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Re: [TowerTalk] [Bulk] Antenna to Shack Ground Connection

To: towertalk@contesting.com
Subject: Re: [TowerTalk] [Bulk] Antenna to Shack Ground Connection
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 03 Feb 2015 11:11:49 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On Tue,2/3/2015 8:37 AM, N3AE wrote:
Interesting side note: 2011 NEC Article 810 says you have to have a "listed antenna discharge 
unit" unless the coax shield is grounded. As far as I can tell, none of the common 50 Ohm coax 
transient suppressors (Polyphaser, Alfa/Delta, I.C.E) are "listed." I've not seen a U.L. 
sticker on any of them. Guess if you had a really finicky inspector he might get you on that. But 
the Code gives you a way out by grounding the coax shield, which is good practice anyway.

Proper installation of a Polyphaser or other similar transient suppressor REQUIRES that the suppressor be bonded to ground, which, of course, ground the coax shield at that point. The proper installation point for a suppressor is as close as practical to both ground and the equipment that it protects. If the suppressor were installed, for example, in an aircraft, the bonding point would be to the chassis/shielding enclosure.

With a tower, good engineering practice calls for the coax shield to be bonded to the tower at both top and bottom.

73, Jim K9YC
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