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DIRECTV Satellite Discussion D-14 @99W

Discussion in 'DIRECTV General Discussion' started by Sixto, Jun 17, 2010.

  1. Jul 14, 2013 #801 of 3078
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "Mr Smith" has seen Ka-lo be inverted from Ka-hi, which happens with a low side conversion so "something" isn't tracking.

    If the LNB was using a high side conversion for Ka-lo, the 17.3-17.8 RDBS would require another LO.

    "Seems like" we might need one of these:

    [​IMG]
     
  2. Jul 14, 2013 #802 of 3078
    HoTat2

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    Los...
    OK, I'll let P. Smith comment to confirm that;

    Since from everything I remember reading on the issue in the past, even from P. Smith, was that both the satellite Ka-lo downlink at 18.3-18.8 GHz and Ka-hi at 19.7-20,2 GHz use the same 18.050 GHz L.O. for low side conversion in the LNBF to 250-750 MHz and 1650-2150 MHz respectively.
     
  3. Jul 14, 2013 #803 of 3078
    P Smith

    P Smith Mr. FixAnything

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    yes, all Ka LNBFs using just one LOF=18.05GHZ for both Ka ranges,

    but for old school tuners (950...2150) DTV made SUP-2400; another converter with a LOF=2.4 GHz to move 250...750 into 1650...2150 with an inversion

    wideband tuners just fine for all three L ranges coming from LNBFs: 250...750, 950...1450 and 1650...2150 MHz
     
  4. Jul 14, 2013 #804 of 3078
    bobnielsen

    bobnielsen Éminence grise

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    This brings up something I wondered about a while ago: With RDBS at 17.3 - 17.8, what is there to keep the existing mixer from combining that with the 18.050 L.O. to make a 750 - 250 MHz output which would interfere with Ka-lo? Or does Ka-lo go away, which would allow the 250-750 MHz i.f. to work for RDBS without any new receiving hardware?
     
  5. Jul 14, 2013 #805 of 3078
    HoTat2

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    Los...
    And perhaps this might be the past mention of a "Ka-lo band inversion" which VOS is confusing with the what's taking place inside the LNBF. That is, the high side frequency conversion used in a B Band Converter (SUP-2400)?
    Yes, as used in the H/HR23 models I suppose.
     
  6. Jul 14, 2013 #806 of 3078
    HoTat2

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    Los...
    Bob, as with the example cited by James Long earlier in the thread;

    For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

    Shouldn't it be possible then to design for sufficient selectivity in the LNBF between the 17.7 and 18.3 GHz band edges in the same manner to prevent such adjacent band interference?

    Note: For the CONUS, the RDBS band is only 17.3-17.7 GHz as authorized by the FCC to prevent possible interference to terrestrial microwave systems operating between 17.7-17.8 GHz.
     
  7. Jul 14, 2013 #807 of 3078
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    This doesn't look to be the same, and is more like how I suggested more bandwidth by adding to Ka-hi.

    To address Bob's question: image rejection mixers can be used for only one "side band".
     
  8. Jul 15, 2013 #808 of 3078
    harsh

    harsh Beware the Attack Basset

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    You've left out an important consideration in your "they simply must have figured this out" argument. This isn't a discussion of whether RDBS will work with an OTARD dish but whether it can work with a dish assembly that is set up for Ku or Ka from the same or relatively nearby slots.

    The experts have been relatively silent on the technical details of how it could be done.
     
  9. Jul 15, 2013 #809 of 3078
    HoTat2

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    Los...
    But as I've stated repeatedly harsh;

    If the current Slimline Ka/Ku dishes can successfully receive the Ka band on one end of the spectrum, and the Ku band on the other end. Then what technological barrier can popup to prevent receiving the RDBS band somewhere near center of the two?
     
  10. Jul 15, 2013 #810 of 3078
    P Smith

    P Smith Mr. FixAnything

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    no barriers here,
    we are guessing if RF engineers will make new LNBF with different LOF or we will continue using old LNBF if they will cleanup 250...750 from Ka-Lo signals
     
  11. Jul 15, 2013 #811 of 3078
    HoTat2

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    Los...
    Oh, I agree it's indeed not the same as to the deleterious effect the RDBS band will cause if it manages to reach the Ka band mixer with sufficient signal strength since it falls in the image frequency range of the Ka-lo band.

