Article: 220081 of rec.radio.amateur.antenna From: "M. J. Powell" Subject: Re: http://niggermania.com/ Date: Mon, 12 Dec 2005 20:19:10 +0000 Message-ID: <6ohVm5H+sdnDFwaB@pickmere.demon.co.uk> References: In message <439dccd3.22632213@news.blueyonder.co.uk>, Peter writes >On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" > wrote: > >>England is still a mainly white Christian Country.. > >What ever gave you that idea??? A very small percentage of the >population go to church in the UK. The rest have more sense. More people go to church than go to football matches. Mike -- M.J.Powell Article: 220082 of rec.radio.amateur.antenna Subject: Re: 'oL STEVEO From: Steveo Date: 12 Dec 2005 21:16:45 GMT Message-ID: <20051212161645.390$nq@newsreader.com> References: <11ppftdm5aij5aa@corp.supernews.com> "void * clvrmnky()" wrote: > On 11/12/2005 7:09 PM, Butch Magee wrote: > > I think it is about time that 'ol Steveo was removed from this group. > > I have just read too much of his trash on these groups. Don't need > > 'im, can't use him. I just detest his vulgar mouth. Anybody can use a > > cuss word now and then, however, Steveo thrives on the most vulgar > > words and in long runs and young people and YLs read these posts and I > > feel very sad for them. > > > Well, this *is* a (somewhat) public forum. If you need to, you can > learn how to remove USENET postings, and not all servers accept removal > postings. (The issues around USENET removal postings can be argued > elsewhere! It _can_ be done, is all I'm saying. Whether it _should_ be > done, or will actually work is another matter.) > Hello Void. Sending bogus cancel messages would be one way for Butch Magee to have himself removed from his posting privileges. :) Best Regards, Steveo. Article: 220083 of rec.radio.amateur.antenna From: Dominique Michel Subject: Re: how to model frequency response of a loaded vertical ? Date: Tue, 13 Dec 2005 01:57:25 +0100 Message-ID: <20051213015725.1734dfa4@pingouin.banquise> References: It is a free antenna simulation software NEC2 at http://www.nec2.org/ You must be able to model your antenna and much more with it. Here is an exemple of what this software can do: http://www.extremetech.com/article2/0,1558,1641191,00.asp Sorry windose user, I believe in free software. If you want this software, it is time to try linux. You must have at least 1 free partition, and the installation process of most of the linux distributions will install a double boot windows-linux for you. Best, Dominique On Sat, 03 Dec 2005 22:43:16 -0800 Roy Lewallen wrote: > I apologize -- I read your earlier posting too hastily. Your antenna > requires the full version of EZNEC because of the inductor. While a > short inductor can be modeled as a lumped load, that doesn't work > well in cases like this where the current changes significantly from > one end of the coil to the other due to radiation. The coil has to be > modeled as a helix. > > A full model of your antenna with the coil properly modeled shows a > feedpoint impedance of 5.03 - j212 ohms at 112 MHz over perfect > ground. Loss in a real ground system will of course increase the > resistance. It resonates at 171 MHz, where the feedpoint resistance > is about 17 ohms. My result is far from your finding of resonance > around 112 MHz, so maybe I didn't interpret the design correctly -- > the antenna I modeled is a total of 11 inches high, the center 3 > inches of that being the 1 inch diameter 5 turn coil. > > With EZNEC and similar programs, you can only connect directly only > to perfect and MININEC-type ground; connection to Real, High-Accuracy > ground results in an unpredictable resistance that has no physical > meaning. More information can be found in the Modeling Ground chapter > of the EZNEC manual under Building The Model. > > Roy Lewallen, W7EL > > dansawyeror wrote: > > Roy, > > > > Thanks, I was able to enter the data into eznec and run the > > simulation. The output was 'confusing'. Eznec predicted 100 Ohm > > over various grounds. Other models predict 5 Ohms for the antenna > > plus ground resistance with a total of 10 Ohms or so. Which is > > correct? How can the differences be reconciled? > > > > Thanks again - Dan > > > > Roy Lewallen wrote: > > > >> dansawyeror wrote: > >> > >>> All, > >>> > >>> I am creating a 'scaled' model of a loaded vertical. The model is > >>> complete and in place. However I immediately realized I had no > >>> idea of the 'theoretical' response. How can I calculate the > >>> expected impedance response of a loaded vertical? It a mid load > >>> construction, > >>> > >>> the base in #10 solid copper 4 inchs, > >>> the coil is .6 pitch, 1 inch diameter, 5 turns #12, measuring .72 > >>> uH, and the top is 4 inch #12. > >>> > >>> The antenna appears to resonate at about 112 MHz. > >>> > >>> The instrumentation, a directional coupler measuring reflection > >>> is located at the base, directly under the 'ground plane'. This > >>> allows measuring input and reflected signal strength. > >>> > >>> The question is: How can I plot the expected impedance from say > >>> 100 MHz to 130 MHz? > >>> > >>> Thanks - Dan > >> > >> > >> > >> The free EZNEC demo from http://eznec.com will give you the > >> information you need. > >> > >> Roy Lewallen, W7EL Article: 220084 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <785op1hamdv09vnnf86vii55k6s8a81upl@4ax.com> <753dc$439c4064$97d56a33$14444@ALLTEL.NET> <439ecd7f.22804080@news.blueyonder.co.uk> Subject: Re: http://niggermania.com/ Date: Mon, 12 Dec 2005 20:46:36 -0500 Message-ID: It has been published in a number of supermarket tabloids. I mean look at him, if he wouldn't suck a dick he at least would hold in his mouth until the swelling went down. The whole bloody Royal lot are dumber that coal buckets. One of the reasons I have to smile when you folks across the pond attack our presidents intelligence.. "Peter" wrote in message news:439ecd7f.22804080@news.blueyonder.co.uk... > On Sun, 11 Dec 2005 10:06:10 -0500, "Fred W4JLE" > wrote: > > >Tell you what, don't comment on George Bush and we will leave your > >bisexual,cheating ,scumbag prince alone. > > Whoooooaaa there! Cheating yes, scumbag not sure, but bisexual(???). > Where on earth did you read that? > Article: 220085 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Coax recomendations Date: Mon, 12 Dec 2005 18:07:46 -0800 Message-ID: <11psb7jjj20qv2d@corp.supernews.com> References: <11pl2ihjg99tbb4@news.supernews.com> <11pmoprb85261b9@news.supernews.com> <11pmtnar3ej7ee3@corp.supernews.com> <11pmujnmbrqan11@news.supernews.com> <11pmve465hco98d@corp.supernews.com> <11pn0gglob7l891@news.supernews.com> <11pn3bvjgt34j22@corp.supernews.com> Reg Edwards wrote: > To find ALL electrical characteristics and performance of > solid-polyethylene transmission line, use program COAXPAIR, from audio > frequencies to UHF. > > Accuracy is of the same order as physical dimensions can be measured. > Use a micrometer to measure inner conductor diameter and diameter over > insulant. Or just guess at it. No need to unwind the cable off the > drum! > > In a few seconds, download COAXPAIR from website below and run > immediately. Have you compared the results to any measurements of real cables? Roy Lewallen, W7EL Article: 220086 of rec.radio.amateur.antenna Date: Mon, 12 Dec 2005 20:35:26 -0600 From: Tom Ring Subject: Re: http://niggermania.com/ References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> Message-ID: <439e3382$0$3756$39cecf19@news.twtelecom.net> Amos Keag wrote: > Peter wrote: > >> On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" >> wrote: >> >> >>> England is still a mainly white Christian Country.. >> >> >> >> What ever gave you that idea??? A very small percentage of the >> population go to church in the UK. The rest have more sense. > > > Peter, I'll remember you in prayers and at my masses. > Superstition is as superstition does. tom K0TAR Article: 220087 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: http://niggermania.com/ Date: Mon, 12 Dec 2005 20:34:26 -0600 Message-ID: <9829-439E3332-440@storefull-3251.bay.webtv.net> References: Reg, G4FGQ wrote: "Americans, as they call themselves, are just "USA Citixens"." That`s about right. Nearly all recently descend from immigrants from elsewhere. Theodore Roosevelt, whise image is among those chiseled on Mount Rushmore had something to say about American citizens in 1907, and it is still true: "In the first place, we should insist that if the immigrant who comes here in good faith becomes an American and assimilates himself to us, he shall be treated on an exact equality with everyone else. for it is an outrage to discriminate against any such ,man because of creed, or birthplace or origin. But this is predicated upon the person`s becomimg in every facet an American... There can be no divided allegiance here. Any man who says he is an American, but something else also, isn`t an American at all. We have room for but one flag, the American flag... Wehave room for but one language here and that is the English language... and we have room for but one sole loyalty and that is a loyalty to the American people. Theodore Roosevelt 1907 Teddy`s test works for me. Best regards, Richard Harrison, KB5WZI Article: 220088 of rec.radio.amateur.antenna Subject: Re: Presenting D-Dimond1 antenna From: Dave Oldridge References: <1134415979.669943.249080@f14g2000cwb.googlegroups.com> Message-ID: Date: Tue, 13 Dec 2005 02:48:43 GMT "Dimitris" wrote in news:1134415979.669943.249080@f14g2000cwb.googlegroups.com: > http://antennas.ee.duth.gr/ooo/dt/05/hli/16/comparison1richwire11analyt > ical.doc I did an analysis of my own (with very poor tools) that indicated that the antenna is resonant at 93.1 percent of the design frequency with an impedance of very close to 75 ohms resistive. -- Dave Oldridge+ ICQ 1800667 Article: 220089 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Re: dipole and balun question Date: 12 Dec 2005 23:38:38 -0600 Message-ID: References: >>>Tuner-balun-ladder-antenna is better.... >> ... wouldn't ChokeBalun-BalancedTuner-ladder-antenna be ... better? >Yes, but that really needs either an expensive floated or balanced tuner >or a remotely controlled one.... Not counting the choke balun (coax coiled on an oatmeal box), my "expensive" balanced tuner consists of a variable capacitor, two inductors, and two alligator clips. When my antenna configurations settle down (probably not soon), I may replace the alligator clips with a two-dec rotary switch. (Of course, if I had two identical rotary inductors, I wouldn't need the alligator clips!) -- --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: 220090 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Coax recomendations Date: Tue, 13 Dec 2005 06:41:08 +0000 (UTC) Message-ID: References: <11pl2ihjg99tbb4@news.supernews.com> <11pmoprb85261b9@news.supernews.com> <11pmtnar3ej7ee3@corp.supernews.com> <11pmujnmbrqan11@news.supernews.com> <11pmve465hco98d@corp.supernews.com> <11pn0gglob7l891@news.supernews.com> <11pn3bvjgt34j22@corp.supernews.com> <11psb7jjj20qv2d@corp.supernews.com> > Reg Edwards wrote: > > To find ALL electrical characteristics and performance of > > solid-polyethylene transmission line, use program COAXPAIR, from audio > > frequencies to UHF. > > > > Accuracy is of the same order as physical dimensions can be measured. ============================================ > Have you compared the results to any measurements of real cables? > > Roy Lewallen, W7EL ============================================ Yes, Roy. Countless times. Have you any more questions? ---- Reg, G4FGQ Article: 220091 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Coax recomendations Date: Tue, 13 Dec 2005 00:26:25 -0800 Message-ID: <11pt1dj9ll4o4f6@corp.supernews.com> References: <11pl2ihjg99tbb4@news.supernews.com> <11pmoprb85261b9@news.supernews.com> <11pmtnar3ej7ee3@corp.supernews.com> <11pmujnmbrqan11@news.supernews.com> <11pmve465hco98d@corp.supernews.com> <11pn0gglob7l891@news.supernews.com> <11pn3bvjgt34j22@corp.supernews.com> <11psb7jjj20qv2d@corp.supernews.com> Reg Edwards wrote: >>Reg Edwards wrote: >> >>>To find ALL electrical characteristics and performance of >>>solid-polyethylene transmission line, use program COAXPAIR, from > > audio > >>>frequencies to UHF. >>> >>>Accuracy is of the same order as physical dimensions can be > > measured. > ============================================ > > >>Have you compared the results to any measurements of real cables? >> >>Roy Lewallen, W7EL > > > ============================================ > > Yes, Roy. Countless times. > > Have you any more questions? > ---- > Reg, G4FGQ Yes. Where can I buy some of that RG-58 that has only 2.2 dB/100 foot loss, or RG-213 that has only 0.89 dB loss, at 50 MHz? Roy Lewallen, W7EL Article: 220092 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Back to fundamentals Date: Tue, 13 Dec 2005 01:30:20 -0800 Message-ID: <11pt55e220k6c62@corp.supernews.com> References: <11pldprad26mca3@corp.supernews.com> Gene Fuller wrote: >. . . >> [I wrote:] >> One final note, regarding the NEC applied plane wave. My earlier >> statement that the resulting field is twice the plane wave source >> magnitude when a ground plane is present is true only when the plane >> wave is applied over perfect ground at exactly grazing incidence >> (zenith angle = 90 deg.). If applied from other angles the resulting >> field strength will be different. If you apply a vertically polarized >> wave over a ground plane, I believe the resulting field strength will >> look like the pattern from a vertical radiator over a perfect ground >> plane -- strongest when applied at the horizon, decreasing when >> applied at higher angles, and dropping to zero if applied from >> directly overhead. I haven't confirmed this, but believe it's >> necessary in order to get a receiving pattern that's the same as the >> transmitting pattern. So use it with caution when a ground plane is >> present, and don't casually make assumptions about the resulting field. > > > > I believe a better way to describe this situation is that the plane wave > field strength does not go to zero, but rather the effective aperture of > the antenna goes to zero as the plane wave is applied from overhead. > This does not change your conclusion with respect to antenna patterns. I'm not sure either one of us quite has it right. In a model experiment, I set up a short open circuited vertical dipole just above a perfect ground plane, and applied a vertically polarized plane wave from the horizon. Let's call the resulting voltage at the dipole center V1. Then I changed the direction of the plane wave so it was coming from an elevation angle of 45 degrees above the horizon, but with the same amplitude. The dipole voltage was about 0.7 * V1, about what we'd expect >from the change in effective aperture of the vertical dipole due to the different arrival elevation angle. But if I tilt the dipole back 