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GTN 650 and GMA 240

echoooo

Member
I have upgraded the avionic of my RV-7.
For the communications, I have installed a GTN 650 and a SL40 connected to a GMA 240.
I got some bugs, 3 with the COM.

First, when I transmit on COM #1 (GTN 650), I don?t understand my voice in my headset. ATC understand me clearly and I understand clearly it answer. Nothing wrong with the COMM 2. I double check the wiring between GTN and the GMA, all seems OK.

Second, I have a message in the GTN saying: Audio panel is inoperative or connection to GTN is lost.

Third, when I synthonyse a VOR frequency, I hear the morse signal that sound like a tok totok tok instead of a usual VOR morse code sound.

Any idea?

Alain
 
On your first issue, just curious if you are monitoring the second radio while transmitting on the first? If so, try it without monitoring the second radio and see if your side tone improves. If it does, then there are solutions to it depending on what intercom systems you have or perhaps other things.
 
I have upgraded the avionic of my RV-7.
For the communications, I have installed a GTN 650 and a SL40 connected to a GMA 240.
I got some bugs, 3 with the COM.

First, when I transmit on COM #1 (GTN 650), I don?t understand my voice in my headset. ATC understand me clearly and I understand clearly it answer. Nothing wrong with the COMM 2. I double check the wiring between GTN and the GMA, all seems OK.

Second, I have a message in the GTN saying: Audio panel is inoperative or connection to GTN is lost.

Third, when I synthonyse a VOR frequency, I hear the morse signal that sound like a tok totok tok instead of a usual VOR morse code sound.

Any idea?

Alain

Hello Alain,

For the first issue, you might try adding a ground wire to GMA 240 connector J2402, pin 30. This is the "Mute on COM TX" input discrete, and when grounded it inhibits the audio from all other monitored radios while transmitting to make sure you don't hear anything they might pick up while you are transmitting. Some customers have reported that doing this fixed an issue like you describe.

For the second issue, the GTN shouldn't know or care that you have the GMA 240 audio panel in the plane. Are you sure that the GTN configuration External Systems page doesn't indicate that an audio panel is being controlled?

For the third issue, have you tried turning off things like your ADS-B Out transponder to make sure that this isn't being picked up? Does it sound like the correct Morse code, but just has an unusual sound? Perhaps you could send us a short video with this audio.

Thanks,
Steve
 
For the VOR, do you see ?ID? displayed in the nav frequency box? If no, push the nav volume control in and release.
 
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