I am attempting to resolve a problem for a customer with a 2008 SS who is having severe problems with transmit on an somewhat intermittent basis. When t happens ATC threatens to ground the aircraft.

The radio is a Icom IC-A200 with a Flightcom intercom. The antenna is a bent whip located on the LH belly just aft of the gear. The original installation by the builder was one of the worst I have seen with numerous shielding and other problems. We rewired it completely the second time around and got a "Clear as a Bell 5 x 5" from ATC while running the aircraft, on the ground, in the hangar. But the problem resurfaced.

We determined that it is possible to get RF feedback into the microphone if the headset is near the antenna, but not apparently when in the normal worn area.

Has anyone else experienced this?