DAVE, I HAVE HAD THAT PROBLEM IN THE PAST ES FOUND IT TO BE "RF" AND/OR "FEEDBACK" FROM A DETUNED ANTENNA (DUE TO WX SITUATIONS)! A BETTER GROUND (ACTUALLY NOW 2) ES TOROIDS AROUND CERTAIN CONNECTING CABLES, ES MOST IMPORTANT, OPERATOR ATTENTION TO THE SWR METER. 73, DON-WN1OTV