Jump to content

unable to transmit...when engine running


Recommended Posts

1975 F

gns430w radio

gma-340 audio panel

 

Just finished a round trip from Georgia to Michigan and back.  Last 30 minutes of the flight I couldn't transmit from my push to talk.  Assumed it was just the pilots ptt so I snagged the headset from the right seater and used the right seat ptt.  It worked but the sound feedback in my headset was scratchy.  ATC assumed the scratchy sound was due to an issue on their end.  I cancelled IFR before I couldn't transmit at all.  

Fast forward a couple days...  I head down to the hangar to isolate the problem.  With the engine OFF I can transmit.  A few radio calls to the FBO using multiple headsets, both installed ptt switches and an old velcro ptt worked great.  Fired up the engine to taxi out and tried a few more radio calls.  Nothing...just crickets...  Once again I tried multiple headsets, both pilot and copilot ptt switches and the old velcro ptt and nothing worked.  FBO said the could only hear some clicking and no voice.  Shut down the engine and voice over the comm worked again.  Ugh...  Any ideas before I head off to the avionics shop in the morning?

Thanks,

Jason

 

Link to comment
Share on other sites

13 hours ago, ArtVandelay said:

Try pulling the alternator circuit breakers.


Tom

Like Tom was getting at, you need to isolate the source of the noise/interference.  The most likely sources are alternator/generator, magnetos, or vibration.

Pulling the alternator/generator circuit breaker will basically turn it off.  Turning your magneto switch to L or R will turn off the other magneto.  Vibration is more difficult, but changing RPM might be able to point you in the right direction. 

  • Like 1
Link to comment
Share on other sites

Thanks everyone.  Drove over to Aircraft Spruce and bought a handheld radio.  Heading down to the hangar to chase this thing down.  Bad news, we cancelled our trip to St. Augustine.  Good news, we will spend a few days camping at the lake instead.  The hangar is 10 minutes away from the lake!  First world problems.  Lol.  

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.