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DECA data point

Discussion in 'DIRECTV - H24/HR24 Field Trial (private)' started by veryoldschool, Dec 8, 2009.

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  1. Dec 8, 2009 #1 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    In your setup posts, it might be good to have the lengths of cable listed.
    You might notice I have it in mine.
    This is because in the DECA adapter testing, there seemed to be a correlation between some anomalies and the lengths of RG6 between splitters, filter, and receivers/DECAs.
    In the RF domain, one DECA signal has multiple paths, so the same signal can end up being at different power levels, or the same but shifted in phase.
    Different levels should be easy for the DECA as it could simply pick the strongest, but if two are at the same levels and one is shifted 180ยบ out of phase, the two should cancel.
    I like the term "DECA Cloud", from the start, as it describes the DECA signal paths quite well.
     
  2. Dec 8, 2009 #2 of 17
    smiddy

    smiddy Tain't ogre til its ogre

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    I'll list mine, but I have none longer than 20 feet from any PI. My longest run is into my main run in the basement from the satellite antenna, 40 feet.
     
  3. Dec 8, 2009 #3 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I've seen changes simply swapping ports on my 4-way splitter, but the most changes came from moving the filter 65' to the dish.
     
  4. Dec 8, 2009 #4 of 17
    Grentz

    Grentz New Member

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    I will guestimate mine when I put up how I am going to set it all up.
     
  5. Dec 8, 2009 #5 of 17
    jasonki32

    jasonki32 Godfather

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    I have my filter at my splitter which is about 10 ft from the SWM. The splitter to the IRDs are all about 20 ft. There has been some correlation with where the filter was placed and having all green lights on the DECA system. At least on my setup.
     
  6. Dec 8, 2009 #6 of 17
    smiddy

    smiddy Tain't ogre til its ogre

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    Attenuation tends to make things happen. :D
     
  7. Dec 8, 2009 #7 of 17
    azarby

    azarby Hall Of Fame

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    My filter will be within 5-6 feet from the LNB. I'm just debating on where to put it, betweeen the LNB and primary splitter or just after the primary splitter and the DECA cloud. My PI and DECA will be about 65 " away inside the house.

    Bob
     
  8. Dec 8, 2009 #8 of 17
    inkahauts

    inkahauts Well-Known Member

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    Well, I will be making my own cable lengths, so I can try both short and long.. Any length in paticular where you have seen problems start to arise that I might want to test? Shorter or longer?
     
  9. Dec 9, 2009 #9 of 17
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    The skywalker splitter is spec'd @:
    2-way
    22 dB isolation [output to output]
    4.4 dB insertion loss [DECA range], so output to input is 1.4 dB

    4-way
    25 dB isolation
    8.3 dB insertion loss [DECA range], so output to input is 2.3 dB

    cable loss: http://www.net-comber.com/cable-loss.html

    Now if you realize the DECA signal bounces [reflects] off the filter, you can do some math and find in some layouts the signal is stronger bouncing off the filter and returning than going from output to output of a splitter.

    [from my layout] H21 to HR24
    through splitter -25 dB
    bouncing off filter -20.11 dB
    Now if I move the filter to the LNB that adds 6 dB to "the bounce" and now it's 26 dB and only slightly over the splitter [output to output] path.
     
  10. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Interesting.

    In my case...it's short and sweet...and no problems.

    SWM1 output>15'cable>filter>splitter>multiple cable runs to receivers
     
  11. azarby

    azarby Hall Of Fame

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    Because of the high isolation from output to output, I've decided to flip the splitter around and use the two outputs as inputs and feed the Ethernet through one of the outs. In my setup that give me the least amount of signal loss plus it adds some additional isoaltion between the Deca and the filter on the main SWM feed.

    Bob.
     
  12. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Some splitters won't pass DC backwards [I'm sure you'll set yours up correctly].
    The DECAs output 0 dBm, so they're designed to "power through" the isolation [loss].
     
  13. azarby

    azarby Hall Of Fame

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    In my preferred sceanrio, the splitter in question doesn't need to pass DC power. I do have a backup scenario for use if/when I convert my system to all DECA that would need a reverse power passing spliter (combiner).

    Bob
     
  14. Groundhog45

    Groundhog45 Hall Of Fame

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    Where's the PI in that setup? I keep trying to visualize all of these different configurations to be sure I get it right when I get my stuff.
     
  15. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Which PI? - if you meant the one with the SWM...

    SWM1 output>15'cable>PI>filter>spliiter>coax to receivers>DECA>short coax
     
  16. Groundhog45

    Groundhog45 Hall Of Fame

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    Got it. Thanks. :D That's what I expect to have, unless they want us to put more than the H24 in the DECA cloud. I would put the first DECA after the filter and either before the splitter to put both legs in the cloud or after the splitter to only put one leg in the cloud. I hope that is correct, or do I have my head completely in the clouds.
     
  17. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    I think you'll be in fine shape there...:)
     
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