Radio squeal

On Tue, 5 Aug 2003 09:23:49 -0500, "Rick Pellicciotti"
wrote:


Just for clarification, are we talking about squeal in the headphones when
you transmit or squeal in the signal that is being transmitted (and heard by
others over the air)?

Normally, microphone and headphone jacks are NOT grounded to the airframe
ground. The common wires run back to the radio connections and the radio IS
grounded. If you use shielded wires for the connections from the headphone
jacks to the radios, the shields should be grounded at the radio end ONLY
and not at both ends.

I get the squeal on both ends. In my headset and on a remote receiver.

I have removed the earpieces from my headset and disconnected the
microphone, but can still hear the squeal on the remote receiver. The
remote receiver is about 150 ft away. When I stand next to the cabin
or sit in it for that matter, I can make the squealing come and go by
moving my arms about or adjusting my body position.

The microphone and headset jacks are not grounded to the aircraft
ground and I am using shielded cable connected to the radio at the
connector marked "speaker, mike and phones ground return"

And yes, the shields are grounded only at the radio end and not at
both ends.

Been there, done that, got a wardrobe full of teeshirts!

Gerrie