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Re: [TowerTalk] Vertical question

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Vertical question
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 16 Mar 2021 22:40:38 -0700
List-post: <mailto:towertalk@contesting.com>
On 3/16/2021 2:50 PM, Richard (Rick) Karlquist wrote:
What has always worked for me is to simply turn down the
RF gain and/or change the AGC threshold such that there
is no AGC action.  It is then possible to switch back and
forth while listening and hear the increase or decrease in
loudness.  This does of course require a signal on the air
to use.

Yes. When I first moved here in 2006, I had both the Tee vertical (although not as tall and not as many radials) and a horizontal dipole at about 110 ft. I did exactly what you suggest, turning down the RF gain or turning off AGC, depending on what the rig provided. I did that for a year or two, learning that on some signals one or the other might be louder, but, especially after adding radials and making it taller, the Tee nearly always won. But just as with RBN 15 years later, you've got to do a lot of A/B switching to take QSB into account. That dipole, even at 110 ft was electrically low on 160, making it a relatively inefficient antenna with relatively little energy at low vertical angles and max gain at higher angles, while the Tee has very little high angle radiation, concentrating it at low angles.

The problem with RBN is that is measures S/N, not absolute
amplitude.  The noise floor is not necessarily the same at
two different frequencies or times.  In this case S/N doesn't
correlate with signal strength.  Possibly you could fix this
by swapping the frequencies every other time.

Yes. I take that into account by TXing TEST K9YC a half dozen times on slightly different frequencies, then switching to TEST KU6W a half dozen times a kHz or so apart, and repeating that process at least a dozen times, QSYing slightly so RBN will spot me again. After taking the data, I average the reports for each station for each antenna. And I always do this on a part of the band with little or no activity (which is pretty easy on 160 CW during the week). My data now consists of average signal reports for each antenna from 15-20 different stations, which I then sort by azimuth.

73, Jim K9YC



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