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OTA split question

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by yesongs, Mar 2, 2007.

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  1. Mar 2, 2007 #1 of 17
    yesongs

    yesongs AllStar

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    I have a roof antenna for my OTA

    Curently it feeds my HR and Samsung 360

    I'm adding a second HR-20 - and would like to split the signal into three

    My question is how many times can you split before there would be signal degradation - I know situations might be different but some general info / opinions would be great

    Eddie
     
  2. Mar 2, 2007 #2 of 17
    texasbrit

    texasbrit Well-Known Member

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    It's entirely dependent on the signal strength for each individual station. For some stations even a two-way split can kill your reception. In other locations a four-way will work OK.
    Remember also your HR20 has an internal splitter to drive the two tuners.

    I would recommend instead of using a splitter you buy a distribution amplifier, to help overcome all the splits. Channel Master has a good range of distribution amplifiers.....
     
  3. Mar 2, 2007 #3 of 17
    mgcsooner

    mgcsooner Legend

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    That depends on your original signal strength, resulting from how close to the transmitting towers you are and the antenna--both quality and whether right type for the application. That said, each split and new termination causes a 3db signal loss, or about 50%. That would mean your signal with 3 terminations is about 25% of the original strength.
     
  4. Mar 2, 2007 #4 of 17
    cpkramers

    cpkramers Cool Member

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    I have a question along these same lines. I have a large antenna in my attic that I'm getting OTA from. I have three seperate lines attached directly to the antenna (that brown twin conductor stuff). Am I degrading my signal by attaching more than one line directly to the antenna? I'm only using one of those lines, so I wonder if I should disconnect the other two for better signal integrity if it matters.

    Thanks
     
  5. Mar 2, 2007 #5 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "Twin lead" is 300 Ohm conductor. that isn't shielded. I don't know how you've connected your other leads, but if you "just" connected them all at the same place, then yes that's not the best thing to do. You would get much better performance if you changed to coax.
     
  6. Mar 2, 2007 #6 of 17
    cpkramers

    cpkramers Cool Member

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    Yeah, the three twin lead conductors are attached to the same antenna studs, and then run through the walls to three points in the house. At my HD set I have the coax converter. Sounds like I should have the converter right at the antenna, and then run coax to my receiver. I don't have a bad signal now for the most part, but a couple channels could use some help.
     
  7. Mar 2, 2007 #7 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    RF can get very "funny". The twin leads could either "add" to the antenna or subtract from it.
    "From the book", I would move the balum [300 to 75 Ohm transformer] up to the antenna & use coax for the down lead. Remember to have a outdoor balum or waterproof what you have.
    Setting it up this way: your antenna is the pickup & your down lead is shielded from the signal, which should give you the best performance.
     
  8. Mar 2, 2007 #8 of 17
    bobnielsen

    bobnielsen Éminence grise

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    Bainbridge...
    Minor point--it isn't balum, but balun (short for BALanced to UNbalanced). Twin-lead is a balanced line, while coax is unbalanced. In most of cases, switching to coax for an attic installation will improve things. Twin lead has less loss, but the signal can be affected by nearby metallic objects (pipes, attic wiring, etc.) which the shielding will prevent.
     
  9. Mar 2, 2007 #9 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Thank you, that's what I get for using google to do my spell check.
    Balum is listed on RF component sites. :D
     
  10. kaminsco

    kaminsco Guest

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    This is similair to my setup, except in attic. I have my 300 to 75 ohm transformer at the antenna also. I have found instead of splitting a single line of it, I just made multiple runs to it. I have three coxial runs directly to the antenna with three 300 to 75 ohm transformers hooked to it. I felt this would give me the optimal reception for multiple TV's. It is a little more work and cost though.
     
  11. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Not really: the air is about 360 Ohms impedance. connecting three 300 Ohm baluns would drop that to around 100 Ohm input. Then the balun designed for 300 to 75 Ohm could be down something like 25 Ohms for the coax instead of 75 Ohms.
    This is all "theory" & as I said RF can be "funny".
    If it is working..fine. If you want to improve it then using splitters is how to have multiple outputs without changing the impedance.
     
  12. kaminsco

    kaminsco Guest

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    I am confused. The three are hooked independently of each other, not sure how that would change a thing. They act like three separate hooks ups, instead of one hookup that is split three ways.

    I cannot see how hooking up to the antenna in three independent places would change the peformance of antenna?
     
  13. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Hooked up in three independent places?
    Every antenna I've worked on as A place to connect the cable.
    :confused:
     
  14. RCinFLA

    RCinFLA Legend

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    Put a balun (also known a matching transformer) at the 300 ohm balanced antenna terminals then run quad shield coax to the splitter. You don't want to fool with 300 ohm twin lead line.

    HD OTA signals are prone to corruption from multipath ("ghost") signals. The quad shield coax (generally also better quality) keeps any direct signal leakage out of the transmission lines.
     
  15. kaminsco

    kaminsco Guest

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    Mechanically, there is no limit. The boom has place to hook the spade terminals onto two lead terminals (basical bolts) with wing nuts..

    You can hook up as many as you want. The only limit is the length of bolts..
     

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  16. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Your picture is just like I thought.
    With some test equipment, I could show you what is happening. You are changing the impedance with three "taps". Since you use a balun/transformer very close, you seem to have some success. If I were to guess at what the test equipment would show is: a low voltage signal [compared to a single tap], since the impedance should be 1/3 the design.
     
  17. yesongs

    yesongs AllStar

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    Well my second HR20 was installed this morning, and a 3-way split of the roof antenna signal has been no issue - still getting all Balt / DC channels I'm supposed to on the two HR20's and my Samsung 360

    Eddie
     
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