Abrupt, instant massive interference

[matt621 0]

Hello,

 

We have a security system with 20 cameras (16 cctv and 4 digital) on a hybrid dvr.

 

These cameras are located on 3 different structures.

 

Of the 16 cctv ones 3 are mounted on one structure and 2 of those suffer from interference from time to time. And when I say time to time, I mean it can go for months with a perfectly clear picture, then massive amounts of interference for months and then it'll disappear again for months and then come back. The interference is instant. (see pictures, note time stamps). I have checked the ends on the DVR, but I can't check the ends on the cameras because they are inside the structure and not easy to get to. But when this happend the 14 other cameras (one of which is located on the same structure) has no problems. The other one has some interference with the same vertical scrolling horizontally bands. This other one is w/in 4 feet of the one with the worst interfernce, and the 3rd one on this structure is about 15' away from these two that have interference and it's fine. All three are 12v dc powered and fed from the same power box which is about 200' from where the cameras are. The power supply is a high quality ps from a professional security supplier and rated for 2.3amps per channel and none of these cameras are rated over 1.1amps even at nigth with the LEDs on.

 

I know the obvious thing is ground loops, but I don't understand how a bad cable end would be working perfectly one second and then not the very next second. You will note the time stamps. No one is working, there is no one fiddling with the cables, dvr or cameras at that time of night/morning.

 

You'll note the date stamp. We just had almost the entire summer with perfectly clear pictures, 6 months or more. Which was preceded by several months of this horrible interference.

 

Does anyone have an suggestions? (Yes the structure has a 6' grounding rod pounded into the ground and all electrial devices in the structure go to this grounding rod.)

[cornz 0]

Could it be moisture related?????

A cable/connector being affected then when it dries out (or even becomes damp) the fault is clearing?

[matt621 0]

No it's not effected by moisture at all. All the wiring is inside the walls of the building. The interference does not change at all. When that picture was captured a few days ago, it was as dry as a bone. Today and yesterday it's been raining constantly. No difference at all.