45 degrees so it's parallel to the incident E field, the voltage drops to about 0.5 * V1, another 3 dB. I believe this indicates that the field in the vicinity of the dipole is oriented normal to the ground plane, and it has a magnitude that's about 0.7 as great as it is when the same amplitude wave is fired from a horizontal direction. A second check was to tilt it 45 degrees the other way, so its end is pointing directly toward the direction of the impinging wave. The result was again about 0.5 * V1, adding proof that the field in its vicinity is normal to the ground plane and not tilted in the direction of the source. So the antenna aperture is indeed changing as we change the orientation of the antenna relative to the field in its vicinity. But that's not the same as the orientation of the antenna relative to the direction from which the plane wave originates. (They are of course the same if the ground plane is absent.) The change in antenna output (in this case) when the source direction is changed is due to the fact that the magnitude of the field strength has changed, not because its orientation relative to the antenna has changed. When the direction of the plane wave is elevated 45 degrees, it has equal horizontally and vertically polarized components. The horizontal components cancel on reflection, while the vertical components reinforce as before. This leaves only the vertical component in the vicinity of the sense dipole, and it's 0.707 * the value when the same amplitude wave is coming in horizontally. The dipole voltage is maximum when it's oriented to be parallel with this field, that is, vertical. At least I think this is a correct interpretation of what I'm seeing. These effects are all tied in together, and I've spent so long looking at the problem from the transmitting direction that I'm having some trouble getting my thinking turned around. But I'm slowly getting there. Roy Lewallen, W7EL Article: 220093 of rec.radio.amateur.antenna From: Andy Cowley Subject: Re: http://niggermania.com/ Message-ID: References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213 Date: Tue, 13 Dec 2005 11:12:13 GMT The Magnum wrote: > "Peter" wrote in message > news:439dccd3.22632213@news.blueyonder.co.uk... > >>On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" >> wrote: >> >> >>>England is still a mainly white Christian Country.. >> >>What ever gave you that idea??? A very small percentage of the >>population go to church in the UK. The rest have more sense. > > > Ok, re-phrase time, England is still mainly a White non-practicing Christian > Country :o) > > Don't forget we are non-practising cannibals, too. In fact the list of what we are not practitioners of is fairly extensive. HTH Andy, M1EBV Article: 220094 of rec.radio.amateur.antenna From: "G1LVN \(for it is he\)" Subject: Re: http://niggermania.com/ Date: Tue, 13 Dec 2005 11:27:43 +0000 (UTC) Message-ID: References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213 @news.blueyonder.co.uk> "Andy Cowley" wrote in message news:IrFoGD.9qD@bath.ac.uk... > Don't forget we are non-practising cannibals, too. > > In fact the list of what we are not practitioners > of is fairly extensive. > > HTH No practising Judo Christian, shirley? ;-) -- -- 73 de G1LVN (M0WWS) NEW QTH Xmas Lights: http://www.g1lvn.org.uk Article: 220095 of rec.radio.amateur.antenna From: Philip de Cadenet Subject: Re: http://niggermania.com/ Date: Tue, 13 Dec 2005 16:18:38 +0000 Message-ID: <1ZDjLTGeRvnDFwZR@philstheboss.freeserve.co.uk> References: >Ok, re-phrase time, England is still mainly a White non-practicing Christian >Country :o) Unlike France:o) -- Philip de Cadenet G4ZOW Transmitters 'R' Us http://www.transmittersrus.com Article: 220096 of rec.radio.amateur.antenna Message-ID: <439F6BDA.8090100@HubbaHubbaTire.com> From: "R. Bubba McGillicutty" Subject: Re: http://niggermania.com/ References: <1133938429.122733.52720@g43g2000cwa.googlegroups.com> Date: Wed, 14 Dec 2005 00:49:11 GMT Steveo wrote: > http://niggermania.com/ > Hey you gotta admit that there is some FUNNY shit on that site. Hey they aren't even racisist. They just hate niggers. Article: 220097 of rec.radio.amateur.antenna Message-ID: <439F6BE9.7070705@HubbaHubbaTire.com> From: "R. Bubba McGillicutty" Subject: Re: http://niggermania.com/ References: <1133938429.122733.52720@g43g2000cwa.googlegroups.com> Date: Wed, 14 Dec 2005 00:49:26 GMT Steveo wrote: > http://niggermania.com/ > Hey you gotta admit that there is some FUNNY shit on that site. Hey they aren't even racisist. They just hate niggers. Article: 220098 of rec.radio.amateur.antenna Message-ID: <439F6C05.20801@microshaft.com> From: "R. Bubba McGillicutty" Subject: Re: http://niggermania.com/ References: <1133938429.122733.52720@g43g2000cwa.googlegroups.com> Date: Wed, 14 Dec 2005 00:49:54 GMT Steveo wrote: > http://niggermania.com/ > Hey you gotta admit that there is some FUNNY shit on that site. Hey they aren't even racisist. They just hate niggers. Article: 220099 of rec.radio.amateur.antenna From: microwaves@blueyonder.co.uk (Peter) Subject: Re: http://niggermania.com/ Message-ID: <439f8b18.136876998@news.blueyonder.co.uk> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <785op1hamdv09vnnf86vii55k6s8a81upl@4ax.com> <753dc$439c4064$97d56a33$14444@ALLTEL.NET> <439ecd7f.22804080@news.blueyonder.co.uk> Date: Wed, 14 Dec 2005 03:09:06 GMT On Mon, 12 Dec 2005 20:46:36 -0500, "Fred W4JLE" wrote: > >The whole bloody Royal lot are dumber that coal buckets. One of the reasons >I have to smile when you folks across the pond attack our presidents >intelligence.. > The important difference is, Fred, that our Royals do not rule the country... ie they don't make decisions to go to war, put up taxes, increase the price of fuel, etc. Your president does and over here most Brits would not agree with his attitude to the Iraq war, especially as it appears to have a religious justification in his mind. I've visited the USA several times over the past few years since the Iraq business started and I've heard much criticism of your Republican government. Bush does not have the whole nation behind him as he likes to think. Peter, G3PHO Article: 220100 of rec.radio.amateur.antenna From: microwaves@blueyonder.co.uk (Peter) Subject: Re: http://niggermania.com/ Message-ID: <43a08cd1.137318052@news.blueyonder.co.uk> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <6ohVm5H+sdnDFwaB@pickmere.demon.co.uk> Date: Wed, 14 Dec 2005 03:11:08 GMT On Mon, 12 Dec 2005 20:19:10 +0000, "M. J. Powell" wrote: >In message <439dccd3.22632213@news.blueyonder.co.uk>, Peter > writes >>On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" >> wrote: >> >>>England is still a mainly white Christian Country.. >> >>What ever gave you that idea??? A very small percentage of the >>population go to church in the UK. The rest have more sense. > >More people go to church than go to football matches. SO ??? I'll bet more people go shopping on Sunday than go to church. ...and I'm not sure you're correct in your assumption Article: 220101 of rec.radio.amateur.antenna From: microwaves@blueyonder.co.uk (Peter) Subject: Re: http://niggermania.com/ Message-ID: <43a18d37.137420350@news.blueyonder.co.uk> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> Date: Wed, 14 Dec 2005 03:13:34 GMT On Mon, 12 Dec 2005 18:48:15 -0500, Amos Keag wrote: >Peter wrote: >> On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" >> wrote: >> >> >>>England is still a mainly white Christian Country.. >> >> >> What ever gave you that idea??? A very small percentage of the >> population go to church in the UK. The rest have more sense. > >Peter, I'll remember you in prayers and at my masses. OH... so you assume I am an atheist.? How wrong can you be! However I like to think for myself rather than be brainwashed by some guy in fancy robes.... especially the brand that do Mass :-) Article: 220102 of rec.radio.amateur.antenna From: Butch Magee Subject: Re: Antenna Modeling (dumb question#305) Date: Tue, 13 Dec 2005 22:00:18 -0600 Message-ID: <11pv66m4hh2qg6b@corp.supernews.com> References: If you have let the left wingers frighten you into saying "happy hollidays" instead of "merry Christmas"man, I feel for you. Jim - NN7K wrote: > Hi.all, and BTW, Happy Holidays! Am attempting to model > a "Cushcrunch" A-627013, yagi and have it all but written, > and modeled what I have of it-- It is a 70 cm, with 6 and 2 > meter yagis, the 6 meter horizontally polarized, both the > 2 and 70 cm are vertically polarized, on the same boom, ofset > by aprox 1 inch , and the beast is mounted on a mast, 6 inch > from the two meter reflector. This is the first time attempted > modeling a multi band antenna, especially with the mast in the > same plane as the yagi. My question is 2 fold: 1; Given it is > behind the reflector, just how much diff does THAT add to the > pattern of the antenna, and 2; If it does, just HOW LONG an > element would this represent?? The mast length? and for the > small portion of mast, ABOVE the mast clamp?? Just curious > as to the effect it has . Your thoughts , please. Jim NN7K Article: 220103 of rec.radio.amateur.antenna From: =?ISO-8859-1?Q?Mexicana_Aeron=E1utica_y_Spacia_Administraci?= Subject: Re: http://niggermania.com/ References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> Message-ID: Date: Wed, 14 Dec 2005 04:29:31 GMT Peter wrote... > On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" > wrote: > > >>England is still a mainly white Christian Country.. > > > What ever gave you that idea??? A very small percentage of the > population go to church in the UK. The rest have more sense. I think he may be using the tradition of defining a person's religion by what his parents' religion was. In other words, xians claim all babies born to xian parents, even though the parents may not even have been particularly religious and were simply born to parents who also were claimed by the xian church. Same with moozlums, any baby unfortunate to be born into that cult is claimed as a member for life. BTW, I was born to xian parents who also claimed me for their cult and the defining moment in my life was when they coerced me into joining their church at age 13. I haven't been to church since, and share Marilyn Manson's hope that I'll be remembered as the person who brought an end to xianity. Hail Satan! Article: 220104 of rec.radio.amateur.antenna From: =?ISO-8859-1?Q?Mexicana_Aeron=E1utica_y_Spacia_Administraci?= Subject: Re: http://niggermania.com/ References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> Message-ID: Date: Wed, 14 Dec 2005 04:34:34 GMT Amos Keag wrote... > Peter wrote: > >> On Sun, 11 Dec 2005 13:09:35 -0000, "The Magnum" >> wrote: >> >> >>> England is still a mainly white Christian Country.. >> >> >> >> What ever gave you that idea??? A very small percentage of the >> population go to church in the UK. The rest have more sense. > > > Peter, I'll remember you in prayers and at my masses. ------------------------------------------------------------------ "Even though the god in all of these religions is basically the same, each regards the way chosen by the others as reprehensible, and to top it all, religionists actually PRAY for one another! They have scorn for their brothers of the right-hand path because their religions carry different labels, and somehow this animosity must be released. What better way than through 'prayer'! What a simperingly polite way of saying: 'I hate your guts,' is the thinly disguised device known as praying for your enemy! Praying for one's own enemy is nothing more than bargain-basement anger, and of a decidedly shoddy and inferior quality!" -- Anton LaVey; "The Satanic Bible" ------------------------------------------------------------------ Article: 220105 of rec.radio.amateur.antenna From: "F7" Subject: Yaesu FT-101 Series Service Manual on sale. Date: Wed, 14 Dec 2005 12:38:55 +0100 Message-ID: <43a004a4$0$347$5fc30a8@news.tiscali.it> http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=5841225485&ssPageName =STRK:MESE:IT Article: 220106 of rec.radio.amateur.antenna Subject: Re: Yaesu FT-101 Series Service Manual on sale. From: "Vonkenboer" References: <43a004a4$0$347$5fc30a8@news.tiscali.it> Message-ID: Date: Wed, 14 Dec 2005 12:57:20 +0100 F7 formuleerde op woensdag : > http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=5841225485&ssPageName > =STRK:MESE:IT Toe maar, bij mods.dk is deze gratis. Free for download at mods.dk Article: 220107 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: http://niggermania.com/ Date: Wed, 14 Dec 2005 17:56:57 -0000 Message-ID: References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> "Amos Keag" wrote in message news:ofadnew7Prglsz3enZ2dnUVZ_tGdnZ2d@comcast.com... > Peter wrote: > > > > > > OH... so you assume I am an atheist.? How wrong can you be! However > > I like to think for myself rather than be brainwashed by some guy in > > fancy robes.... especially the brand that do Mass :-) > > When I wear my robes at Mass I'll still pray for you. There's nothing > you can do about it. Pray for me to win the lottery please :O) Regards, Graham -- _._. _... ._. ._ _.. .. _ _ _ Radio is only a Hobby. Don't let it rule your life... 73's - Graham (www.open-channel.co.uk) Article: 220108 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: http://niggermania.com/ Date: Wed, 14 Dec 2005 18:00:31 -0000 Message-ID: References: <7017833.8F8789@tarrnews.net> <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> Same with moozlums, any baby unfortunate to be born > into that cult is claimed as a member for life. Unless they are captured doing something naughty whan abroad then they swear they are Englishmen and demand Tony Blair help them :o) > BTW, I was born to xian parents who also claimed me for their > cult and the defining moment in my life was when they coerced > me into joining their church at age 13. I haven't been to > church since, and share Marilyn Manson's hope that I'll be > remembered as the person who brought an end to xianity. > > Hail Satan! I doubt you'll be remembered for that :oP Regards, Graham -- _._. _... ._. ._ _.. .. _ _ _ Radio is only a Hobby. Don't let it rule your life... 73's - Graham (www.open-channel.co.uk) Article: 220109 of rec.radio.amateur.antenna From: "jiinks" Subject: New FT-990 Group Date: Wed, 14 Dec 2005 18:38:41 -0000 Message-ID: <43a066ab$0$82664$ed2619ec@ptn-nntp-reader03.plus.net> This is a multi-part message in MIME format. ------=_NextPart_000_0008_01C600DD.9AF381E0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Just to let everyone know that a new Yahoo group has been set up for = owners of the Yaesu FT-990. To visit your group on the web, go to: http://groups.yahoo.com/group/ft_990/=20 Jon G2FHF ------=_NextPart_000_0008_01C600DD.9AF381E0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Just to = let everyone know=20 that a new Yahoo group has been set up for owners of the Yaesu=20 FT-990.
