[TowerTalk] Station Ground

K8RI on Tower Talk k8ri-tower at charter.net
Fri Jan 14 23:24:25 EST 2005

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)

> 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
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