[PCR-1000] Polarity & lightning

Mon, 18 Aug 2003 14:28:40 -0400

Man we run three of those Klystron tubes in an old RCA transmitter.  =
70kw up
to about 1ghz.... That thing takes some juice (480 3 phase to be =
exact)...
Vapor phase cooling and all.  It's a fun beast :)

Here is my take:  It's already arcing 5 or more miles through the
atmosphere.  Not much is going to stop it from finding ground =3D)

-----Original Message-----
From: John [mailto:[email protected]]=20
Sent: Monday, August 18, 2003 1:17 PM
To: [email protected]
Subject: [PCR-1000] Polarity & lightning

All electricity has polarity, even the static kind.  The polarity of a
lightning charge does determine how you position diodes if that is what =
you
are doing, but the bottom line is the electricity in a passing cloud is
seeking a ground and it tends to follow the path of least resistance.  =
If
you have a convenient lightning rod (your antenna) encouraging it to =
come
home it does just that, and ZAP, the deed is done, and usually vaporizes
everything along the way.

If you provide lightning a path to ground, your little coils and diodes =
will
be an absolute JOKE.  Years ago when I was in the USAF and a  =
maintenance
guy on a 50KW SSB transmitter hooked to a LPS antenna we took a =
lightning
hit.  We had every protection is place it was possible to have, but it
really didn't matter.  First the lightning blew out a 2 foot long hole =
in
the side of our 6 inch nitrogen filled copper tube transmission line.  =
Then
it finally grounded in the foot square, 3/4 inch thick aluminum encased
final amp.  That box had four ceramic/metal klystron tubes, each of =
which
weighted several pounds, along with associated circuitry.  When we =
finally
removed it's cover the only thing left was a half inch thick red dust
coating on that enclosure.

I suspect you might be saver disconnecting your antenna and not =
grounding at
all but that is just my theory.

John

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