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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