Working 300 countries is also not an indicator of antenna performance but
it is the gauge that many people use. SWR is the easiest thing that we
can measure and if it does not match the antenna design it is a good
indicator that something is wrong. If the antenna had 1.3:1 SWR and now
it's 2:1 something in the antenna system changed and it is worth
investigating. If it is just interaction, often this effects SWR and F/B
more than gain and it may be acceptable. I model all of my antennas before
installing them to see what the interaction effects will be, sometimes the
results are surprising.
John KK9A
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Need balun advice
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 10 Nov 2015 13:51:40 -0800
I don't think it's coax, I think it's simply interaction between antennas
and Les's misunderstanding of the importance of SWR as an indicator of
antenna performance.
Repeat after me --
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
OTOH -- the "balun" used should be exactly what the antenna designer
recommends. The word "balun" is used to describe (at least) a dozen
different things that are VERY different from each other. The operation of
the antenna, as well as the match between antenna and feedline can be
greatly affected by which is used.
So -- study the instructions for the antenna, use exactly with the mfr
recommends, and if you want to minimize RX noise, ADD a common mode choke
on the coax side of the mfr's recommended matching device, as described in
by Cookbook. k9yc.com/RFI-Ham.pdf
73, Jim K9YC
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