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Re: [TowerTalk] another Lightning Protection Question

To: towertalk@contesting.com
Subject: Re: [TowerTalk] another Lightning Protection Question
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Date: Tue, 14 Sep 2010 13:20:02 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>

On 9/14/2010 8:29 AM, Bill NY9H wrote:
> The tower is 130 feet from the house, the cables coming down from the
> crank up, off the tower into a cabinet where the different
> polyphasers are affixed to the bussbar&  ground lines to the 9 ground
> rods on radials,,,,
>
> my question :  at he house i have redundant polyphasers
Jim has already said it, but the redundant polyphasers are the ones at 
the tower.  What do they protect there?
The only thing I'd add would be a heavy grounding cable from the tower 
to the house and a "radial ground system" out from the tower with ground 
rods about every 16' along all those ground cables including the one 
between the tower and house.  130' is not all that far.

Another point is the capacitance and inductance in the coax as well as 
capacitance from shield to earth will reduce the voltages from a strike 
at the tower so the lightning protection at the house entrance does not 
have to work quite as hard. OTOH this is neglecting induced voltages 
which can even be coming from the wiring *within* the house. Hence put 
the protection and single point ground as close to the expensive 
equipment as possible.  The farther from the equipment those are placed 
the less effective they are in protecting it.

It's not normally practical to put the SPG and lightning arrestors at 
the equipment BUT if the SPG is fairly close to the equipment voltages 
on the grounds, house wiring, and coax at that point will tend to rise 
and fall together.

73 and good luck on the installation,

Roger (K8RI)
> ( already own
> them )...on another set of 5 ground rods at the house...    would you
> think it makes much difference whether the protection devices(
> assuming an induced wave) need to be outside... this stuff is going
> in this week ,,,I was just thinking of putting the second set
> inside,,,, the wall is cement board.......shouldn't burn"
>
> tnx
>
> bill /     new to 3 land
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