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DirecTV National HD Listing/Maps Discussion Thread (Technical - Not Anticipation)

Discussion in 'DIRECTV Programming' started by Sixto, May 29, 2012.

  1. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    From some work at Space Systems, the number of tps that can be switched is a finite number. Spares are brought online, but with the switching, another tp needs to be taken off line.

    [my guess] co-located SATs could share frequencies as needed.
     
  2. LameLefty

    LameLefty I used to be a rocket scientist

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    Spoken like a true armchair engineer. "Design and operating conditions" are not appropriate terms for the discussion. Design conditions and operating conditions are two things which are HOPEFULLY the same, but which to an engineer do not mean what you appear to think they mean. To an engineer, such terms refer to the external environmental and operation conditions experienced by the system. The term you seem to mean is "requirements."

    For full redundancy - assuming of course that full redundancy is a true design requirement (it may not be) - design and operating conditions must be the same for primary and backup systems, as either system may be forced to carry the full load of fulfilling the mission requirements.

    That being said, there are differing philosophies for achieving functional redundancy to meet operational requirements. Depending on the specific system or subsystem, one approach might be to implement backup systems that are second identical copies of the the primary systems. Alternately, the backup system may be a set of analogous components designed to perform the same functions of the primary system in a different manner or with different specifics as compared to the primary system.

    For example, certain life support functions on the International Space Station are performed by multiple copies of the same system that are identical in every major way, located in physically separated sections of the station. Each system can operate at half-capacity carrying part of the load or, in a contingency, operate at full capacity and carry the full load all by itself. If both systems fail independently, the same functions can be carried out by several different pieces of equipment while repairs are attempted or an emergency evacuation of the facility is prepared and executed.

    By contrast, a different method of fulfilling the requirement for redundancy is used in flight control software for some high-value spacecraft. In some of those spacecraft, the primary flight software runs on several independent identical processor units that are periodically polled to compare the outputs of each system to one another. If one unit puts out data that disagrees with the others, the computers "vote out" the anomalous unit and it is considered failed. If too many of the processors running the primary software disagree, the entire system will switch to backup software control systems running on totally independent hardware. The backup software starts with the same exact operational requirements but is developed by a completely separate team using a completely isolated development and verification process. That way any systemic errors that might have been made in the development of the primary software are not repeated accidentally by the backup software.
     
  3. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I'm not going to disagree, but to add that there is a check in place, so any hardware wanting to be used by one group can't be used by the other. There is a middle group that keeps them isolated, but knows what both are using.
     
  4. tonyd79

    tonyd79 Hall Of Fame

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    Great post, Lefty.
     
  5. inkahauts

    inkahauts Well-Known Member

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    I would propose that it Depends on if the problem with the primary was the result of a design issue or a anomaly caused by an outside force, like the launch, assuming that the backup system is identical in the first place.

    Edit...

    Or what lefty said... :) :) :)
     
  6. inkahauts

    inkahauts Well-Known Member

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    Maybe move one sat to the failed ones location, and then fire up all spares on both a sat that is in the new location, and one at the location that was vacated by the rescue sat, since the freq would then be available because both slots would be short a sat....

    And don't forget there is freq to spare that isn't be used right now it appears, since they are launching another sat to both locations 99 and 103, or at least that's what it appears they are planning on doing with d14 and d15...
     
  7. P Smith

    P Smith Mr. FixAnything

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    If we could see all blueprints ...
     
  8. georule

    georule Hall Of Fame

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    What he said.

    The problem with the "one kidney failed" analogy is that in the human system both kidneys are supposed to work all the time.

    In a hardware system, maybe not so. And even if they are, component failure can be caused by many factors, not all having to do with the operating conditions and design parameters. Maybe it was a weak component that got thru testing. Doesn't necessarily require that the redunandant component is.

