Analogue HDTVI is the new CCTV technology and supposed to be almost immune to interference. However, I have obtained a four channel HDTVI NVR with the makers name of Video Park 0800. But with my system it is not living up to its "immune" reputation - please see the upload JPEG. I am trying all the obvious well known anti-ground loop solutions but, so far, without success. Even more aggravating is the system will go hours, sometimes, without any sign of the interference. Even with one camera connected on a short RG59 cable the problem can appear. One aspect that occurs is if with a single camera and the interference visible, I totally cover and block the camera lens, the picture naturally vanishes but so does the interference. I hear the camera click over from visible light to the infra-red LED's. If I turn off all natural and room light and let the infra-red's alone do the job - then zero interference. My next try is to obtain some ferrite beads and attach to the camera cables as this may assist if it is an RFI problem. But I need help - please!