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Sonora LA141R

Discussion in 'DIRECTV Installation/MDU Discussion' started by Jodean, Mar 25, 2012.

  1. Jodean

    Jodean Icon

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    Ive read all the post here about this amp and have seen all the diagrams that sonora has.

    What it doesnt show is a best location for this amp.

    The diagram shows 100' from dish to amp, then out of a 8 way you can go 250'

    At a show room we have a dish about 400' from the booth.

    Right now they have dish >> 400' rg6 >> PI >> LA141R with 24v >> 4 way

    Its working most of the time, then starts searching.

    Would it be better to have the amp closer to the dish and be power by the PI? There is no power source by the dish.

    Right now its a 21V PI, and they are bringing out a 29V tomorrow. Not sure if moving the amp would improve anything.
     
  2. P Smith

    P Smith Mr. FixAnything

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    By rule of thumb - keep amplifier close to source of a signal, especially if you have long cable(s).
    Find other one what has PowerOverCoax.

    Edit: the device can be powered over coax:
    For long run coax with a power use max voltage power supply and copper coax cable.
     
  3. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I think the current results are to be expected.
    The loss and gain are borderline, which the results are showing.
    400' is a lot for a 21 volt PI.
    If you could change the 4-way to a 2-way, and use a 29 volt, it might just work.
     
  4. P Smith

    P Smith Mr. FixAnything

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    I would go for the Sonora amp, the 400" run is not that forgiven with 2x vs 4x splitter.
     
  5. wallfishman

    wallfishman Icon

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    Dec 31, 2008
    Jodean cant you tywrap a dish onto something closer ?
     
  6. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    The amp is still needed, but so is more than 13 dB of gain.
    400' ~ 25-35 dB loss.
    SWiM has ~30 dB loss range.
    2-way splitter ~ -5 dB
    4-way splitter ~ -10 dB.

    Anyone can do the math.
     
  7. doctor j

    doctor j Hall Of Fame DBSTalk Club

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    Sonora Design Makes a LA281 amp with 28 dB gain that would do better.

    Doctor j
     
  8. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    LA281R-T looks to be a good pick.
     
  9. AntAltMike

    AntAltMike Hall Of Fame

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    I hadn't seen the Sonora LA-281T and LA-281T-24 products, but they seem a good fit fit for Jolean's situation.

    The Model LA281T comes with a 12 volt, .250 MA power supply, so if it is used, power for the SWiM unit would have to be injected into the downlead, which means the LA-281-T would have to be at a point where power insertion could be implemented. As I picture this, that would mean 400 feet from the dish. The sustenance of digital signal quality is actually easier than is the sustenance of analog signal quality, and a line extender amplifier could be inserted 400 feet from the LNB, where the signal has dropped down to the mid -60dBm range, but if it were mine, I'd sleep better if it were installed near the downlead's midpoint.

    Unfortunately, for those who want to engineer an optimal implementation of it, Sonora's own published specs are, as always, inadequate, vague and contradictory. Sonora claims that the model 141 amplifier can handle a 32 transponder input with an average level of -28dBm, which, if taken literally, would enable it to be installed right at the LNB, but while I consider Sonora products to be sufficiently reliable for commercial use, they cut their specs awfully close. I remember back when DirecTV was running two weak transponders at 101 (30 and 32) customers who maintained systems in the center of strong spotbeams had overload problems with Sonora's premium stacker, the SAL 20-24, which were difficult to remedy by just padding the input because the AGC would compensate for the reduced input and jack the gain up to the point at which the IMD still degraded the weaker transponders, whereas I had no trouble with Sonora's more primitive microstacker and wound up substituting them for their more expensive products. The problem with Sonora's AGC is that it was for total output wattage, but when one transponder was disproportionately strong, and, in that case, two were weak, enough IMD fell on the weak ones to degrade them even though the amp was operating at its putative safe out level. Sonora furnishes IMD figures for two "tones" but for some reason does not call them two "transponders". I remember that the IMD ratings that Spaun used to furnish were near useless for digital signal overload calculations because they were for analog waveforms.


    When Sonora claims that the LA141 can handle an input of 28dBm, yeah, it can if it is used alone, but if you then put a second one downstream, as Jolean's situation needs, the additional IMD developed by this two amplifier cascade goes up by 6dB and that may excessively degrade the signals, whereas if you put the first LA141 200 feet from the dish, then the approximately 15dB signal loss at 1,800 MHz will result in a 30dB reduction in IMD developed by that amplifier, so when a second one is cascaded in, the combined IMD will still be 24 dB less than would be developed if the first one was at the LNB and if the second one were similarly loaded.

    The LA281-T24 costs a good deal more than the LA281-T, but not only does it come with a 24 volt, 2 amp supply, it passes the LNB voltage through, whereas the LA281T blocks it, so when you figure that Jolean was concerned about LNB voltage at 400 feet as well as with adequate amplification, the LA281T-24 looks like an easy-to-implement remedy to both concerns.
     

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