On Mon, 20 Sep 2004 08:59:21 -0400, "Justin H" wrote:

The airplane does not have an electrical system so there arent any
transponders etc.. the mags are bendix s4ln. the mic has a muff but its not
getting any impulse air anyway (doesnt seem to be anyway) .

the sound reminds me of a car stereo system getting alternator whine, but
amplified. going to try varying the power and talking today.

Another thing you might try is switching one mag off when transmitting. I
have a high noise level on receive; fiddling with the mag switch, I found
the noise was a lot less when I turned off the right mag. I bought a
replacement noise filter capacitor, but haven't gotten around to installing
it.

If killing one mag eliminates the noise, then you've at least narrowed down
the source of the problem. Looking online, it appears the Bendix SC series
does not have an external noise capacitor, so it sounds like a repair would
be a bit more complex.

If the problem doesn't appear to lie in the mags, you might try a different
headset and headset adaptor. Also, are you using the "rubber duckie"
antenna or do you have an external antenna?

Ron Wanttaja