Transponder and Nav Receiver noise.

[N5796C]

I have a KT76a that has started to emit a high pitched (loud, yet almost to high pitched to hear) whine when powered up. It does this regardless if other electronics are powered up, or if the engine is running or not. I first noticed it after messing around with the wire bundles trying to sort out a navcom antenna issue. The whine is noise emitted accousically btw, not interference heard through either receiver.

Also, the nav side of the Michel MX-300 navcom is picking up a low frequency buzz (guesing about 30hz) heard through the speaker and headphones. Again, this is regardless of other electronics in operation, or the engine running. I'm thinking I either have a bad radio or an antenna issue.

Any thoughts?

[markeg1964]

I had a similar problem with my Narco AT150 transponder causing a buzz in my ValCom. The local avionics shop replaced the board in the AT150 and the problem went away. As I recall it cost me around $150.