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Re: [TowerTalk] Shielding of antenna switching/interstation interference

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Shielding of antenna switching/interstation interference
From: Steve London <n2icarrl@gmail.com>
Reply-to: n2ic@arrl.net
Date: Wed, 26 Aug 2009 07:49:10 -0600
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Sounds like you're making an assumption that the inter-station interference has 
something to do with the TopTen 6-way box. What makes you believe that ? Have 
you tried bypassing the 6-way box and connecting the coax lines from the 
station 
directly to the antennas ?

Can you describe the nature of the interference ?  Broadband hash on every band 
when transmitting on XX meters ?  Loud, raspy harmonics ?  etc...

73,
Steve, N2IC

-------------------------------------------------------------------------
I am trying to track down a source of inter-station interference between
my two radios when using them for SO2R contest operation.

My SO2R antenna switching system is located at the tower base.  Two
TopTen 6-way relay boxes are mounted on an aluminum plate, as well as 6
minibox-enclosed A/B relays.  The plate is grounded to my tower ground
by a short, direct #2 copper wire.

The TopTen boxes are bolted to the plate.  The Miniboxes are mounted to
it with a pair of metal tapping screws each.

I did not use Noalox between any of these enclosures during
construction.  My question -- can I rely on the bolts and metal tapping
screws to make a good connection between the shielding boxes and the
aluminum plate?  In terms of RF shielding, how important is it to have
the shield boxes well connected to a common ground?  Would it likely be
worthwhile to disassemble everything and apply Noalox?  Alternatively,
should I figure out how to run some sort of dedicated grounding
conductor among the boxes and down to the tower ground?

TIA

-- 
73, Pete N4ZR
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