The station equipment is all on the same main, but the arc was between two
coax cables, both tied to the main grounding bulkhead.
I think I'll follow Polyphaser's recommendation on the grounding point.
It's worked so far and the tower gets hit on an average of 3 times a summer.
Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
To be completely properly done, the AC power should also come in through
your bulkhead "ground window" with power line protectors at the ground
window. It doesn't take much of an impedance difference between lines
coming in to let the voltage rise very high.
If you can't get the power in through the window, the next best thing is
to run the feed for all the power in the shack over to the ground window
and place protectors there and then feed the shack from that point only.
73
Gary K4FMX
In that case, explain this:
My cables come in through a bulkhead. Each cable goes through a
PolyPhaser (bulkhead connector type) in that bulkhead. The radio station
is on a large desk that sets against the West wall. To the left of that
desk is a computer desk with the computer that serves as control, packet,
and sometimes logging.
I had the cable to the 440 array disconnected from the Alpha-Delta coax
switch for the UHF/VHF antennas. The end of the cable with the PL-259
attached was laying on the desk top, below and a bit to the side of the
antenna switch for a total distance of about 10 inches. Both duo-band
144/440 rigs set on top of the hutch above the antenna switch. The
switch was in the 144 MHz position.
Remember, all these cables and others go back through that grounding
bulkhead.
I was at the computer keyboard on the main computer which is on a desk
against the South Wall which is directly to the East of the other
computer desk. Both Duobanders (the second connects to a colinear
vertical side mounted low on the tower) and the 756 Pro were operating as
well as all 4 computers on the Cat-5e (hard wired) network.
Lightening struck the tower and there was a briliant flash from a very
bright arc accompanied by a lound "bang" from the end of that cable up to
the antenna switch.
Other than Both UPSs resetting and the network reconnecting there was no
indication that anything had happened.
However it's only 8 feet at most back to where the cable laying on the
desk and the cable tied to the switch connect together. There was no
damage to any polyphaser.
It must have been a very rapid rise time to that strike, but with all
rigs bonded together externally as well as through the cables there was
no damage.
Maybe that low inductance ground doesn't do anything, but after that, I
will certainly continue using them in all my installations.
Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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