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[TowerTalk] Auto tuners, Baluns and open wire feeders

To: Tower Talk <towertalk@contesting.com>
Subject: [TowerTalk] Auto tuners, Baluns and open wire feeders
From: Mark Spencer via TowerTalk <towertalk@contesting.com>
Reply-to: Mark Spencer <mspencer12345@yahoo.ca>
Date: Tue, 17 Jul 2018 10:43:44 -0700
List-post: <mailto:towertalk@contesting.com>
Hi:

I spent some time trying out various wire antennas at the summer cottage and 
have more or less settled upon a dipole antenna fed with a short length of open 
wire feeder that runs from the antenna feed point to slightly above ground 
level, the open wire feeder is in turn connected to a Johnson match box (a 
tuner with a balanced line connection), which in turn feeds a coaxial cable 
that runs to the radio.  The tuner sat on top of a short step ladder during my 
tests.

The coaxial cable had various mix 31 and mix 43 ferrite chokes applied.  It all 
more or less worked as I expected it would on various bands.  

Moving forwards I'd like to replace the Johnson Matchbox with an auto tuner.  
At this point I'm leaning towards purchasing a suitable Balun from DX 
engineering, connecting that to the output of my SGC231 tuner and replacing the 
Johnson Match box with the Balun and the auto tuner.   I'll have to do some 
modelling (to figure out the likely range of feed point impedances  for the 
dipole antenna at various frequencies) before deciding on what ratio Balun to 
buy.   I expect I'll install the auto tuner and Balun on top of a wooden pole 
perhaps 10 feet or so from the ground.

I am curious if anyone else has done something along these lines and if there 
are any issues with doing so ?  Any comments would be welcome.

I'd like to move away from using a commercially made trap dipole at that 
location.   (The appearance, lower weight and wind loading of a simple wire 
dipole with a short open wire feeder is attractive to me, plus I need to use a 
tuner to match the existing trap dipole.)

73

Mark S
VE7AFZ
mspencer12345@yahoo.ca

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