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Grounding issue?

rfchisholm

Active Member
I have GTR200 ... been flying without issue for 3+years.

I have recently begun to experience an intermittent tone over the intercom when I transmit while airborne. It doesn't happen when I'm on the ground, and it does not happen every time I fly. When it happens a passenger can hear it also. I do not know if those receiving the transmission can hear it ... or if it is only over intercom.

I would describe it like the stall horn tone, only it is not bold and loud, but sort of subtle in the background. And it does not last the full transmission. For example, if I make a ten second transmission, it may only be audible during a couple of those seconds, and it might repeat during longer transmissions.

While flying last night I also noticed that my fuel flow reading moved up a couple gallons during a transmit when this odd tone was present. When I saw this, as an experiment, I made a longer transmission, and watched fuel flow reading climb all the way to high fuel flow warning. When transmission stopped, fuel flow reading returned to normal. Obviously I'm suspecting electrical noise causing this ... and that my transmissions are not changing my fuel flow.

I'm wanting to know if others have experienced this. I could not locate other posting describing this, but will admit I may not have exhausted the search feature here. If there are postings already on this issue, I would welcome sharing links with me.

Those with good electric knowledge, ... do you have any ideas what I'm experiencing and suggestions as to where I should start troubleshooting this?

Thanks in advance.
 
What is the grounding point for your Red Fuel flow Cube, and what is the grounding point for you GTR-200? I'd clean them up.

Just wondering out loud if they share a common grounding point.

Or wait for Mitch from MI to respond, he's exceptional with troubleshooting these electrical gremlins.
 
What kind of COM antenna do you have? Check to make sure your antenna is properly grounded. If you have access to a VSWR meter, check that while transmitting. I had some similar issues with my RV4, when I installed a GTR200B com radio. My original Microair COM didn’t have the problem. My cure was to replace my original RAMI AV-534 antenna with a Delta-Pop COM antenna. I installed new RG400 cable to the antenna, but that didn’t help. I was getting RFI that was affecting some of my engine readings, and causing noise. The new antenna fixed it.
 
I had a background noise issue and I found out that my music aux input gain was at maximum (not an input I ever use) - turning that off resolved my issue.

I also know if it’s not the above that people have had issues with paint and the paint preventing a good ground
 
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