Hi Don,
That was a well thought-out post but I'd like to clarify one thing:
> The VHF antenna, many wavelengths above the ground, needs only 3 or
> 4. It follows that any practical Marconi-type antenna on 160M will
That depends on how you define "enough" and what else you do at
the feedpoint. With only three or four radials, there will be
substantial feedline radiation unless something is done to isolate
the feedline for common-mode current.
You can actually watch the SWR change on a 1/4 wl groundplane
with four radials as you alter the cable length or grounding, and
some VHF/UHF antennas actually make controlled use of that
radiation to add collinear gain!!
There also is considerable radiation from each radial, until you are
at least 1/2 wl from the radials. Radiation from the radials ONLY
cancels in the far field, no matter how carefully you balance
currents in each radial.
73, Tom W8JI
W8JI@contesting.com
|