Al The worst length for a raised radial is a resonant quarter wave. Two together form a half wavelength. The problem is that the ground on one side of the "dipole" is not exactly the same as the ground on the other side so the "dipole" has a life of it's own and becomes a slightly off-center driven resonant dipole. It will radiate some of your energy because of it's stored energy. Energy will be wasted because it will be radiated so close to ground. The radials should be shorter or longer than a quarter wave so they do not form resonant dipoles. Bring the overall antenna system to resonance by adjusting the length of the monopole or adding appropriate reactance. This is very well covered by Moxon [SK] in his book 'HF Antennas For All Locations' and elsewhere in the amateur press. 73 Good luck on your project. George Badger W6TC
----- Original Message ---- From: Alan Bloom <[EMAIL PROTECTED]> To: Ken Kopp <[EMAIL PROTECTED]> Cc: [email protected] Sent: Wednesday, November 5, 2008 8:47:39 AM Subject: Re: [Elecraft] OT: Vertical antenna ground systems N6LF has done some wonderful experimental work on vertical antennas. He found that a radial laid on the ground experiences a velocity factor similar to coax cable. A quarter wavelength is only about 60% of its free space value. If you make the radials a physical quarter wavelength long, they are actually closer to a half-wave electrical length (anti-resonant). With 4 radials he actually got about a 3 dB improvement by making them SHORTER! For my next vertical I will definitely plan to tune the radials. I think I'll try laying out a 1/2-wave dipole on the ground and then trim it to resonance. Then cut all the radials to equal the length of one half of the dipole. Al N1AL On Tue, 2008-11-04 at 19:10, Ken Kopp wrote: > Of potential interest to those who use verticals with their Elecraft > rigs. > > http://www.antennasbyn6lf.com/ > > > 73! Ken Kopp - K0PP > [EMAIL PROTECTED] > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
