Composite video over untwisted 18AWG wire

Discussion in 'The Projects Forum' started by 3nx7a13, Jun 22, 2016.

  1. 3nx7a13

    Thread Starter New Member

    Jun 22, 2016
    Hey guys,

    Not sure what the best place to find the answer to this question would be so here it goes:

    I have an automotive CCTV video system which consists of a flash-based recorder and analog cameras which output a composite video signal and have a 4-pin Mini-DIN connector (same as S-Video) and what I believe is the same type of cable as S-Video.

    The recording unit is mounted in the trunk and one of the cameras will be mounted to the front windscreen. I have a 7-conductor, 18AWG, untwisted, unshielded cable that runs from the front of the car to the back already in place, and I'd like to use a few pairs of this cable to hook up the camera, but I have no idea what its impedance is or if it'd even work well for this type of application.

    If I directly soldered the 18AWG wire to a mini-DIN connector, and used a standard BNC screw terminal connector on the other end at the recorder, would I notice any loss in quality as opposed to using a long S-Video cable? I have no problem running an additional cat5 cable if necessary, I'm just trying to avoid using coaxial cable because they take up a lot of room and, from what I've read, actually perform worse than cat5 for video with the proper baluns installed.

    The total length of the cable run is about 20 feet. The recorder appears to use 50 ohm BNC connectors, I would have expected these to be 75 ohm.

  2. wayneh


    Sep 9, 2010
    My opinion: It will work fine. You didn't mention if the 18 gauge cable is shielded or carrying other signals. Those could be issues, but otherwise I would expect it to work fine.
  3. Sensacell


    Jun 19, 2012
    It will work, but expect noise.
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    You might get ghosting on the video signal, due to not being screened should be ok.
  5. wayneh


    Sep 9, 2010
    I stand corrected. You did say unshielded.
  6. DickCappels


    Aug 21, 2008
    A "ghost" 40 to 50 nanoseconds delayed behind the arriving signal might be present is you don't use a receiving end termination the same impedance as you cable's characteristic impedance, but if the bandwidth of your display is low you might not even notice it.