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Old December 6th 05, 11:51 PM posted to rec.radio.shortwave
 
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Default Lightning Induced Voltage Transients Into An Antenna


Robert11 wrote:
Hello:

We get a lot of lightning strikes around here, and was wondering about this:

Presently have a receive-only random length wire running around the inside
of my attic.

Guess I'm not really too worried about "direct" lightning strikes; if there
is one I imagine I have a lot more to worry about than the radio.

But, does the roof provide any protection from nearby lightning strikes
inducing a high transient voltage
into the indoor attic antenna wire, as compared to if I had the wire antenna
strung outside the house ?
Again, from an induced voltage standpoint concern.

Or, is the fact that it is indoors really meaningless ?


Thanks,
Bob

----------------------------------------
Since 1962 I have always had a "long" wire antenna of one sort or the
other up.
And in that time I think I have never had a direct strike. I did have a
nearby bolt
take a nearby tree down. Reduced it to pencil sized splinters. That one
damaged
the coax lead in.

I used to enjoy paling a neon buld (NE-2) from my antenna to ground.
This was
before I knew about matching transformers. I gave that practice up
during the
aprroach of a nasty T-storm that was about 20 miles away. My little NE2
was
flashing to beat the band. Then BANG!. the bulb was gone. I was lucky
in
that I had the bulb inside of a pyrex florintine flask. It cracked the
flask. My
parents came storming upstairs, they thought I had set a firecracker
off or
dischaged a firearm. This followed an event that happened about 2AM.
Dry snow induced enough electricy into my antenna that the "lightning
protector", spark gap, was sanping loud enough to awaken my parents.
I slept through it,,,, heck I have slept throu a 3 alarm fire 2 doors
down.
Dad insisted that I ground the the antenna lead in. We installed a
classic
horrow movie knife switch the next evening.

So yes, lightning can and will induce enough energy to be damaging.
It is possible to have enough protecton equipment to minise the risk.
But it isn;t easy or cheap. The best solution for most of us is to
disconnect
the antenna and short it to ground when not in use.

posted a link to a very good web page that shows,
as RHF said, "getting the job done right"

www.knology.net/~res0958z

Like I said, it ins't easy or cheap.

I wish my system was even half as good as his!

Terry

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