Jerry:
My coax switching arrangement is identical to yours, i.e., the switch
is at the tower and the coax runs enter through a steel box. I chose to
install arrestors at each coax where it enters this box, before it connects
to the switch. In this way I have protected all my incoming coax lines
BEFORE they hit the switch. I have thus also protected the switch in case a
strike hits while an antenna is connected to it.
At the shack end I have no additional protectors. The underground run
to the tower is fifty feet and I cannot convince myself that sufficient
lightning energy will be coupled to the underground coax's center conductor
to be of concern. (I also ground the coax shields at a SPG panel outside
the shack.) Others on Towertalk will disagree, saying that a ground strike
near my coax run COULD induce energy INSIDE the coax, where another arrestor
would be helpful at the shack end. You decide for yourself whether this
belts-and-suspenders approach is for you.
If you follow my approach, you ought to make sure that you have an
adequate lightning ground system protecting your tower and that you provide
a positive connection to it from within the steel box the switch is in.
Don't rely on mounting hardware to provide this connection through the tower
steel; it could corrode and there goes your ground connection. I left
excess length on my tower leg ground wires so I could extend at least one
into the box. I grounded it to the back of the inside of the box with
appropriate hardware. I ran this wire into the box through a plastic
insulating that I filled with electrician's putty once the wire entered it.
I suppose you could ground the wire adequately to the exterior of the steel
box as well, but I preferred to bring it inside where it would come into
contact with the steel box in an environment protected from direct rainfall.
73 de
Gene Smar AD3F
----- Original Message -----
From: "Jerry" <grf@uneedspeed.net>
To: "Tower Talk" <towertalk@contesting.com>
Sent: Saturday, January 09, 2010 9:50 AM
Subject: [TowerTalk] Lightning Arrestor Question
>I have a box at the base of my tower housing my DX Eng. antenna switch
> box that also provides a central entry point for all the antenna cables
> (prior to going underground to the house). Will placing an arrestor
> only on the output coax from the antenna switch to the house be
> sufficient or do I need to place an arrestor on each antenna line
> entering the box and switch (the shields are all grounded to the ground
> system in this box)? Additionally, do I need to place an arrestor at
> the house's central grounding point (where it enters the shack)?
> Overkill? The grounding system is all tied together (tower, switch box,
> house entry point, and home's electrical system).
> Thanks for any help/ideas you can give me.
> Jerry France
> K7LY
> Lake Havasu City, AZ
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