>From: Randy Kaufman <krandy@hubcap.clemson.edu>
>Don Newcomb, W0DN, writes:
>If an antenna is mounted at ground level there's no point in
>cutting radials to any particular length cuz the earth will detune
>them anyway. All you want to do is make the surface of the earth
>around the antenna more conductive than it is ordinarily, and if you
>can't copper-plate the back yard the best approach is to run out as
>many radials as possible, each as long as possible around the antenna
>in all directions.
Hi Randy, thanks for posting Don's statements. This is definitely true
for ground mounted verticals. If one doesn't believe it, one should
ask oneself the following:
When modeling, why does an infinite perfect ground plane yield the
highest gain? Is an infinite perfect ground resonant?
Salt water is the best natural ground plane that we know of. Is salt
water resonant? We want a conductive ground plane out as far as is
feasible. There's no loss in a perfect conductor whether it is
resonant or not. The purpose of radials in a ground mounted vertical
is to force the RF currents to flow in a low-loss conductor, not in
lossy earth.
Will 1/4 WL radials work for a 5/8 WL ground mounted vertical? Nope,
the high current point is far up the antenna and the radiation from
that point will tend to miss the 1/4 WL radials entirely and instead
of being reflected from the radials will tend to dissipate in the
ground.
73, Cecil, W6RCA, OOTC
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