I have a Sports Cub with a Garmin SL-40 (not installed by the factory). On the ground when I transmit everything works fine but in the air using the pilots PTT I get either nothing or really broken transmissions. I figured out pressing the co-pilots PTT allows me to transmit fine. Looking at the SL-40 manual I'm figuring the PTT button grounds the TXKey line causes the radio to transmit.

So I'm guessing I've either got a bad PTT switch or a bad ground (caused by vibration in flight). Any thoughts ?

Does anyone know the pin out for the connector from the stick so I can check out the switch. Where is it grounded I assume both wires from the PTT switch run back to the radio ? As far as I can see they disappear into the battery box. The stick was replaced in the factory a few weeks ago so I'm assuming it's not likely to be a bad PTT switch.

I would like to stop flying with one hand in the wing root pressing the co-pilot switch ;-)

Robert