there are many video interference products out there- like humbuckers- or ground loop isolation transformers-
this is an american site - i do not have any knowledge of the products-
http://www.21best.com/21_best/electr...for_sale_.html
HUMplug-e
Hum buckerSimply plug your equipment through this, to cure it of Ground Loops. Filters out unwanted voltage and current in the ground line that cause ground loop hum while simultaneously maintaining a solid, safe ground
The Video Hum Bucker Premium eliminates interference and hum on video lines. The Hum Bucker simply connects in series with the video line