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
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.
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