 

To visit your group on the web, go = to:

http://groups.yahoo.com/group/ft_990/

Jon G2FHF

------=_NextPart_000_0008_01C600DD.9AF381E0-- Article: 220110 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Classic Dipole Question Date: Wed, 14 Dec 2005 23:58:47 -0000 Message-ID: <11q1cdnoe7rr087@corp.supernews.com> References: >I understand that If the dipole is fed with coax, one leg is tied to the >outer coax shield. > >Regarding the end at the radio - > >Is the coax shield "always" tied directly to the radio's chassis ground, >(which is also earth ground for my set) ? This is almost always the case. The coax shield may also be grounded at one or more locations between the antenna and the radio chassis (e.g. where it enters the building), for both RF-grounding and lightning-safety-grounding reasons. >Or, are the outer and inner coax conductors sometimes fed into an >isolation transformer, and therefore the coax shield would not connect >directly to the radio chassis ? This can be done (with an isolated "unun" transformer) but it is rarely done. -- 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: 220111 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Classic Dipole Question Message-ID: <6bd1q1pelotmqqc486m5squ0naje23pihg@4ax.com> References: Date: Thu, 15 Dec 2005 00:24:13 GMT On Wed, 14 Dec 2005 18:52:00 -0500, "Robert11" wrote: >Hello, > >Have just started reading about, and studying antennas. > >Simple question regarding the classic dipole for receiving (although I >imagine it's exactly the same for transmitting): > >Hope I can explain my question clearly: > >I understand that If the dipole is fed with coax, one leg is tied to the >outer coax shield. The coax shield does not *have* to be tied to one leg of the dipole, a balun could be used to connect the unbalanced transmission line to the approximately balanced load. A balun is a device which accomodates the transition from balanced to unbalanced or vice versa, without significantly disturbing either environment. If the coax shield is directly connected to one leg of the dipole (and that is often done), the coax doesn't just provide a means for transferring energy from the feed point to the receiver (using the outside of the inner conductor and the inside of the outer conductor), but the outside of the outer conductor is now connected at one end to the dipole leg, and it and everything connected to it forms part of the receiving antenna itself. The ins and outs of it! Owen -- Article: 220112 of rec.radio.amateur.antenna Subject: Re: Looking for fiberglass antenna part From: Ed References: <43A0BF7B.542367F9@shaw.ca> Message-ID: Date: 15 Dec 2005 02:09:32 GMT > Buy a long 3/8"x24 bolt, hacksaw off the head, then expoxy some pipe > with 1/2" inside diam in over the end. Make sure the part extending > into the pipe is long enough. Thanks, Irv. Possibly workable for me, but the threaded end needs good RF continuity to the 1/2" tube end, which will be soldered to a helical winding running up the fiberglass rod. Ed Article: 220113 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Looking for fiberglass antenna part References: <43A0BF7B.542367F9@shaw.ca> Message-ID: Date: Thu, 15 Dec 2005 04:06:16 GMT Ed wrote: > Thanks, Irv. Possibly workable for me, but the threaded end needs good > RF continuity to the 1/2" tube end, which will be soldered to a helical > winding running up the fiberglass rod. Connect the helical winding to a 3/8" automotive lug and slip it over the 3/8" threaded section. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220114 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Classic Dipole Question Date: Wed, 14 Dec 2005 22:40:36 -0600 Message-ID: <26465-43A0F3C4-117@storefull-3254.bay.webtv.net> References: B. wrote: "Is the coax shield "always" tied directly to the radio chassis ground, (which is also earth ground for my set)?" "Always" may embrace too much. Usually, the coax shield is almost directly connected to the radio chassis ground. B already implied that his dipole has a potential problem as its connection to the grounded inner surface of the coax shield is shared at this point by connection to the outer surface of the same coax shield. This inherently unbalnces the load on the inner surfaces of the coax. The center conductor has only one load, its half of the dipole. The inner surface of the coax shield has two loads, its half of the dipole and the outer surface of the coax.. This is fixed by by a balun between the balanced dipole and the unbalanced coax. On the other hand, you may have no objection to distortion of the dipole`s pattern by radiation from the coax exterior. In some cases it won`t hurt. In other cases it may be beneficial. It is somewhat unpredictable, but many dipoles are directly fed by coax and are satisfactory. Best regards, Richard Harrison, KB5WZI Article: 220115 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Program GRNDWAV4 Date: Thu, 15 Dec 2005 06:32:15 +0000 (UTC) Message-ID: It may be recalled I recently reported an error in program GRNDWAV3 which deals with groundwave propagation from a short vertical antenna versus frequency and type of terrain. Although the field strength at the receiving site was correctly computed, the available receiver input power was exactly 6 dB greater than it should be. The error was due to a misunderstanding of vertical antenna gain relative to an isotrope when mounted above a groundplane. It appears some of the learned text books are unclear on this point. My immediate problem was eventually sorted out by Roy and proved by EZNEC-type programs which are not interested in man-made notions about antenna gain and isotropes. The faulty program has now been replaced by program GRNDWAV4 which makes no use of antenna gains at either end of the path. Download it and delete the older version. I am grateful to Icelandic radio amateur, Villi, TF3DX for informing me of the error. He went back to fundamental principles to prove me wrong. I have no idea what aroused his suspicions and we are not in contact with each other at present. He said he intended to write a paper on the subject. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220116 of rec.radio.amateur.antenna Message-ID: <9vl773-89t.ln1@ursine.ca> From: Paul Johnson Subject: Re: One experience with noise References: Message-ID: <1134637337.c857a55f3cab0d38109173525afb1f55@roc.usenetexchange.com> Date: Thu, 15 Dec 2005 09:02:17 +0000 Wes Stewart wrote: > Furthermore, my wife and rarely watch anything live (except for local > news), but use two DVRs for time shifting and commercial elimination. > So with my system, if I can get a picture at all, I would need three > STBs (set top boxes) that are programmable or a couple of new digital > recorders and a new TV set. Odds are you'll need the STB for each PVR, not TV. PVR's are basically a VCR with a computer instead of a video slot, same limitations apply with the signal you feed it. The video coming out of the PVR isn't going to change magically overnight, though. > (If I was poor enough, my idiot government would buy this stuff for me, > but instead, I believe I will be taxed to buy it for someone else.) Show me where I can sign up for a free TV from the government... > And then they are changing the aspect ratio so my 35" screen is > obsolete and any replacement would have a smaller screen if I want to > keep it in my $7,000 piece of furniture. Actually, they're fixing the aspect ratio. 16:9 would allow most movies to run without having to be butchered by some trained monkey that thinks they're a pan and scan editor to fit the screen, or black bars to bring the aspect ratio back to the original film ratio as it was intended to be shown. 4:3 aspect was a technical limitation that really should have died long before my birth, much less now. Good riddance. -- Paul Johnson Email and Instant Messenger (Jabber): baloo@ursine.ca Got jabber? http://ursine.ca/Ursine:Jabber Article: 220117 of rec.radio.amateur.antenna From: "F7" References: <43a004a4$0$347$5fc30a8@news.tiscali.it> Subject: Re: Yaesu FT-101 Series Service Manual on sale. Date: Thu, 15 Dec 2005 11:11:28 +0100 Message-ID: <43a14389$0$338$5fc30a8@news.tiscali.it> "Vonkenboer" ha scritto nel messaggio news:mn.73097d5c73344edb.19251@hotmail.com... > F7 formuleerde op woensdag : > > http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=5841225485&ssPageName > > =STRK:MESE:IT > > Toe maar, bij mods.dk is deze gratis. > Free for download at mods.dk On the web you can see young nude girls for free, but is not as have her onto your hands nor in you bed. ;-))) Article: 220118 of rec.radio.amateur.antenna Subject: Re: Yaesu FT-101 Series Service Manual on sale. From: "Vonkenboer" References: <43a004a4$0$347$5fc30a8@news.tiscali.it> <43a14389$0$338$5fc30a8@news.tiscali.it> Message-ID: Date: Thu, 15 Dec 2005 11:57:07 +0100 Na rijp beraad schreef F7 : > "Vonkenboer" ha scritto nel messaggio > news:mn.73097d5c73344edb.19251@hotmail.com... >> F7 formuleerde op woensdag : >>> http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=5841225485&ssPageName >>> =STRK:MESE:IT >> >> Toe maar, bij mods.dk is deze gratis. >> Free for download at mods.dk > > On the web you can see young nude girls for free, but is not as > have her onto your hands nor in you bed. > ;-))) LOL, I never tried to print those out :-)) Mark Article: 220119 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: Program GRNDWAV4 Message-ID: Date: Thu, 15 Dec 2005 13:45:17 GMT "Reg Edwards" wrote in message news:dnr2lf$lak$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com... > It may be recalled I recently reported an error in program GRNDWAV3 > which deals with groundwave propagation from a short vertical antenna > versus frequency and type of terrain. > > Although the field strength at the receiving site was correctly > computed, the available receiver input power was exactly 6 dB greater > than it should be. > > The error was due to a misunderstanding of vertical antenna gain > relative to an isotrope when mounted above a groundplane. It appears > some of the learned text books are unclear on this point. > > My immediate problem was eventually sorted out by Roy and proved by > EZNEC-type programs which are not interested in man-made notions about > antenna gain and isotropes. > > The faulty program has now been replaced by program GRNDWAV4 which > makes no use of antenna gains at either end of the path. Download it > and delete the older version. > > I am grateful to Icelandic radio amateur, Villi, TF3DX for informing > me of the error. He went back to fundamental principles to prove me > wrong. I have no idea what aroused his suspicions and we are not in > contact with each other at present. He said he intended to write a > paper on the subject. > ---- > ........................................................... > Regards from Reg, G4FGQ > For Free Radio Design Software go to > http://www.btinternet.com/~g4fgq.regp Thanks Reg. My NEC2 agreed with your previous program, so do not know where I went wrong. Will try and figure it out. Regards, Frank Article: 220120 of rec.radio.amateur.antenna Subject: Re: N8WWM COWERING KEYBOARD SISSY From: Steveo Date: 15 Dec 2005 14:34:20 GMT Message-ID: <20051215093420.036$yd_-_@newsreader.com> References: <1133938429.122733.52720@g43g2000cwa.googlegroups.com> <7017833.8F8789@tarrnews.net> <20051210000303.410$Bv@newsreader.com> <701733.245F79@tarrnews.net> <20051211080613.845$3K@newsreader.com> <8mpho7833.2458F8789@tarrnews.net> <20051211103213.451$vn@newsreader.com> <1134599578.663161.146550@o13g2000cwo.googlegroups.com> "moparholic at hotmail dot com is a sissy" wrote: > gay mparholic's ISP is Valley Internet > Nope, Adelphia just like always. N8WWM's a tough guy in front of a monitor. N8WWM's a hunch backed cowering sissy in front of me. http://n8wwm.4t.com Article: 220121 of rec.radio.amateur.antenna Subject: Re: moparholic at hotmail dot com loves men in truckstop toilets From: Steveo Date: 15 Dec 2005 14:36:17 GMT Message-ID: <20051215093617.895$Rc@newsreader.com> References: <1133938429.122733.52720@g43g2000cwa.googlegroups.com> <7017833.8F8789@tarrnews.net> <20051210000303.410$Bv@newsreader.com> <701733.245F79@tarrnews.net> <20051211080613.845$3K@newsreader.com> <1134599454.929089.225360@g47g2000cwa.googlegroups.com> N8WWM@arrl.net posting as "moparholic at hotmail dot com is a sissy" wrote: > Steveo wrote, while stroking his wand and praying to watch gay porno > flix: > > Hey fucknut, newsreader.com is not my isp. Pull your head out of your > > lardass. > > Why, so you can lick his face and his piles? > N8WWM's a tough guy in front of a monitor. N8WWM's a hunch backed cowering sissy in front of me. http://n8wwm.4t.com Article: 220122 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 09:15:54 -0600 Message-ID: <12709-43A188AA-141@storefull-3253.bay.webtv.net> References: <11p322i7mfa917d@corp.supernews.com> Roy, W7EL wrote: "If the wavelength is >> 1m, the voltage induced in the center of an open-circuited 1m dipole by a 1V/m field is 0.5 volt, not 1 volt." An open-circuited dipole (has a small gap in its middle) is mot resonnant at a wavelength of 2 meters, but its individual pieces are resonant at a wavelength of 1 meter. At 2 meters, not a wavelength >> 1m, each 0.5 m piece of the half-wavelength, 1 meter long dipole has a high reactance because 0.5 m is too short at a wavelength of 2 meters to be resonant. At longer wavelengths, the reactance rises.. High reactance does not oppose non-existing current in an open-circuit. I agree the voltage induced in 1/2-meter of wire properly placed within a 1V/m uniform field is 0.5 volt, not 1 volt. The induced voltage in a wire within a uniform field sweeping the wire rises uniformly along the wire. It can be assumed to be the summation of tiny increments of voltage all along the wire. The voltages of the too-short dipole halves add just as two cells in some flashlights add. Their vectors are head to tail. But, current will be limited by radiation and loss resistances of the wires. It will also be limited by reactance in the wires. Open-circuit, 0.5 V + 0.5 V = 1V. Best regards, Richard Harrison, KB5WZI Article: 220123 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 09:03:00 -0600 Message-ID: <27842-43A193B4-186@storefull-3251.bay.webtv.net> References: <11p9h1kn73bctd4@corp.supernews.com> Roy Lewallen, W7EL wrote: "A short while ago, I explained why your Faraday cage doesn`t separate E and H as you claim." There are many examples of Faraday screens at work removing the E field while allowing H field coupling. I chose the Faraday sdreens in medium wave broadcasting used to reduce radiation of harmonics of the channel frequency. More numerous examples abound. These are the Faraday screens used in isolation power transformers between primary and secindary coils to prevent transient high-frequency energy coupling. My 19th edition of the ARRL Antenna Book contains yet another example on page 14-2 which says: "Fig 2 - Shielded loop for direction finding. The ends of the shielding turn are not connected, to prevent shielding the loop from magnetic fields. The shield is effective against electric fields. Best regards, Richard Harrison, KB5WZI Article: 220124 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 16:47:32 +0000 (UTC) Message-ID: References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> Richard (Harrison), What is the voltage measured between the bottom end and ground, of a 1 metre high vertical antenna, above a perfect ground, when the vertically-polarised field strength is 1 volt per metre, and antenna height is shorter than a 1/4-wavelength. Just a number please. ---- Reg. Article: 220125 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: http://niggermania.com/ Date: Thu, 15 Dec 2005 17:55:39 -0000 Message-ID: References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> "Amos Keag" wrote in message news:cY2dnQllc9uTMD3eRVn-gA@comcast.com... > The Magnum wrote: > > "Amos Keag" wrote in message > > news:ofadnew7Prglsz3enZ2dnUVZ_tGdnZ2d@comcast.com... > > > >>Peter wrote: > >> > >>> > >>> OH... so you assume I am an atheist.? How wrong can you be! However > >>>I like to think for myself rather than be brainwashed by some guy in > >>>fancy robes.... especially the brand that do Mass :-) > >> > >>When I wear my robes at Mass I'll still pray for you. There's nothing > >>you can do about it. > > > > > > Pray for me to win the lottery please :O) > > > > Regards, > > Graham > > You have to watch the movie "Bruce Almighty". I did that once! 14,000 > winners of $17 each or something like that :-0 Yes I saw that film. Quite funny in places although i dont really like Jim Carey. BUT..... as he's only praying for me to win the lottery I might be ok ;o) Regards, Graham -- _._. _... ._. ._ _.. .. _ _ _ Radio is only a Hobby. Don't let it rule your life... 73's - Graham (www.open-channel.co.uk) Article: 220126 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1134669154.987966.56010@g43g2000cwa.googlegroups.com> Subject: Re: Looking for fiberglass antenna part Date: Thu, 15 Dec 2005 12:56:08 -0500 Message-ID: <15cc4$43a1ae47$97d56a33$1932@ALLTEL.NET> The ham spirit is still alive and well. Great to know hams are still willing to lend a hand to a brother ham. You are to be commended! wrote in message news:1134669154.987966.56010@g43g2000cwa.googlegroups.com... > Do you ever get to Central Oregon? Or send a drawing with dimensions. > Like how long is the threaded portion? How long is the tube part? If > you can make to Redmond, I will volunteer to make it for you. > > Paul, KD7HB > Article: 220127 of rec.radio.amateur.antenna From: Bill Turner Subject: Re: Classic Dipole Question Date: Thu, 15 Dec 2005 10:35:32 -0800 Message-ID: References: <11q1cdnoe7rr087@corp.supernews.com> On Wed, 14 Dec 2005 23:58:47 -0000, dplatt@radagast.org (Dave Platt) wrote: >and the radio chassis >(e.g. where it enters the building), for both RF-grounding and >lightning-safety-grounding reasons. