I have a client with Geovision GV1480, and there´s  problem with interference. I use cat5e cable and videobalun and the distance is 
about 60m. The camera is standard CCTV 540Tvlines 12V. When I check the picture in a test monitor there´s no problems but then I connect it  
to the PC system I get a bad interference , it also make other cameras in the system to be unstable with bad interference.