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Old October 1st 10, 12:14 AM posted to rec.radio.amateur.antenna
Richard Fry Richard Fry is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 440
Default Elevated vs buried radials

On Sep 30, 4:44*pm, Jim Lux wrote:

never underestimate the power of tradition. *It was written by BL&E that
120 radials work, and the FCC accepts that for broadcast, so by golly,
that's what we do.


A minor point, but in the interest of accuracy - the greatest number
of buried radials used in the BL&E experimental work was 113.

There's also the whole "the radials must be resonant" misconception..


While the physical lengths of the buried radials in the BL&E
experiments were stated in free space wavelengths, that does not mean
that those physical lengths will behave the same when buried as they
will when not buried.

As shown in the link I posted earlier in this thread (and by NEC), a
few elevated wires used as a counterpoise in place of the BL&E buried
wires need to have an electrical wavelength of 1/4-lambda for best
antenna system radiation efficiency, even with "short" vertical
monopoles. And even when those elevated counterpoise wires are close
to the earth in terms of a free space wavelength, their electrical
length is not much different than their physical dimension in terms of
a free space wavelength -- as is the case when they are buried.

Theory and practice both show that such wires perform differently when
they are buried than when they are elevated above the surface of the
earth.

RF