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ As has been explained here many times before, you can not "RF ground" your coax in the sense of connecting it to earth ground. The wavelength of the ground wire prevents a true ground from happening. You do need a safety ground (for the AC mains) and a "ground" to your radio chassis, but that's all. I put "ground" in quotes because it isn't really connected to earth. The word "common" would be more accurate, but most hams think of their chassis as "ground". So be it, as long as the true condition is understood. 73, Bill W6WRT Article: 220128 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 13:04:52 -0600 Message-ID: <7808-43A1BE54-299@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "What is the voltage measured between the bottom end and ground of a 1 metre high vertical antenna above a perfect ground when the verticallly-polarized field strength is 1 volt per metre, and antenna height is shorter than a 1/4-wavelength?" I see no tricks in the question. The field strength is given as "1 volt per metre". >From page 23-3 of the 19th edition of the ARRL Antenna Book: "The standard of measure for field intensities is the voltage developed in a wire that is 1 meter long, expressed as volts per meter." While field strength is not the same as the volts delivered to a receiver, because of the voltage division between antenna impedance and receiver input impedance, there is no voltage division when the antenna is loaded with an open circuit. We assume the r-f voltmeter used to measure voltage at the base of the antenna has an infinite input impedance. The antenna used for field strength measurements is often a loop, but we are not concerned with the measurement itself. Reg had a very simple question, "What`s the voltage at the base of a 1-meter high wire? The voltage at the base of an open-circuit 1-metre wire iis one volt because it goes straight to the definition of field intensity in volts/m. Best regards, Richard Harrison, KB5WZI Article: 220129 of rec.radio.amateur.antenna Subject: Re: Looking for fiberglass antenna part From: Ed References: <43A0BF7B.542367F9@shaw.ca> Message-ID: Date: 15 Dec 2005 19:34:36 GMT Good information, (below), thanks. On the issue of availability, though, I have to wonder why they would NOT be available for sale? Obviously, certain manufacturers of the multitude of ham-stick type antennas use them. There must be a large scale source, somewhere! Ed > > As a modification to this, since you can stand 1/2 inch thread, how > about using a 1/2 inch bolt and brazing or silver soldering some 1/2 > inch ID tube over it? Not only will this be easier than trying to > center the 3/8 and potentially stronger than epoxy, but it would keep > that RF continuity. > > This is the sort of part that's expensive to turn out as a one-off > part, but very easy to manufacture on an NC lathe -- even a cam-driven > automatic screw machine would handle this with ease. Because of this > I suspect that there aren't any on the open market; rather a > manufacturer would just send drawings to their favorite screw machine > place to have them made 10000 at a time. > > It's also the sort of part that's fun to make in limited quantity -- > it looks pretty, you get to practice your threading, yet its not too > critical. So you might want to take up Paul's offer, perhaps with a > nice drawing. Just don't ask him to make too many. > Article: 220130 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 11:54:41 -0800 Message-ID: <11q3ig4brs1a92b@corp.supernews.com> References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> Richard Harrison wrote: > . . . > I agree the voltage induced in 1/2-meter of wire properly placed within > a 1V/m uniform field is 0.5 volt, not 1 volt. The induced voltage in a > wire within a uniform field sweeping the wire rises uniformly along the > wire. It can be assumed to be the summation of tiny increments of > voltage all along the wire. The voltages of the too-short dipole halves > add just as two cells in some flashlights add. Their vectors are head to > tail. But, current will be limited by radiation and loss resistances of > the wires. It will also be limited by reactance in the wires. > Open-circuit, 0.5 V + 0.5 V = 1V. There are two incorrect statements here. First, the voltage induced in the wire doesn't rise uniformly along the wire. It's sinusoidal, even for a very short wire. This is different >from the transmitting case but interestingly doesn't interfere with reciprocity. Secondly, the voltage at the center of an open-circuited 1 meter (electrically short) dipole in and parallel a 1 volt/meter field is 0.5 volt as I said earlier, not 1 volt. I'll be glad to provide a number of references. Both these statements can also be verified by modeling. The definition of field strength, incidentally, has nothing to do with the voltage of a dipole immersed in that field. Roy Lewallen, W7EL Article: 220131 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 11:55:51 -0800 Message-ID: <11q3ii9tknov759@corp.supernews.com> References: <7808-43A1BE54-299@storefull-3257.bay.webtv.net> Richard Harrison wrote: > . . . > The voltage at the base of an open-circuit 1-metre wire iis one volt > because it goes straight to the definition of field intensity in > volts/m. Do you have a reference which defines field strength in terms of voltage induced in a wire? Roy Lewallen, W7EL Article: 220132 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Classic Dipole Question Date: Thu, 15 Dec 2005 12:09:57 -0800 Message-ID: <11q3jcoj7jfmma3@corp.supernews.com> References: <11q1cdnoe7rr087@corp.supernews.com> Bill Turner wrote: > > As has been explained here many times before, you can not "RF ground" > your coax in the sense of connecting it to earth ground. The > wavelength of the ground wire prevents a true ground from happening. > > You do need a safety ground (for the AC mains) and a "ground" to your > radio chassis, but that's all. I put "ground" in quotes because it > isn't really connected to earth. The word "common" would be more > accurate, but most hams think of their chassis as "ground". So be it, > as long as the true condition is understood. > "Ground" is one of the most misued terms among amateurs that I encounter. Somehow, labeling something "ground" imparts magic properties -- "grounded" things don't radiate, you can't get a shock or rf burn >from "grounded" items, "grounded" items are free from the same rules that all other conductors must follow. None are true. If your rig is mains-powered, you need a mains safety ground, as Bill said. This effectively connects the equipment to the Earth at mains frequency. If lightning is a threat, you also need a lightning ground, which effectively connects your antenna to the Earth when lighning strikes the antenna or nearby. Making an effective safety ground is simple; making a lightning ground is an art and science in itself. If you have a balanced load for your rig (for example, a coax or twinlead feedline with equal and opposite currents on the two conductors), you don't need a "radio ground", that is, a low impedance connection between your radio and the Earth at radio frequencies. The only time you need one is if you've managed to make your rig a part of the antenna by allowing currents on the outside of a coax feedline, or unbalanced currents on a twinlead feedline. And getting this low impedance connection can be difficult -- or impossible, if multiple frequency bands are involved. Roy Lewallen, W7EL Article: 220133 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 15:03:41 -0600 Message-ID: <27842-43A1DA2D-217@storefull-3251.bay.webtv.net> References: <11q3ii9tknov759@corp.supernews.com> Roy Lewallen wrote" "Do you have a reference which defines field strength in terms of voltage induced in a wire?" Here is more of one I already posted. It is from the 19th edition of the ARRL Antenna Book on page 23-3: "The strength of a wave is measured as the voltage between two points lying on an electric line of force in the plane of the wave front. The standard of measure for field intensity is the voltage developed in a wire that is 1 meter long, expressed as volts per meter. (If the wire were 2 meters long, the voltage developed would be divided by two to determine the field strength in volts per meter.)" Best regards, Richard Harrison, KB5WZI Article: 220134 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 13:28:09 -0800 Message-ID: <11q3nvbnol50356@corp.supernews.com> References: <11q3ii9tknov759@corp.supernews.com> <27842-43A1DA2D-217@storefull-3251.bay.webtv.net> Richard Harrison wrote: > Roy Lewallen wrote" > "Do you have a reference which defines field strength in terms of > voltage induced in a wire?" > > Here is more of one I already posted. It is from the 19th edition of the > ARRL Antenna Book on page 23-3: > "The strength of a wave is measured as the voltage between two points > lying on an electric line of force in the plane of the wave front. The > standard of measure for field intensity is the voltage developed in a > wire that is 1 meter long, expressed as volts per meter. (If the wire > were 2 meters long, the voltage developed would be divided by two to > determine the field strength in volts per meter.)" > > Best regards, Richard Harrison, KB5WZI > Thanks. I'll contact Dean Straw to get that corrected. Roy Lewallen, W7EL Article: 220135 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Thu, 15 Dec 2005 17:18:25 -0600 Message-ID: <3647-43A1F9C1-257@storefull-3258.bay.webtv.net> References: <11q3nvbnol50356@corp.supernews.com> Roy Lewallen , W7EL wrote: "Do you have a reference which defines field strength in terms of voltage induced in a wire?" Here is a reference from a professional source. B. Whitfield Griffith, Jr. was Director of Advanced Development at General Dynamics Corporation at Garland, Texas when his book, "Radio-Electronicc Transmission Fundamentals" was published by Mc Graw-Hill in 1972. On page 322, Griffith writes: "The strength of an electromagnetic wave is generally measured in terms of the intensity of the electric field; this is expressed in volts per meter, or millivolts or microvolts per meter, as the conditions may indicate. This value may be understood as being the numbeer of volts which would be induced in a piece of wire one meter long placed in the field parallel to the electric lines of force; the induction of voltage would result from the movement of the magnetic flux across the wire. Griffith agrees with Terman. Best regards, Richard Harrison, KB5WZI Article: 220136 of rec.radio.amateur.antenna From: "DrDeath" Subject: Re: http://niggermania.com/ Date: Thu, 15 Dec 2005 17:45:12 -0600 Message-ID: <11q4003qm1ndb7f@corp.supernews.com> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> "Amos Keag" wrote in message news:cY2dnQllc9uTMD3eRVn-gA@comcast.com... > The Magnum wrote: >> "Amos Keag" wrote in message >> news:ofadnew7Prglsz3enZ2dnUVZ_tGdnZ2d@comcast.com... >> >>>Peter wrote: >>> >>>> >>>> OH... so you assume I am an atheist.? How wrong can you be! However >>>>I like to think for myself rather than be brainwashed by some guy in >>>>fancy robes.... especially the brand that do Mass :-) >>> >>>When I wear my robes at Mass I'll still pray for you. There's nothing >>>you can do about it. >> >> >> Pray for me to win the lottery please :O) >> >> Regards, >> Graham > > You have to watch the movie "Bruce Almighty". I did that once! 14,000 > winners of $17 each or something like that :-0 > I watched that movie 4 times, I didn't win any money. Article: 220137 of rec.radio.amateur.antenna Subject: Re: Looking for fiberglass antenna part From: Ed References: <43A0BF7B.542367F9@shaw.ca> Message-ID: Date: 16 Dec 2005 00:53:17 GMT > > Actually my point was that this is exactly the sort of market where > there _won't_ be a large-scale source, at least not an open one. It's a > market dominated by a few vertically integrated manufacturers, who have > no vested interest in commonality of parts and _do_ get advantages from > having design control over the parts they get. If nothing else it make > it much more expensive for the guy down the road to start up his own > operation. > > Consider that nuts and bolts were not truly standardized until around > 100 years ago. Before (AFAIK) then manufacturers would specify by size, > but there were no commonly used standards until the SAE got together and > made it happen. As a result nuts and bolts became commodity items and > the price went down. > Understand what you are saying, but this item I am describing is pretty much standardized, near as I can tell. Soooo many mobile antenna manufacturers, including CB, use it on their 1/2" fiberglass rod based antennas, that I am pretty sure there must be a sizable source, somewhere. Ed Article: 220146 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Program GRNDWAV4 Date: Fri, 16 Dec 2005 19:47:43 +0000 (UTC) Message-ID: References: Punchinello has no time to waste on drivel and says "phooey". Article: 220147 of rec.radio.amateur.antenna From: fmmck@aol.com (Fred McKenzie) Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Fri, 16 Dec 2005 16:35:18 -0500 Message-ID: References: <7ss5q1te23aum095cdcidaql6tjnbpoe4v@4ax.com> In article <7ss5q1te23aum095cdcidaql6tjnbpoe4v@4ax.com>, Bill Turner wrote: > On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11" > wrote: > > >But, as a more or less theoretical question, to minimize the possibility of > >lightning hitting the antenna at all, or inducing large voltages in it, is > >it better to just leave the now "floating" antenna alone, or is it better to > >ground one end of it ? > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > I doubt it matters. A lightning bolt, having traveled thousands of > feet to the vicinity of your antenna, will not be deterred by a few > more inches. Bill- That's what I was going to say! I recall a field day activity where the club was using the press box of a high school football field, with antennas strung between light poles. As a storm approached, there were sparks several inches long jumping between disconnected antenna connectors and nearby grounded equipment. These sparks were induced by lightning strikes that were some distance away. Grounding would have eliminated the sparks by providing a metalic path for the discharge. I doubt it would have had any influence on whether an antenna would be directly hit, or would have provided any substantial protection in the event of a direct strike. Traditional wisdom is that having tall trees nearby, as well as tall objects such as light poles, will shield you from lightning. But there are no guarantees. And lightning doesn't always strike the top of tower! 73, Fred, K4DII Article: 220148 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 13:56:12 -0800 Message-ID: References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> <11q3ig4brs1a92b@corp.supernews.com> Roy Lewallen wrote: > Richard Harrison wrote: > >> . . . >> I agree the voltage induced in 1/2-meter of wire properly placed within >> a 1V/m uniform field is 0.5 volt, not 1 volt. The induced voltage in a >> wire within a uniform field sweeping the wire rises uniformly along the >> wire. It can be assumed to be the summation of tiny increments of >> voltage all along the wire. The voltages of the too-short dipole halves >> add just as two cells in some flashlights add. Their vectors are head to >> tail. But, current will be limited by radiation and loss resistances of >> the wires. It will also be limited by reactance in the wires. >> Open-circuit, 0.5 V + 0.5 V = 1V. > > > There are two incorrect statements here. > > First, the voltage induced in the wire doesn't rise uniformly along the > wire. It's sinusoidal, even for a very short wire. Interesting. Assuming a plane wave sweeping broadside, with the field being the same at every point along the wire, one might be inclined to argue that the voltage induced on a wire should be the same at every point along a finite length. The "rise" in voltage as the field sweeps past would be with respect to time, rather than with respect to position. Sort of explains why a radio receiver works just fine with only one wire attached when you think about it. ;-) 73, ac6xg Article: 220149 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: References: Date: Fri, 16 Dec 2005 22:55:09 GMT On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11" wrote: >Hello: > >Have been reading up on lightning a bit, and it certainly >is a confusing subject. > >Let's say I have an Inverted-L or a Sloper in the yard (receiving only). > >If a lightning storm is in the vicinity, obviously the best protection >possible is to just disconnect the radio from the antenna. No differences >of opinion here, I would imagine. > >But, as a more or less theoretical question, to minimize the possibility of >lightning hitting the antenna at all, or inducing large voltages in it, is >it better to just leave the now "floating" antenna alone, or is it better to >ground one end of it ? > >Why ? You have to think carefully about what you are trying to protect. It seems to me that in the event of a lightning stroke in the near vicinity of your antenna, large voltages will be induced in the antenna wrt "ground", whether or not your antenna or its support structure features as a streamer, or takes the current from a leader. That voltage may be sufficient for insulation breakdown, and charge will flow to ground via some path, not necessarily of your choosing. Substantial physical damage may occur where insulation breaks down, the path of the side-flash current may result in further damage to persons or equipment. If you make a substantial connection from the feedline to some thing, you have some degree of control over the path that the discharge current flows. Properly chosen and implemented, that might be better than doing nothing, but if poorly designed or implemented, it could be worse than doing nothing. Side-flash can still occur where you have provided a path to ground. Very often, the target of effective lighting protection of radio installations is minimisation of voltage drops or potential differences internal to an installation as a result of lightning discharge current rather than trying to minimise the voltage to "ground" resulting from the current. Owen -- Article: 220150 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> <11q3ig4brs1a92b@corp.supernews.com> Message-ID: Date: Sat, 17 Dec 2005 01:23:38 GMT Jim Kelley wrote: > Sort of explains why a radio receiver works just fine with > only one wire attached when you think about it. ;-) It doesn't work fine when you don't think about it? