Sirius and underpasses
JK Super Freak
Joined: Dec 2006
Posts: 1,002
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Buffer
The longer the buffer the longer the wait between changing channels... you have to load up the buffer, the music is played real time, not like a CD that u can spin faster to load the buffer faster...
JK Enthusiast
Joined: Aug 2007
Posts: 269
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according to their site, they do...
8. Why has my radio lost its signal?
While we do have an extensive network of ground repeaters (towers that rebroadcast our satellite signal to help give maximum coverage) in many metropolitan areas, factors such as microwaves and physical obstruction (bridges and tunnels) can still temporarily disrupt your radio’s reception.
However, this problem is largely held at bay by the four-second buffer created by slight broadcasting delays between our two satellites orbiting over the continental United States and our extensive ground network of repeaters.
8. Why has my radio lost its signal?
While we do have an extensive network of ground repeaters (towers that rebroadcast our satellite signal to help give maximum coverage) in many metropolitan areas, factors such as microwaves and physical obstruction (bridges and tunnels) can still temporarily disrupt your radio’s reception.
However, this problem is largely held at bay by the four-second buffer created by slight broadcasting delays between our two satellites orbiting over the continental United States and our extensive ground network of repeaters.
JK Enthusiast
Joined: Aug 2007
Posts: 127
Likes: 0
From: Plymouth, MA
Let's not forget that Sirius and XM have (or will soon) merge.
http://money.cnn.com/2007/02/19/news...rius/index.htm
This may alleviate some of these issues in the near future
http://money.cnn.com/2007/02/19/news...rius/index.htm
This may alleviate some of these issues in the near future
JK Freak
Joined: Jul 2007
Posts: 568
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From: Fort Collins, Colorado
From my understanding Sirius has 2 geostationary satellites (this means that they are always in the same position relative to the earth and that they rotate with the earths rotation.) Anyway, they are suppossedly located centrally over North America, one to the north and one to the south. This would mean that as you reach either coast the angle from your vehicle to the satellite(s) would be much lower, closer to the horizon. Buildings, trees, mountains, etc. would interfere more so than if you were located in say Nebraska where the sat's are located directly overhead. The sat's position should also benefit those traveling in midwestern canyons and maybe why others have found Sirius better than XM in those locations. Though I have no idea the position of XM's sat's... 
Sirius has three satellites with at least one and usually two always high in the sky (within a cone 45 degrees above the horizon):
http://en.wikipedia.org/wiki/Sirius_....27_satellites
XM has four satellites in orbit directly above the equator. Only two of which are currently transmitting. The angle of these satellites above the horizon depends on your position within the US:
http://en.wikipedia.org/wiki/XM_Sate...dio#Technology
IEEE Spectrum had a great article on Sirius's technology a few years back, but I can't find it in their archives now.
-Glen
JK Freak
Joined: Jul 2007
Posts: 568
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From: Fort Collins, Colorado
Read claim 1 of US patent 6,223,019. They specify about 0.5 second in the claim, but use 4 seconds in practice:
1. A method of providing audio satellite broadcast transmissions to fixed and mobile receivers .... transmitting, from two or more of said satellites, audio broadcast signals that are substantially identical in content; transmitting at least two radio broadcast signals having frequencies in the range of about 1 to about 4 GHz from at least two satellites in said constellation substantially simultaneously, said radio broadcast signals having substantially the same content, to a plurality of mobile receivers for said signals in said area and at or near the earth's surface, including the steps of: broadcasting a first radio broadcast signal to said plurality of mobile receivers; after a time delay of sufficient length to substantially eliminate outages in said area, said delay being at least about 0.5 seconds, following the broadcast of said first radio broadcast signal, broadcasting a second radio broadcast signal containing substantially the same program content as said first radio broadcast to said plurality of mobile receivers;
Two systems using this invention were designed for audio satellite broadcasting. One system was designed for service to the contiguous 48 United States. The input requirements were to have one satellite in the northern portion of the service area always in view with at least 60.degree. elevation angle to mobile receivers in the area and a second satellite always visible with at least 25.degree. elevation angle.
JK Enthusiast
Joined: May 2007
Posts: 370
Likes: 0
From: Southwest CT
I get the overpass and tree thing too - also on another vehicle with a Sirius unit that I installed. Still, it is far better than FM, and it works deep into the mountains, unlike FM which limits me to maybe one or two stations on some trips. The traffic istation s pretty great for metro NYC too.
JK Enthusiast
Joined: Sep 2007
Posts: 105
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From: Texas
