A GFCI measures the common mode current flowing on the "hot" and
"neutral" conductor combination, and is designed to trip quickly when
this exceeds a small, set value (indicating that the individual currents
on the two conductors are unequal). And common mode current is just what
your signal is inducing on those wires. What you need to do is block the
common mode RF without upsetting the detection of common mode 60 Hz AC.
What I'd try is to clamp a ferrite core over the combination of black
and white wires on each side of the GFCI. A single pass through most of
the common ferrite cores should have a very low impedance at 60 Hz, so
shouldn't inhibit normal GFCI operation, but would add significant
impedance to the common mode RF. I've never had to do this, though, so
it would be interesting to hear from people who have had to deal with
this problem.

Roy Lewallen, W7EL

John, N9JG wrote:
I am using an Orion to drive my Drake L-4B, and I operate mostly on 40
meters. My antenna is a 110 feet long dipole, center-fed with open-wire feed
line, and elevated about 30 feet with the support for one end attached to
the house chimney. My shack is in a 2nd floor bedroom, and the circuit
breaker panel is located in the basement at the opposite end of the house.
The house has a brick exterior, and one end of the antenna is only a few
feet from the shack.

When I operate high power on 40 meters, a GFCI equipped circuit breaker,
which is located in the house circuit breaker panel, moves to the open
position. None of my station equipment is attached to this breaker; this
particular breaker powers four outlets in the garage and two outlets on the
house exterior. None of these outlets are normally in use. Is it possible
(or even desirable) to install one or more bypass capacitors inside the
breaker panel, and immediately adjacent to, the ground-fault circuit
interrupter? If so, what type of capacitor is recommended?

John, N9JG