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RCA to Coax modulator schematics

Discussion in 'Electronic Repair' started by parahumanoid, May 26, 2007.

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  1. parahumanoid

    parahumanoid Guest


    I am sure I am not the first one to ask, but I didn't find a
    straightforward answer to this.

    I DID search the web for this, but I only found some schematic
    drawings on RF modulators, but the input on those is COLOR, LUM, AUDIO
    rather than the expected AUDIO LEFT, AUDIO RIGHT, VIDEO. So I guess
    they aren't what I need.
    Please don't suggest buying one in RadioShack - I don't have
    RadioSchack in my country (at least I am not aware of its presence on
    our market). Or reading 300 books after which I will be able to think
    up a schematic of my own. I need a practical fix to a practical
    problem. It's a small town with no such devices on the shelves (I
    tried to do special order, but to no avail). We do have the radio
    parts market here, though, so with proper schematics I want to try to
    produce the modulator on my own.

    In case it matters, both the signal source device (DVD deck) and the
    TV set are PAL.

    Thank you for your input.
  2. Gary Tait

    Gary Tait Guest

    Just purchase a replacement RF modulator, or pull one from ta dead VCR
    or the like.

  3. That is not a stereo modulator, but you can tie the color and
    luminance together to feed it composite video and sum the two channels
    together for a mono audio signal.

    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
  4. parahumanoid

    parahumanoid Guest

    Like I said in my post, there isn't a chance to purchase a factory-
    assembled one, believe it or not. I wouldn't ask for schematics if it
    weren't the last resort.
  5. parahumanoid

    parahumanoid Guest

    Thank you Michael. Looks like we have a winner. I'll give it a go.
  6. parahumanoid

    parahumanoid Guest

    Hmm. I just recalled I DO have an old VCR that is dead somewhere in
    the shack. Thanks for reminding me. Now, the modulator shouldn't
    care about the NTSC/PAL differences, right?
  7. Might then help if you stated your country.
    You'd need to say which type of PAL as there are several which would
    effect the design of the modulator. Also you appear to want stereo. In the
    UK 'PAL' stereo involves NICAM which is a digital signal on a sub carrier.
    Other countries do have multiplex stereo, though.

    To design and build a modulator from scratch is no mean task - and
    *really* not worth the effort, given the cost of them to buy. If you
    ignore stereo that broadens your choice of ready made ones - they are used
    for games consols and security cameras as well as normal AV purposes.

    Surely you must have somewhere that does mail order even although you
    don't have an RS store? Or the DIY stores sell modulators for use with
    security cameras. Check that it does have sound too, though.

    If you live in the UK, Maplin is a rough equivalent to RadioShack.
  8. Gary Tait

    Gary Tait Guest

    Not for the video signal itself likely. However the audio might be
    modulated at a specific frequency, and the RF frequency might be specific
    too one format.
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