Todd, I had the exact same problem when I tried to use my K3 with my amplifier. I did not have a ground on the K3. This was a test in a high RF environment. When I grounded the K3 the problem disappeared. When I grounded the power supply the problem disappeared. I now have both grounded. The K3 is performing as it should. 73's Ron WB4OOA K3/100 #604