Like mentioned above, it's unlikely that 60 Hz is interfering with the digitally modulated RF signal and even if it did, it wouldn't manifest itself as a hum in the detected audio. It's possible, though, that a ground loop is conducting 60 Hz interference into analog audio stages that are after the RF signals are detected and processed. In this case an isolator that has "DC blocking" on the outside shield such as the one in post #23 should be effective. However, there may be bonding/grounding issues that are the root cause of the interference.