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About a TV vhf/uhf combiner circuit

Discussion in 'Radio and Communications' started by gaetan8888, Oct 5, 2011.

  1. gaetan8888

    gaetan8888 New Member

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  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Probably, as it's only low and high pass filters - but why not just buy one?, they are freely available and cheap.
     
  3. gaetan8888

    gaetan8888 New Member

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    Hello

    In that web site it wrote 144/432MHz of cuting frequencies of that filter.

    But VHF stop at 216MHz, so I was presuming that this circuit are cuting the VHF to low or that the text are not clear about the cuting frequencies of this diplexer (combiner) ?

    I live in Canada, in mountain, far from any cities, so there is none of combiner sold here arround, and the mail ordering stores for those are only in US and cost more shipping than the cost of the combiner.

    Thank

    Bye

    Gaetan
     
  4. dave

    Dave New Member

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  5. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    No you can not. That circuit is for combining two transmiters to one antenna.
    What are you trying to do?
     
  6. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    You failed to mention important things like coax vs twinlead.

    A CATV splitter can be used as a combiner in reverse as long as the U and V portions are frequency limited.

    e.g. It work with a UHF antenna and a VHF antenna, but a UHF/VHF with a UHF antenna would not work unless one paid attention to phasing and orientation of the stacking of the antennas on the mast.

    What do you plan to do?
     
  7. gaetan8888

    gaetan8888 New Member

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    Hello

    I have installed a uhf antenna, so now I have a VHF antenna and a UHF antenna, I need to do a combiner to connect to two antenna to my digital tv converter. It's not working to connect to two antenna without a VHF/UHF combiner.

    Since I can't find a combiner sold here arround, I need a schematic to made one.

    Thank

    Bye

    Gaetan
     
  8. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Knowing a lot more info on your design would help. I don;t know if www.TVfool.com works in canada.

    This website gives you expected stations and levels that you can expect. Amplifying at the antenna is usually the way to go and then amplify again for the distribution.

    The 300-75 UHF balun at the antenna is a loss.
    The 300-75 VHF balun is a loss
    The UHF frequencies will die quickly if not pre-amplified.

    You do gain someting when you have a 300 U/300 V to a coax combiner.

    Amplifying early is the best way. Amplify (U and V and combine), one unit at the antenna.

    UNLESS your U and V signals are good, then just use a splitter in reverse.

    Been there, done that.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Canada is a modern first world country, such combiners will be freely available at any TV/Aerial/Electrical shop (and probably DIY shops) - obviously they will also be easily available via post from within Canada - it's a standard item.

    Bear in mind you will need an outside one to go on the roof, and an inside one to separate them back inside.

    We don't even use VHF TV in the UK, yet such diplexers are freely available here - and in fact I've taken one off the roof earlier this year and thrown it away.
     
  10. davenn

    davenn Active Member

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    That design is not for TV use. its specifically designed for the 2metre 144MHz and 70cm 432MHz amateur radio bands
    and as one other poster said its for putting 2 tranceiver radios into a single dual band antenna

    cheers
    Dave
     
  11. 4pyros

    4pyros Well-Known Member Most Helpful Member

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  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Transmit and receive makes no difference, apart from one designed for transmitting will be of much better quality - receive only ones can be cheap.

    But that filter isn't specifically tuned, it's just low-pass and high-pass - depending on the actual design frequencies it's quite possibly pefectly fine for TV use, and certainly the UHF side of it is (70cm is the bottom end of UHF TV).
     
  13. RCinFLA

    RCinFLA Well-Known Member

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    See attached. Coils are close wound on drill bits to make them more reproduceable.
     

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