G'day, > While I can't think of any definite reasons, but it sounds like you are > hearing a carrier somewhere near where the K2 input is tuned (28 mHz band). 7th harmonic of the 4 MHz clock in the KPA100? It runs all the time. Easily heard at the bottom end of 28 MHz. Similarly the 4 MHz clock on the K2 control board. Regards, Mike VP8NO