Yes, I guess a more accurate test would be to run them all in vertical
polarization on a fiberglass mast or end mounted for gain comparisons. Then
mount them on a PVRC mount and flip them vertically to get the pattern and F/B
(still vertical polarization). Perhaps you could to the gain tests on the PVRC
mount as well. At least this would eliminate all debate about ground effects
The thing I found more disturbing about the tests were the unexplained anomolies
such as the KLM KT34XA on 15, which supposedly had no F/B, yet mine have at
least 10 db across the band (yeah, not great, but not near zero either!) As
someone mentioned, this report should have used all new antennas straight out of
the box, carefully assembled per the manufacturers instructions.
73, Ty K3MM
To: "Towertalk" <towertalk@contesting.com>
cc: (bcc: Tyler G Stewart/BENN/CEC)
Subject: [TowerTalk] Triband tests
Reflector crew. . .
Just a thought on the triband testing thread. I work in the land mobile
business (for Motorola) and have had my fair share of experience over the
years with antennas used in our industry (which, obviously, are radically
different than our HF antennas). While we don't build many antennas
ourselves (leave that for others who have that core competency), we do test
them, sometimes extensively.
While I have not been involved much with the testing myself, I'm aware of
the procedures, results, etc. Our testing methods are not all that
different than those used by K7LXC and company although we do "A/B" test
antennas. Steve's methods, while not necessarily yielding totally accurate
numbers in an absolute sense, should yield reasonably accurate numbers in a
comparative sense. I would guess easily within a db.
In the land mobile world, our only concern with antenna performance is
radiation focused on the horizon. Obviously, the more the better since our
only mode of propagation is ground wave.. This validates our goal of
maximum radiation on the horizon. It also validates us using two antennas
at reasonable heights above ground level (at least high enough to have
fresnel clearance).
Our situation in the HF world is completely different. If you have two
stations (a few thousand feet or a mile apart) with antennas at reasonable
distances off the ground (say 50 or 100'), it would seem to me that you're
measuring the ground wave capability of the antenna (which does little or
nothing toward working most DX). I'm not sure how one would go about
measuring the gain of a given HF antenna at reasonable launch angles (say 10
to 40 degrees). . . but the methods used as I understand them, aren't going
to evaluate this aspect of performance.
Who cares what the ground wave gain performance is? Am I missing something
here??? Perhaps so (I don't claim to be an antenna design engineer).
73 to all. . . Dave
W0FLS
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