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[TowerTalk] Protecting a Tower Relay Box

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Subject: [TowerTalk] Protecting a Tower Relay Box
From: "Mark Robinson" <>
Date: Tue, 17 Aug 2010 19:40:13 -0400
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I am intending to fit this relay box at the 80 foot level on my tower

I planned on using wire like this to feed 12V to the relay

since it was readily available and cheap. I know that I don't need wire this 
thick but it is cheap. I plan on using a cheap Radio Shack 12V psu in the 
shack. I  don't want this cable tied into my expensive Astron 12V supply 
which could be damaged by lightning and then feed the pulse into any other 
equipment tied to the shack 12V DC bus.

I am planning on protecting the 12V line with "MOV Metal Oxide Varistor 
24Z50 Harris 100J" on each line to ground at the base of the tower and at my 
SPG box. Adding some inductance just before the entry to the house might 
help too.  I started thinking about this and was figuring that it might help 
to ground the 12V return wire to the tower at the top and bottom of the 
tower and at the SPG box. I wouldn't need MOV's on that return line then. I 
am not sure if this will provide any benefit from lightning. Taking this 
thought a bit furrther, maybe I could run the power down the tower using 
some old coax. The center conductor would carry the 12V positive and the 
return would be on the shield which would be grounded at the top and bottom 
of the tower and at the SPG box. Will using coax in this way provide any 
benefit over the wire from Lowes

thanks  Mark N1UK


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