Scott, me ol’ China, Yep EVERYBODY gets the squeal – and complains “CZJ – ya got a loud background squeal in yer transmission!!!”

Dom,

 

Oh, so glad I went back and read your first transmission with understanding.  I guess the squeal was blocking me wee brain out.

 

Let's see, it shouldn't be caused by any wiring of the PTT since that is usually just a switch making to ground (unless the ground is not a good one).

 

The radio can produce a side tone so that you can hear yourself talk and be reassured that someone else would be able to hear you, too.  An intercom can also produce such a side tone back to your headsets (listening to yourself over the intercom, just like your unfortunate passenger.  Neither of these should be a problem with a transmission unless the vox operated intercom gives you a squeal without touching the transmit key.

 

Hmmmm, this seems isolated to the mike circuit, but only when the intercom is on............... Hmmmmm..  Wired by an avionics shop, eh?

 

I wonder if both side tones are in conflict?  Have you tried to make sure the headset cannot feed the mike when transmitting with the intercom on - i.e. remove the plugs for the passenger side, make sure the mike opening is facing your mouth (not pointing at the ear piece) and cover it somewhat with hand - or completely with your hand and see if your buddy, around the corner with the handheld, hears a squeal when tx but no voice.  In other words, can you check this on the ground without the engine running by using another radio. 

 

Try to isolate this condition even more.  Have you swapped headsets from side to side?  Make sure you turn off the other radio also since there can be problems if they are tuned to the same freq and/or they share an antenna without a transmit isolator.

 

Scott

 

PS: My GSM phone (RAZR) can cause noise in audio circuits, but it is just annoying, not a squeal.  I shut the sucker off when I fly.