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220151 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 17:38:47 -0800 Message-ID: References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> <11q3ig4brs1a92b@corp.supernews.com> <7af6q1t0iktaem520dvkr31r9nuajr23a1@4ax.com> Richard Clark wrote: > On Fri, 16 Dec 2005 13:56:12 -0800, Jim Kelley > wrote: > > >>one might be inclined to argue that the voltage induced on a wire should be the same at every >>point along a finite length > > > One might, if it were an exceptionally short piece of wire. Otherwise > it must exhibit some greater reactance than nearly 0 and support a > difference of potential in proportion to the current through it. There > is also the radiation (non-0) resistance to consider (same observation > of a potential difference there too). You seem to be arguing that the induced potential in the wire is due to IR or IZ. I don't think that's true. According to JC Maxwell, the magnitude of the induced voltage and current should depend on the EM field and on the in situ permitivity and permeability of the wire. As long as those things are constant along the length of that wire, there is no reason to expect anything but uniform voltage and current along the length of the wire. As Roy said, an antenna does not behave the same on receive as it does on transmit apparently. A receive antenna does not appear to behave like a transmission line. > Presumably, this all hinges on what is meant, in practical terms, for > "finite length." Finite here just means small compared to any curvature of the wave front. Were the wire long enough compared to the distance to the source, one couldn't expect the fields to be uniform along the length of the wire. >>The "rise" in voltage as the field sweeps >>past would be with respect to time, > > With respect to what time? The time for the wave to sweep past? What > frequency? The full wave, or its peak? or its average (0)? It just means voltage as a function of time - like the waveform induced by the fields of a passing electromagnetic wave for example. >>rather than with respect to position. > > > Position of what? It means position along the wire - as in the topic of the conversation you've joined. I apologize for any lack of clarity on my part. 73, ac6xg Article: 220152 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 19:45:01 -0800 Message-ID: <11q72e0a35vpab1@corp.supernews.com> References: <22405-43A2C421-15@storefull-3256.bay.webtv.net> This thread has presented a clear illustration of the danger of quoting >from a book, even an authoritative one, without fully understanding the context. Before I continue, let me stipulate that the conductors being talked about here are all electrically short (much shorter than a wavelength), and are placed parallel to the E field. The following statements won't be generally true if both those conditions aren't met. I've been saying that the voltage at the center of an open circuited 1 m dipole immersed in a 1 V/m field is 0.5 volts. Richard has quoted some references which say that the voltage induced in a 1 m wire immersed in a 1 V/m field is 1 volt, and implying that it follows that the voltage at the center of an open circuited dipole of that length is 1 volt. It isn't, and I'll try to explain why. The voltage drop, or emf, across a very short conductor in a field of E volts/meter is E*L volts, where L is the length of the very short conductor in meters. This is undoubtedly the reason for the statements like the ones Richard has quoted. If we look at the emf generated across each tiny part of a one meter long dipole by a 1 V/m field and add them up, we'll find that they total 1 volt. But what's the voltage across the dipole, from end to end? The answer to that is it's just about anything we want it to be. Any time we try to measure the voltage between two points in space when there's a time-varying H field present, the answer we get depends on the path we take between the two points. Crudely but not entirely accurately put, it depends on how we arrange the voltmeter leads. We can, however, measure the voltage at the dipole center, across a gap that's arbitrarily small. So what's that voltage? I can't think of any line of reasoning which would deduce that it's equal to the total emf along the wire (1 volt for our example). You can casually open various texts and find the answer to that -- it's either 0.5 volts, as I've said, or 1 volt, as Richard has said. To understand the reason for the apparent contradiction requires digging more deeply into the texts. Most of the texts I have analyze field-conductor interactions with a special kind of dipole which has a uniform current distribution -- that is, the current is the same amplitude all along the dipole's length. There are a couple of ways you can physically make a dipole like this. One is to begin with a conventional (but short) dipole and add large end hats, like a two-ended top loaded vertical. A number of authors (e.g., Kraus) show a diagram of such a dipole. Another way to get a distribution like this is to stipulate that the dipole really be only a tiny segment of a longer wire. The short conductor with uniform current is often called a "Hertzian dipole", sometimes an "elemental dipole", sometimes just a short or infinitesimal dipole, or by Terman, a "doublet". As Balanis (_Antenna Theory - Analysis and Design_, p. 109) says, "Although a constant current distribution is not realizable, it is a mathematical quantity that is used to represent actual current distributions of antennas that have been incremented into many small lengths." The voltage at the center of a one meter antenna of this type in a 1 V/m field is 1 volt. But this fictitious dipole, used for conceptual and computational convenience, isn't a real dipole. A real dipole -- that is, just a single, straight wire with a source or load at its center and no end hats -- doesn't have a uniform current distribution. Instead, the current is greatest in the center, dropping to zero at the ends. When transmitting, the current on a short dipole drops nearly linearly from the center to the ends. When receiving, the current distribution is nearly sinusoidal. The net result of this non-uniform current is that the voltage at the center is less than it is for a uniform-current dipole -- exactly half as much, actually. Conceptually, it's because the current near the ends contributes less to the voltage at the center. I'm going to wave my hands over the significance of the different receiving and transmitting current distributions, except to say that reciprocity is still satisfied in all ways, including the transmitting and receiving impedances being the same. To add confusion, the gain, directivity, and effective apertures of both types of dipole are the same -- 1.5, 1.5, and 3 * lambda^2 / (8 * pi) respectively. This means that you can extract the same amount of power from an impinging wave with either type of antenna, provided that you terminate each in the complex conjugate of its transmitting feedpoint impedance. The radiation resistance of the uniform-current dipole is 4 times that of the conventional dipole. (Remember, these are all electrically short.) There's a common term for the relationship between the field strength and the length of a conductor, called the "effective height" or "effective length". The voltage at the center of a dipole in a field of E volts/m is simply E * the effective length. The concept is valid for any length conductor, not just short ones. The effective length of a uniform-current dipole is equal to the wire length. The effective length of a short conventional dipole is 0.5 times the wire length. The effective length for receiving is the same as the effective length for transmitting -- in transmitting, it relates the strength of the field produced to the *voltage* -- not power -- applied across the feedpoint. If you apply 0.5 volts to a standard dipole and 1.0 volts to a uniform-current dipole, the power applied to each will be the same because of the 1:4 ratio of radiation resistance, and the generated fields will be the same. This is consistent with the antenna gains being the same. As I mentioned, most text authors use a uniform-current dipole for analysis. One which directly derives the voltage of a standard short dipole is King, Mimno, and Wing, _Transmission Lines, Antennas, and Wave Guides_. Many others, including Kraus, _Antennas_ (2nd Ed. p. 41), derive the effective length for a short conventional dipole as 0.5 * the physical length, from which the open circuit voltage due to an impinging field can easily be determined. As a last note on a point of contention, electric field strength is usually defined not by the voltage induced in a conductor but from the force between charges using the Lorenz force law. The unit of electric field strength is found to be newtons/coulomb, which is the same as volts/meter. Among the texts using this definition are Kraus (_Electromagnetics_), Terman (_Radio Engineering_), Ida, Majid, and Ramo et al. Roy Lewallen, W7EL Article: 220153 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Program GRNDWAV4 Date: Fri, 16 Dec 2005 19:46:31 -0800 Message-ID: <11q72gqq39466d9@corp.supernews.com> References: Hopefully my recent posting on the "Antenna reception theory" thread will clarify things a bit. Roy Lewallen, W7EL Reg Edwards wrote: > > Frank, > > The situation changes by the hour so I suggest you don't spend a great > deal of time trying to sort things out. Either the program is in error > or you have entered incorrect data. Or (see below) both you and I have > the correct answer in the first place. > > From the situation at present we have :- > > It seems the numerous Bibles written by learned professors don't agree > on the subject. > > Computer programs, whose results are falsely taken as being gospel > truths, don't agree on the subject. > > The 'experts' who contribute to this newsgroup can't agree on the > subject. But, from the frequency of arguments which result. this is > perfectly normal. > > I remain as an innocent, neutral bystander, in danger of being > unjustly accused of being a troll, whereas - > > All I need is an answer to my simple but essentially fundamental and > practical question - > > "What is the voltage measured between the bottom end of a 1 metre high > vertical antenna and ground, when the field strength is 1 volt per > metre?" > > It goes without saying, a perfect ground is assumed, the antenna > height is less than 1/4-wavelength and the radio wave is vertically > polarised. > > Is the measured voltage 1 volt or is it 0.5 volts? > > There's a simple factor of 2 involved somewhere. Should I take a > statistical average of the replies if there are any? > > What happens on an isolated dipole is irrevalant. It is just a > time-wasting diversion. > > I don't have access to the 'learned Bibles' or to computer programs > (except my own). So there is no point in referring to them. But I > don't consider this to be any handicap. Short, logical, convincing > explanations in plain English and perhaps a little arithmetic would be > welcome of course. > ---- > Reg, G4FGQ. > > Article: 220154 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 19:49:47 -0800 Message-ID: <11q72mv8aldhj29@corp.supernews.com> References: <11p322i7mfa917d@corp.supernews.com> <12709-43A188AA-141@storefull-3253.bay.webtv.net> <11q3ig4brs1a92b@corp.supernews.com> Jim Kelley wrote: > > Interesting. Assuming a plane wave sweeping broadside, with the field > being the same at every point along the wire, one might be inclined to > argue that the voltage induced on a wire should be the same at every > point along a finite length. The "rise" in voltage as the field sweeps > past would be with respect to time, rather than with respect to > position. Sort of explains why a radio receiver works just fine with > only one wire attached when you think about it. ;-) > The Earth's (static) electric field is about 120 V/m at ground level on a stormless day. Better not walk too fast. Jogging might be fatal! Roy Lewallen, W7EL Article: 220155 of rec.radio.amateur.antenna From: "west" Subject: Gap Antenna Message-ID: Date: Sat, 17 Dec 2005 05:05:43 GMT Anyone have experience with GAP Antennas? On paper they look almost too good to be true, but I know that word of mouth can be more informative. All comments welcomed. west AF4GC Article: 220156 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Program GRNDWAV4 Date: Fri, 16 Dec 2005 21:56:19 -0800 Message-ID: <11q7a46jtvo9jf9@corp.supernews.com> References: Frank wrote: > > Repeating what was previously posted. The following model treats a 1 meter > (perfect conductor) monopole, of 0.814 mm diameter, connected to a perfectly > conducting ground. I have applied a vertically polarized incident E-field > of 1 V/m (peak). The base of the antenna is loaded with the antennas > complex conjugate of 1.747 + j823.796. NEC2 computes the current through > the load ast 0.2863 Amps (peak), which is 0.5001 V peak. This appears to > agree with Reg's program. > . . . > Possibly someone can point out if there are any errors in the following > code: > > CM 1 Meter Vertical > CE > GW 1 50 0 0 1 0 0 0 0.000814 > GS 0 0 1 > GE 1 > GN 1 > EX 1 1 1 0 90 0 0 1 1 1 > LD 4 1 50 50 1.747 823.796 > FR 0 3 0 0 19.9 0.1 > RP 0 181 1 1000 -90 90 1.00000 1.00000 > EN You've specified a plane wave of 1 V/m peak arriving in a horizontal direction over a ground plane. This results in a field strength of 2 V/m peak at the antenna. For more information about this, look at my postings over the last couple of weeks on the thread "Antenna reception theory". Roy Lewallen, W7EL Article: 220157 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Fri, 16 Dec 2005 22:09:02 -0800 Message-ID: <11q7as26ibspr8e@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> Toni wrote: > Hi, > > I've seen here before suggestions about using a tuned loop to increase > the gain of radio controlled clocks. Do you think this could also be > used to increase the gain of a gps receiver? No. If you were to increase the gain of your GPS antenna, either by redesign of the antenna or by an external parasitic structure of some sort, it would have to result in a narrower pattern. So you'd reduce the reception in some directions. > I guess that loop should be 1wl circumference, or about 2 1/2 inch > diameter, easy enought to cary in a pocket and play with. > > I know one can not have more than 0 dB with full omni, I just guess the > minimalistic antenna in pocketable gps is way below 0 dB and could > maybe be improved a little. 