Hum on video is caused by a multitude of reasons, all of which are common throughout the world. Hum in general is induced by four distinct causes: 1) ground loop caused by difference in ground potential, 2) electrostatic coupling, 3) magnetic coupling and/or 4) faulty circuit elements causing leakage. Hums caused by ground loops can be as large as several hundred volts & can be dangerous to a TV crew preparing the site.
Common mode hum caused by differences in ground potential is often found in long video cables, incoming and outgoing lines and separate power distribution systems. The Humbucker eliminates 99.6% of a 10V p-p, 60 Hz ground induced hum in a 200 ft. RG-59/U coax run. Eliminates up to 20V p-p ground induced hum; up to 60 dB hum reduction. Nominal impedance: 751/2; BNC type connectors; either connector may be used as input. Comes in an aluminum die-cast box, with Handles.