Kevin N8IQ wrote: I've been playing around with EZNEC trying to come up with a DX antenna that will work at my QTH. The vertical dipole seems to have a fantastic pattern for DX with low takeoff angles. I may be able to hang a vertical wire dipole in one of my trees and have it nearly invisible. Anyone have experience with vertical dipoles that they could share?
---------------------- Are you modeling over a "real earth" in EZNEC, Kevin? The limitation verticals face is that vertically-polarized waves induce strong ground currents. In most grounds that means substantial loss of lower angles of radiation. For that reason, most verticals show their maximum lobe at somewhere between 20 and 30 degrees above the horizon. Everything lower is absorbed by the earth. Until the radiator gets so long the patter breaks up (up to about 5.8 wavelength) there is a slight improvement in gain as the radiator is made longer. Using a dipole does eliminate the requirement for a ground for a Marconi type radiator, but it does nothing to reduce the far-field ground losses from what I read. The "gain" of such a vertical will be about 0 dBi or the same as an "isotropic" radiator. By comparison, a horizontal antenna 7 MHz, will over 6.5 dBi gain at 20 degrees as long as the horizontal wire is about 1/4 wavelength (33 feet at 40 meters) above the ground. That is equal to a 4:1 power increase just by making the dipole horizontal! Of course, the horizontal requires a lot more "horizontal" space! That gain comes from just the reverse of the situation that costs a vertical signal. The waves from the horizontal are reflected from the ground to form a sort of "two-element" beam. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
