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[Towertalk] grounding system

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Subject: [Towertalk] grounding system
From: (Tom Rauch)
Date: Mon, 29 Jul 2002 22:02:46 -0400
> Don't be bashful Tom, tell us how in detail please. With all this talk
> about SPG's, etc., it is still hard to visualize. I do have the
> 'Grounds for lightning' and have looked at all of the web pages, but
> it is still difficult to determine what is right.

Think of what you don't want, and avoid it. What you absolutely don't 
want is a loop that allows current to flow through equipment from the 
power lines, telco lines, or tower (they are likely "hit" in that 
order) into the heating system, water pipes, the other utility lines, 
or the feedlines or control cables.

Getting the stuff to **ground** is the job you should do at the tower 
and at the service entrance of the house. 

Now if the leads run some distance from a common ground, unless they 
are all inside a huge Faraday shield like a real screen room, you had 
better keep them all in an equal conductor length tight bundle or 
reconnect all of them again at the end where the gear all is.

Otherwise you have different path lengths and paths, and you can have 
a loop through your gear.
> I have a 5 foot 1" by 1/4" copper bus bar running on the wall on
> stand-offs behind my equipment and the equipment grounded to it (in
> different places along its length) with webbed straps and it connected
> to my outside ground system with about 7 feet of 3/0 copper wire, but,
> no bulkhead panel.

What is very important is the power line safety ground be connected 
to that buss system, and the line bypassed with MOV's to that ground 
along with telco and any other conductors entering the room...and 
that means every conductor including cables.

I'm doing a system now for a friend who unwisely built a room with no 
hope of a ground system anywhere close, and he has antennas and 
feedlines scattered all around different directions.

What I am doing is using a high current rated outlet strip with MOV's 
that has telco and CATV connectors on it, and mounting that behind 
his desk on a metal plate. That plate is connected with flashing to a 
plate about a foot away outside the wall that has bulkhead 
feedthroughs. There is a 240 volt outlet with MOV's inside a metal 
box on the shack plate also for his amp.

All of that stuff plugs into his outlets in the room, and all of his 
gear runs off those outlets. The feedline I put in runs about 50 feet 
laying on the ground under the house to the service entrance where it 
has a grounding kit, and the others he will just have to live with, 
reroute, or remove because they are impossible to get to the service 
entrance. I suggested he just cut them off, because they are directly 
built into the wooden frame of the room and unwisely enter about 10 
feet above ground through the wooden eve of the house, where a large 
thick patio below and a big slab for a garage (with sewer pipes 
someplace in it) prevents grounding. We will take those leads and run 
them into an RCS-8 and then take one cable all the way to the service 
entrance outside before coming back in on a new cable.

He won't have a lightning or RF room ground, because he can't.  All 
he can have is a long AC safety ground to a few driven rods, and 
another long lead to the service entrance 50 feet away. 
> My cables come to the house from the tower at an eight foot height,
> which is frowned upon, but it clears everything. 

> Also, if you disconnect everything, as Pete said, what do you plug the
> inside cables into when disconnected? Grounded females on the
> bulkhead??

No, if you are going to disconnect than disconnect everything! Yank 
the wall plugs, the telco lines, and disconnect the coaxial and 
control cables **outside**. That is what my friend has to do, and now 
it will be only a few cables and plugs. If he forgets, will be a lot 
better off than he was with a mess of wires coming in from all 
directions ten feet high.73, Tom W8JI 

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