Radio issues (RV-12)
I'm trying to track down a transmit issue with the SL40 and Flightcom 403 intercom in my RV-12. My radio installation has never worked particularly well, and initially had a loud squeal until I adjusted the SL40 settings as others have previously posted, so I know they are OK. However every time I press the PTT button, I get a loud steady tone in the headset (sidetone?). It is possible to hear voice over the tone on a nearby handheld radio, but the reception is pretty bad, and in the air is reported as unreadable. This happens even with just the master and radio on and everything else off. My mic jack has isolation washers on it as per the plans, and both pilot and co-pilot sides have the same problem. Swapping headsets makes no difference. It was suggested the problem may be in the 403 rather than the SL40. Pilot/passenger conversation works OK. The problem only occurs when the PTT button is pressed. Any ideas?