    Sure, there is increased risk when you're "naked" to single-point-of-failure. But it doesn't necesarily follow that the risk is increased because a failure already occurred. And if you survive the switchover and immediate period following, the risk curve goes down greatly.
     
  9. HoTat2

    HoTat2 Hall Of Fame

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    Los...
    To be honest I'm still trying to fully grasp the concept of a "spare transponder" because the satellite manufacturers speak in terms of "spare Traveling Wave Tube Amplifiers" (TWTAs). Its as though the actual "transponder" is broken into two parts with a single RF receiver and frequency translation circuit path for each unlink/downlink channel which is separate from the final transmit power amplifier(s), the TWTA(s), which are switchable and have spares.

    For instance, from the SS/L specs. for D10-12

    National/Alaska Ka-band

    28 active TWTAs
    8 spare TWTAs

    (with 32 active TWTAs, and possibly eight spares for D12)

    National/Hawaii Ka-band

    4 active TWTAs
    4 spare TWTAs

    Spotbeam Ka-band

    55 active TWTAs
    15 spare TWTAs


    But don't the RF receive and freq. translation circuits prior to the final transmit PA need failure back up as well?
     
  10. harsh

    harsh Beware the Attack Basset

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    Could it be that "spare" in this case simply means that there's no plan to use them in the current configuration?
     
  11. HoTat2

    HoTat2 Hall Of Fame

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    Los...
    The point is though, whenever replacement is required in the event of failure of a transponder in the "current configuration." Why only carry spare replacements for the power amplifier part of the transponder, the "TWTAs," and not the LNA, mixer, and LO parts as well as indicated in this simplified functional block diagram of a satellite tp.?

    [​IMG]

    I don't understand the design approach in carrying spares for the transponder PA only, unless "TWTA" in this context is just loose terminology for the entire transponder assembly which includes the RF receiver and freq, down conversion circuitry.
     
  12. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Having actually worked on a SAT, there are lots of rotating waveguide switches, on both sides of the TWTs. These switches were indicated on the monitoring screen as a crossing, where it would be open for one path and closed for the other which was at 90º. Think of this as a large railroad switching yard, where the antenna gets switched to a TWT, which gets switched to the TP, which gets switched to another TWT, which gets switched to the antenna.
    "The whole yard" can mix and match many paths, but there is a limit to how many can be connected.
     
  13. HoTat2

    HoTat2 Hall Of Fame

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    Los...
    Thanks VOS;

    With the "spare TWTAs" mentioned by SS/L I can understand such switch-ability and redundancy on the power amp. or TWT side of matters, but how is a failure on the LNA, mixer, and LO side of a given transponder handled in your estimation, as the specs. only mention spare TWTAs?
     
  14. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "I'm fairly sure" there are spare TPs too. The count may be less than the amps, because the TWTs are "tubes" and so they age.
     
  15. cypherx

    cypherx Hall Of Fame

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    What does a "transponder" look like? Any pictures? Is it something you can see or is it just a name for a collection of tunable circuits?
     
  16. Sixto

    Sixto Well-Known Member

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  17. Justin23

    Justin23 Hall Of Fame

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  18. Sixto

    Sixto Well-Known Member

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    Same question. :)
     
  19. mws192

    mws192 Godfather

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    BBWR= Blocking Back, Wide Receiver = PAC12 plus a few others to aide in the confusion. ;)
     
  20. maartena

    maartena Hall Of Fame

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    BBWR = BBC World. :D
    BBWR = Brazilian Backyard Wresting Revolution.
    BBWR = A radio channel for BBW's?

    I'm thinking they are testing something, and it hasn't got much to do with existing channels or new channels. Maybe they are just placeholders though, perhaps they are preparing for PAC12 and are figuring out where to put them.

    660 is weird though, those channels are in use by current RSN's. 660 and 661 are SD though with temp feeds on 660-1 and 661-1 for games. FS Ohio and FS Cincinatti. 662 is already full HD. Perhaps they are making 660 and 661 full time HD?
     

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