Re: problems with cctv , srolling bands through image

Discussion in 'Computer Support' started by rd, Sep 3, 2009.

  1. rd

    rd Guest

    "securiy" <> wrote in message
    > Thanks for reply , some were useful ....
    > What does OP mean , when someone talks abput
    > waiting for OP to reply ?
    > Anyways I hav discovered that one camera is causing a
    > lot more interference than the others , the cable i using is just the
    > cable that came with cameras so i guess its sheleided etc but
    > yes the more i read the mroe this sounds liek a ground loop
    > which i dont really undestand but will continue to read about
    > and try to resolve
    > --
    > ------------------------------
    > No links here , nup
    > "securiy" <> wrote in message
    > news:...
    >> Hi Folks
    >> Would apprciate any indications you can offer or troubleshooting methods.
    >> Ebay purchase of vandal proof , dome type cameras with IR leds
    >> Picture is surprinsgly good with the exception of constant scrolling
    >> lines
    >> which sets off the motion sensor in softwares.
    >> I have tried changing DVR card position in PCI slots
    >> I have tried a totally different PCI card , both a cheap chinese
    >> ebay DVr card and a Swann branded £90 model from maplin ( Uk )
    >> both set up for PAL
    >> The cameras are WIRED , and attach to DVR cards via BNC fitting , power
    >> is supplied on the same cable as the image cable via a power adaptor.
    >> Im guessing this interference is coming from this ? or not , any ideas ?
    >> I have noticed that when you remove a camera , the interference reduces
    >> just slightly but enough to be noticable , I have 4 cameras and with only
    >> one attached the interference is about 50% of what is was but still
    >> annoying
    >> and still sets off the motion detection software
    >> I would appreciate any ideas to troubleshoot further or any ideas
    >> for magic bullet ? that resolves , I guess this must be a common
    >> issue ?
    >> --
    >> ------------------------------
    >> No links here , nup


    I was trying to point you in the direction of a "ground loop" in my earlier
    post. I should have mentioned that term and didn't.
    In a perfect circuit in a perfect piece of gear connected to other perfect
    equipment there is a common ground that should be 0 volts. What happens is
    some of the various grounds get a bit of stray voltage on them. Say BNC
    connector shield was supposed to be ground but because of the various
    equipment interconnected it is not 0 any more "relative" to other so called
    ground points. When ever someone complains of a slowly rolling vertical line
    in a TV type monitor the problem has always been a ground loop in my world.
    In the field it was only an annoyance and a ground lifter almost always
    fixed it.
    So take a look at the whole of your equipment and note everyplace a ground
    is introduced. For example if you plug a power supply into a grounded outlet
    you have introduced a ground. If you plug a different power supply into
    another outlet on the other side of your home... that ground maybe be
    different. If you connect your cable company cable to this setup you have
    introduced another ground potential.
    I once had a flashlight bulb lit by connecting one pole to my TV cable
    shield and the other to my water pipe.
    rd, Sep 3, 2009
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