Re: [Elecraft] Verticals on mountaintops
If you are really connected to the earth and the resistance of the earth is really infinite then your efficiency is zero and it has the same effect as if you only have a shielded wire connected to the radiator. But this is impossible in real life, but is you install a counterpoise that is resonant at your frequency then you may radiate well. Remember that antennas have directivity in both azimuth and elevation. Read the ARRL Antennna Book over and over until you understand it if you want a good antenna. Your efficiency from your antenna connector on depends on the resistance of your counterpoise connection, your counterpoise and the length of your radiator. You get full credit for the radiator from the feed point to the loading coil and some credit for the whip length but very little for the coil itself, maybe a bit less than the coil length. Antenna installations always obey Ohm's law and the other laws of physics whether you understand them or not. Whether you want to believe or not! Save your desire to believe for religion, they say it works! Willis 'Cookie' Cooke,TDXS Contest Chairman K5EWJ Trustee N5BPS From: Al Lorona alor...@sbcglobal.net To: elecraft@mailman.qth.net elecraft@mailman.qth.net Sent: Monday, July 20, 2015 11:58 AM Subject: [Elecraft] Verticals on mountaintops [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.] When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle. But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop. Al W6LX __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to wrco...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Verticals on mountaintops
If you feed your antenna as a dipole, then your counterpoise is the lower leg. Your radiation resistance will be low if your antenna is short. You need something to raise it to about 50 ohms which will be either a coil across the feed point or a capacitor. I have found that there are so few stations with good 80/75 meter antennas in Field Day and many sites are so noisy, either with man made noise or atmospheric noise that it is hardly worth the effort to erect an 80/75 antenna for Field Day unless you have a high transmitter count. Willis 'Cookie' Cooke,TDXS Contest Chairman K5EWJ Trustee N5BPS From: Jim Brown j...@audiosystemsgroup.com To: elecraft@mailman.qth.net Sent: Monday, July 20, 2015 12:14 PM Subject: Re: [Elecraft] Verticals on mountaintops Hi Al, As it happens, W6GJB and I are building a custom 80M vertical for FD use on a mountaintop. As part of the design process, I've compared it to an inverted Vee at the height where we could rig it without trees. The model, of course, is for flatland, and while HFTA can tell us how being on that mountain affected the horizontally polarized inverted Vee, we have no comparable modeling for a vertically polarized antenna. So I asked Dean Straw, N6BV, retired ARRL Antenna Book editor and author of HFTA how he thought being on the mountain might affect the vertical. His answer was I don't have a guess. Our vertical will be built from that modular army-surplus mast that comes in 4 ft sections that fit together with a 40 ft telescoping tube mounted to the top, with a wire taped to it. We will feed it as a vertical dipole, and there will be loading both at the bottom and top. Not at all suitable for backpacking. :) 73, Jim K9YC On Mon,7/20/2015 9:58 AM, Al Lorona wrote: [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.] When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle. But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to wrco...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Verticals on mountaintops
Keep in mind that the self-supported antenna may not be on a mountaintop. 73 -- Lynn On 7/20/2015 9:58 AM, Al Lorona wrote: [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Verticals on mountaintops
Hi Al, As it happens, W6GJB and I are building a custom 80M vertical for FD use on a mountaintop. As part of the design process, I've compared it to an inverted Vee at the height where we could rig it without trees. The model, of course, is for flatland, and while HFTA can tell us how being on that mountain affected the horizontally polarized inverted Vee, we have no comparable modeling for a vertically polarized antenna. So I asked Dean Straw, N6BV, retired ARRL Antenna Book editor and author of HFTA how he thought being on the mountain might affect the vertical. His answer was I don't have a guess. Our vertical will be built from that modular army-surplus mast that comes in 4 ft sections that fit together with a 40 ft telescoping tube mounted to the top, with a wire taped to it. We will feed it as a vertical dipole, and there will be loading both at the bottom and top. Not at all suitable for backpacking. :) 73, Jim K9YC On Mon,7/20/2015 9:58 AM, Al Lorona wrote: [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.] When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle. But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] Verticals on mountaintops
[I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.] When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle. But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop. Al W6LX __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
