8 of the _ARRL Antenna Book_. Roy Lewallen, W7EL Maarten wrote: > Hi, > > I seek some help, advise or suggestions on HF antenna's. I've bought a > house with a plot of approx 330 x 80 ft / 100 x 23 mtr available for HF > antenna's. > But when I research HAM HF antenna's, home build or commercially > available, I only find a lot of small, smaller and smallest HF > antenna's (eg. wire antenna's, inverted V, T2DF) that don't take full > advantage of the size of my land available. On the other end of the > spectrum there are plans for very, VERY large antenna's like Rhombic > and Beverage. For this size of antenna's my plot is to small. > > Do you have suggestions for HF antenna's I should check out? Let me > know in this forum or pm me. Thanx in advance. 73 > > Maarten > maartenkoning2002 (at) yahoo.com > Article: 221085 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Larger size HF antenna's Message-ID: References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Date: Wed, 18 Jan 2006 00:28:16 GMT On Wed, 18 Jan 2006 00:06:04 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Don't forget that guyed structures consume space for the back guys. > >A friend of mine in AZ solved that problem like this. ... Ok. I am assuming that there is 1 back guy and two front guys (not shown). If you do the structural analysis, you will see why that configuration is not common. Owen -- Article: 221086 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Message-ID: Date: Wed, 11 Jan 2006 04:25:59 GMT Owen Duffy wrote: > Cecil Moore wrote: >>You already know what I am trying to say. I must not be saying it >>very well. When a parallel cap is used on a 75m screwdriver antenna >>to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e. >> ^ should be - >>slightly inductive. When a parallel coil is used, the screwdriver >>is tuned to 1/50 - j1/X, i.e. slightly capacitive. >> ^ should be + > Negative susceptances are inductive. An inductive reactance of j5 is a > susceptance of 1/j5 or -j1/5. > > I agree with your words, the sign of the admittances is wrong. Yes, you are correct - sorry. But it now seems that you understand what I was trying to say. If one takes an ordinary G5RV and installs a parallel 1000pf capacitor at the coax/twinlead junction, one will raise the resonant frequency and lower the SWR on the coax for 75m operation. Very close to 50+j0 ohms can be achieved on 75m through that simple act. When I lived in AZ, I switched that cap in automatically using a relay and the frequency output signal on my IC-745. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221087 of rec.radio.amateur.antenna From: "Earl Needham" Subject: Re: WTB Outbacker Mobile HF Antenna Date: Wed, 11 Jan 2006 09:10:22 -0700 Message-ID: <11sabfebrvtljda@corp.supernews.com> References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> "Cecil Moore" wrote in message news:1sYwf.5083$fb4.758@newssvr14.news.prodigy.com... > Jerry wrote: > > How about someone who simply doesn't LIKE alcoholic drinks? :) > > That someone has never tasted Bailey's. :-) > -- > 73, Cecil http://www.qsl.net/w5dxp Or Amaretto, or Drambuie, or Captain Morgans in a vanilla Pepsi, or... Earl -- Earl Needham Clovis, New Mexico USA Article: 221088 of rec.radio.amateur.antenna From: ml Subject: Re:Amoskeag Lightning Arrestor Questions References: Message-ID: Date: Wed, 18 Jan 2006 01:59:16 GMT Hi FYI, seems your email addr here dosn't work, if it's a real one Dear Amos i saw your post and hope you wouldn't mind if i asked you a quick quesiton Your Icom that was damaged, was unplugged from everything so how did lightning 'get to it'?? I was kinda distrubed trying to figure it out V sory to hear of your damage ml In article , Amos Keag wrote: > Robert11 wrote: > > > Hello: > > > > The more I read up on this subject, the more confused I get. > > SNIPPED > > > Questions: > > > > a. For either unit, is the arrestor placed between the Balun and the > > antenna, or between the Balun and the radio ? Why ? > > First, the comment in another response regarding direct strike is mostly > valid. No arrestor will protect from direct strike. [up to 100,000 > amperes in less than 1 microsecond, with a 20,000 volt per meter E field.] > > Second, for near strike, the arrestor should be installed depending on > arrestor design. For coax based designs installation should be between > balun and radio. For open wire design it should be installed at the wire > to balun interface. Near strike is a non precise technical term. For > near strike in the 10,000 E field zone the arrestor probably won't > provide the protection you seek. For the 1,000 E field zone you should > get some protection. > > Why? When the arrestor ignites, fires, actuates there still is a voltage > across the arrestor. This is the net voltage from the plasma in the > spark gap or in the ionized internal gasses. This net voltage transient > has a power density that extends from BC/MF [<160 meters] to the HF/VHF > boundary around 30 MHz. It is a broadband pulse. The question