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Help installing broadband DECA

Discussion in 'DIRECTV Installation/MDU Discussion' started by vanzant, Mar 30, 2011.

  1. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    While the NF is fairly well "nailed" in the LNB, you still have losses to the receiver and the more you have/use the sooner the receiver reaches minimum detectable signal levels.
    If you work through the losses of a non SWiM system and a SWiM, you'll find the SWiM needs the gain it has to give the same dynamic range and still run through splitters.
     
  2. harsh

    harsh Beware the Attack Basset

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    Splitters on the IF side, regardless of configuration, do not impact the satellite signal strength.

    Splitters cut into the IF signal coming from the LNB and the DECA signal traveling to and fro.
     
  3. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    This is so dumb, someone had to PM me about this.
    ANY receiver is going to be affected by the loss feeding it. I doesn't matter if it's the LNB output, or the IF out of the SWiM.
    Loss is loss,Redacted.
    The only difference at all is the frequency since this affects the amount.
    An 8-way splitter adds another 15.5 dB of loss to the coax, so the SWiMs try to compensate for this by having 15 dB of gain when the SAT levels drop below -45 dBm.

    Redacted
     
  4. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    I feel your pain VOS.

    What the heck is a Dish subscriber who has likely never set eyes on a DirecTV WHDS/SWiM setup himself, let alone the actual SWiM hardware (in person), let alone operated at all with it as a DirecTV customer...doing giving ANY advice on this topic?

    Redacted.

    Over-the-top-utterly ridiculous.

    OP - please listen to VOS...he is an expert on this stuff.
     
  5. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Loss 101:
    The dish outputs x dBm

    With setup "A":
    The receiver is 200 feet away, so the coax loss can be -18.6 dB @ 2 GHz.

    With setup "B":
    The receiver is 50 feet away, so the coax loss can be -4.6 dB @ 2 GHz.

    Which receiver will lose signal first/longer when the rain gets heavy?

    Redacted
     
  6. K4SMX

    K4SMX Hall Of Fame

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    Many thanks, Bob, and good to hear from you! Understand about the crawl spaces; I don't even like to get on my knees on the floor anymore. Painful!

    Another question I have involves the router connection to the splitter through the DECA. The Solid Signal diagram on their web page shows this being connected to the power passing port of the splitter. Currently, of course, that port is occupied by the coax coming from the SWM power inserter on one of the IRD lines. Does it really make any difference which port is used from the router/DECA?

    Also, it wouldn't be any trouble to put a Band Stop filter ahead of the SWM3 upstream of the splitter, but can that be done with the SWM power inserter remaining downstream of the splitter on the IRD line? (The SS diagram shows: splitter ---> BSF ---> SWM PI ---> SWM ---> 5LNB Dish)

    Thanks again! I've lost track of all this stuff while building towers and antennas at the NC location.
     
  7. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I'm not bob [duh] but:
    The BB DECA [or any other DECA] doesn't care if the port is power passing or not, since the DECA isn't outputting and DC.
    The filter does pass DC, so it too can be inline with the SWiM PI and the SWiM.
     
  8. K4SMX

    K4SMX Hall Of Fame

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    And that's what I needed confirmed, thanks, VOS, and a pleasure once again. So I can go: IRD ---> SWM PI ---> Splitter ---> BSF (or not, per Bob, "YMMV") ---> SWM3

    It is somewhat confusing that they put this particular diagram on their web page, with the SWM PI upstream of the splitter and the router/DECA using the PP port of the splitter.
     
  9. harsh

    harsh Beware the Attack Basset

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    I stand by my statement that SWiM splitters have no impact on the satellite signal readings and moreover that they cannot create a situation that manifests as rain fade. What you suggested is false and misleading.

    The satellite signal (as reported in Satellite setup menu option) is uniquely a measure of the satellite downlink signal quality received at the LNB feed horn. It does not evaluate the IF signal from the amplifier to the receiver. This is true of pretty much all consumer satellite setups (including broadband and SARS).

