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A better phantom power

Discussion in 'Electronic Design' started by Adam Stouffer, Jul 24, 2006.

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  1. I acquired an old black and white Magnavox MC 3511 CCTV camera (old
    meaning it uses a camera tube) which runs off phantom power. The only
    connector is coax style like a car radio antenna but smaller. I removed
    the connecter and applied 12vdc and coupled the video output through a
    2200uF cap in parallel with a .1uF ceramic cap. The format is RF and
    switchable to channel 3 or 4.

    The overall picture quality is pretty bad. Lots of ghosting and
    distortion and some scan lines going diagonally. What is a better way to
    couple the RF out? Should the capacitor sizes be any different, should
    there be some type of choke in series with the incoming power? To answer
    the least of my questions, what voltage does this camera take? Varying
    from 9-13vdc gives different results none of which look very good.


    Adam
     

  2. You need a choke in the +12 VDC power line to keep the video from
    being shunted through to ground by the power supply. The secondary of a
    filament transformer might work ok, as long as you don't saturate the
    core with the DC.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  3. amdx

    amdx Guest

    I agree with Michael about the choke. I would add, if the camera output is
    rf (channel 3/4) the 2200uf may be to large and have excessive losses at
    65 mhz.
    Mike
     
  4. blah

    blah Guest

    That same thought crossed my mind shortly after posting. Must have been
    thinking composite video, not RF. I'll try some lower value caps and
    adding a choke maybe a few hundred uH. Thanks for the input.


    Adam
     
  5. Tam/WB2TT

    Tam/WB2TT Guest

    You need an RF choke in the DC feed. A 2 - 5 uH is about right. I hope you
    meant 2200 PF, not uF.

    Tam
     
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