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Re: [TowerTalk] Grounding Roof-Mounted Mast

To: "Kevin Hemsley" <>, <>
Subject: Re: [TowerTalk] Grounding Roof-Mounted Mast
From: Jim Lux <>
Date: Wed, 06 Sep 2006 17:11:18 -0700
List-post: <>
At 02:05 PM 9/6/2006, Kevin Hemsley wrote:
>I had a question posed to me today that I'm not sure what to 
>recommend. The installation is at a commercial building. They wish 
>to install a 2M vertical on top of a two-story building. They 
>currently have a 60' tower with HF antenna that is located 150' from 
>where a new mast will be installed for the 2M vertical. They want to 
>ground the mast, and wanted to know if they should run a separate 
>ground wire for this mast, or to run a ground wire to the tower 
>which is approximately 150' away. A direct ground wire will be about 
>75' from the mast to the ground. Any thoughts?

Direct ground wire of 75 ft vs a wire that is 150ft plus whatever the 
length is from tower to ground?

Seems a fairly straightforward choice.. go with the shorter wire.

Commercial building implies complying with NEC which also has stuff 
to say about such things, not the least of which is that direct 
connections to the ground are preferred. Probably with a AWG 6 copper 
wire, but possibly AWG 10.  It depends on the situation: 810-21 
requires AWG 10 copper run in as straight a line as possible.

for a good handbook that will point to the right sections of the NEC 
(specifically Article 810)

But one thing you didn't describe.. where is the coax from this 2m 
antenna going?
NEC will require some form of grounding of the shield at the entrance 
point (and possibly the center conductor) (i.e. listed antenna discharge unit)

Jim, W6RMK 


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