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[Towertalk] HI SWR during rain - EXP-14

To: <towertalk@contesting.com>
Subject: [Towertalk] HI SWR during rain - EXP-14
From: k9rz@radiks.net (Bill Jackson)
Date: Fri, 08 Nov 2002 06:59:00 -0600
Frank Davis wrote:

>I cranked the tower over and did a visual inspection and did have 
>to reposition the inside end caps back over the ends of the driven
> element traps.  They had vibrated out of place in the gusts.  I 
>couldn't see any other issues to deal with. 
>

Frank,

You didn't say you did anything to keep the end caps from coming loose 
again.  If they were loose enough to come off on their own, they 
probably have some UV deterioration, have become stiff and are not 
sealing the ends of the trap very well.

I have had two KLM KT-34 series antennas over the last 20 years.  They 
use lots of small plastic caps over the capacitance tubes, which are 
smaller versions of the same type of cap you would have over the end of 
a trap.  Experience has shown that even a very small hairline crack in a 
cap will allow enough moisture in to raise havoc with the performance of 
the antenna.  Based upon your description, I would say it was the driven 
element that is having the problem.

I would recommend you replace the end caps on all your traps.  At least, 
wrap them with some good quality electrical tape until you can get them 
replaced.  A small bead of silicon seal where the cap meets the tubing 
may not hurt either.

Also, don't run high power into your antenna until it dries out.  If you 
happen to flash over the inside of the trap, you will really have a 
problem, since a permanent carbon trail will form inside the trap and it 
will be suspect even after it dries out.

Hope this helps.

73 de Bill



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