What could be a symptom caused by a ground loop in your station’s audio connections?

A ground loop occurs when there are multiple paths to ground between pieces of station equipment, creating a closed loop. Because of slight differences in potential, alternating current (AC) from the power line can flow through the shielding of your audio cables. This stray AC voltage introduces a 60 Hz or 120 Hz modulation into your microphone or audio lines. As a result, the transmitting equipment picks up this noise, and receiving stations will hear a distinct, low-frequency "hum" riding on your transmitted voice signal. Ground loops only affect the low-frequency audio and ground potential aspects of your station. They do not cause high SWR, which is an antenna system issue, nor do they generate RF harmonic interference or cause excessive DC current draw.