is how > much voltage can the radio be exposed to without damage? > > > > > b. The Polyphaser unit apparently, when triggered, shunts the charge (only) > > to the coax shield. The only path to ground would then be up to the radio, > > thru the > > chassis, and then to the AC power ground. > > > > Or, I guess, possibly back the other way via the Balun's ground ? Or both ? > > I would also image that the Balun's windings would probably blow too quickly > > to truly shunt any pulse to its ground ? > > > > There doesn't seem to be any separate ground lug, like the ICE units > > have from their pictures. > > > > I'm a real novice with this lightning protection stuff, so I am > > probably missing something, particularly with the Polyphaser > > shunting-to-the-shield-only approach which > > doesn't seem too great regarding how an adequate RF ground is reached for > > any > > diverted strike/pulse. > > > > What am I missing or not considering with the Polyphaser approach ? > > Thoughts on ? > > > > c. Any opinions on the Polyphaser vs. the ICE units for a receiving only > > application ? > > > > Much thanks, > > Bob > > > > The best solution is to disconnect the antenna and move it away from the > radio when not in use.!! > > I'm a retired Aerospace/Electrical engineer who spent years designing > for lightning strikes both direct and near strikes. My station is 100% > conforming to electrical code and lightning mitigation techniques. Last > July, a near strike lightning pulse caused the ground fault interruptors > for the pool, the bathroom and the kitchen to function. The circuit > breakers in the service panel for the basement power distribution > opened, and the power transformer on the utility pole about 1/2 mile > away exploded. I lost my ICOM 756 ProII which was disconnected from the > power lines, notebook computer, USB damage in a second computer on the > in-house LAN, and one telephone. The ICOM 756 Pro II was disconnected > from the antennas, and the lightning surge protectors did not actuate. A > post fault failure analysis indicated that there was a surge in the > utility power neutral to ground. The entire neighborhood of over 50 > homes suffered some degree of damage. It is estimated by the power > utility that the strike was 1/2 mile away. > > My ICOM 746, my Kenwood TM-G707, and the numerous power supplies > suffered NO damage. Go Figure :-) > > CONCLUSION: Lightning finds way to kill electronics no matter how well > the equipment is installed. > > > > > > > > Article: 221089 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Larger size HF antenna's References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 18 Jan 2006 04:19:26 GMT Owen Duffy wrote: > Ok. I am assuming that there is 1 back guy and two front guys (not > shown). If you do the structural analysis, you will see why that > configuration is not common. As I remember, my AZ friend had some sort of A-Frame support about half-way down the pole. I don't recall more than one guy wire at the top of the pole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221090 of rec.radio.amateur.antenna From: jimg Subject: EzNEC Antenna Voltages Message-ID: Date: Wed, 18 Jan 2006 04:42:38 GMT EZNEC4 computes the antenna currents. Knowing the voltages would be interesting. Unlike the feeder line where the voltage or current are easily determined from the characteristic impedance, the line parameters, and the terminating impedance, how do you determine the antenna voltages? First blush says, uh, 377ohms relates the voltages and current, but that's in free space. The antenna has radiation, inductive, and electric fields (well, the radiation field is actually the transverse electric field component), so how does one go about getting the voltage as a function of antenna position (EZNEC current). I'm sure the answer is obvious but I'd appreciate confirmation (of an answer and my clouded intellect). Thanks. jimg Oregon USA Article: 221091 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: EzNEC Antenna Voltages Date: Tue, 17 Jan 2006 21:08:32 -0800 Message-ID: <11srjamv81gr17@corp.supernews.com> References: jimg wrote: > EZNEC4 computes the antenna currents. Knowing the voltages would be > interesting. Unlike the feeder line where the voltage or current are > easily determined from the characteristic impedance, the line > parameters, and the terminating impedance, how do you > determine the antenna voltages? You don't. Voltage is a measure of the potential between two points. When those points are separated in space and in the presence of a changing magnetic field, which is the situation near an antenna, the voltage you would measure depends on the path you take between the two points. Crudely and not completely accurately put, it depends on how you orient your meter leads. First blush says, uh, 377ohms relates > the voltages and current, but that's in free space. No. 377 ohms is the ratio of E to H field of a plane wave in free space. It isn't the ratio of any voltage to any current anywhere. There