[TowerTalk] 80 M 4 SQUARE MODELING
rxdesign at ssvecnet.com
Fri Jul 21 19:08:17 EDT 2017
Agreed - to an extent.... I don't think the programs are THAT sensitive ...
at least that hasn't been my experience re interaction modeling. I did lots
of it for the tower with the antennas to see the impact of the guys - wasn't
overly critical in making changes and I could pretty readily see the
results. Ended up with the fact that one does not need to have full length
philly - about 40% of the length, of course at the tower, was enough to
reduce the interaction to less than 1.5 db on the FB (which is the only
thing it effects unless REALLY severe)... I made them 50% long as the
manufacturer says you can't do less than 50% without upsizing.
So of course one can just build it - and see. As I had said 'anecdotal'
results are, at least for me, taken with a very large grain of salt... I've
seen too many reports of "best antenna ever" for what obviously wouldn't
come close to that claim - its all relative. ALL relative... that said the
FB is THE variable one looks to for knowing if interaction is in play - not
the gain or the SWR - if they are impacted you REALLY have problems ... and
the one comment here, saying he routinely sees FB values in the 20's for his
tower supported one, would say his is working just fine thank you very much!
that stated the results were disconcerting enough for me to decide not to do
it. Besides in my case if the published data re ground characteristics is
correct, poor in this area, then my rotary dipole at just over 1/2 wl on 80
equals or beats a 4 sq a good part of the time. So I just put it back up. If
one WERE going to just do it - I'd have a plan in place on how to mitigate
it, if indeed it is there .
My guess, Bill, is that your tower w/ antennas will look like, easily, a
120'+ tower ...
From: Kenneth Goodwin
Sent: Friday, July 21, 2017 1:18 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] 80 M 4 SQUARE MODELING
Whether it works or doesn't work, what's your alternative? Biggest problem
with antenna modeling software is that the software can't take into
consideration the physical constraints without extensive sensitivity
analysis. And if you move your baseline model by 6 inches, the whole thing
changes and you don't have the means to control the physical parameters to
that degree. Here is what you are supposed to have learned in numerical
analysis, the optimum solution is not necessarily the best solution. Ken
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