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Re: [TowerTalk] Grounding of Amateur Radio installations

To: Pete Smith <>, (Phil Camera),
Subject: Re: [TowerTalk] Grounding of Amateur Radio installations
From: Jim Lux <>
Date: Fri, 08 Dec 2006 11:25:42 -0800
List-post: <>
At 06:36 AM 12/8/2006, Pete Smith wrote:
>At 09:18 AM 12/8/2006, Phil Camera wrote:
> >"Something to bear in mind is that, in general, most jurisdictions 
> don't bother enforcing the NEC for amateur radio antennas"
> >
> >
> >Which actually is too bad because these guidelines are exactly the 
> measures one should do for a properly installed safety & lightning 
> prevention grounding system.  And every single measure must be in 
> place or else you're leaving an entry route for Mother Nature to bite you.
> >
> >Phil  KB9CRY
>Which is fine if your shack is in an optimal location so that you 
>can do everything by the book, but what if it's on the second floor 
>of an old house?  I attempt a single-point ground in the shack, but 
>it is a long way from earth ground.  I am not so naive as to believe 
>I'm going to be able to survive a hit if the cables from my tower 
>are connected.  Is simple disconnection at the shack entrance up to 
>code?  I don't know, but it's all I have.

Nothing in the NEC would prevent you from doing things on the second 
(or, for that matter, the tenth) floor.  All it says is you've got to 
interconnect the grounds (in a specified way), keep things away from 
other circuits, and that stuff about copper clad steel or bronze wire.

The NEC requirements aren't about withstanding a lightning hit, for 
the most part.  It's more about avoiding shocks and fires from more 
mundane causes.

Interestingly, disconnecting things may actually make you 
non-compliant, depending on whether you break the ground.  Here's a 

You have a grounded (as in bonded to the system safety ground per 
NEC.. not necesarily at "rf ground") coax entrance panel with 
feedthrough bulkhead connectors, so there's a coax connector on the 
outside (connected to the antenna feedline) and a coax connector on 
the inside (going to your rig).  If you disconnect the inside 
connector, you're probably OK, NEC wise.  If you disconnect the 
outside connector, odds are, you're no longer NEC compliant, because 
that connector was the way that the "antenna grounding" conductor 
(i.e. the coax shield) was bonded to the ground system.  (in the 
cable TV biz, they run the coax through a little block that 
permanently connects the shield to ground, and isn't intended to be 

Likewise, depending on how your relays are set up (particularly with 
openwire line, where both sides usually get switched) you might have 
a situation where there's no path from antenna to ground.

It's sort of an open question whether an antenna with no DC path from 
antenna to feedline (e.g. capacitively or inductively coupled) could 
be NEC compliant.

Jim, W6RMK


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