XM Radio technology

[biggestmuff]

Does anyone have any technical specs on this system? I like checking out new technology even though I wouldn't buy it. I only know a few things about it.

Two satellites in geo-syncronous orbit are used.
Downlink is in the 2.3 GHz range.
A perceptual audio coder from Lucent is used.
Average bitrate is 40 Kb/s, with a max of 65 Kb/s.

 

[RussianSoldier]

<< Downlink is in the 2.3 GHz range. >>



heh, my cordless phone transmits at that....

 

[Passions]

If you goto howstuffworks.com they have a detailed article on it. pretty interesting, not as bad as you would think xm is.

 

[Nefrodite]

40kb/s ? omg i didn't know it was that low

 

[Idoxash]

hahaha dude around 40Kb/s darn AM has to sound better!

 

[Nefrodite]

hm thats what ii thought, supposedly its more like 128kbs mp3 atleast... so either really good compression or numbers are funky.

 

[biggestmuff]

40 Kb/s means nothing without knowing what the codec is capable of doing. Lucent has had some good results with their past codecs.

 

[brxndxn]

I wonder about tunnels, trees, clouds... Will that stuff block out XM radio? What's the point of having it in my car if driving near trees ruins it?

 

[Heisenberg]

<< I wonder about tunnels, trees, clouds... Will that stuff block out XM radio? What's the point of having it in my car if driving near trees ruins it? >>



I would guess that only fairly solid overhead obstructions (like tunnels) would be a problem. Trees and clouds really shouldn't matter if they did any kind of decent testing with the signal strength. In any event, it's probably better reception than regular radio since the signal is space-based.

 

[biggestmuff]

just to back up heisenberg's answer, the signal will either be there or it won't. there is no fading in or out like fm and am.

 

[Zambonni]

I would guess the head unit has buffer of some sort that would get you through most tunnels, etc.

 

[MrMet]

hmmmmmmmm

 

[Retro2001]

Hi. From what I've read about XM, trees, buildings and all but the most sever weather will not effect transmission. Tunnels, however can, depending on their depth. Also, the sound quality is said to destroy FM and easily rival CD. Is that 40kb/s or 40kB/s, I would beleive that the latter is much more plausable than the former.

Peace,
Will

 

[Nefrodite]

40kB/s = 320kb/s

now that would be certainly sweet! and probably undistinguishable from cd by 99.5% of the population

 

[RobK]

I'd say that at 320kb/sec NO ONE could distinguish from CD. Our ears just aren't that good. People might *think* they can tell a difference, psychologically, but physically this should not be possible.

 

[dew042]

<< Hi. From what I've read about XM, trees, buildings and all but the most sever weather will not effect transmission. Tunnels, however can, depending on their depth. Also, the sound quality is said to destroy FM and easily rival CD. Is that 40kb/s or 40kB/s, I would beleive that the latter is much more plausable than the former.

Peace,
Will >>




i gotta think when bb king hits a tree or building he's gonna hurt. i am just surprized he survives all those falls through barn ceilings. whew, they must be paying him well. no wonder they are going to go bankrupt.

dew.