VHF Com transmit problems

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?

Hi sebrof
Welcome aboard.
I believe you will find an extensive thread on this issue. I fly a Vixen with an A210 and antenna in similar location.
Occasionally I get feedback on transmit using my lightspeeds but not with DC .
Can't figure it out so now I just carry the old DC in case it screws up.
Where is your SS stationed? Not many kfers in our area. Come on down ,I'm in Penticton .
Good luck
Don

Hi Don,
Well the aircraft is in Oliver and it is Penticton ATC that usually complains.

I own an avionics shop in Kelowna and have occasionally had instances of RF getting into unshielded or poorly shielded headset cords so I was looking for this. In this case the owner has 2 new DC's and we rewired the entire VHF com and intercom with properly shielded wiring.

I suspected the RF because being fabric the aircraft is not a good shield and the antenna is very close to the pilots. Not very easy to move now unless we can prove that is the problem.

Of course I have never observed the problem, and we were on the ground in Oliver when I got the "Clear as a bell" report. Which I also got again when I was in Oliver a third time.

Sorry not much help here. I made up a aluminum ground plane that lies on the fabric floor at the antenna. Not sure it helped. I use the built-in intercom.
Both CYYF and CYLW towers report 5x5 but with background noise. Probably ignition interference. Good luck
Don