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How does satellite radio work?

Discussion in 'Technical Chat' started by astral, Apr 23, 2010.

  1. Apr 23, 2010 at 4:29 AM
    #1
    astral

    astral [OP] On my second taco now....

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    If this is in the wrong section, I apologize.

    I was gleefully listening to my XM while driving my taco earlier, and it occurred to me that I didn't know how exactly my radio knew it was allowed to play. I mean I know how satellites work in general, and I have a very good knowledge of how GPS devices work, and I assume, like GPS, that our radios don't actually send any signals back to the satellite.

    My initial theory is that XM has a list of radio ID's that have valid subscriptions and that list is uploaded to the satellites. The list would be modified anytime someone starts or stops their subscription, the list is updated. Every 10 minutes or so (just a wild guess on the time), the list is included in the data stream that is sent out from the satellites. If the radio finds its key in the list, then it knows it is allowed to play. I have three problems with my theory:

    1. With 18 million subscribers, it seems like the list would be too big to be transmitted in the data stream without robbing bandwidth from the audio.

    2. Wouldn't people just figure out how to clone the radio ID like you can do with MAC addresses?

    3. It seems like people also would figure out how to bypass the list or add their ID to the list once it has been received with some sort of mod.

    I am working on another theory that involves encryption keys, but it is still a work in progress. Any fellow nerds out there wish to enlighten me? I don't know where this curiosity came from, but it will bug me until I know how this works :eek:
     
  2. Apr 23, 2010 at 4:43 AM
    #2
    DDD

    DDD Shine bright like a hymen

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    I believe that when you activate a receiver, SiriusXM's satellite sends an activation signal to the receiver which unlocks it so it can receive only the channels you paid for. Later they can send another signal to deactivate your receiver or remove some channels.

    Bandwidth is not an issue, if Sirius can add a seemingly unlimited number of channels which are all broadcasting CD quality audio and Program-Assisted Data for each channel, then they should have no problem dedicating one channel for activations/deactivations (Sirius 184).
     
  3. Apr 23, 2010 at 8:34 AM
    #3
    btkicker

    btkicker Well-Known Member

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    Sounds like a question for the Juggalos out there.
     
  4. Apr 23, 2010 at 9:26 AM
    #4
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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  5. Apr 24, 2010 at 10:45 AM
    #5
    astral

    astral [OP] On my second taco now....

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    Hmm, interesting. Makes sense.

    Stupid clowns!

    I can google too ;) but that doesn't address my question in the slightest.
     
  6. Apr 24, 2010 at 10:53 AM
    #6
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    Maybe you can specify what your question actually is?

    This seemed to point to your encryption theory:

     
  7. Apr 24, 2010 at 11:20 AM
    #7
    Cars0n`

    Cars0n` Well-Known Member

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    Kenwood DDX-512 Deck, Boston Acoustics G5 Sub in Ported Bassworx Box, Kenwood eXcelon KAC-X10D Amp, Sirius Satellite Radio, Magellan GPS, DDM 55w bi-xenon headlights, 2 HID Hella 500ff's mounted behind grill, 4 pc ebay Billet grill, Fog Lights (my truck didnt have them stock), Pioneer Speakers 6x9's(front) 6.5's(rear) AFE Cold Air Intake, Hose Clamp Mod, Tailgate Strengthen Mod, Removed Gay Mud Flaps, De-Badged, BHLM, 245/45/20 on velocity wheels. VW865a, Extra D Rings In Box, OEM Cruise Added Optima Red Top Battery
    my raido was cancelled but i still get signal and listen to it all the time:anonymous:

    so it couild be a list of subscription id's. i think anyways.
     
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