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CCTV-Rolling Image

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  • 03-06-2013 10:33pm
    #1
    Mazotasan
    Registered Users Posts: 72 ✭✭


    Hi all,

    I am installing a basic 4 camera cctv system at home over cat5. The cable runs are 5m, 10m, 20m and 150m. The 150m cam is powered locally whilst the others are powered from a dedicated 12Vdc power supply located near the dvr. I have used passive baluns both sides on all cameras.

    When I individually connect each cam to the TV the image is ok. However when all the cameras are connected to dvr and the dvr connected to the TV the image is Rolling and Fuzzy (noisy I think).

    I need to make a few measurements but does anyone have any suggestions...active balun? Ground loop isolater? I think its a voltage issue...Can a voltage issue on one camera cause a problem for the quad view on the dvr?


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    #2
    Jnealon
    Registered Users Posts: 2,062 ✭✭✭Jnealon


    Check the voltage at the suspect camera, also the video signal coming out of it, should be 1V pk to pk.
    Poor quality baluns, camera on a different phase, ground loop problem, process of elimination.
    Is there anything else in the duct going to this camera


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    #3
    Mazotasan
    Registered Users Posts: 72 ✭✭Mazotasan


    Nothing else in the duct but have realized that cat5 is running close (less than 0.5m) to the mains power cable entering the house...I think that's the culprit...Would an issue like that cause an issue on the video output from the DVR? Each camera image looks ok when connected directly to monitor? Thanks


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    #4
    balunman
    Registered Users Posts: 1 ✭balunman


    A rolling image could be symptomatic of a ground loop.

    In my experience I have a heard of installations where a multichannel 12VDC CCTV power supply has been the source of a ground loop issue.

    Try individual 12VDC transformer-based power supplies to power each camera instead of a multichannel psu.

    Another option is to break the potential ground loop on the video line with a ground loop isolation balun such as the MuxLab 500132.


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