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Max TV antenna coax length?

Discussion in 'Radio and Communications' started by AGCB, Nov 22, 2014.

  1. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Hence why I suggested a mains powered 'launch amplifier' :D
     
  2. AGCB

    AGCB Member

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    Looking at some launch amps on line brings up another question. Would it be possible, rather that rotating an antenna to two or 3 different stations, to use 2 or even 3 antennas, each permanently pointed at a different TV station and input into the same coax cable?
     
  3. nsaspook

    nsaspook Well-Known Member

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    Sure you can but normally the other directions from the main antenna would have an antenna cut just for that frequency to reduce multi-path reception when they are mixed for the cable run. Multi-path is a killer for DTV even with strong signals but the newer receiver DTV chipsets are much better than the originals.

    http://forums.solidsignal.com/content.php/190-What-is-multipath-and-what-can-I-do-about-it
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    yes, Tinlee ought to be able to make the requisite combiner/filter. I think Wingard made an dual antenna combiner. I have it for future use. www.blondertongue.com

    They make some "very sweet" single channel antennas. I have one, that I plan to use. http://www.blondertongue.com/store/item.aspx?ItemId=616#tabid_0 You will likely need to get an account to login. The antenna actually spans about 5 or 6 channels from the center channel.

    If there is no possibility of another signal, you can use a splitter in reverse.

    ==

    Other possibilities for power is a DC bus like 24 VDC or 48 VDC and DC-DC convert at the endpoints.
     
  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes a higher source voltage would mean you could run a smaller wire.
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I thought one of the major advantages of DDT (and why the particular modulation scheme was chosen) was to eliminate almost all multipath problems, with multiply echos simply adding to the signal strength.

    However, it's generally a VERY bad idea to try and connect aerials together - although using narrow band channel specific filters on each one would help.
     
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    If they are directional and are like at least 90 degrees apart it should be fine.
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Except they still pickup considerable signal off line, and also any reflections from where they are pointing - most reputable installers wouldn't generally do it - if you want multiple aerials, then have a selection switch.
     
  11. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I did it at home and it was fine for me, but as you say the setup may have to many hart aches for commercial use.
    But if the OP wants to try it why not, ether it will work for him or not.
    Worst case set up a remote antenna switch.
    Still may be more reliable then a rotor.
    My roof top rotor that I spent good money for quit in a year or two and that's why I used two antennas, but my local stations were in two clusters on different hills 120 degrees apart.
     
  12. nsaspook

    nsaspook Well-Known Member

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    This (multi-path) was one of the major objections to 8VSB ATSC modulation during the US DTV evaluation. The sensitivity of 8VSB/ATSC to phase shifts in signal paths makes it almost impossible to receive while moving even with the best of antennas using the best receiver technology today.
    http://articles.baltimoresun.com/19...signals-sinclair-broadcast-group-digital-tv/2
     
  13. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    When combining, the signals can add or subtract and I know of no easy way to reverse one. In my case I could reverse the antenna to coax connector box, but not the signal to the single channel antenna. This will be a trial, maybe next year.

    Blonder tongue generally wants you to amplify and then combine because of the losses. As I said earlier, Tinlee should be able to make a customizeable product. See: http://www.tinlee.com/MATV_headend.php?active=4#MULTIPLECHANNELCOMBINER

    See also: http://www.solidsignal.com/pview.as...ase&utm_medium=organic&utm_source=google_base
     
  14. AGCB

    AGCB Member

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    Thanks again for all the info. I've learned much as I always do on this forum, thanks to knowledgeable and selfless people. I'll be away from home for a few days so expect no posts from me till back.

    Aaron
     
  15. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Have a good trip
     

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