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Re: [TowerTalk] grounding

To: Dave Vondrasek <n5ito@davidv.net>
Subject: Re: [TowerTalk] grounding
From: Gary Schafer <garyschafer@comcast.net>
Reply-to: garyschafer@comcast.net
Date: Sun, 09 Oct 2005 22:37:31 -0400
List-post: <mailto:towertalk@contesting.com>

Dave Vondrasek wrote:
  On the radio side of the
> Bulkhead connectors, each has a Alpha Delta Transi-Trap Lightening Surge
> Protector (ATT3GHP) rated at 2000 watts each up to 3GHz. The ground post
> from each of these is also feed down to the Grounding Bar with #4 stranded
> copper wire. 

Hi Dave,

It sounds like you are on the right track. I would install more ground 
rods with more radials going out from your common connection point. 
Especially at the house end. It sounds a little light there. Even just 
some buried radial will help.

You should also install some protection device for the power system. A 
whole house protector would not be a bad idea. With the main panel right 
at your single point ground it should work rather well.

I am not sure but I think that the NEC wants to see a direct connection 
to a ground rod right from the service entrance panel. If 2 rods are 
required because of high ground resistance the second rod, if I remember 
right, is supposed to be connected with a continuos length of wire with 
the first and the panel.
You can then run as many leads as you want from those ground rods or the 
power ground lead over to your common point ground connection

I don't know much about the alpha delta coax devices but I don't think 
that they have a capacitor to isolate the equipment end. If not that 
means that the lightning voltage on the line would first have to burn 
through, for example, the receiver front end coil in order for the 
voltage on the cable to rise high enough to fire the gas tube. Not what 
you want.
Also a single device that is rated up to 3 ghz will probably not have 
the proper gas tube in it either for the band of interest. That means 
that the arc point will be way higher than optimum.

If I remember right, the only thing that is in the polyphaser rotator 
protection boxes are some large mov's from each line to the ground 
connection. I put those on my rotator line and got the mov's from 
mouser. About 69 cents each??

Just remember to keep your lead in jumpers from your common ground point 
clear of the cables on the other side of the protection devices and away 
from the ground leads to the rods.

73
Gary  K4FMX


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