0 dB relative to what? Once you get the desired coverage angle, the only way to improve the reception of the GPS is to improve the receiver signal/noise ratio. The only way you can do that from outside the GPS is to use an external antenna with a preamp having a lower noise figure than the GPS's receiver. > Could this be modeled in EZNEC, one segment with some series resitance > for high loss antenna and the other 19 to simulate the loop? I'm not sure what the "high loss antenna" is. If you mean the GPS antenna, it's not high loss at all, but is likely very efficient. If it's a patch antenna, you can't model it at all with EZNEC. But even if it's a quadrifilar helix, you can't model it with one segment. Roy Lewallen, W7EL Article: 220158 of rec.radio.amateur.antenna From: " hillbilly3302" References: Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 01:48:24 -0600 Message-ID: I always tell new Hams to ground everything they can.... but if they get a direct hit then they will be too busy fighting fire to worry about the antenna... -Dave- K5DRC Since 1969 BULL SHOALES LAKE http://www.bullshoals.org/lake.htm AR/MO STATE LINE Some day someone will give a WAR and nobody will go "Owen Duffy" wrote in message news:h4g6q11d07grvg4o8cc0mim6r5qsmsqteh@4ax.com... > On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11" > wrote: > >>Hello: >> >>Have been reading up on lightning a bit, and it certainly >>is a confusing subject. >> >>Let's say I have an Inverted-L or a Sloper in the yard (receiving only). >> >>If a lightning storm is in the vicinity, obviously the best protection >>possible is to just disconnect the radio from the antenna. No differences >>of opinion here, I would imagine. >> >>But, as a more or less theoretical question, to minimize the possibility >>of >>lightning hitting the antenna at all, or inducing large voltages in it, is >>it better to just leave the now "floating" antenna alone, or is it better >>to >>ground one end of it ? >> >>Why ? > > You have to think carefully about what you are trying to protect. > > It seems to me that in the event of a lightning stroke in the near > vicinity of your antenna, large voltages will be induced in the > antenna wrt "ground", whether or not your antenna or its support > structure features as a streamer, or takes the current from a leader. > > That voltage may be sufficient for insulation breakdown, and charge > will flow to ground via some path, not necessarily of your choosing. > Substantial physical damage may occur where insulation breaks down, > the path of the side-flash current may result in further damage to > persons or equipment. > > If you make a substantial connection from the feedline to some thing, > you have some degree of control over the path that the discharge > current flows. Properly chosen and implemented, that might be better > than doing nothing, but if poorly designed or implemented, it could be > worse than doing nothing. Side-flash can still occur where you have > provided a path to ground. > > Very often, the target of effective lighting protection of radio > installations is minimisation of voltage drops or potential > differences internal to an installation as a result of lightning > discharge current rather than trying to minimise the voltage to > "ground" resulting from the current. > > Owen > -- Article: 220159 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Sat, 17 Dec 2005 00:49:52 -0600 Message-ID: <23342-43A3B510-367@storefull-3252.bay.webtv.net> References: Reg, G4FGQ wrote: "What do photons have to do with winning a contest?" I don`t know. But, B.Whitfield Griffith, Jr. has some observations in "Rado-Eledtronic Transmission Fundamentals" that may be a useful check on your computations. I expect he checked, rechecked, then checked again before publication. He put a transmitter on an elemental antenna but it would work the same in reverse. From page 325: "An Elemental Antenna Since the length of an antenna is commonly expressed in electrical degrees and since this allows the convenient use of trigonometric tables in computing the ratios of currents in various parts of an antenna, let us choose as our elemental antenna a piece of wire which is 1-degree in length and in which the current is constant from one end to the other.We shall first assume that this elemental antenna is located far out in space, so that its field is not disturbed by reflections from the surface of the earth or from any other object. This, of course, is a most improbable set of conditions, but we can certainly imagine that we have a situation such as this and compute from the field equations its electromagnetic result. These computations will show, first of all, that the maximum field intensity will be produced in the directions which are at right angles to the direction of current flow. This is a reasonable result, since the magnetic field which is produced by the current surrounds the wire in concentric rings and thus gives rise to a radiation field which moves outward at right angles to the wire. As a matter of fact, the field intensity, measured according to our standard procedure at a distance of 1 mile in any direction from the radiating element, will be found to be proportional to the sine of the angle between the direction of the current flow and the direction in which the measurement is taken. If we represent the field intensity at 1 mile in any direction by the length of a vector starting at the center of the element and extending in that direction, the tips of the vectors will mark out the radiation pattern of the antenna element. A cross section of the entire radiation pattern of this element is shown in Fig. 39-2; the entire pattern would be obtained by rotating the figure about the axis of the antenna element. But this pattern tells us only the relative signal strength in various directions; it is a normalized pattern, with the intensity in the direction of maximum radiation being considered simply as unity. We need much more information than this; we must know the relationship between the current and the actual value of the field it produces. Further computation from the field equations gives this relalationship; we find that a current of 1 amp flowing in the antnna element will produce a field intensity of 0.3253 mv/m at a distance of 1 mile iin the direction of maximum radiation. We have said nothing about the frequency, and we do not need to; as long as the wavelength is shorter than 1 mile, so that there are no serious induction-ffield effects to upset our calculations, this figure will be correct at any frequencyfor which the length of the element is 1/360 wavelength. The field intensity of the elemental antenna is directly proportional to the current. Therefore, if the current in the element is 15 amp, the field intensity will be 15 X 0.3253, or 4.8795, mv/m at 1 mile. Similarly, the field intensity is directly proportional to the length of the element; an element which is 2-degrees in length, carrying a current of 1 amp, will thus produce a maximum field intensity of 0.6506 mv/m at 1 mile. Best regards, Richard Harrison, KB5WZI Article: 220160 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 23:52:47 -0800 Message-ID: <11q7gujb3kps066@corp.supernews.com> References: <23342-43A3B510-367@storefull-3252.bay.webtv.net> Richard Harrison wrote: > > I don`t know. But, B.Whitfield Griffith, Jr. has some observations in > "Rado-Eledtronic Transmission Fundamentals" that may be a useful check > on your computations. I expect he checked, rechecked, then checked again > before publication. He put a transmitter on an elemental antenna but it > would work the same in reverse. From page 325: Yes, it should. > . . . > . . . We need > much more information than this; we must know the relationship between > the current and the actual value of the field it produces. Further > computation from the field equations gives this relalationship; we find > that a current of 1 amp flowing in the antnna element will produce a > field intensity of 0.3253 mv/m at a distance of 1 mile iin the direction > of maximum radiation. . . > > The field intensity of the elemental antenna is directly proportional to > the current. Therefore, if the current in the element is 15 amp, the > field intensity will be 15 X 0.3253, or 4.8795, mv/m at 1 mile. > Similarly, the field intensity is directly proportional to the length of > the element; an element which is 2-degrees in length, carrying a current > of 1 amp, will thus produce a maximum field intensity of 0.6506 mv/m at > 1 mile. A short dipole antenna with 1 amp of current at the center has an average of 0.5 amp of current along the whole length. So it should be obvious from the above analysis that the field from a dipole is half the field from the elemental antenna with uniform current which the author is discussing. Or, instead of just taking the average, you can integrate I * delta L to get the same result. Roy Lewallen, W7EL Article: 220161 of rec.radio.amateur.antenna From: "Asimov" Subject: Underwater Message-ID: Date: Sat, 17 Dec 2005 15:01:28 GMT Hi, I was thinking about why radio wave communications are not generally used underwater. Basically I'm asking what are the quantitative components of the underwater medium that makes it impractical except for perhaps very short ranges. Things like attenuation, impedance, etc... Does any one here know these details or have them handy? A*s*i*m*o*v ... Acme Corp: Unlimited credit for disadvantaged coyotes. Article: 220162 of rec.radio.amateur.antenna From: "Denton" Subject: Re: Gap Antenna Date: Sat, 17 Dec 2005 07:59:23 -0800 Message-ID: <11q8devosgcmp2b@corp.supernews.com> References: I picked up a used one last sprng, set it up about 3 ft off the ground in the back yard...and took it back down within a couple of weeks. Signals were way down compared to my 450 ohm ladder line fed 80 meter doublet on all bands. I remade the Titian into a 40 ft vertical dipole that I use on 40 thru 10 meters, fed with twin lead, and much better results. "west" wrote in message news:H0Nof.37181$6e.33307@tornado.tampabay.rr.com... > Anyone have experience with GAP Antennas? On paper they look almost too > good > to be true, but I know that word of mouth can be more informative. All > comments welcomed. > > west > AF4GC > > Article: 220163 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Gap Antenna References: <11q8devosgcmp2b@corp.supernews.com> Message-ID: Date: Sat, 17 Dec 2005 16:15:35 GMT Denton wrote: > I picked up a used one last sprng, set it up about 3 ft off the ground in > the back yard...and took it back down within a couple of weeks. > Signals were way down compared to my 450 ohm ladder line fed 80 meter > doublet on all bands. I had the same experience with a 1/4WL 40m vertical. Now I wish I had run some A/B transmitting tests as well as the A/B receiving tests which the vertical flunked mainly due to an extremely high noise level. I'm thinking about putting the vertical back up as a 1/4WL 30m vertical fed at the base with an SGC-230 that I already have. Such an antenna should work pretty well on 40m-10m, at least for transmitting. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220164 of rec.radio.amateur.antenna From: "RST Engineering" References: <23342-43A3B510-367@storefull-3252.bay.webtv.net> <1134840466.191509.133910@g47g2000cwa.googlegroups.com> Subject: Re: Antenna reception theory Date: Sat, 17 Dec 2005 09:50:34 -0800 Message-ID: <40597$43a44fe5$42513e92$9501@DIALUPUSA.NET> How did you quote damned near 75 lines of text to ask a 9 word question? Jim "EE123" wrote in message news:1134840466.191509.133910@g47g2000cwa.googlegroups.com... >> Best regards, Richard Harrison, KB5WZI > > > > How did you get .3253 mv/m at 1 miles? > > Dave > Article: 220165 of rec.radio.amateur.antenna From: "Denton" Subject: Re: Gap Antenna Date: Sat, 17 Dec 2005 09:55:08 -0800 Message-ID: <11q8k7ui4660548@corp.supernews.com> References: <11q8devosgcmp2b@corp.supernews.com> Hi Cecil....let us know if you do that. When I redid the back yard lawn, I installed an extensive buried radial system for such experimentation. I have all the aluminum tubing left over from the Titian's tuning stubbs to turn my 40 ft vertical dipole into something wth some capacity hats...to get it to work on 80 thru 20 meters, if I desire. "Cecil Moore" wrote in message news:HQWof.42734$Zv5.24256@newssvr25.news.prodigy.net... > Denton wrote: >> I picked up a used one last sprng, set it up about 3 ft off the ground in >> the back yard...and took it back down within a couple of weeks. >> Signals were way down compared to my 450 ohm ladder line fed 80 meter >> doublet on all bands. > > I had the same experience with a 1/4WL 40m vertical. Now I wish > I had run some A/B transmitting tests as well as the A/B > receiving tests which the vertical flunked mainly due to an > extremely high noise level. I'm thinking about putting the > vertical back up as a 1/4WL 30m vertical fed at the base with > an SGC-230 that I already have. Such an antenna should work > pretty well on 40m-10m, at least for transmitting. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 220166 of rec.radio.amateur.antenna From: Bill Turner Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 09:49:13 -0800 Message-ID: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> References: On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302" wrote: >I always tell new Hams to ground everything they can.... but if they get a >direct hit then they will be too busy fighting fire to worry about the >antenna... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This summer my 80 foot tower took a direct hit, the first in my 48 years of hamming. The tower was grounded and there was no fire, but it tripped a circuit breaker in my house and damaged a radio connected to it. My point is that fire is not an automatic consequence. Incidentally, the sound of thunder from a hit that close is remarkably different from a hit some distance away. First, you hear the clap from the nearest part of the bolt and then from parts successively farther away, a long, rolling sound that continues much longer than one at a distance. If I don't ever hear it again, that will be ok by me. :-) 73, Bill W6WRT Article: 220167 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 13:01:28 -0600 Message-ID: <11q8o4cqvcda5f5@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> Bill Turner wrote: > On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302" > wrote: > > >>I always tell new Hams to ground everything they can.... but if they get a >>direct hit then they will be too busy fighting fire to worry about the >>antenna... > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > This summer my 80 foot tower took a direct hit, the first in my 48 > years of hamming. The tower was grounded and there was no fire, but it > tripped a circuit breaker in my house and damaged a radio connected to > it. My point is that fire is not an automatic consequence. > > Incidentally, the sound of thunder from a hit that close is remarkably > different from a hit some distance away. First, you hear the clap from > the nearest part of the bolt and then from parts successively farther > away, a long, rolling sound that continues much longer than one at a > distance. If I don't ever hear it again, that will be ok by me. :-) > > 73, Bill W6WRT Bill; Ain't been there, Ain't done that, Don't want no stinkin t-shirt. ;^) Seriously though glad that nothing really serious happened. When I was in retain sales I sold many electronic items to people that suffered both direct and indirect hits. Lots of damage no injuries everyone was lucky. Dave WD9BDZ Article: 220168 of rec.radio.amateur.antenna From: "kd5sak" References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: Date: Sat, 17 Dec 2005 19:01:37 GMT "Bill Turner" wrote in message news:3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com... > On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302" > wrote: > This summer my 80 foot tower took a direct hit, the first in my 48 > years of hamming. The tower was grounded and there was no fire, but it > tripped a circuit breaker in my house and damaged a radio connected to > it. My point is that fire is not an automatic consequence. > > Incidentally, the sound of thunder from a hit that close is remarkably > different from a hit some distance away. First, you hear the clap from > the nearest part of the bolt and then from parts successively farther > away, a long, rolling sound that continues much longer than one at a > distance. If I don't ever hear it again, that will be ok by me. :-) > > 73, Bill W6WRT Long years ago, 50 yearsor so before I reached Ham status, a thunderstorm awakened me in the wee hours and proceeded to dance around in the shallow hill pasture near the house. Stroke after stroke occurred and all so near I could hear a loud click as the strike occurred and then the diminishing rumble. I still haven't figured out the initial click sound, it came from outside so wasn't a house internal electric phenomenon. Harold KD5SAK Article: 220169 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Underwater Date: Sat, 17 Dec 2005 13:06:27 -0600 Message-ID: <11q8odoll28kde5@corp.supernews.com> References: Tim Wescott wrote: > Asimov wrote: > >> Hi, >> >> I was thinking about why radio wave communications are not generally >> used underwater. Basically I'm asking what are the quantitative >> components of the underwater medium that makes it impractical except >> for perhaps very short ranges. Things like attenuation, impedance, >> etc... Does any one here know these details or have them handy? >> >> A*s*i*m*o*v >> >> ... Acme Corp: Unlimited credit for disadvantaged coyotes. >> > The conductivity of water causes great attenuation at all but very low > frequencies. Think "skin effect". > > That having been said, the US Navy (and probably all other folks with > subs) use extremely low frequency RF (30kHz IIRC) to communicate with > strategic nuclear subs. > Penetration of water by radio waves is directly proportional to wavelength. The longer the wave length the further the penetration of water. That's why the Navy uses extremely long wave length signals to contact deep submergence subs. Even then it takes a very long time to transmit a very short three or four letter message. Of course the sub then has to raise up to just below the surface and extend an antenna mast to contact the COMNAVSAT for its full message. Dave WD9BDZ Article: 220170 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Sat, 17 Dec 2005 13:21:49 -0600 Message-ID: <23342-43A4654D-432@storefull-3252.bay.webtv.net> References: <1134840466.191509.133910@g47g2000cwa.googlegroups.com> EEE 123 wrote: "How do you get .3253 mv/m at 1 mile?" The formula to calculate the field strength produced by an dlementaarry doublet is difficult for me to reproduce with my keyboard. It is found on page 770 of Terman`s 1943 "Radio Sngineers` Handbook. In my prior posting, Griffith hhas done the work for us. Best regards, Richard Harrison, KB5WZI Article: 220171 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> Message-ID: Date: Sat, 17 Dec 2005 19:37:09 GMT Bill Turner wrote: > If I don't ever hear it again, that will be ok by me. :-) Consider that there might be two ways that you would never hear it again and one is NOT OK. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220172 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Underwater Date: Sat, 17 Dec 2005 12:44:06 -0800 Message-ID: <11q8u4qpl7fft16@corp.supernews.com> References: The attenuation of a radio signal through water is staggeringly high except at extremely low frequencies. Fresh water is lossy for two reasons: one is that the polar molecules attempt to align themselves with the oscillating electric field. This physical motion results in loss. The other is that "fresh" water generally has dissolved salts which increase its conductivity. Salt water's loss is dominated simply by its conductivity. Here are a few numbers for attenuation per meter. It's hard to find good data on loss in real fresh water, but I did locate a representative number for one frequency. F MHz Fresh water Salt water 0.01 3.9 dB 0.1 12 1 39 10 121 100 ~ 50 dB 369 Roy Lewallen, W7EL Asimov wrote: > Hi, > > I was thinking about why radio wave communications are not generally > used underwater. Basically I'm asking what are the quantitative > components of the underwater medium that makes it impractical except > for perhaps very short ranges. Things like attenuation, impedance, > etc... Does any one here know these details or have them handy? > > A*s*i*m*o*v > > ... Acme Corp: Unlimited credit for disadvantaged coyotes. > Article: 220173 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: WorldRadio Magazine Article References: <7xpjf.141728$yS6.37907@clgrps12> Message-ID: Date: Sat, 17 Dec 2005 22:03:28 GMT Frank wrote: > Thanks Cecil, very interesting. Will look forward to reading your other > articles. Part II was published in the Dec. 2005 edition of WorldRadio. I have combined Parts I+II and posted it to my web page below. -- 73, Cecil http://www.qsl.net/w5dxp/energy.htm Article: 220174 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: <2p29q1lcl44g6rrnluqv7h9r70ca3k8tu6@4ax.com> References: Date: Sat, 17 Dec 2005 22:20:11 GMT On Fri, 16 Dec 2005 22:55:09 GMT, Owen Duffy wrote: >Very often, the target of effective lighting protection of radio >installations is minimisation of voltage drops or potential >differences internal to an installation as a result of lightning >discharge current rather than trying to minimise the voltage to >"ground" resulting from the current. I should have expanded that to say: Minimisation of potential differences is often obtained by one or more of: - providing an alternate low impedance path to ground so that less current flows through the equipment room; - single point earthing to reduce the voltage drop in earthing conductors internal to the equipment room; - equipotential bonding to reduce the voltage drop between the equipment room earth and other parts of the building, and other services or structures (eg water, gas, telephone, power). There may be standards or codes that apply to lighting protection in your area, they are worth checking, and while they may not mandate lighting protection, they may mandate the way in which it is done if it is done. That may have implications for your insurance. Effective lightning protection is a very expensive business, and if you don't need "continuous operation" and have a simple configuration, it is much cheaper and effective to ensure that feedlines and similar conductors (like rotator cables) are totally disconnected from the shack at times of high risk. Owen -- Article: 220175 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Underwater Date: Sat, 17 Dec 2005 14:45:11 -0800 Message-ID: <11q957rdvpv4m34@corp.supernews.com> References: <11q8u4qpl7fft16@corp.supernews.com> I hope this will format better (viewed with fixed width font): F MHz Fresh water Salt water 0.01 3.9 dB 0.1 12 1 39 10 121 100 ~ 50 dB 369 Roy Lewallen, W7EL Roy Lewallen wrote: > . . . > Here are a few numbers for attenuation per meter. It's hard to find good > data on loss in real fresh water, but I did locate a representative > number for one frequency. > > F MHz Fresh water Salt water > 0.01 3.9 dB > 0.1 12 > 1 39 > 10 121 > 100 ~ 50 dB 369 Article: 220176 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 14:48:12 -0800 Message-ID: <11q95dgt1j45l93@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> kd5sak wrote: > > Long years ago, 50 yearsor so before I reached Ham status, a thunderstorm > awakened me in the wee hours and proceeded to dance around in the shallow > hill pasture near the house. Stroke after stroke occurred and all so near I > could hear a loud click as the strike occurred and then the diminishing > rumble. I still haven't figured out the initial click sound, it came from > outside so wasn't a house internal electric phenomenon. I've read that this click is due to the ear's reaction to the strong electromagnetic pulse. If that's what you heard, it comes from the ear itself, not from outside. Roy Lewallen, W7EL Article: 220177 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: Date: Sat, 17 Dec 2005 23:18:47 GMT "Roy Lewallen" wrote in message news:11q95dgt1j45l93@corp.supernews.com... > kd5sak wrote: > > > > Long years ago, 50 yearsor so before I reached Ham status, a thunderstorm > > awakened me in the wee hours and proceeded to dance around in the shallow > > hill pasture near the house. Stroke after stroke occurred and all so near I > > could hear a loud click as the strike occurred and then the diminishing > > rumble. I still haven't figured out the initial click sound, it came from > > outside so wasn't a house internal electric phenomenon. > > I've read that this click is due to the ear's reaction to the strong > electromagnetic pulse. If that's what you heard, it comes from the ear > itself, not from outside. > > Roy Lewallen, W7EL This is the first time I have seen it mentioned the ear reacting to the electromagnetic pulse. Most of the time it is described as the same way the old WW2 depth charges sounded in the submarines. YOu get the click and then the boom. I forgot the term used but it is something like an impulse or pressure shock wave traveling faster than the speed of sound and then the actual sound wave. Article: 220178 of rec.radio.amateur.antenna From: "DrDeath" Subject: Re: http://niggermania.com/ Date: Sat, 17 Dec 2005 17:27:09 -0600 Message-ID: <11q97mfbt474cda@corp.supernews.com> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> "The Magnum" wrote in message news:dnuq09$61c$1@newsg3.svr.pol.co.uk... > >> >> Pray for me to win the lottery please :O) >> >> >> >> Regards, >> >> Graham >> > >> > You have to watch the movie "Bruce Almighty". I did that once! 14,000 >> > winners of $17 each or something like that :-0 >> > >> >> I watched that movie 4 times, I didn't win any money. > > That's because Amos (eyy up Mr wilks ;o) wasn't praying for you... > > Regards, > Graham > -- > _._. _... ._. ._ _.. .. _ _ _ > > Radio is only a Hobby. Don't let it rule your life... > > 73's - Graham (www.open-channel.co.uk) > > Well that's not very Christian like of him. Article: 220179 of rec.radio.amateur.antenna From: "kd5sak" References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <1134870501.772593.144520@z14g2000cwz.googlegroups.com> Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: Date: Sun, 18 Dec 2005 02:48:10 GMT wrote in message news:1134870501.772593.144520@z14g2000cwz.googlegroups.com... > I've read that this click is due to the ear's reaction to the strong > electromagnetic pulse. If that's what you heard, it comes from the ear > itself, not from outside................................ > > According to old Gary Coffman posts, he says it's picked up by the > auditory nerve. Also, deaf people can hear that click. Thanks OM, I've wondered for nearly 50 years what the "click" mechanism was. I've told the story several times, but never to anyone I thought it would be useful to ask for an explanation of the "click". Harold KD5SAK Article: 220180 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 19:10:25 -0800 Message-ID: <11q9kp64odvvu17@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <1134870501.772593.144520@z14g2000cwz.googlegroups.com> nm5k@wt.net wrote: > I've read that this click is due to the ear's reaction to the strong > electromagnetic pulse. If that's what you heard, it comes from the ear > itself, not from outside................................ > > According to old Gary Coffman posts, he says it's picked up by the > auditory nerve. Also, deaf people can hear that click. > I've had two strikes to my mast with me sitting 15 ft away from the > base of the mast. I could hear that click, but I also could hear > the arc sound of the strike going to ground outside. Sounded > like a light bulb being thrown to the ground outside my window. > Not that loud really. I'm fairly convinced the quality of the ground > connection effects the loudness of the strike. The strikes that hit > my well grounded mast are fairly quiet, not counting the overhead > sonic boom. The strikes to the trees in the yard are super loud > in comparison. A loud crack, instead of the quieter arc sound. > MK I couldn't remember where I picked it up, but that's probably where. Thanks. But I wasn't able to find any reference to that phenomenon in a brief web search, so it might not be true. Roy Lewallen, W7EL Article: 220181 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 19:12:31 -0800 Message-ID: <11q9kt36n4utv5e@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> Ralph Mowery wrote: > > This is the first time I have seen it mentioned the ear reacting to the > electromagnetic pulse. Most of the time it is described as the same way > the old WW2 depth charges sounded in the submarines. YOu get the click and > then the boom. I forgot the term used but it is something like an impulse > or pressure shock wave traveling faster than the speed of sound and then the > actual sound wave. I do believe that any mechanical wave, such as a pressure or shock wave, travels at the speed of sound, no more and no less. To travel faster, it would have to be an electromagnetic wave. Roy Lewallen, W7EL Article: 220182 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Program GRNDWAV4 Date: Sat, 17 Dec 2005 23:38:13 -0500 Message-ID: <11q9prkb4b1mt28@corp.supernews.com> References: <11q7a46jtvo9jf9@corp.supernews.com> I can no longer resist the urge.... As with most things: it depends. The whole antenna world knows that a short, thin, uniform metal rod that is normal to a conducting plane has an open circuit voltage at its base that is equal to one half of the size of the incident vertically polarized E field multiplied by the rod's length. Such an antenna has a "height" that is one half of its physical length. Note: open circuit voltage Note: short - less than 0.1 WL Note: the current distribution of the subject rod tapers linearly to zero at the distant end of the rod Note: the voltage or power delivered to something other than an open circuit is not discussed Note: many references that discuss short rods are assuming a constant current along the rod's length - such rods have a "height" equal to their physical length I have dealt with approximations of the subject device. In each case, an extremely high input impedance amplifying device is placed at the base of the antenna that has a known voltage amplification and a 50 ohm output impedance. Knowing that a close approximation of the open circuit voltage is amplified by a known amount, a calibrated, tuned voltmeter (at 50 ohms) is able to measure the size of vertically polarized E (with the usual uncertainties). (and a bit of arithmetic) 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net Article: 220183 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Sat, 17 Dec 2005 22:32:29 -0600 Message-ID: <27482-43A4E65D-609@storefull-3255.bay.webtv.net> References: Reg, G4FGQ wrote: "Just a number please." Given 1 volt per m as the field strength, and a 1-m antenna parallel to the electric vector of the wave, the open-circuit voltage at the end of the wire is 1 volt. The best you can get across the receiver input is 0.5 volt when there is a conjugate match between the receiver and the antennna. Most of the explanations are irrelevant when the field strength is specified at the antenna. Terman preached scientific gospel. He had proof to back what he said. In Terman`s 1943 "Radio Engineers` Handbook" he wrote: "The strength of a radio wave is expressed in terms of the voltage stress produced in space by the electric field of the wave, and is usually expressed in either millivolts or microvolts stress per meter. The stress expressed this way is exactly the same voltage that the magnetic flux of the wave induces in a conductor one meter long when rhe wave sweeps across the conductor with the velocity of light." This is found on page 770. There is no qualification or equivocation. Terman also posts the same statement with no change in substance on page 2 of his 1955 edition of "Electronic and Radio Engineerinng". It means what it plainly says. Best regards, Richard Harrison, KB5WZI Article: 220184 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Underwater Message-ID: References: <11q8u4qpl7fft16@corp.supernews.com> Date: Sun, 18 Dec 2005 07:03:23 GMT "Roy Lewallen" bravely wrote to "All" (17 Dec 05 12:44:06) --- on the heady topic of "Re: Underwater" RL> From: Roy Lewallen RL> Xref: core-easynews rec.radio.amateur.antenna:221425 RL> The attenuation of a radio signal through water is staggeringly high RL> except at extremely low frequencies. Fresh water is lossy for two RL> reasons: one is that the polar molecules attempt to align themselves RL> with the oscillating electric field. This physical motion results in RL> loss. [,,,] Thanks for the info. I had read that submarines communicated in a band of a few 10's of Hz because of the problems with water. As for the polar molecules aligning themselves, this implies it takes some time to achieve. Thus there is a resonnant point in this and if there is resonnance then there might be anti-resonnance too. Might you know where this natural molecular resonnance is? Might this be the standard microwave oven frequency? A*s*i*m*o*v Article: 220185 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Sun, 18 Dec 2005 07:04:06 +0000 (UTC) Message-ID: References: <27482-43A4E65D-609@storefull-3255.bay.webtv.net> Richard (Harrison) I'm sorry Richard, you have not anwered my question. I will repeat it. "What is the voltage measured between the bottom end and ground of a 1metre high vertical antenna when the field strength is 1 volt per metre?" Assume a perfect ground and antenna height is much less than 1/4-wavelength. A measured voltage is always relative to or is between TWO specified points. ---- Reg, G4FGQ Article: 220186 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Underwater Date: Sun, 18 Dec 2005 00:43:34 -0800 Message-ID: <11qa89qo8d8mmbb@corp.supernews.com> References: <11q8u4qpl7fft16@corp.supernews.com> Asimov wrote: > > Thanks for the info. I had read that submarines communicated in a > band of a few 10's of Hz because of the problems with water. As for > the polar molecules aligning themselves, this implies it takes some > time to achieve. Thus there is a resonnant point in this and if there > is resonnance then there might be anti-resonnance too. Might you know > where this natural molecular resonnance is? Might this be the standard > microwave oven frequency? Sorry, I don't know. If any of the readers of this newsgroup do, I'd really appreciate your enlightening us. Roy Lewallen, W7EL Article: 220187 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Sun, 18 Dec 2005 00:45:11 -0800 Message-ID: <11qa8crtbkspgec@corp.supernews.com> References: <27482-43A4E65D-609@storefull-3255.bay.webtv.net> Reg Edwards wrote: > . . . > A measured voltage is always relative to or is between TWO specified > points. And when measuring in the presence of a time-varying H field, those two specified points have to be physically very close together. Roy Lewallen, W7EL Article: 220188 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Sun, 18 Dec 2005 00:52:58 -0800 Message-ID: <11qa8rfircarnda@corp.supernews.com> References: <27482-43A4E65D-609@storefull-3255.bay.webtv.net> Richard Harrison wrote: > Reg, G4FGQ wrote: > "Just a number please." > > Given 1 volt per m as the field strength, and a 1-m antenna parallel to > the electric vector of the wave, the open-circuit voltage at the end of > the wire is 1 volt. Relative to what? The other terminal has to be extremely close to the end of the wire in order for the voltage to be single valued. The best you can get across the receiver input is > 0.5 volt when there is a conjugate match between the receiver and the > antennna. Sorry, that's not just a little wrong, it's wrong by orders of magnitude. For example, a 1 meter long 10 mm diameter dipole, terminated in the complex conjugate of its self impedance (load Z = 0.8855 + j6030 ohms), in a 1 V/m field, has about 1667 volts across the load. Hardly a half volt! > . . . Roy Lewallen, W7EL Article: 220189 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Sun, 18 Dec 2005 03:33:54 -0800 Message-ID: <11qai96o29uk97c@corp.supernews.com> References: <27482-43A4E65D-609@storefull-3255.bay.webtv.net> <11qa8rfircarnda@corp.supernews.com> Roy Lewallen wrote: > . . . > Sorry, that's not just a little wrong, it's wrong by orders of > magnitude. For example, a 1 meter long 10 mm diameter dipole, terminated > in the complex conjugate of its self impedance (load Z = 0.8855 + j6030 > ohms), in a 1 V/m field, has about 1667 volts across the load. Hardly a > half volt! For the casual reader, I should emphasize that this analysis, like all the others on this thread, assumes zero loss. The conditions I described could never be achieved in real life because of unavoidable loss. But it's important to first understand how