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SL-3 SWM: 21 or 29 volt PI

Discussion in 'DIRECTV Installation/MDU Discussion' started by BennyGregg, Oct 3, 2012.

  1. Oct 3, 2012 #1 of 13
    BennyGregg

    BennyGregg Legend

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    I believe that the PI for the SL-3 SWM initially was 21 volts but that recently 29 volt PI's for the SL-3 SWM have been recommended. Is either PI acceptable, and is one voltage PI better than the other for some reason?
     
  2. Oct 3, 2012 #2 of 13
    jimmie57

    jimmie57 Hall Of Fame

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    From what I read,
    The 21 volt is the proper one for the SWM dishes. They were originally tested with the 29 volt and in some cases where there is a lot of coax with long runs you could see a voltage drop and then the 29 volt might be used for that instance.

    I am not an installer or tech.
     
  3. Oct 3, 2012 #3 of 13
    BennyGregg

    BennyGregg Legend

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    What prompted my question was a specification I saw on the Solid Signal site which says "The SL3-SWM LNB is designed with an built-in 8-channel multiswitch which allows you to have multiple satellite feeds at once. This product requires the SWM PI-29 29v (NOT INCLUDED) Power Inserter ..."
     
  4. Oct 3, 2012 #4 of 13
    jimmie57

    jimmie57 Hall Of Fame

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    It sure does say that on the Solid Signal site. I would have bet big money that it said 21 volt.
    I just was upgraded in June from a legacy system to the Slimline 3 SWM system and they installed the 21 volt on mine.
    Veryoldschool and some of the others will have more information about this.

    Edit: I just went to the DirecTV Installers forum and did not see anything about a change in the power inserter.
     
  5. Oct 3, 2012 #5 of 13
    dielray

    dielray Legend

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    The PI-21 is the power inserter most commonly used with a SWM LNB.
     
  6. Oct 3, 2012 #6 of 13
    Stuart Sweet

    Stuart Sweet The Shadow Knows!

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    Agreed, but I'll say two things. First of all the extra voltage won't hurt the LNB, in fact it may allow for a stronger signal over long lines. Second, I've heard from several sources that the 29 volt power inserter will be the recommended choice in the future.
     
  7. Oct 3, 2012 #7 of 13
    dielray

    dielray Legend

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    What do you mean by stronger signal? I've never observed this characteristic regarding SNR. I'll have to look in to power level.

    Would be interesting if it becomes standard. One of their reasons for the new broadband DECA was to decrease the number of different power supplies manufactured.
     
  8. Oct 3, 2012 #8 of 13
    Stuart Sweet

    Stuart Sweet The Shadow Knows!

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    I was told the signal strength was a little higher with the 29 volt.
     
  9. caseyf5

    caseyf5 Member

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    Hello BennyGreg,

    I have read on this site that the people doing the hardware testing used the 29v Power Inserter due to the fact that there was no 21v PI. That was used at a later time but the 29v PI was used as one alternative if the signal level was lower than optimum after all other methods of increasing the signal level were tried without much success. This seems to be a case where more than one power adapter can be used to substitute for another. :confused: :) :cool:
     
  10. P Smith

    P Smith Mr. FixAnything

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    I wouldn't bet on the additional 8 volts as a factor of increasing a signal level.

    Usually such devices has voltage regulator (someone has bad SL3 LNBF for dismantling ?) and the PI should deliver 2 or 3 volts higher then Vout of the internal VR.
    So, increase Vin to 29 V shouldn't change parameters of internal circuit eg gain, SNR, etc.
     
  11. Stuart Sweet

    Stuart Sweet The Shadow Knows!

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    P,

    I'll take the advice of about a dozen DIRECTV engineers, including the product manager for SWMs, and all of them disagree with you.
     
  12. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "You're right, but" if the 21 volt wasn't supplying enough due to a voltage drop through the coax, then the change to a 29 volt would get the SWiM back up to full supply power.
     
  13. P Smith

    P Smith Mr. FixAnything

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    It would be simple as see your face :) - post a schematics !


    Or give me the damn SL3 for dismantling.
    Who has broken one ?!
     

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