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[TowerTalk] Stange SWR/AttenuationpProblems, goes away when the sun come

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Subject: [TowerTalk] Stange SWR/AttenuationpProblems, goes away when the sun comes up
From: Richard Thorne <>
Date: Sun, 01 Apr 2012 10:01:08 -0500
List-post: <">>
I finished my tower/antenna install Friday.  77' of 45g with 15' of mast 
out the top.  I have a F12 D240 mounted 10' up the mast and a F12 C31 at 
about 1' up the mast.  The swr is where they are supposed to be on both 

Now for the strange part.

Some time after dark my D240 becomes attenuated and the swr is very very 
high.  But after the sun comes up for about 2 to 3 hours, the 
attenuation goes away and the swr is right where its suppose to be and 
signals are clear and strong.

Its been clear with no rain since the antenna has was put up Friday 
morning.  There must be some moisture in the air as dew does form on the 
grass and the roof of my steel building/shop.

So I'm scratching my head on this one.  I've switched out coax cables at 
the shack, bypassed the polyphaser lightning suppressors, used the 
different antenna inputs to my Elecraft K3, checked to be sure I didn't 
have a receive antenna selected on the K3 etc.

I have a single 158' run of coax from my entrance panel to the top of 
the tower and have it terminated with one of these{DBD52E00-E4FA-4BB0-A7B9-1EDCD8FCDE17}&PartNo=DXE-CGB-150
then another length of coax that forms the rotor loop, goes up the mast 
then to the f12 balun (f12 B1) at the feed point of the D240.  I have 
the same setup via another coax cable going to the C31XR which doesn't 
exhibit this strange problem

I have two weep holes drilled in the bottom of each trap cover for 
moisture to escape.

All connection points are weatherized using 3m rubber splicing tape 
which is then wrapped with Scotch Super 33.  All coax, connectors etc 
are brand spanking new.

The next step is to climb the tower and check the connections at the top 
of the tower, if that's not the problem it will be time to bring out the 
crane again and check the connections at the feed point.

Before I get to far into this I'd like to know if any else has run into 
this symptom and what the final resolution was.


Rich - N5ZC


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