[TowerTalk] lightning protection at towers and bunkers on former AT&T microwave relay sites

[Roger (K8RI) on TT]

I can only give anecdotal (results for one site) on damage mitigation 
from lightning strikes.
I do not use porcupines.  I use a "conventional" approach: IIRC The coax 
shields are grounded at the top and bottom of the tower as well as at 
the CPG.  I use polyphasers at the CPG as well.  The entire system is 
grounded though a network of ground rods and bare #2 copper cable. There 
is also a double run of bare #2 from the tower, along the conduit to the 
CPG. There are 3 runs of bare #2 about 80 feet long radiating out from 
the tower with 8' ground rods about 6' out from the tower base and every 
16 feet thereafter. All junctions between the bare #2 and the ground 
rods are cad welded.  There is a total of 32, or 33 ground rods and a 
bit over 600 feet of bare #2 purchased before the price went up.

The first 6 years after the ground system was finished the tower took 17 
visually verified strikes. One strike removed ALL of the water proofing 
and silver plating from the connectors at the top of the tower.  The 
rigs were rarely disconnected, yet there was no damage to any rig.  
Unfortunately, I can't say the same for my CAT5 network and induced 
voltage from a nearby strike.
http://www.rogerhalstead.com/ham_files/cablebox.htm

The system is in a constant state of change  and has been reorganized 
(rerouted) so at present I can and normally do disconnect the rigs in 
the house when they are not in use.

"My opinion" is "there is no substitute for a good ground system, but no 
practical system offers 100% protection."

I would add that in my opinion, just disconnecting the coax and throwing 
it on the floor is a very dangerous practice. Disconnected coax should 
be grounded, otherwise you're repeating Ben Franklin's experiment using 
wire instead of string/twine.

73, Roger (K8RI)


On 5/20/2017 Saturday 5:12 AM, David J "Dave" Windisch wrote:
> Hi, all concerned:
>
>   
>
> Tks much for the speedy replies and suggestions.
>
>   
>
> Searched NFPA discussion site and found no refs to the Nott Ltd "porcupine
> device" debunking mentioned in this thread.
>
> Anybody have a cite, pls?
>
>   
>
> At some time, after my site was decommissioned, it was stripped to the
> walls, and most ferrous and non-ferrous materials not too heavy, red-hot or
> nailed down, disappeared.
>
> There's lots of empty conduit.
>
> Still, I've found all if not most reconnect-points to the building and tower
> grounds.
>
> My crude ground testing is simply running an AC hot conductor around the
> site to ground wires and temporary driven rods, and seeing how brightly
> tungsten lamps will glow.
>
> It was suggested offlist that there is prolly a ground mat under the whole
> property.
>
>   
>
> Brgds,
>
>   
>
> Dave, N3HE
>
>   
>
> _______________________________________________
>
>
>
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-- 

73

Roger (K8RI)


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