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LF: Re: Static effects

To: [email protected]
Subject: LF: Re: Static effects
From: "Tenty" <[email protected]>
Date: Tue, 19 Jun 2001 18:29:24 +0100
Organization: Holland Data and Wireless
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
I had this problem when I was still living in the Netherlands and my
antenna  for HF was on top  of a 13 story building..
My very thick coax was running true the living room to the shack and I
heard from time to time...tick... tick and my wife didn't know where it was
coming from...No storm was audible ..
Well it  was.... little sparks  jumping between the shield
and the inner conductor!
Also did see sparks jumping between the center of a PL259 connector
and the outside ring at other times!..
So be aware!

73, Bob ve3tok / pa0tok

----- Original Message ----- From: "Alan Melia" <[email protected]>
To: "LF-Group" <[email protected]>
Sent: June 19, 2001 14:48 PM
Subject: LF: Static effects


Hi All, I am not too sure about Dick's theory. During a period when
electrically charged clouds are passing overhead there are extremely high
vertical gradients. Imagine a cloud at 3000m charged to 900kV (a modest
amount) .....underneath it there would be a gradient of 300V /m thus a wire
at 10m would acquire a charge of 3kV wrt gound (This may be modified by the
fact the the cloud will induce an equal and opposite charge in the ground so
the field may be 600V/m) Thus even Dick's floating wire will become charged
up to about 3kV and a 600pF cap charged to 3kV makes quite a nice flash when
shorted. I have certainly seem little sparks bridging from a disconnected
aerial wire to earthed metallic trunking and central heating radiators, even
when there was no storm audible. This is why TV braid breaker filters have a
bleeder resistor installed. Rik's bleeder resistors would do the job nicely.
Being a coward, I ensure that if possible, the end of the aerial is outside
the house and grounded during a storm. This is probably one time when lossy
wet trees around the aerial are a positive benefit !!

Cheers de Alan G3NYK
[email protected]

Cheers de Alan G3NYK






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