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Recent Transmit background issue

So the other day I taxied from the T-hangar across the field (towered airport) to a local FBO to have them do a compression check. All radio communications with the tower/ground controller were fine, no issues.

When I picked it up the next day and called ground to request taxi back to the T-hangars, I noticed a sort of squeal/buzzing in my headset when I keyed the mic to request taxi clearance. It wasn't super loud, but enough so that the Ground controller mentioned it to me in his reply. ODD, it wasn't there the day before.

Anyway, today I removed the cowl to check for any loose or broken connections to the alternator or plug wires since it just had the compression test done. Note: The pitch of the noise goes up and down with rpm. Anyway, I found nothing apparent in the engine area. Next I did a few transmit tests outside my hangar and noticed that it only occurs when I use the front seat push to talk button/trigger regardless of if its running or not running, BUT, transmission is perfectly clear with no noise whatsoever if I used the rear seat push to talk on the rear stick. (RV-8)

So, seems I have narrowed it down to the front stick's push to talk as a culprit, but so very odd that it showed up after picking it up from the fbo.

Sorry for the long winded explanation but what might be a good place to start looking into... wiring or ground to the front sticks connections? Is the switch on it's way out ?? I have Infinity Sticks with the trigger as the transmit.

Thank you in advance for any thoughts on how to fix it.
 
Doubt the PTT switch has anything to do with it, the pilot headphone/mic wires/jacks are more likely the cause.
When you use the CP ptt those inputs/outputs are separate from the pilots.
My guess is the pilot jacks are grounding against the structure.
 
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My guess is the pilot jacks are grounding against the structure.

I agree, depending on where the mike / phone jacks are mounted, someone unfamiliar with aircraft can bump or kick the mike / phone plugs causing the jack to make contact with the panel.
 
Doubt the PTT switch has anything to do with it, the pilot headphone/mic wires/jacks are more likely the cause.
When you use the CP ptt those inputs/outputs are separate from the pilots.
My guess is the pilot jacks are grounding against the structure.

So today after work, I went to the hangar and removed the jacks (unscrewing the 1/2" nut and isolation washers) and taking it out of the holes and just laying them on a rag so it wasn't touching any part of the frame. I plugged in the headset, keyed the mic, and the noise remains :(.

When I tested the rear seat PTT I didn't hear it before because I had that stick disabled. (I have a disable switch for the rear stick because I used to do a lot of young eagle rides and I didn't want the kids messing with trim, flaps or transmitting) As soon as I enable the rear stick and used the PTT it could be heard the same as from the front PTT.

Additional Thoughts, suggestions ?
 
clean the antenna

Are the antennas in the exhaust slipstream or otherwise oily? This is just one pellet in the shotgun blast approach, but it is free and only takes 5 minutes. I had some comm issues pop-up and I received a suggestion to clean the antennas. Evidently, they can get oil covered and that can lead to grounding issues. Thoroughly clean them, as in with a degreaser, then some scotchbrite buffing, then acetone or similar. This solved my problem.
 
Some sort of Power cable against headset cable?

I had a power cable run from my USB power port under my panel to where I plug into my iPhone or iPad mounted on LH side of panel. It is an ordinary Apple charging cable that runs under the seat cushion. I also have my headset cables runs along under seat cushion. I had never had static in my headset but did recently for the first time. I separated the cables running under the seat cushion and every thing seems fine. They must have just been crossing or running along side each other enough to cause the static.
 
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