FW: [TowerTalk] Re: getting coax into shack thru wall

[Dave D'Epagnier]

> Hi Steve,
> 
> >        " A nice low impedance path from the tower to the house" is a
> good
> > start. Yes, it's not a 'ground system' but it's something that needs
> to be
> > done.
> 
> Tom Rauch wrote:
> You are welcome to do that at your house, but I won't do that as a 
> "rule" at my house or at most of the commercial installations I 
> oversee.
> 
> My next closest tower is 250 feet from the house, and 200 feet tall. 
> It is grounded by many thousands of feet of radials covering a ten 
> acre pasture. That radial field cuts off before reaching the power 
> line ground and house.
> 
> At my "last line of defense" at the edge of the pasture, I have 
> lightning retarding chokes both before and after a separate 
> driven rod independent ground. When I know of a storm, or when I go 
> away, I pull the plugs on ALL the cables at that point and pull 
> them back several feet.  
> 
> Tom, with this senerio aren't you providing a low impedance path to
> house ground through your antenna coax shields? The idea of providing
> a low impedance alternate path to ground via copper strap is to let
> the current flow through it to your house ground grid (outside the
> home) instead of through your coax shield and into your home. 
> 
> The last thing in the world I want is to bring any direct strikes 
> that might elevate the earth around the tower into the house, where 
> the current might cause problems. I want to minimize coupling between 
> the tower and tower ground and the house and house ground, while 
> letting EVERYTHING in the house rise together and everything at the 
> tower do the same. 
> 
> How do you isolate your coax shield from house ground then?
> 
> >What a 'lightning protection system' should do is have everything 
> >bonded
> > together to minimize potential differences. It's these potential
> differences
> > that cause the arcing and assorted damage to equipment.
> 
> That's true IN the house, or ON the tower, but you certainly don't 
> need to make the house ground follow the tower ground if you can 
> avoid it. If the tower is right against the house, the best idea is 
> to bring grounds and cables all up together with minimal potential 
> difference. If the tower is remote from the house, keep the grounds 
> isolated but STILL use the common point method at each end of the 
> system.
> 
> If the distance is greater, the problem becomes one of  isolated 
> systems. Keep them that way if possible.
> 
> 73, Tom W8JI
> w8ji.tom@MCIONE.com
> 
> 
> regards,
> Dave
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> 

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