Garmin GTN750 Comm Issue and GPS Lost Signal

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tacrispy

Filing Flight Plan
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tacrispy
Hey all,

We recently had a GTN750 and GTX 345 installed into our Socata Tobago. Overall we are very happy with the unit and are learning more how to use it but we have had a couple of small issues I am looking for help with.

1. The COMM on the 750 is clear when listening to communications and ATC seems to hear us fine but when we engage the push to talk on the 750 COMM, there is a considerable amount of feedback and noise when you hear yourself talk over the radio. There is no issues with the intercom audio or the number 2 COMM which is a King KX 155.

2. the 750 GPS and ADS B signal is lost when you push to talk on COMM 2 which is the KX 155. Very strange.

Do any of you have experience with these issues or can comment?
 
Sounds like a come back to the installer to me. Why mess with it? It's under warranty AND just installed.
 
tacrispy said:
Hey all,

We recently had a GTN750 and GTX 345 installed into our Socata Tobago. Overall we are very happy with the unit and are learning more how to use it but we have had a couple of small issues I am looking for help with.

1. The COMM on the 750 is clear when listening to communications and ATC seems to hear us fine but when we engage the push to talk on the 750 COMM, there is a considerable amount of feedback and noise when you hear yourself talk over the radio. There is no issues with the intercom audio or the number 2 COMM which is a King KX 155.

2. the 750 GPS and ADS B signal is lost when you push to talk on COMM 2 which is the KX 155. Very strange.

Do any of you have experience with these issues or can comment?
Click to expand...

Most likely:

1. Sidetone audio level is set too high. That one should be the simple fix.

2. Improper installation with possibilities like the com 2 antenna being too close to the amplified GPS antenna, or large amounts of RF leakage from a bad cable or connector, or improper level of coax shielding. We replaced all coax to all antennas when we did ours. Could also be a com 2 antenna broke internally and is exhibiting high SWR putting more RF inside the aircraft than radiating it away.
 
Unit74 said:
Sounds like a come back to the installer to me. Why mess with it? It's under warranty AND just installed.
Click to expand...
Yeah we are going to have to go back to installer at some point.
 
denverpilot said:
Most likely:

1. Sidetone audio level is set too high. That one should be the simple fix.

2. Improper installation with possibilities like the com 2 antenna being too close to the amplified GPS antenna, or large amounts of RF leakage from a bad cable or connector, or improper level of coax shielding. We replaced all coax to all antennas when we did ours. Could also be a com 2 antenna broke internally and is exhibiting high SWR putting more RF inside the aircraft than radiating it away.
Click to expand...
How do I fix the side tone audio?
 
tacrispy said:
How do I fix the side tone audio?
Click to expand...

Not sure. Buried in the installer portion of the radio’s menus probably.

I wouldn’t wait on the RF problem. Could fry the amplifier in the GPS antenna if it’s subjected to that for too long. They’re supposed to essentially shut down when overloaded by off frequency RF like that but it’s not good for them. And those amplified antennas in the airplane world get spendy. In the automotive world they’d be $10.
 
Sounds like the same issue I had on my 650. Press and hold the home button on start up. Once in the setup adjust the Com sidetone down to around 45db. For some reason they ship at the max level.
 
USAF JD said:
Sounds like the same issue I had on my 650. Press and hold the home button on start up. Once in the setup adjust the Com sidetone down to around 45db. For some reason they ship at the max level.
Click to expand...

That’s awesome info. I didn’t know how to get into the GTN menu for that. Knew how to get into the GTX menu for admin stuff.
 
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