    But I cited it as an example of how good selectivity can be designed into two very nearby microwave RF bands this way to prevent either from entering the receiver circuitry of the other at a sufficient level to cause any sort of significant spurious response.
     
  12. Jul 15, 2013 #812 of 3078
    bobnielsen

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    It's been a while (~50 yrs) since I have designed any microwave filters but the kind of selectivity needed isn't easily achieved in something that will be mass-produced (good grief, I AM getting old).

    Image reject mixers would work, but would that have been a design criterion for the existing Ka band LNBFs? I recall seeing some photos of the insides of the Slimline feed assembly several years ago which might provides some insight.
     
  13. Jul 15, 2013 #813 of 3078
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.
    :confused:
    I don't know what Dish does, "but" if their LO was 10.7 GHz, the output would be between 1 and 2 GHz.
    I don't see this being any different than DirecTV 8 & DirecTV 4S at 101 that makeup the TPs.
     
  14. Jul 15, 2013 #814 of 3078
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "My guess" is that DirecTV isn't using image rejection mixers due to cost, and for the same reason they haven't added another LO for RDBS as if it cost only $1, it would be tens of millions for the LNBs in service, for something that is only in the testing/proving stage.
     
  15. Jul 15, 2013 #815 of 3078
    HoTat2

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    Los...
    Well AFAIK the Dish 500+/1000+ use perhaps four L.O.s;

    Due to their frequency stacking approach, two (10.75 and 11.25 GHz) using low side conversion for the lower blocks (950-1450 MHz) of the two received bands, and the remaining two (13.850 and 14.350 GHz) to form the upper frequency blocks (1650-2150 MHz), using high side conversion.

    But that's beside the point which I was trying to make which was to simply show that two close satellite bands can be successfully received, with each having sufficient out of band rejection of the other to prevent mutual interference, and I see nothing to prevent the same for separating the 17.3-17.7 GHz RDBS band from 18.3-20.2 GHz Ka bands.

    D8, D9S, and D4S, all operate within the same 12.2-12.7 GHz band and are separated into odd and even transponder sets with high isolation by being of both offset frequencies and opposite polarities.

    The two adjacent bands received by the Dish 500+/1000+ both use the same odd/even polarity and therefore separation can only be accomplished through their being in different frequency ranges.
     
  16. Jul 15, 2013 #816 of 3078
    HoTat2

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    Los...
    While I can agree a L.O. and other necessary receiver circuitry for the RDBS band may not be in the current LNBFs, but "might" be.

    If there is no image rejection type mixer for the Ka band , then how can DIRECTV power up the RB-2A payload on D12 or the upcoming RB-1 on D14 and future RB-2 without interfering with customers' reception of the Ka-lo band?
     
  17. Jul 15, 2013 #817 of 3078
    HoTat2

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    Los...
    As I just asked VOS;

    If the Ka band mixers aren't of an image reject type, how can DIRECTV power up any RDBS payloads at 99 and 103 without potential image interference to subscribers Ka-lo band reception?

    They were, and I think they were originally posted by RobertE for a Andrews Ka/Ku SL-5 back in '06 here;

    http://www.dbstalk.com/topic/58211-a-look-inside-an-andrew-kaku-lnb-not-dialup-friendly/

    Unfortunately all the images hosted by Photo Bucket except for 1 I think, have long been removed.
     
  18. Jul 15, 2013 #818 of 3078
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    You've got me more :confused: with your "Well AFAIK the Dish 500+/1000+" as not much makes sense, but since "the point" was about the SAT downlink, 17.3-17.7 GHz and 18.3-20.2 GHz aren't any problem.
    "The problem comes" when you're trying to use a 18.050 GHz LO which will "low side" the 17.3-17.7 and "high side" the 18.3-18.7 GHz into the same 250-650 MHz.
    If you filter the unwanted sideband to [each] mixer, then you have two 250-650 MHz signals that can't be put on the same coax, if you're using the same LO.
    "Seems like" we're running in circles [as in it's been posted before].
     
  19. Jul 15, 2013 #819 of 3078
    P Smith

    P Smith Mr. FixAnything

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    if they will use different tpn's ranges for different sats and occupy upper 100 MHz part mostly for Ka-Lo ... but who knows
     
  20. Jul 15, 2013 #820 of 3078
    bobnielsen

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    Yup....

    Hopefully someone "in the know" will jump in here eventually.
     

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