[TowerTalk] Single Point Grounding question

[K1TTT]

> 
> 
> K1TTT wrote:
> > There will always be a potential difference between them during a
> lightning
> > stroke, you can't prevent that.  The concept of a spg is to protect
> > equipment in a building.  All the wires coming in through the spg are
> > connected together so they are all at the same potential so there should
> be
> > no chance for arcing and sparking inside the building.
> >
> 
> Even that only sota, kinda, almost works.  All of my cables come in
> through a bulkhead.  The coax cable shields are grounded at the base of
> the tower AND they are grounded at the bulkhead along with the other
> coax cables,  rotator cables, remote antenna switch cables, where they
> come in the house. I've mentioned this before, but two of the cables are
> from the 144 and 440 arrays.  Both have pigtails that run from the
> bulkhead to the antenna selector switch.  I had one of them disconnected
> and laying on the desk about 8" to 10" from the switch. Lightning hit
> the tower and there was a tremendous flash from the coax laying on the
> desk to the selector switch. Yet both cables are the same length and run
> to the same grounding bulkhead.  Why the flash-over?  It sounded like
> some one fired a 12 gage here in the den. BTW both antennas are at DC
> ground.


How long are the jumpers from the bulkhead to the switch?  Could you tell
where the arc initiated on the coax, the connector shell or the center
conductor??



David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
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