is no current in free space, and voltage depends on the path you take, as I said above. > The antenna has > radiation, inductive, and electric fields (well, the radiation field > is actually the transverse electric field component), so how does one > go about getting the voltage as a function of antenna position (EZNEC > current). You don't. It's not possible. Which is why EZNEC doesn't do it. > I'm sure the answer is obvious but I'd appreciate > confirmation (of an answer and my clouded intellect). > Thanks. Roy Lewallen, W7EL Article: 221092 of rec.radio.amateur.antenna From: "Asimov" Subject: Re:Amoskeag Lightning Arrestor Questions Message-ID: References: Date: Wed, 18 Jan 2006 05:11:04 GMT "ml" bravely wrote to "All" (18 Jan 06 01:59:16) --- on the heady topic of "Re:Amoskeag Lightning Arrestor Questions" ml> From: ml ml> Xref: core-easynews rec.radio.amateur.antenna:222810 ml> Hi ml> FYI, seems your email addr here dosn't work, if it's a real one ml> Dear Amos ml> i saw your post and hope you wouldn't mind if i asked you a quick ml> quesiton ml> Your Icom that was damaged, was unplugged from everything so how did ml> lightning 'get to it'?? ml> I was kinda distrubed trying to figure it out I'm guessing his radio was most likely damaged from EMP. An acquaintance had a direct hit on his tower and even his tv's remote control fried. A*s*i*m*o*v Article: 221093 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: EzNEC Antenna Voltages References: <11srjamv81gr17@corp.supernews.com> Message-ID: Date: Wed, 18 Jan 2006 05:52:33 GMT Roy Lewallen wrote: >> The antenna has >> radiation, inductive, and electric fields (well, the radiation field >> is actually the transverse electric field component), so how does one >> go about getting the voltage as a function of antenna position (EZNEC >> current). > > You don't. It's not possible. Which is why EZNEC doesn't do it. The current reported by EZNEC is the net standing-wave current (for standing-wave antennas). That current is associated with the standing-wave's H-field which can be measured. The standing- wave also has an E-field. Is there any way to measure the magnitude and phase of the E-field? I vaguely remember a florescent light bulb being turned on by the E-field, glowing brightest at the tip of a mobile antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221094 of rec.radio.amateur.antenna From: jimg Subject: Re: EzNEC Antenna Voltages Message-ID: References: <11srjamv81gr17@corp.supernews.com> Date: Wed, 18 Jan 2006 07:05:03 GMT yep, that was silly, what was i thinking about?!?! i guess what i was really after was the peak E field near the antenna.actually it's there in the NF Tab...just have to figure out how run/plot the result... anyway, thanks... i still can't believe that's what I asked for...like i forgot what a line integral was for... ok, bye >jimg wrote: >> EZNEC4 computes the antenna currents. Knowing the voltages would be >> interesting. Unlike the feeder line where the voltage or current are >> easily determined from the characteristic impedance, the line >> parameters, and the terminating impedance, how do you >> determine the antenna voltages? > >You don't. Voltage is a measure of the potential between two points. >When those points are separated in space and in the presence of a >changing magnetic field, which is the situation near an antenna, the >voltage you would measure depends on the path you take between the two >points. Crudely and not completely accurately put, it depends on how you >orient your meter leads. > > First blush says, uh, 377ohms relates >> the voltages and current, but that's in free space. > >No. 377 ohms is the ratio of E to H field of a plane wave in free space. >It isn't the ratio of any voltage to any current anywhere. There is no >current in free space, and voltage depends on the path you take, as I >said above. > >> The antenna has >> radiation, inductive, and electric fields (well, the radiation field >> is actually the transverse electric field component), so how does one >> go about getting the voltage as a function of antenna position (EZNEC >> current). > >You don't. It's not possible. Which is why EZNEC doesn't do it. > >> I'm sure the answer is obvious but I'd appreciate >> confirmation (of an answer and my clouded intellect). >> Thanks. > >Roy Lewallen, W7EL jimg Oregon USA Article: 221095 of rec.radio.amateur.antenna From: wood@itd.nrl.navy.mil (J. B. Wood) Subject: Re: Speaking of A.M. reception Date: Wed, 18 Jan 2006 07:35:12 -0500 Message-ID: References: <11nk0sb9lh2jq82@corp.supernews.com> In article , "hossdaddy" wrote: > Hi Bill, > > You might actually be right. I think that's what they are trying to do to > hams with the possibility of BPL. > > I think that AM (as it is) should stay that way FOREVER. I am not opposed > to these stations using a parallel form of digital broadcasting (IBOC?) but > to turn the AM-DSB transmitters off I think would be a tragedy. It is the > only form or radio that can be easily demodulated. A grandfather can sit > down with his grandson, a bunch of wire, an oatmeal box, and a few other > cheap components and in a few hours have a working (and demonstratable) > radio - FREE RADIO - and discounting lightning it is 100% safe too! It's > that kind of thing that got me into the hobby - and with the numbers of > licensees dwindling and our RF bandwidth at stake it is high time that we > get the next generation interested. > > 73! > Paul > KD4GNU Hello, and I share your sentiments but technology moves on. You either keep up with it or be left behind. I get nostalgic over old vacuum tube radios like the Collins KWM types or some Drake models but I wouldn't want to be stuck in that period. Lots of wonderful things to discover in the here-and-now, even pour moi (who passed forty about 16 years ago). There's plenty of electronics out there to interest young minds if you look for it. Ramsey offers some electronic lab kits I wished I'd had as a kid. And speaking of AM-DSB wasn't a spark-gap transmitter using morse code even simpler (well maybe not if you were using a Branly coherer on the receive end and those transmitting antennas sure seemed to require a lot of wire and towers)? I built crystal and one-tube radios as cub/boy scout projects but what I really wanted to construct was a superhet (or maybe a TRF type) since I knew they could pull in lots of stations without requiring an outdoors antenna. For simplicity and ease of construction the majority of those DIY home radio projects excluded the RF and/or IF amplification required to provide a requisite level of receiver sensitivity with an internal antenna. Never built a superhet but I constructed an FM broadcast receiver using a tunnel diode (a componont one of my later Va Tech EE profs would refer to as an "electronic Edsel") as a junior high science fair project. Just a few thoughts. Sincerely, and 73s from N4GGO, John Wood (Code 5550) e-mail: wood@itd.nrl.navy.mil Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 Article: 221096 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Larger size HF antenna's Date: Wed, 18 Jan 2006 11:23:01 -0600 Message-ID: <5543-43CE7975-1637@storefull-3256.bay.webtv.net> References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Maarten wrote: "Do you have suggestions for antennas I should check out?" I am listening to Radio Marti and too jammers on the same frequency. Cuba is the target. Who knows where the transmitters are? Marti is said to be in Miami but that is not necessarily its transmitter location. Likewise the jammers may be in Cuba or elsewhere. LocaL Jammers must be much more numerous to cover the same territory for a large area, but they are more effective. The band is 25 meters, about 12 MHz, a year-round performer. Monitoring Radio Marti in Houston with a small battery portable complete with its telescopic antenna convinces me that a listener is better served using horizonta polarization due to the nulls off the antenna tips which reject interference. The antenna should also be rotatable for maximum signal and, or, minimum interference. A large antenna is usually impractical to rotate. Curtains and rhombics can have high gain and directionality. You can erect enough of these to cover all azimuths desired, then you don`t need to rotate any antennas. So many antennas are usually not possible for the amateur. For the radio amateur, an assortment of Yagis mounted on rotators can cover all desired frequency bands and directions effectively and efficiently. Best regards, Richard Harrison, KB5WZI Article: 221097 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re:Amoskeag Lightning Arrestor Questions Date: Wed, 18 Jan 2006 12:17:51 -0600 Message-ID: <19272-43CE864F-1277@storefull-3255.bay.webtv.net> References: Asimov wrote: "An acquaintance had a direct hit on his tower and even his tv`s remote control head." Did he hear a voice boom from the clouds saying: "Dammit! Missed again!"? A good tower ground should mitigate lightning`s fiversion through a TV remote control. But, I`ve seen stories of "ball lightning" chasing about inside a house. Best regards, Richard Harrison, KB5WZI Article: 221098 of rec.radio.amateur.antenna From: Bruce in Alaska Subject: Re: Antenna Seperation References: Message-ID: Date: Wed, 18 Jan 2006 18:41:44 GMT In article , Ted wrote: > I've been working with some fishing boats and these guys want to have > redundent VHF setups - two radios, two antennas. Only one would be used > and turned on. My concern is that the unused antenna could couple as a > parasitic element and effect SWR of the operating antenna. Do I really > need to worry about it? If so haw far apart do the two antennas have to be? These must be very small fishing boats, as ALL vessels over 65 Ft MUST have two Vhf receivers operational while navigating. Marine ch16, and marine ch13. this is required by The Bridge to Bridge Radiotelephone Act. It really isn't a big deal as long as the two antennas have some seperation either vertical or horozontal. I have installed multiple MORAD 