Noise with right seat mic plugged in

[Skates97]

Now that I have a decent radio and am not dealing with all the noise from the old Narco I have another issue. When the mic is plugged in at the right seat there is some background noise. To describe the sound, you are hearing a low hum of the engine that changes with the rpm. It is not actual engine sound as if you unplug the mic it is gone from the headset and is quiet again so I am picking up interference from somewhere. Ideas? Check ground wire?

[carusoam]

Sounds like magneto electrical interference...  rpm related noise.

Often, around here, is a discussion on proper grounding of everything.  From the engine to the instrument panel and everywhere else....

Checking cleanliness of the connections may be helpful...

PP thoughts...

Best regards,

-a-

[Browncbr1]

Look for your alternator field wire going to your breaker.   Make sure your audio lines are tied away from it.  If you have a portable hardwired into your audio panel, also make sure those lines are away from the field wire. 

[Skates97]

Thanks, I'll have to stick my head under there and take a look. I suspect it's always been like this but the old radio had so much other noise I couldn't hear it. 

[Marauder]

Make sure the connectors for the jacks aren’t touching anything. If they are attached through a metallic plate or panel that the insulators are present.


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[bradp]

Look at the wire going to the mic in addition to its routing. It should have a shield.  The shield should be cut at the mic jack end and not connected to anything there.  The shield should be brought to a common airframe ground with everything else at the audio panel end of the wire.  

I had a similar problem with my old intercom system plus bleed of phones (music)  into mic intercom audio ... turns out the rear pax mic and phones were literally wired together :-/ and shields were not grounded at the box.  

[Skates97]

Update: A few weeks back I spent some time twisted under the right side of the panel. I found a couple of things that I thought might be contributing. First, one of the grounds going to the mic plug was barely hanging on by a couple of strands of the wire. Second, there was a wire coming off of the mic plug that was resting right against the field wire. I replaced the ring terminal on the wire that was falling off and re-routed the wires away from the field wire. The end result is that the background noise is gone and it is nice and quiet now. Thank you for all of your help.