Hi, I would discuss with you solutions ro reduce this annoying effect.
Since I put the DVR on the same 12V of cameras (and it should be that, since I'm using a big battery 12V to keep system always on) on some cameras (depending on the leght of cable, model, and maybe some other factors) appear those annoying lines when the HDD records, this is for sure an RF noise, catched by ground loop between DVR negative pole, camera's negative pole and shield of coaxial cables. I think it happens...
How reduce HDD noise "clicks" on Dahua XVR
Since I put the DVR on the same 12V of cameras (and it should be that, since I'm using a big battery 12V to keep system always on) on some cameras (depending on the leght of cable, model, and maybe some other factors) appear those annoying lines when the HDD records, this is for sure an RF noise, catched by ground loop between DVR negative pole, camera's negative pole and shield of coaxial cables. I think it happens...
How reduce HDD noise "clicks" on Dahua XVR