156HD antennas on a Masthead Tree, using 24inch Standoffs, and not had any problems with simulataious operations as long as the radio's frequencies were seperated by 50Khz or more. Of course I was working with good commercial type Vhf's like Modar55/75 or SEA156's, and not the RayJeff consumer crap that one would usually find on noncommercial vessels. Bruce in alaska -- add a <2> before @ Article: 221099 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Larger size HF antenna's Date: Wed, 18 Jan 2006 11:08:25 -0800 Message-ID: <11st4h9qcfv0td5@corp.supernews.com> References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> <5543-43CE7975-1637@storefull-3256.bay.webtv.net> <1137610604.343094.102730@z14g2000cwz.googlegroups.com> You'll find information on this kind of antenna in many publications. It's commonly called a "discone". Roy Lewallen, W7EL Maarten wrote: > Tnx fer ur ideas OM's, I will surely check the books out. > I might choose a monopole conical antenna for broadband vertical > omnidirectional radiation (if I discover building plans somewhere) (if > you do'n know what a monopole conical antenna is, check out > http://www.antenna.be/vm.html ) > I will keep researching this subject, so as before, all ideas and > suggestions are more than welcome. > > 73 > Article: 221100 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Amoskeag Lightning Arrestor Questions Date: Wed, 18 Jan 2006 19:33:01 -0000 Message-ID: <11st5vd8qeie574@corp.supernews.com> References: In article , Amos Keag wrote: >Ground Loop. Took time to find it though. > >The Astron RS-35 power supply connects utility power neutral to the >case. It also connects the 13.8 volt return to the case. [This is >commercial common practice but is prohibited in Military Systems >design.] *yoicks*! The latter, I can believe is common practice. The former - tying the powerline neutral directly to the case - strikes me as being *extremely* contrary to electrical code and common sense. It'd turn the supply into a deathtrap-waiting-to-happen if it were plugged into an outlet having the hot and neutral reversed... and these are (alas) not at all uncommon. Now, having the utility power safety ground wired directly to the case, I can very well believe... this is quite common. -- 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: 221101 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Lightning Arrestor Questions Date: Wed, 18 Jan 2006 13:30:42 -0600 Message-ID: <12633-43CE9762-1365@storefull-3254.bay.webtv.net> References: Robert 11 wrote: "For either unit is the arrester placed between the Balun and the antenna, or between the Balun and the radio? Why? It likely is superflous. Coax connectors make lightning arrestors of sorts. They clamp voltage to the arc sustaining voltage (less than 100 volts), once they fire. If you are transmitting, r-f may keep the arc alive. Broadcast transmitters sense the arc and shut the transmitter down for an instant to quench the arc. Communications radios usually don`t bother as their transmissions are sporadic and usuallly short. Remember, coax shield is impenetrable to r-f. D-C conducts right through. R-F does not due to skin effect. In countless VHF antenna installations atop tall towers around rhe world we never used a Polyphaser or similar arrestor on the coax, yet never had damage to radio antenna circuits, even to transistorized radios. We always used folded driven antenna elements. We grounded the coax at the top and bottom of the antenna tower. The tower due to its size has lower surge impedance and carries the bulk of the lightning current to ground. The tower is well grounded. We found it necessary to use brute-force pi-filters on every power wire feeding the radio including the neutral wire. We used tower lighting chokes in the pi-filters to cary the current required to power the radios. We shunted the filter inputs and outputs to ground with MOV`s (across the a-c capacitors).This limited surge voltage on the radio and on the powerline. It eliminated all damage to the power supplies in the radios. These filters were found necessary only when transistor radios were introduced. Before that, the grounded antenna system sufficed for tube-type radios. Best regards, Richard Harrison, KB5WZI Article: 221102 of rec.radio.amateur.antenna Subject: Re: Larger size HF antenna's From: Dave Oldridge References: <1137539656.712611.283320@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 18 Jan 2006 21:00:34 GMT "Maarten" wrote in news:1137539656.712611.283320@g47g2000cwa.googlegroups.com: > Hi, > > I seek some help, advise or suggestions on HF antenna's. I've bought a > house with a plot of approx 330 x 80 ft / 100 x 23 mtr available for HF > antenna's. > But when I research HAM HF antenna's, home build or commercially > available, I only find a lot of small, smaller and smallest HF > antenna's (eg. wire antenna's, inverted V, T2DF) that don't take full > advantage of the size of my land available. On the other end of the > spectrum there are plans for very, VERY large antenna's like Rhombic > and Beverage. For this size of antenna's my plot is to small. > > Do you have suggestions for HF antenna's I should check out? Let me > know in this forum or pm me. Thanx in advance. 