Radio gremlin. SL-40

I'm trying to solve a little problem with my SL-40 radio and don't seem to be having much luck.

When I'm on the ground it transmits loud and clear, but when I get up to cruise speed all I get is crackling static whenever I transmit. When I'm back on the ground it's fine again. Same problem with both the Bose and Dave Clarkes.

I set the parameters to what others have recommended on the forum, changed the PTT ground location, bypassed the intercom, looked for loose or ungrounded wires, checked the antenna, connectors etc and nothing has worked.

If anyone can solve this one for me, the beer is on me next time we meet.

Thanks.

Did someone say beer!!

Assuming the crackling audio is in your headset while you transmit (side tone) and the transmitted signal is clean and clear, I suggest checking the SL40's internal intercom is not activating with the cabin noise.

I'll take a stab at it. Sounds like possible static electricity. That is why some a/c have static wicks. More prevalent with speed and a smooth glossy paint job. I would look at the grounding and ground plane of the antenna.

Try adjusting the mic gain to a lower setting. the installation guide has instructions on how its done in the settings. had same thing in mine, lowered the mic gain to about 60 in the settings and it helped a lot.

more info

Do you mean that you do not hear yourself when transmitting? But others hear you okay? And on receive you hear others okay?

same problem

Paul, did you ever resolve this problem? I am having the exact same crackling sound when in the air. Also poor reception when talking to some (...) ATC's. On the ground and nearby control towers good reception.
Due to the 8.33 requirement I recently swapped the SL40 for an ICOM 210E, still have the same behaviour.

Static buildup local to antenna?

The BNC connector was getting by disconnected the heel of my passengers left shoe.

I cleverly solved this problem by cutting the side of a rattle can cap in a way that it would clip onto the coax and cover the joint. I also used some expanding foam and saran wrap, clipped it on and it form a perfect fit.

It took me a while to figure it out, but this created a static problem on my main com that reduced intelligibility of reception, and also regular squelch breaks.

This would continue on the ground after a flight, but not before.

The "aha" moment came when I removed it in flight and the noise instantly went away.

I don't know if something like this is happening in your case or not