If you've tested everything and tried to isolate your system as much as possible and you still can figure out why you're getting distortion, I would suggest you give these a try. If you are a professional installer it wouldn't hurt to carry a few on hand just to try them if you encounter problems, then you'll know if this is what you need. They've worked a couple of times for me, especially in newer office building with a lot of electrical and computer wiring and metal studs in the walls.

Gotta have this if you encounter interference or distortion. They work well and ended my problems.

I recently did an install using typical RG59 and on two of the cameras I kept picking up all sorts of interference. I tried using this ground loop isolator to see if it would work and it cleared it right up. I have no idea of the source of the interference but I do know that it worked and I've never had a call back.

Works great to help prevent distortion and interference in cable.

I recently performed an install where a couple of the indoor cameras gave me some problems with a little distortion. Typically, if a ground loop isolator is called for it's because there is an unbalanced power load between the DVR and the camera for example. I couldn't really detect that to be the case, although it might have. One common point between the two cameras is that they were installed in two different office rooms that were adjacent to each other and the offices were constructed using metal studs instead of wood. Whatever the exact reason, these BNC video ground loop isolators eliminated the problem and I left the job looking like a scientist!

I am a professional security camera installer and recently I had an install that really gave me some grief. I had one camera that repeatedly gave poor, distorted video. At first I thought it was the camera but after switching it out with several others I realized it must be some sort of electromagnetic interference. There were several possible factors that could contribute to the distortion including but not limited computer lines, telephone lines, cable lines, neon signs, and other factors. Anyway, I tried using the Video Ground Loop Isolator and it worked perfectly. No more distortion and all I had to do was screw it in line with the camera feed. I suggest that if you're having distortion problems on only certain cameras on your system, try using other cameras and if the distortion continues, get one of these. It's a cheap easy solution to what can be a giant headache.