Just stumbled upon this thread doing some googling. Can't believe it's still going 3 years later.
I understand there are differences in the compression algorithms used but how can the XM side be sounding better when all the new channels are on the XM network? All the Xtra channels and the "SiriusXM" channels are broadcasted from the XM satellites.
I know of last three satellites launched two (FM-5 and FM-6) were both originally designed to be on the sirius network. Maybe they operate on both frequencies?
I wish they would invest in the tundra orbit satellite model that the original sirius birds use. Seems like it gives better signal penetration from directly above instead of geosynchronous birds that XM and the latest satellites use. The XM network has a large array of ground repeaters to provide signal in areas where you dont have a clear view of the southern horizon.
With the decommissioning of sirius's tundra orbit satellites in the near future coupled with a lack of ground repeaters us sirius listeners are about to have some pretty poor reception.
Current SiriusXM satellites-
FM-1 - Orignal Sirius satellite, tundra orbit. Lifetime expires in 2015
FM-2 - Orignal Sirius satellite, tundra orbit. Lifetime expires in 2015
FM-3 - Orignal Sirius satellite, tundra orbit. Lifetime expires in 2015
FM-5 - Sirius satellite launched 2009, geosynchronous orbit
FM-6 - Sirius satellite launched 2013, geosynchronous orbit
XM-1 - Orignal XM satellite, geosynchronous orbit. Lifetime expires 2016
XM-2 - Orignal XM satellite, geosynchronous orbit. Lifetime expires 2016
XM-3 - XM satellite launched in 2005, geosynchronous orbit.
XM-5 -XM satellite launched in 2010, geosynchronous orbit.
Saw this in another thread about the technical reasons for the move to XM. I dont have enough posts to post links
* XM uses an audio codec known as HE-AAC, or aacPlus v1. It's designed to deliver higher quality audio at bitrates lower than 96 kbps (192 kbps MP3). Sirius uses a less efficient codec called ePAC, which takes more data to deliver at the same quality as HE-AAC. XM also uses the AMBE codec for its voice only data channels, aka the robot voice channels, which uses a mere 4 kbps.
* XM's infrastructure has the ability to move bandwidth around at will, turning channels on and off as needed and turning bandwidth up and down. Sirius channels stay on all the time, unless they're permanently deleted. They find ways of preserving bandwidth using a system like Statmux, where a group of channels have varying bitrates based on what other channels need. Satellite TV uses this too.
* XM is able to alter the channel information on its units at the push of a keystroke. If a channel is replaced by a new one, they can simply change the channel name and logo on the units. Sirius is unable to do this without shutting down the entire system and rebooting it, which causes all units to go dark for a few minutes. For a while this was routine, but Sirius hasn't done a reboot for over two years now.
* While all XM units can receive all channels, many Sirius units have a limit of 135 channels, and this includes a LOT of OEM radios. This is why XM has been adding several Sirius channels to its platform but Sirius has hardly added any XM channels. Sirius has mainly added XM channels to its Best of XM premium package, which brings the platform total over the 135 channel barrier, so the limited Sirius units have simply been deemed Best of XM incompatible. This is also why the newest Sirius XM channel, Spice Radio, has a full time channel on XM while existing part time on Sirius, sharing channel space with Sirius XM Stars Too.