a lossless system behaves before we add the complicating factor of loss. Roy Lewallen, W7EL Article: 220190 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: http://niggermania.com/ Date: Sun, 18 Dec 2005 11:51:12 -0000 Message-ID: References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> "DrDeath" wrote in message news:11q97mfbt474cda@corp.supernews.com... > "The Magnum" wrote in message > news:dnuq09$61c$1@newsg3.svr.pol.co.uk... > > > >> >> Pray for me to win the lottery please :O) > >> >> > >> >> Regards, > >> >> Graham > >> > > >> > You have to watch the movie "Bruce Almighty". I did that once! 14,000 > >> > winners of $17 each or something like that :-0 > >> > > >> > >> I watched that movie 4 times, I didn't win any money. > > > > That's because Amos (eyy up Mr wilks ;o) wasn't praying for you... > > > Well that's not very Christian like of him. Im sure he would pray for you if you asked him to, but please don't ask him to pray for you until next week as I want to win it this week ;o) Regards, Graham -- _._. _... ._. ._ _.. .. _ _ _ Radio is only a Hobby. Don't let it rule your life... 73's - Graham (www.open-channel.co.uk) Article: 220191 of rec.radio.amateur.antenna From: "David J Windisch" Subject: Trade Message-ID: <5Xepf.183870$Hs.118503@tornado.ohiordc.rr.com> Date: Sun, 18 Dec 2005 15:07:45 GMT Trade Drake L4-B in excellent working order for HyGain TH11DX/HamM rotator in same good order. Antennas can be shipped in cardboard concrete-form tubes :o) 73, DTradeave, N3HE 513-674-7202 Article: 220192 of rec.radio.amateur.antenna From: "Frank" References: <11q7a46jtvo9jf9@corp.supernews.com> Subject: Re: Program GRNDWAV4 Message-ID: <6Hfpf.12069$wg4.4975@edtnps84> Date: Sun, 18 Dec 2005 15:58:58 GMT "Roy Lewallen" wrote in message news:11q7a46jtvo9jf9@corp.supernews.com... > Frank wrote: >> >> Repeating what was previously posted. The following model treats a 1 >> meter (perfect conductor) monopole, of 0.814 mm diameter, connected to a >> perfectly conducting ground. I have applied a vertically polarized >> incident E-field of 1 V/m (peak). The base of the antenna is loaded with >> the antennas complex conjugate of 1.747 + j823.796. NEC2 computes the >> current through the load as 0.2863 Amps (peak), which is 0.5001 V peak. >> This appears to agree with Reg's program. >> . . . > >> Possibly someone can point out if there are any errors in the following >> code: >> >> CM 1 Meter Vertical >> CE >> GW 1 50 0 0 1 0 0 0 0.000814 >> GS 0 0 1 >> GE 1 >> GN 1 >> EX 1 1 1 0 90 0 0 1 1 1 >> LD 4 1 50 50 1.747 823.796 >> FR 0 3 0 0 19.9 0.1 >> RP 0 181 1 1000 -90 90 1.00000 1.00000 >> EN > > You've specified a plane wave of 1 V/m peak arriving in a horizontal > direction over a ground plane. This results in a field strength of 2 V/m > peak at the antenna. For more information about this, look at my postings > over the last couple of weeks on the thread "Antenna reception theory". > > Roy Lewallen, W7EL Not sure I really understand what is going on, but have been aware of your previous postings, also on the NEC-list. What I should have said is that the above program agrees with Reg's previous assumption -- but not with his new program "grndwav4.exe". In any case, just to satisfy my curiosity, I ran the following code, which is, in essence, almost identical to your NEC-list post with 5.555.... kW input producing 1V/m peak at 1000m. The following agrees exactly with Reg's new program. CM Short Monopoles CE GW 1 50 0 0 1 0 0 0 0.000814 GW 2 50 1000 0 1 1000 0 0 0.000814 GS 0 0 1 GE 1 GN 1 EX 0 1 50 00 65698.12106 0.00000 LD 4 2 50 50 1.747 823.796 FR 0 3 0 0 19.9 0.1 RP 1 1 360 0000 0 0 1.00000 1.00000 1000 RP 0 181 1 1000 -90 45 1 1 EN Noting the comments by others, obviously familiar with ATR measurement techniques, this exercise with NEC is purely academic. There is no way you could experimentally prove these results. Since I have never made measurements on an "Open-air" test site it will be interesting to verify Mac's assumptions, which I am sure are correct. The confusions I have are now related to the fact that NEC results depend on how the incident E-field is generated. I will check all previous posting by Roy to see if I can figure out this anomaly. For some reason I have not received any update concerning the NEC list postings. Frank Article: 220193 of rec.radio.amateur.antenna From: fmmck@aol.com (Fred McKenzie) Subject: Re: Gap Antenna Date: Sun, 18 Dec 2005 11:30:22 -0500 Message-ID: References: In article , "west" wrote: > Anyone have experience with GAP Antennas? On paper they look almost too good > to be true, but I know that word of mouth can be more informative. All > comments welcomed. West- I've heard third-hand about one Ham Engineer who was having trouble getting a Gap to perform to specs. After discussing it with the company, he decided they misrepresent the antenna and is in the process of filing a class-action suit against them. I couldn't find any information via Google. Fred Article: 220194 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Program GRNDWAV4 Date: Sun, 18 Dec 2005 12:00:37 -0500 Message-ID: <11qb5bl3u0jdka1@corp.supernews.com> References: <11q7a46jtvo9jf9@corp.supernews.com> <11q9prkb4b1mt28@corp.supernews.com> Dear Richard: I am obliged to you for your useful comments. In the large TEM cells that I use to about 200 MHz (with care above about 150 MHz) a very small probe is inserted through the roof of the cell. That probe is used, with the sort of processing you mentioned, to provide one verification of the E inside of the cell. (The other verification comes >from measuring the power going in and coming out of the cell, and the internal dimensions.) The probe-scheme's success is helped by the fact that E can go up to 200 v/m (or more) so a lot of signal is available. Interesting things happen to some electronic equipment well before 200 v/m. A TEM cell with a spectrum analyzer can inform about what a device is radiating. Still, outdoors, a one meter rod over a large ground screen placed well clear of other structures provides the means to measure (with reasonable uncertainties) the low TOA vertical E field up to 20 or so MHz. A scheme that I saw at NBS circa 1975 (now NIST) to measure an estimate of total field uses orthogonal, very small doublets with diodes at their center. They received a patent on the idea. To bring the DC to a measuring device, lossy transmission lines were used so as to make the transmission lines "invisible" to the field. In other words, the step up from rod-and-screen is a big step. In my youth, I measured VHF signals propagated by FM broadcast stations in the "hills" of West Va. to enhance the VHF propagation models that then existed. The purpose was to be able to predict interference to a radio astronomy site. We used tuned dipoles elevated some standard distance that I do not remember. As many here have said: It is not easy to measure fields. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net "Richard Clark" wrote in message news:a84aq1lah3lqffds1d86uer44rclo8462h@4ax.com... > On Sat, 17 Dec 2005 23:38:13 -0500, "J. Mc Laughlin" > wrote: > > > I have dealt with approximations of the subject device. In each case, > >an extremely high input impedance amplifying device is placed at the base of > >the antenna that has a known voltage amplification and a 50 ohm output > >impedance. Knowing that a close approximation of the open circuit voltage > >is amplified by a known amount, a calibrated, tuned voltmeter (at 50 ohms) > >is able to measure the size of vertically polarized E (with the usual > >uncertainties). (and a bit of arithmetic) > > Hi Mac, > > I too, will jump in with alternatives to this short, thin rod feeding > an infinite Z. It makes for a simple specification, but when the > frequency begins to climb such is not very practical. Input Z's tend > to be dominated with strays and that "short" rod begins to become > enormous. Such artifacts of the MF era are quickly discarded. > > The NIST methods (NIST technical note numbers 1309 and 1098) employ > resonant sized dipoles feeding a DC Hi R (and hence AC Hi Z load) at > the gap of the elements. By DC Hi R, the detector filter employs > 50KOhm components in a balanced cascading filter that in turn feeds a > Hi R voltmeter through 250KOhm leads (carbon impregnated plastic > conductors to decouple both loading and induction). > > Uncertainty, worst case, is 1dB. > > Schelkunoff's algorithm is used to find the length of the dipole (no > real surprise here for halfwave length). The effective length is not > half, but rather closer to 62 - 63%. > > 73's > Richard Clark, KB7QHC Article: 220195 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: <11qa8rfircarnda@corp.supernews.com> Date: Sun, 18 Dec 2005 17:11:05 GMT "Roy Lewallen" bravely wrote to "All" (18 Dec 05 00:52:58) --- on the heady topic of "Re: Antenna reception theory" RL> From: Roy Lewallen RL> Xref: core-easynews rec.radio.amateur.antenna:221453 RL> Richard Harrison wrote: > Reg, G4FGQ wrote: > "Just a number please." > > Given 1 volt per m as the field strength, and a 1-m antenna parallel to > the electric vector of the wave, the open-circuit voltage at the end of > the wire is 1 volt. RL> Relative to what? The other terminal has to be extremely close to the RL> end of the wire in order for the voltage to be single valued. RL> The best you can get across the receiver input is > 0.5 volt when there is a conjugate match between the receiver and the > antennna. RL> Sorry, that's not just a little wrong, it's wrong by orders of RL> magnitude. For example, a 1 meter long 10 mm diameter dipole, RL> terminated in the complex conjugate of its self impedance (load Z =3d RL> 0.8855 + j6030 ohms), in a 1 V/m field, has about 1667 volts across RL> the load. Hardly a half volt! All this talk of high RF voltage has got me a little peckish. Anyone up for hotdogs and smores? A*s*i*m*o*v ... I'm precise. He's discriminating. You're picky. Article: 220196 of rec.radio.amateur.antenna From: Mike Subject: Re: Gap Antenna References: Message-ID: <7fhpf.30969$BZ5.8675@newssvr13.news.prodigy.com> Date: Sun, 18 Dec 2005 17:51:37 GMT I would like to hear more about that suit. I bought a GAP Titan many years ago after listening to the hype (lies) from the GAP booth at Dayton. The only thing that was not a lie is the reasonable match it had on all bands, but then so does a dummy load. Mike Fred McKenzie wrote: > In article , "west" > wrote: > > >>Anyone have experience with GAP Antennas? On paper they look almost too good >>to be true, but I know that word of mouth can be more informative. All >>comments welcomed. > > > West- > > I've heard third-hand about one Ham Engineer who was having trouble > getting a Gap to perform to specs. After discussing it with the company, > he decided they misrepresent the antenna and is in the process of filing a > class-action suit against them. I couldn't find any information via > Google. > > Fred Article: 220197 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <11q8u4qpl7fft16@corp.supernews.com> <11qa89qo8d8mmbb@corp.supernews.com> Subject: Re: Underwater Date: Sun, 18 Dec 2005 13:18:05 -0500 Message-ID: <19d70$43a5a7f1$97d56a33$19178@ALLTEL.NET> As I remember, we used 18 Kc and 13 Kc. We didn't have hertz in those days :>) We were able to copy Jim Creek when submerged in the Red Sea. Jim Creek had 13 miles of wire suspended between two mountains in what was probably the worlds biggest capacitance hat. All CW , because even a 150 cycle shift for rtty would have thrown the tank circuit out of resonance. Now no one would be able to copy it... "Roy Lewallen" wrote in message news:11qa89qo8d8mmbb@corp.supernews.com... > Asimov wrote: > > > > Thanks for the info. I had read that submarines communicated in a > > band of a few 10's of Hz because of the problems with water. As for > > the polar molecules aligning themselves, this implies it takes some > > time to achieve. Thus there is a resonnant point in this and if there > > is resonnance then there might be anti-resonnance too. Might you know > > where this natural molecular resonnance is? Might this be the standard > > microwave oven frequency? > > Sorry, I don't know. If any of the readers of this newsgroup do, I'd > really appreciate your enlightening us. > > Roy Lewallen, W7EL Article: 220198 of rec.radio.amateur.antenna From: Russ Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <11q9kt36n4utv5e@corp.supernews.com> <1134924107.312230.237810@z14g2000cwz.googlegroups.com> Date: Sun, 18 Dec 2005 19:28:40 GMT On 18 Dec 2005 08:41:47 -0800, nm5k@wt.net wrote: >I do believe that any mechanical wave, such as a pressure or shock >wave, >travels at the speed of sound, no more and no less. To travel faster, >it >would have to be an electromagnetic wave. > >Also, the deaf person wouldn't hear the mechanical wave. Well, >unless they had "some" hearing still available. If it was proven that >a totally deaf person could hear it, that would pretty much nail it >down as >electromagnetic. If that came out to be true, then Coffmans theory >about the auditory nerve picking it up would probably be true unless >some other nerve was actually involved. >MK Doesn't the delta P of a fuel-air bomb travel at greater than the speed of sound? R Article: 220199 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Sun, 18 Dec 2005 14:02:53 -0600 Message-ID: <23343-43A5C06D-131@storefull-3252.bay.webtv.net> References: <11qa8rfircarnda@corp.supernews.com> Reg`s question was: "What is the voltage between the bottom end and ground of a 1 metre high vertical antenna, above perfect ground, when the vertically-polarized field strength is 1 volt per metre, and the antenna height is shorter than 1/4-wavelength?" A very clear and succinct question, I thought. Roy Lewallen wrote: "Relative to what?" Reg left little to assume. I inferred that Reg had meant a ground-mounted 1-meter whip on a small base insulator. That would have left a short distance between the points of voltage determinarion. The 1-meter whip directly over flat perfect earth must have a conjugate match to its receiver to extract all available power and get maximum voltage at the receiver input. This requires a low-loss coil to tune out the high capacitive reactannce of a too-short whip. It was specified as being less than 1/4-wavelength. Standing wave antennas must be resonant to allow maximum current flow. An unbalanced whip antenna must consist of two electrical parts just as a balanced antenna does. The ground or ground plane used with a whip substitutes for the missing half of a dipole. It provides a virtual image of the whip above it, to complete a dipole-like antenna. In this instance, the ground surface intervenes splitting the antenna into real and virtual parts. Radiation comes from the real part above ground. This part has only half the impedance of a totally real dipole. We don`t need to have problems in determining the base voltage of a whip antenna. We can measure the antenna`s base impedance with a bridge, and its current with a thermoammeter with good accuracy, then we can calculate the voltage at the base of the whip. The answer to Roy`s question is: The r-f voltage at the base of the antenna is determined with respect to ground at the base of the antenna, Best regards, Richard Harrison, KB5WZI Article: 220200 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sun, 18 Dec 2005 12:39:09 -0800 Message-ID: <11qbi7i9pegj1db@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <11q9kt36n4utv5e@corp.supernews.com> <1134924107.312230.237810@z14g2000cwz.googlegroups.com> Russ wrote: > > Doesn't the delta P of a fuel-air bomb travel at greater than the > speed of sound? No. Roy Lewallen, W7EL Article: 220201 of rec.radio.amateur.antenna From: "DrDeath" Subject: Re: http://niggermania.com/ Date: Sun, 18 Dec 2005 14:40:09 -0600 Message-ID: <11qbi9ao07pnuf7@corp.supernews.com> References: <6gtmp1dqk4qglmcigdvc42tj3ojndi2rcv@4ax.com> <81mnp15vlj99jaf5dv7lohfdr15m7l8dq3@4ax.com> <1nonp1d2gvk7sk4m0p661954croitbeeg9@4ax.com> <5v4op1t9672ed489hk38dsebnqok6hij4t@4ax.com> <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> "The Magnum" wrote in message news:do3icl$s0$1@news6.svr.pol.co.uk... > > "DrDeath" wrote in message > news:11q97mfbt474cda@corp.supernews.com... >> "The Magnum" wrote in message >> news:dnuq09$61c$1@newsg3.svr.pol.co.uk... >> > >> >> >> Pray for me to win the lottery please :O) >> >> >> >> >> >> Regards, >> >> >> Graham >> >> > >> >> > You have to watch the movie "Bruce Almighty". I did that once! > 14,000 >> >> > winners of $17 each or something like that :-0 >> >> > >> >> >> >> I watched that movie 4 times, I didn't win any money. >> > >> > That's because Amos (eyy up Mr wilks ;o) wasn't praying for you... >> > > >> Well that's not very Christian like of him. > > Im sure he would pray for you if you asked him to, but please don't ask > him > to pray for you until next week as I want to win it this week ;o) > > Regards, > Graham > -- > _._. _... ._. ._ _.. .. _ _ _ > > Radio is only a Hobby. Don't let it rule your life... > > 73's - Graham (www.open-channel.co.uk) > > LOL, you got it. Article: 220202 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <11q9kt36n4utv5e@corp.supernews.com> <1134924107.312230.237810@z14g2000cwz.googlegroups.com> <11qbi7i9pegj1db@corp.supernews.com> Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sun, 18 Dec 2005 16:04:16 -0500 Message-ID: The denotation is supersonic, while the flame spread is subsonic. "Roy Lewallen" wrote in message news:11qbi7i9pegj1db@corp.supernews.com... > Russ wrote: > > > > Doesn't the delta P of a fuel-air bomb travel at greater than the > > speed of sound? > > No. > > Roy Lewallen, W7EL