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[TowerTalk] Re: Coax shield grounding

Subject: [TowerTalk] Re: Coax shield grounding
From: James <>
Date: Sun, 31 Aug 2003 11:45:27 -0500
List-post: <>
>    All commercial coax runs are grounded by removing some of the outer 
>jacket and installing a compression ground clamp (Andrew, Polyphaser, etc.) on 
>shield. The whole thing is weatherproofed and the ground wire sticking out is 
>attached to the tower. 
>    Commercial specs call for cable grounding down the tower every 100' and 
>at the bottom where it turns horizontal to go into the building. 
>    There's no problem with more connectors inline - the insertion loss is 
>insignificant. The biggest potential problem is poor weatherproofing. A couple 
>layers of tape, a layer of butyl rubber vapor wrap, more layers of tape, and 
>you're good to go with a commercial, bombproof joint.
>Steve     K7LXC
>Professional tower services for commercial and amateur 

On cellular/PCS and 2.4 GHz antenna and coax jobs, we often install lightning
arrestors and grounding straps. These are pretty high frequencies, so any 
line loss or other impairments will show up real quick.

Grounding straps are attached by peeling back about a two inch width of the
outside black vinyl jacket and placing a compression clamp of the copper
outter conductor. Since it does not open up the coax line, there is no
insertion loss or any other line impairment.

Lightning arrestors are placed at the bottom of the coax run a few feet 
from the building or outdoor cabinent entrance. There is negligable 
insertion loss.

The biggest potential problem is water entry. Proper water proofing has
already been discussed and someone had a link a a manufacture's applications
page. Basically you'll want to do a single layer of half inch tape (the
courtesy wrap - as the next layer of butyl rubber will adhere to the 
outer jacket to the point it will never come off, its called "self-fusing"
for a good reason!), next comes the butyl rubber layer and its shaped like 
a football, then several layers of one inch wide tape, followed by two 
wraps of half inch again. Always wrap "downhill" like roofing shingles to 
keep out water. Never pull the tape to cut it, use a knife or scissors.
Don't stretch the last layer too tight, just pull it about an inch extra.

For your gounding straps or ten gauge wire, make them short as possible.
Nice gentle curve, no sharp bends. Bring them out pointing downwards, no
upward swings. Crimp connect (with a professional two handed crimping 
tool - one hand if you're a tower climber) or solder them to grounding lug.
Use anti-oxidant cream on lug and mounting hardware.


See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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