> One might want to check the NEC to see if flashing meets
the code
> requirement. In my recollection it requires only that the
lightning ground
> be bonded to the service entrance ground with an AWG
something wire of
> either aluminum or copper (the gauge is different for the
two metals).
That won't save you or even help much for lightning.
Especially if the lead is long.
> Lightning needs to get to ground by the shortest path,
hopefully not
> including your rig. I'd keep the lighnting path totally
separate from all
> the other grounding paths, with a single interconnection
to meet NEC
> requirements.
How do you sort lightning out from other broad spectrum
signals? I've never seen such a device.
You need ONE ground system common to everything. That one
ground system should be designed to do it all.
>Hopefully, your lightning ground is lower impedance than
the
> utility ground and negligible current will flow through
the interconnect.
That would be the worse possible situation Jim. If lightning
hits the power line, the path would be through the house
wiring and the radio into the lightning ground. This is why
we should ALWAYS have a good lightning ground common to
everything. The loop currents from the powerline into the
station ground are the worse possible and most common
events.
> If it's the "3rd prong" electrical safety ground (chassis
ground for
> equipment), it needs to be connected to the wiring system
green wire ground
> in an appropriate manner. It's just there in case the
line AC shorts to the
> case so that you don't get shocked. I'd go as far as to
think about putting
> an RF choke (rated for the expected fault current, say
30-40 Amps) in
> series, just to make sure that your green wire ground
doesn't become an RF
> path.
So what about the other two wires, the neutral and hot (or
two hots and a neutral for 240)? They are RF paths also.
Choking one out of three won;t work, and will actually
subject the radio gear to even more stress than not having a
choke.
If you have an RF ground issue where the station power line
ground is carrying high RF current, the antenna system needs
repaired!!!
> If by station ground you mean some sort of single point RF
ground, that's
> quite an ordeal to create with any sort of collection of
equipment, and
> would theoretically require some sort of galvanic
isolation (transformers,
> usually) in the rf feed lines, so that the shield doesn't
wind up being an
> "alternate path". Classical tree grounding systems are
very difficult to
> arrange, even with stuff that's theoretically designed to
be used in such a
> system (like HP/Agilent lab gear). At work, we spend a
fair amount of time
> and money trying to do these kinds of things for ground
support equipment
> (GSE) racks to hook up to spacecraft, and wind up with
lots o'bucks in AC
> isolation transformers and RF isolation transfomers and
such like.
If the gear is properly grounded, the cables aren't an issue
at all. Isolating cable shields is unnecessary unless the
staion is laid out wrong and has antenna issues.
73 Tom
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