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Difference between P.I.s and amps.

Discussion in 'DIRECTV Installation/MDU Discussion' started by sysakpa, Jan 10, 2013.

  1. sysakpa

    sysakpa New Member

    Jan 8, 2013
    What exactly is the difference between a power inserter such as a PI-29 used to power a LNB and an amplifier such as a SA6AL?

    I read that some parameters used to measure amp. performance are power gain and efficiency. This seems to me to be characteristic of a power inserter.

    A power inserter locks lines to any of the 4 signals, 13V, 18V, 13V 22KHz, 18V 22KHz.

    I guess my question is what is the difference between the two devices since they both seem to increase power levels?

    I should know this but I dont; what is the relationship between power and voltage?

    Doesnt a greater amplitude imply greater power assuming the frequencies stay the same?

  2. P Smith

    P Smith Mr. FixAnything

    Jul 25, 2002
    W.Mdtrn Sea
    what exactly you need to know ? (you did post a lot ... misunderstanding )

    PI is just a source of DC with certain parameters: stabilized DC voltage 29V and max current (2A ?). Nothing else.

    Amplifier is a device what do increase a RF signals (and pass DC to LNBF; max 1 A and voltage 10..20 VDC depend of it's own power brick)
  3. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

    Dec 9, 2006
    The PI-29 is a DC power supply for SWiM.
    The SA6AL is an RF amplifier, used before a SWiM, or other switch.
  4. BattleZone

    BattleZone Hall Of Fame

    Nov 13, 2007
    All SWM switches require external power to operate, and don't rely on power coming from the receivers. External SWM switches, like the SWM8, SWM16, and SWM32, have a built-in power-locker, which keeps each of the 4 lines from the LNB locked to a specific switch position, and for that reason, requires more power. That's one of the reasons why it uses a higher-voltage power supply (PI29) vs the PI21 of a SWM LNB. But we're strictly talking about DC power here, not signal strength.

    The SA6AL is a signal amplifier. It's designed for commercial applications where the cable runs from the dish are over 100', or where the signals from the dish are split a number of times and require further amplification. The SA6AL actually blocks DC power from passing through it, so it requires a separate power locker between it and the dish, and cannot be used without one. Multiple SA6ALs can be used down-stream from the dish, though, to split the signal multiple times or to carry it longer distances.

    Is there something you're specifically trying to accomplish, or are you just curious?
  5. JosephB

    JosephB Icon

    Nov 14, 2005
    Birmingham, AL

    Power inserter provides power outbound *from* your house to the dish itself. An amplifier takes a signal and, well, amplifies it, so that it is stronger inbound *TO* your house. As mentioned above, only the amplifier directly impacts signal strength. The power inserter does not directly impact signal strength, it is simply a required part of the chain...though you will have zero signal without it :)

    A PI is required in SWIM situations, because the electronics in the dish (or external SWIM switch) require more power than your receiver is designed to provide. An amplifier is not always required, and is only used on very long cable runs. In non-SWIM installations a power inserter is not required because the receiver(s) are able to provide enough power for the less complicated electronics in those dishes

    And you were incorrect in your initial description of a PI. A polarity locker is the device that locks different feeds to 18/13v or 18/13v22khz. These are used in non-SWIM LNBs when you are going to be splitting feeds for large installations (which could theoretically be SWIM or non-SWIM, but practically all new installs would be some number of external SWIM switches)

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