73 You have enough room for a full dipole at 1.8mhz. That's about 260 feet long and, if you feed it at the center with twinlead or 450 ohm ladder line or 600 ohm open wire line and run a tuner in the shack, it will also function as an extended double zepp on 3.5mhz. Fed this way, these antennas are incredibly frequency tolerant. You will be able to use it right up through 10 meters, but be aware that it will have an increasingly crazy pattern the higher you go. For best low-band performance, you also want it as high as you can get it, depending on whether your interest is DX or NVIS (near-vertical incidence nearby contacts on 160 and 80m). If DX is what you're after, you may want to consider some alternative strategy, depending on how much height you can achieve. But for NVIS, 85 feet is about optimum and the antenna will play well all the way down to around 30 feet. Below that you'll see some ground effects. If DX is your goal, you may want to consider phasing verticals. On 160m, spacing them about 130 feet apart can make for a fairly steerable array. This would still leave you room for full-size radials on two sides of the antennas. If you use smaller, base-loaded verticals, then you can get away with even shorter radials. On 80m, you actually have a LOT of room. I once put two Electrospace HF verticals 65 feet apart (E-W) on a lot quite a bit smaller than this. The Electrospace verticals played quite well with just 8 radials each of 32 foot length (about the same as the verticals' height). I brought equal length feedlines into the shack and made a delay box with 65 feet ELECTRICAL length of RG8X in it, cut up into pieces of 1/2, 1/4 and two of 1/8 the total length with dpdt switches to but them in and out of the loop. Adding one more dpdt switch for reversing the delay to the other side completed the box. This antenna was VERY effective on 80m off its ends. On 40m (they were 80-40- 20m verticals), the pattern was more bipolar, but sharper than the more oval pattern on 80m when the zero-delay setting was selected (for N-S) pattern. Similarly, it began to be a bit grassy on 20m. Still, the main lobe of it went the same place on every band for the same settings. And the thing was efficient and had a low radiation angle. It was easily S9+ in New Zealand and Syria from Halifax, NS on 75m. The only drawback was that, with short antennas like that, I had to either tune at the rig and put up with losses on the coax or go out and tune the antennas to cover the whole 80m band. If I had the real estate today, and the gear I have now to tune antennas with, I'd probably try something similar, though maybe in a four-square array for 80. 80 feet is a bit tight for one of those, but you MIGHT just squeeze it in if you're careful. -- Dave Oldridge+ ICQ 1800667 Article: 221103 of rec.radio.amateur.antenna Subject: Re: Antenna Seperation From: Dave Oldridge References: Message-ID: Date: Wed, 18 Jan 2006 21:05:04 GMT Dan Andersson wrote in news:SJWcncusIopg6VDeSa8jmw@karoo.co.uk: > Ted wrote: > >> I've been working with some fishing boats and these guys want to have >> redundent VHF setups - two radios, two antennas. Only one would be >> used and turned on. My concern is that the unused antenna could >> couple as a parasitic element and effect SWR of the operating >> antenna. Do I really need to worry about it? If so haw far apart do >> the two antennas have to be? > > > Ted, > > One way is to place the aerials at a "non 1/4 or 1/8" wavelength apart > from each other but VHF is really not that bothered if you are more > than a 1/4 away. > > If you really want to be sure, just tilt the spare aerial 90 degrees > in the horizontal plane. That will limit the interaction even further. And render it useless for calling the coast guard, since they are vertically polarized (unless you hinge it to come up when deployed, but that's one more thing to break). Basically just make sure they are more than about 4 feet apart horizontally and that, if really close, the spare radio is switched off the feeder unless it's needed. If they are mounted vertically, one over the other, you don't even need to do that. But the lower one will not be as efficient or effective as the higher one. -- Dave Oldridge+ ICQ 1800667 Article: 221104 of rec.radio.amateur.antenna From: "W. Watson" Subject: ARRL Antenna Software CD Message-ID: Date: Wed, 18 Jan 2006 22:05:38 GMT I was making inquiries about antennas a few weeks ago and someone mentioned the antenna software was available from the ARRL from either a separate CD or a CD in the Antenna Book. The post expired. Was it separate, and is their a description of the contents? I really don't need the book. Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet -- "Predictions are hard to make. Especially about the future. -- Yogi Berra Web Page: