T. A. Russell wrote:
> LIGHTNING STRIKE SURVEY
> 1 - Have you ever taken a direct hit to either antennas or towers?
It's hard to tell whether a hit is direct or not, but I have had two
hits,one last year (#1) and one last week (#2).
> 2 - If YES, was your damage
> MAJOR, MINOR, NONE ?
#1 Major - radio, computer, printer, 2 tv's, vcr, phone answering
machine,about $1500 total.
#2 None - unless you count 3 fuses blowing.
> 3 - How is your tower grounded?
> Direct burial in ground
> Concrete base with ground rods (number? How attached?)
#1 & #2 Tower into 4' concrete base with 8' long buried copper strap
-about 8" wide. Feedlines in conduit with ground wire outside conduit.
Cable & power had separate grounds. 2 - 4' ground rods (ledge).
#2 - Added #2 wire between tower & service entrance ground.
(They are 100' away from each other.) Bonded cable and power grounds.
> 4 - Are your feedlines and rotor/control cables
> Above ground
> At ground level
#1 & #2 - Buried about 4-6" in a 4" PVC pipe. A 40' run to the house.
> 5 - How do you protect / isolate your radios / rotor control boxes /
#1 - no protection#2 - Radios were unplugged, but connected to the
antennas and each
other. Antennas were grounded by antenna switches.
The rotor & antenna switch control cables were protected by
Polyphaser 8 wire lightning arrestors. (I think they are gas
discharge tubes.) The antennas were also protected by
Alpha-Delta lightning arrestors.
Most importantly, all of this stuff was mounted to a 6"x2' long
piece of aluminum channel stock, acting as my "ground window".
The 110 & 220 power lines were also brought to this ground
window and protected with Polyphaser 600 joule arrestors.
The three fuses that blew were on the 110v & 220v lines.
Here is what I think happened. During a large storm this week,
either the tower was hit, or a large voltage was induced into the
tower and feedlines. Most of the energy went to the tower or
power grounds, but some went towards my equipment via the
feedlines, looking for an alternate route to the power line ground.
It traveled to my ground window and somehow found
a path (I don't know how) to the hot leads of the 110 & 220.
This current blew one 110v-15A and two 220v-20 amp fuses.
I have not noticed any other damage. Needless to say,
I'm *very* pleased.
Some other notes -- I don't have lightning protection on my phone
line for the computer, nor on the network cable to my son's
computer. This omission could have ruined the ground window.
Fortunately, I had disconnected both of them before the storm.
No other fuses/circuit breakers in the house blew.
The first storm (#1) was worse, but I'm still pleased with
the results of the steps that I've taken to protect things.
> 73, Tom N4KG
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