Eliminate common mode hum with ADC's Hum bucker. It accounts for differences in ground potential found in long video cables, incoming and outgoing lines, and separate power distribution systems. The ADC Hum bucker silences 99.6% of a 10Vp-p, 50/60Hz ground induced hum in a 200' RG59 coax run.
The precise amount of hum reduction depends upon cable length, cable type, ground loop potential, and ground loop frequency.