    The satellite downlink signal travels no farther than the LNB. Within the LNB, the signals are block converted down to the IF and retransmitted by the amplifier section. Adding or subtracting loads on the output of the IF amplifier doesn't impact the quality of the signal the dish reflects into the feed horn one iota.

    If you placed a variable attenuator in the line ahead of a receiver, the satellite signal readings would remain constant until that receiver could no longer "see" IF signal. Even then, the satellite signal levels would remain more or less unchanged on any other receivers.

    If you don't know or believe what I'm saying to be true, test it. I'm guessing you have access to or can assemble an unbalanced attenuator pad.


    As an aside, I would suggest that when you speak of gain or loss, you use percentages instead of dB as those not intimate with the concept of decibels have trouble relating it to anything meaningful. I would suggest using percentage gain or loss.
     
  10. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Again someone had to PM me about this, as I've told you several times your being ignored.
    I'm not misleading or suggesting false information. You on the other hand don't seem to grasp the concept.
    what this is [quality] is the carrier to noise ratio, which as long as the signal is ~10 dB above the noise floor, does stay constant.
    Well if you actually had DirecTV AND SWiM, you'd then know that the setup menu does have a screen to measure the IF. It's labeled "SWM" and shows the nine IFs.
    Cable & splitter losses have nothing to do with the SAT feed to the LNB, and if this was where the receiver was, then the losses wouldn't be there. Since the receiver is what receiver the signal, losses to the LNB plus the losses to the receiver all add together. If these didn't, then Sonora would have the business they do and coax lengths and amps wouldn't matter. If "the load" on the LNB's IF doesn't "impact" the quality of the signal, then coax runs could be hundreds of feet and the receivers would still work fine.
    Since I do have DirecTV, SWiM, and know what I'm talking about, I have run some tests like this to see how low the signal can be before the receiver starts showing "the quality" degrading. I found this to be at about -71 dBm, which was where the highest IF showed a drop of 5% and I ran out of attenuation to go farther. The receiver chip is spec'd to -70 dBm.

    Percentages work well for bit error rates, but don't for losses, which is why decibels are used.
    3 dB is easy @ 50%
    6 dB is easy @ 25%
    9 dB is easy @ 12.5%
    10 dB is easy too @ 10%
    20 dB isn't so much @ 1%
    30 dB is sort of pointless @ 0.1%
    Since we're dealing with dynamic ranges of 50 dB, percentages are basically meaningless.

    Now to bring this whole thing back to my post that you replied to:

    Using a larger splitter than one needs, will add more loss to the receiver. Since the whole signal path losses all add up, when the SAT signal drops to the LNB, the output of the LNB drops and the losses between the LNB and the receiver causes the receiver's signal to also drop. Reducing the cable/splitter losses, means the receiver will still be above it's minimum detectable signal levels longer.
    Using a 4-way splitter instead of an 8-way splitter is much like having 50' less coax between the dish and the receiver.
     
  11. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    To try to have all of this make some sense to those that don't have an RF background:

    [​IMG]

    The green is the part of the signal the receiver uses.
    The blue is the part that the receiver doesn't show in the setup screens.
    The more blue [power] you have the more resistance to rainfade you have.
    You can't do anything about the weather, so all you can do is to align the dish as well as you can and keep the loss from the dish to the receiver as low as you can.
     

    Attached Files:

  12. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Thanks VOS.

    You have forgotten more on this topic than most folks will ever know on the subject.

    It's a shame that legitimate questions and your legitimate responses have to be diluted by misinformation and uniformed posts from non-DirecTV customers, especially those who actually have field experience with SWiM, green splitters, and the like.

    Your great data is appreciated.
     
  13. vanzant

    vanzant New Member

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    This just occured to me. Do I need 2 BB DECA units? One for each receiver???

    I only purchased one and was thinking that it would enable VOD on all receivers on the home network. Is that a correct assumption? Or do I need 1 DECA per receiver?
     
  14. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Going off your diagram, where you have "24s", the only other DECA you need is the BB DECA, since the 24s have one internally.
     

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