To: <topband@contesting.com>
> Date: Sat, 14 Mar 1998 13:34:01 -0500 (EST)
> From: CQ K8DO <CQK8DO@aol.com>
Hi Denny,
As Eric pointed out, and I keep pointing out, changing the radials
does NOT affect wave angle. It's part of Hamlore and common but
incorrect rumor that they do. I would add two exceptions, however:
1.) If the radials are radiating and acting like antennas that
contribute radiation in the farfield, they certainly affect
radiation pattern.
2.) If the radials are VERY long, several full wavelengths, then they
affect pattern.
In any case, we are talking about under 1/2 wl long systems that have
minimal radiation.
> I am having a problem parsing the above paragraph... Did 64 ground radials
> have a 5 dB advantage over 4 elevated radials?...
Absolutely, but let's say "about 5 dB or so". Then it is true not
only here in my tests, but also in measurements made at WVNJ
radio. At WVNJ radio the difference was larger when operating with a
directional pattern, because the particular directional array they
used had some very concentrated currents in and around some elements.
> If they did and if the 4
> elevated radials had a "few dB" advantage at the 16 ground radial point,
> where the the break even point occur , in terms of the number of ground
> radials compared to the 4 elevated radials?
At four radials, the elevated system had 1.2 dB advantage but was
still 4.3 dB down from 60 radials.
At 16 radials, elevated radials had only a 1/2 dB advantage, and
were 2.4 dB down from 60 radials.
At 32, the difference was less than instrument tolerance, and about
.7 dB down from 60.
At 60 radials the ground mounted system measured slightly stronger,
but that could have been instrument tolerance.
With a shorter vertical, or a close spaced directional array, the
difference would be greater from best to worse.
73, Tom W8JI
w8ji.tom@MCIONE.com
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