Just a general question about Satellite radio

Discussion in 'Mobile Phones / Entertainment' started by Zach Foster, Jun 24, 2003.

  1. Zach Foster

    Zach Foster Stunt Coordinator

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    I heard a few days ago that satellite radio can not work as well when driving in between tall buildings. Makes sense, it does depend on satellites. My question is, how does it work if it depends on a satellite? TV satellites have to be left in a stationary position to get a clear signal, but obviously, in a car, you are always moving. Does it somehow send out a 360 degree signal for the satellite to retrieve? Another question, if it doesn't work in between tall buildings, is it worth it, since it won't necessarily work in all aspects of daily life? Thanks!
     
  2. Robert_J

    Robert_J Lead Actor

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    I've only had XM for a few days and only had one loss of signal. It will not work inside a multi-level parking garage. It will work inside the garage at my house and inside the service bay at the local Nissan dealership. XM has installed over a thousand repeaters to combat the drop outs while Sirius has installed less than ten. XM uses a geo-stationary orbit like satellite TV while two of the three Sirius satellites are visible as they orbit the northern hemisphere.

    -Robert
     
  3. David-S

    David-S Second Unit

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    I'd like to point out that sirius is less liable for those kind of drop-outs, as while transmitting their satellites are almost directly overhead, rather than orbiting at the equator...

    I have never had problems(Sirius), even while driving through underground sections of Philadelphia. I will lose signal while under a bank drive-through canopy, and in gas stations (i live in a smaller area, with no repeater), but other than that I have had maybe 5-10 dropouts in 3 months (and yes, it's constantly on [​IMG])
     
  4. Zach Foster

    Zach Foster Stunt Coordinator

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    And Sirius advertises "commercial-free" programming too, don't they? (Although, I have heard that the commercials XM has are short and far in between anyway)
     
  5. David-S

    David-S Second Unit

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    Yes, sirius is commercial free...
    (You can get tons of comparison threads at both www.xmfan.com and www.siriusbackstage.com ) both a bit biased in obvious directions...

    ps: i was looking at siriusbackstage, and they say sirius has closer to 100 repeaters, in major areas...

    Zach, do you live in a large city, or what? I drive through some small streets on my college campus surrounded by large, 4-5 story buildings without a problem... i've had a few problems in downtown wilmington (DE), a small city (probably no repeater) w/ a few small high-rise type buildings...
     
  6. Robert_J

    Robert_J Lead Actor

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  7. Zach Foster

    Zach Foster Stunt Coordinator

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    Actually David, lol, I live in the country surrounded by cows. I was just talking about the tall buildings to get some insight on the capabilities of satellite radio. [​IMG]
     
  8. David-S

    David-S Second Unit

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    lol, well, if it makes you feel any better, i recently took a drive down I-81 from I66 to blacksburg, and didn't experience a single drop out on the round trip... [​IMG] so it works in lands of cows too...

    (note, if you do live in a rural area, there are less likely to be XM repeaters, so Sirius might get a better signal, less likely to be blocked by hills/trees etc... I am just guessing, but from what i've heard this seems logical)
     
  9. Gary Silverman

    Gary Silverman Stunt Coordinator

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    TV satellite dishes are mostly 18" diameter. Makes for a small area to trap the signal. My understanding is that the car rooftop antennas for satellite actually use the roof of the car as the dish, obviously a much larger area than an 18" dish. Tunnels(there's only one where I live) and parking garages have been the only places where I lost signal. Not a big deal.
     
  10. Paul_Medenwaldt

    Paul_Medenwaldt Supporting Actor

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    I have driven in downtown Minneapolis and have had no dropouts in signal. I was told there is a repeater on top of the IDS tower, which may help out with the signal.

    Also I drive through a tunnel once in a while which is about 1/2 mile long and I have never lost a signal going through. But once I pull into my garage the signal is gone.

    Paul
     
  11. Joey

    Joey Stunt Coordinator

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    The XM car antenna does not use the car or the sheet metal that it is stuck on as part of the antenna. It's wholly contained and is omni-directional. The signals from ROCK and ROLL (the two satellites) are beamed down and received by the antenna.

    Unlike TV satellite dishes, whose parabolic design is to reflect the received signal to the LNB for maximum signal strength which requires the dish to be pointed toward the satellite, the XM car antenna just receives the signal no matter which direction the signal is coming from.

    In cases where there are many tall buildings that may block the signal - there is a good possibility that XM has installed repeaters in the area to compensate for any possible dropouts. Repeaters' transmissions don't need to have any line-of-sight as the satellites do.


    Joey
     
  12. Brett DiMichele

    Brett DiMichele Producer

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    Joey,

    The XM and Sirius Car Antena's are Low Gain and they do use
    the sheet metal for more surface area to enhance reception.
    No they obviously don't have an LNB and a parabolic dish to
    focus the signal but the roof is somehow attributed to
    boosting the antena's sensitivity. Why else would the
    manuals state that the antena must be mounted to such and
    such inches of metal?
     
  13. Gary Silverman

    Gary Silverman Stunt Coordinator

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    Also, the Terk instruction manual states that, in the case of mounting on a composite surface, you must attach an aluminum foil "ground plane" of at least 2 1/4 sq. ft., centered under the antenna.
     
  14. Joey

    Joey Stunt Coordinator

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    Bretty, Gary - sorry I think I misunderstood. I should have said that the XM car antenna does not need to be stuck to metal in order to operate. As far as it using the metal as a ground plane - I've read conflicting statements despite what it says in the Delphi manual, but I believe it does indeed go on to say that it is not a necessity to mount it on metal. I am not familiar with the Terk antenna, so I couldn't comment on that.
     
  15. Gary Silverman

    Gary Silverman Stunt Coordinator

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    Apology accepted.
    I seem to have this auto-defense mechanism built into my brain that makes me reply to any rebuttals to my posts.
    And, what the hell does a ground plane do, anyway?
     

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