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[TowerTalk] Tuned Feeders

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Subject: [TowerTalk] Tuned Feeders
From: (L. B. Cebik)
Date: Sat, 27 Sep 1997 06:11:16 -0400 (EDT)
On Fri, 26 Sep 1997, Tom Osborne wrote:
> In reading about the feedline it 
> stated that the foam 300 ohm solid ribbon is not that good to use 
> because when it gets wet the SWR changes.  Is that a problem other than 
> the fact that I may have to adjust the tuner a bit to get the SWR back 
> down.  Will it detract from the operation of the antenna?  Thanks
> Tom W7WHY

If you are willing to adjust the tuner, 300-ohm line should not create
significant additiona losses compared to windowed 450-ohm line.  However,
there may be advantages to using one of the heavier duty, large wire size
lines in terms of both physical strength and current handling ability.
You may also want to consider using something like a "line grabber" or
similar to ensure a good junction of the line to the antenna.

I have had reports that some auto waxes have been used with good success
in slipping moister from vinyl coated lines--renewed with each semi-annual
inspection.  However, I do not know the chemical structure of all of them,
and hence do not know if any may disrupt the design feedline impedance.  I
have also heard that some bare antenna wire users have delayed corrosion
with the same sort of waxes--with semi-annual renewal as well.

OK, the "semi-annual" part is my addition, part of my compulsive antenna
maintenance subconscious.

However sophisticated the antenna farm, a good old doublet with open wire
feed and an ATU still makes one of the world's best back-up antennas,
especially when run through a cost-effectiveness analysis.



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