43 feet is a 5/8 wavelength on 20 meters.The 5/8 wave is the length at
which the field strength is highest. I believe the same reasoning is used
with it as the G5RV which is a gain-type antenna at 20 meters and a
compromise at 40 meters. I worked a K9 in the Chicago area that was using
a Zero-5 vertical ground-mounted(it is just over a 1/4 on 40) and it was
doing a very good job into AL/TN while I was mobile.IIRC, the feedpoint
impedance of a 5/8 wave is 60 ohms resistive,and 140 ohms capactive
reactance, hence the need for a coil at the bottom to cancel out the 140
ohms.This is, of course, for the band at which it was designed to a 5/8
wave.
Joe
W4AAB
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