[RFI] Ground rod placement
JACK ALTHOUSE <Palomar@compuserve.com>
Wed, 13 May 1998 00:46:14 -0400
<With a field strength meter I determined the ground strap and rod were
both radiating RF - w4des>
The problem of RF current in the ground strap is not the fault of the
grounding. As WA9ENA pointed out, if your load is balanced and fed with
open feeder lines through a tuner, your ground current should be
negligible. This is also true if you are feeding the antenna with coax.
All the transmitter's RF output, except for a few microwatts leakage, comes
out the SO-239 antenna connector. With coaxial cable all the RF goes up the
inside of the cable to the antenna where it is radiated. Ground is not
But if the antenna is without a balun or if the cable does not come
straight down from the center of the antenna there can be RF current on the
outside of the shield. This will show up in the ground lead. You can also
pick up RF on the rotor cables or any other wires coming down. That ground
current has to come from somewhere. By treating the cables with ferrite
chokes or rerouting them you can eliminate this current and there will be
none in the ground lead.
My suggestion is to start up in the air to get rid of the ground current.
The RF clamp-on ammeter is helpful in tracing the problem. It is made by
(I do have a connection with Palomar Engineers)
Jack Althouse, K6NY
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