Can I combine two antennas from opposite directions

Discussion in 'TiVo Bolt DVR/Streamer' started by LilBear, Nov 1, 2019.

  1. snerd

    snerd Well-Known Member

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    The backward splitter weakens the signal by about 3.5dB from each antenna. That reduces the received power to 44%. So, weak signals become weaker when using a splitter as a combiner.
     
  2. snerd

    snerd Well-Known Member

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    For those who are lucky enough to be in your situation, a 15-2586 VHF/UHF diplexer has lower loss than a splitter, and completely avoids phase/multipath issues.
     
  3. kpeters59

    kpeters59 Well-Known Member

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    There's higher quality units than that. I'm pretty sure Holland has one. If you're combining UHF and VHF. VHF for TV is becoming pretty rare.

    -KP
     
  4. ggieseke

    ggieseke Well-Known Member

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    There will be a lot more stations in the VHF high band after the repack finishes.
     
  5. Mikeguy

    Mikeguy Well-Known Member

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    Really? They look to be the same as always for mainstay OTA TV.
     
  6. ke3ju

    ke3ju Ed Ludwig

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    Actually not true, splitting the signal weakens, combining does not, as long as all channels are on different frequencies. We do this all the time in ham radio.

    Sent from my SM-N960U using Tapatalk
     
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  7. kpeters59

    kpeters59 Well-Known Member

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    I suppose I should have been more clear, but I'm not sure which of my points you're questioning.

    Surely it must be the 2nd as there really can't be any question about the quality of a Radio Shack splitter, can there?

    -KP
     
  8. Mikeguy

    Mikeguy Well-Known Member

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    LOL, yep, I meant the second. Isn't VHF still pretty much a staple for OTA TV?
     
  9. kpeters59

    kpeters59 Well-Known Member

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    I was under the impression most everything was moving to UHF, but GG says there will be plenty in upper VHF...

    -KP
     
  10. snerd

    snerd Well-Known Member

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    Actually true.

    A splitter is a 3 port passive device for which reciprocity applies. This implies that the 3.5dB loss experienced when power flows into the IN port and out of either OUT port will exactly match the loss when power is flowing in the opposite direction.

    Internally, a 2-way splitter is constructed from a four port directional coupler that has one (reverse direction) port terminated internally. So, when power flows backwards through the splitter, about half the power goes to the IN port while the other half is dissipated by the internal termination.

    Also easy enough to prove experimentally.
     
  11. snerd

    snerd Well-Known Member

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    You are probably thinking of the Holland DPD2 or STVC models. Those are used to separate and/or combine satellite frequencies on the SAT port with everthing below about 806MHz on the VHF/UHF port. The Radio Shack VHF/UHF diplexer is used to separate and/or combine VHF from one source with UHF from another source.
     
  12. kpeters59

    kpeters59 Well-Known Member

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  13. ke3ju

    ke3ju Ed Ludwig

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    I
    Hmm...I'm gonna have to tear one apart and look at it. My understand is it's just a 1.41:1 unun (unbalanced to unbalanced impedance transformer) with the 1.41 turn to the single side, and 1 turn to the split side keeping the impedance at 75 ohms. What happens if you connect the two 300 ohm outputs of each antenna and then run it through the 300 ohm to 75 ohm balun into one wire? It does get interesting when working with log periodics rather than single band yagis.
     
  14. snerd

    snerd Well-Known Member

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    Perhaps we're talking apples vs. oranges. I'm talking about regular 2-way splitters such as this Holland GHS-2PRO-M that is 75 ohms at all ports.
     
  15. snerd

    snerd Well-Known Member

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    That page says "Discontinued" and 0 stock.

    I'd be happy to recommend the UVSJ if it were readily available on Amazon or ebay, or anywhere else that keeps it in stock. You can bag on the Radio Shack part if you like, but at least it has the redeeming feature that it is still available.
     
    Last edited: Nov 5, 2019
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  16. ke3ju

    ke3ju Ed Ludwig

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    I'm pretty sure its Apples to Apples. These are some diagrams I found poking around on Google for a few minutes.
     

    Attached Files:

  17. CIR-Engineering

    CIR-Engineering Video Calibration & Electronics Repair Engineer

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    If your towers are nearly 180 degrees from each other, I would suggest trying an 8 bowtie antenna with the reflector removed. This will allow the antenna to pickup stations from both directions with the least negative impact on the signal.

    Or something similar. Chanel Master and Wingaurd used finale better ones...
    https://www.walmart.com/ip/Antennas...MIkem_n9Pb5QIVyEXVCh1YsgTcEAQYByABEgLiB_D_BwE

    Just remove the screens from the back and see what you get.

    Good luck!
    craigr
     
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