Video Ground Loop Interference for CCTV 21



Video Ground Loop Interference
Video Ground Loop Interference

Joe calls from the county jail, he just finished installing 16 cameras for the jail and now that he has all the cameras up on the monitor there are small lines running through the screen on each camera.  His first thought is that there is defective equipment.  Either the CCTV cameras or the DVR are bad.  Neither are bad, the culprit here is video ground loop interference.


Ground Loop

I will spare you the science of a ground loop (which looks like this)…

Just know that they cause horizontal lines in the video monitor.


This can be caused by many different factors and tracing the issue can be a pain.  One cause is running your security camera cable over a high power source. This can also be caused by load unbalance when high power is shut on and off.  To avoid this, make sure to run camera wires away from power lines (a minimum of 12 inches) if possible and especially not directly on top of them.

If you are using 24vac power transformer and you have this problem you can reverse the wire on the power supply to get the bad signal to go away.  This is an old trick that some of the Veteran CCTV installers use (let us know if you’re looking to become a CCTV installer).

Keep Camera Cable Away From Power Lines


Another issue with ground loops are metal buildings.  There are times when customers mount cameras to the side of a metal building and the entire building is one large conductor.  Often I tell them to put a piece of wood between the camera and the wall and that will fix the interference caused by video ground loops.

Piece of Wood Between Camera and Wall


Lastly there are video ground loop isolators (or “isolation transformers”).  They are small pieces that are run in the line between the camera and DVR.  Most of the time adding this piece will solve any ground loop interference in the video feed.  I sold some to Joe and they worked great!

2MCCTV sells ground loop isolators for only $8.

Ground Loop Isolator
Ground Loop Isolator


  1. Yes, from experience using a CCTV GL isolator solved the problems 95% of the times.

  2. I have a single camera, wireless cctv system in my house. It has worked with no problems for the last 2 years. The other day I turned it on and I have the ground loop lines on the monitor. What would cause it to work fine for years then have this problem? Wouldn’t one know instantly they had a ground loop problem the moment you use the system for the first time?

  3. You get a lot of respect from me for writing these helpful articels.

  4. it was quite informative for the people who who are very keen about the installed cameras and there video quality while recording ! these all features re mainly acknowledged by the security surveillance team but it will be very beneficial if you install by yourself!

  5. Hi,

    I have recently plugged 12 cctv cameras to 16 Channel DVR, now the problem is with 2 cameras. When i switch to channel 1 in full screen mode, i can see in the background the live of channel 4, and in channel 4 in the background, i can see the live of channel 1, rest all the channels are perfect and quality is good. I have checked these two cameras on the other DVR, it has no problem. I tried to plug these two cameras into differnt channels as i have 4 channel still to be occupied, now they are interfering into the channels. What could be causing this interference.

    Anticipating your quick help on this.

  6. I have one camera on a 6 camera system scrolling horizontal lines. It just started today and lasted for about 6 hours, then stopped. They are all DC 12V Cameras connected to the same power supply. Could the power supply be going bad. We used a diffrent power supply on this system than we normally do and we suspected problems from the beginning. It has 8 different connections with their own fuses.

    Thanks in advance.

  7. i have a speed dome every connection is ok but he not on moving mode?please tell me what is the problem?

  8. I’ve configured 4 CCTV cameras in outdoor housings that contain heaters & fans. When the the heater turns on I get the rolling bars. At all other times they work fine. Will a ground loop isolator reslove this? Is there a better way to fix the problem rather than cover it up?

    Tks, Jeff…

  9. Your answer on PTZ cams was extremely helpful. Im trying to troubleshoot a single camera, and after your comment, I rechecked my monitors and noted that half the PTZ cams had the same problem. Specifically; the cameras I used a secondary controller on. Within seconds of unplugging this suspect controller, the interference patterns vanished. If only all tech support was that easy!!

  10. Related to the article, if the cameras are plugged to the 16ch dvr one at a time, the video is clear. But when i start putting them together waves appear on some cameras. Any thoughts on this?

  11. Mac…

    I seem to have the same problem with my system. Ive tried a switching power supply with adjustable voltage because I suspected voltage drop, and it did not fix the problem. Were you able to resolve your issue, and if so may I ask how?

  12. I have a 16 channel lorex eco system with 2 ptz cams and 14 (720 tvl cams) that work great. Cables run from dvr to each camera which are Siamese bnc and power cables. All my cams work great except for 4 cameras. My issue is that 4 stationary cams have interference and only those 4 cams show it on the screen which looks like faint thick horizontal lines on the view that is random areas not scrolling. I have tested the cams with for sure working cams, switch ports on dvr, and good to go cables, however the cable runs for these four cameras are separate routes than all other cameras that work just fine except the 2 PTZ cams (which were routed the same as the 4 issue prone cams) the PTZ cams work fine without distortion but I have narrowed down the biggest issue were the video feed go completely black (no video at all) DVR view four only these channels are black. When the video goes blank there is still power to the cams and working (tested by covering IR sensor and working) the issue is when outdoor sign comes on and triggers video to cut all the way out. Will the use of BNC box you recommend help with this issue and if yes where should the box be connected if 2 set of runs are used (ie. 75 foot run cable from to dvr to coupler with addition 75 foot run to camera) to each camera?

  13. I have eight still cameras and four, always the same four cameras I have a problem with. Sometimes one camera will flicker and then it goes out saying video loss. Then after it will come back on. One camera of the four goes out at one time, not all four. I never have a problem with the other four and they are all connected to a eight channel dvr. Can you tell me what the problem might be?

  14. I have 3 camera s on 1 pole the cabling is in one pipe underground ,cameras are tested and recorder tested AIO ,the Main Problem is that the one video feed roles over the other ones feed
    What can I check next to solve this..

  15. I am having a problem at a site where am installing 6 IP cameras with NVR, 4 static are working and 2 Speed dome are saying Server Broken on NVR Display, what is the way out please help

  16. hai dear team I have one query regarding cctv operation,In our office recently we have faced problem that is cctv controlling unit has got turned off due to power failure,from that time onwards cctv monitor showing nothing simply it displays cam sequance on the screen,wheather can i able to view recording footage in that scenaries,

    weather it works for 24/7,or depndented on system configuration

  17. hello,
    my old power supply just crapped out. I got a new AGPtek® 18 Channel CCTV Security Camera Power Supply Box 12V 10A DC. Now, most of the screens have static lines running up and up.
    Is there a better power supply for the money i should get? – I have a 20 camera system.
    Also i have a couple of cameras i should replace that have gone out. I have a car lot with about an acre and a half to cover. What cameras are good for the money, and what specs should i get?
    Thank you very much!

  18. hi, my problem with the hikivision camera is, there are horizontal lines on the screen, what should I do

  19. Hi I just connected a hikvision 16 channel camera set but there is one camera that wen connected causes 2 channels to stop working

    You can call our direct line 972-206-1212 and dial 2 for tech support they can walk you through it.

  20. I just installed a 16 channel hikvision system with 16 5 megapixels ahd cameras, these are all powered by a 30 amp distribution box because some of the cat 5 cable runs are a bit lengthly. only two of the cameras in the afternoon are giving me vertical lines as if its a ground loop but not horizontal. All cables are in pvc conduit and are not touching any of the metal poles that they are mounted on. I have even boosted the power on these two cameras but still get the vertical lines only in the late evening, but in the daytime no problems. What do you think is causing this?

  21. I connected a 2021 model hikkvision cameras on a DVR that 8 2019 model hikvision cameras are connected.Anytime d 2021 model camera is connected ,the closest 2019 camera connected will go off and vis- Bess
    Pls how can dis be rectified

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