On Wed, 8 Sep 2004 22:39:22 +0100, Ian White, G3SEK wrote:
>The cure was to place an RF block in the shack mains
>feed, using a three-wire filter which includes a ground-line choke.
What you really did was reduce the current flowing in those unintential
antennas by adding
impedance to the return path. That was a band-aid made necessary by the pin 1
problems
in the gear. The more fundamental fix would have been to prevent those currents
from
flowing into the gear by fixing the pin 1 problems.
Also, it is NOT a good or safe technique to place high impedances in ground
leads.
Lightning wants to see a low impedance path to earth. The peak energy of
lightning is
around 1 MHz, and it is a very broad peak (that is, lots of energy both above
and below 1
MHz). When you place a choke in the ground lead, you essentially throw away any
lightning
protection by defeating the required bond between safety grounds. Not a good
thing.
Mother nature has a way of reminding us that such techniques are not a good
idea.
Jim Brown K9YC
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