I've been learning a lot more about Sirus and XM Radio satellite positioning in the last few days but frankly am still a rank beginner.

The little bit of knowledge I have gleaned suggests that Sirius is a superior service in terms of reception and if you want a home receiver.

Anybody out there knowledgable in this and would like to elaborate?

Thanks in advance
Hugh

Hugh, Sirius works great for vehicles, but can be problematic for home systems. You may see dropouts from time to time as the satellites move about possibly behind trees or other obstructions. Xm is much lower to the horizon but atleast if you find it, it will not move.

I have a xm system hooked up to my mothers stereo system and the antenna actually looks right through the roof of her house. It's abit picky to find a sweet spot but once found it's a pretty stable signal.

All this could be moot if we see repeaters setup :)

I suspect that most people are like me and have only one system. (Sorry, my friend has only one system.) :D So I can't do a comparison.

My friend says that his Sirius would be superior for most Canadian locations if both applications to CRTC go ahead. He says that the two XM satellites are geostationary above the equator, so the further north a person goes, the lower the line of sight to the satellites and the more interference from objects such as buildings, hills, trees, etc.

The three Sirius satellites are geosynchronous. They follow the same pattern constantly, but don't stay in the same location (relative to an earth observer). This gives them the opportunity to have a higher location above the horizon in Canada, making interference from objects less of a problem.

This difference is reflected in the two CRTC applications. XM's application is heavy on terrestrial repeaters while the Sirius application is light on terrestrial repeaters. XM will likely provide good signals in major centres where there will be lots of repeaters, but will likely drop significantly as one leaves major population centres and travels north.

There is also a difference in the content. XM has music channels, but they are not commercial-free. Sirius has commercial-free music channels. The systems compete for various professional sports coverage. (My friend thinks that XM has MLB and maybe basketball, while Sirius has NFL and will soon have NHL.)

The systems compete for American brand-name on-air personalities. XM has a couple called O & A and Sirius will have Howard Stern. I'm not sure if they all share the same interest in bodily fluids.

My friend has driven over much of BC and has never had any significant problem with Sirius reception. He says that he rarely has any problem with reception at home. The three Sirius geosynchronous satellites cross just south of Winnipeg. If a person can have a pretty clear shot toward that location, they shouldn't have a problem getting a signal. Because there are three satellites, there are always two over North America. The receiver will pick up the stronger of the two signals. If that signal is lost, it will automatically switch to the other satellite.

Or so says my friend.

Just a couple corrections on the previous post.



The three Sirius geosynchronous satellites cross just south of Winnipeg. If a person can have a pretty clear shot toward that location, they shouldn't have a problem getting a signal.


close but not quite. The Apogee of the Sirius satellites is actually located near Hudson Bay in Northern Manitoba, although at that altitude of apogee the look angle is still pretty much 90 degrees anywhere in Manitoba.


Because there are three satellites, there are always two over North America. The receiver will pick up the stronger of the two signals. If that signal is lost, it will automatically switch to the other satellite.


Actually the receivers do not switch from one source to the next, they receieve all of them simultanously and try to reconstruct the original bitstream by grabbing the data-packets from either one of the two satellites or a repeater all at the same time. One of the satellites is flagged as the LIVE satellite while the other is flagged as DELAYED by 4 seconds. Your reciever is designed to buffer by 4 seconds to allow the receiver a "2nd chance" to recover missing data packets 4 seconds later from the 2nd satellite for uninterupted playback. This is why when you drive underneath an overpass the signal does not cut out unless your view remains obstructed for a few seconds. What is happening is that your reciever is always buffering the data for 4 seconds so when the datasteam suddenly cuts-out since it can't see a satellite, it continues to play-back for the next few seconds, then as long as you come out of the underpass within a few seconds, your receiver is able to grab those missing packets it needs while it was obstructed from the 2nd satellite before the audio buffer is empty.

Hugh, I have had both services and they both work equally well in most of Canada. Sirius works better in the very far north and NFLD but XM because of the heavy use of repeaters works best portable. I dropped Sirius because of the music which I thought was repeated too much and I wanted a portable unit to take on my travels.
The best thing to do is sign up for their "3 day free on-line service" and give a listen...it is a bit like Coke vs Pepsi...about the same product just slighly different :eek:

Interesting. My post was strictly on the technical side of things.

I don't spend a lot of time in the car so my primary use will be in-home. Because of the CBC offerings, I'm leaning towards Sirius but I am concerned about reception in my home

I live in Nfld, and am interested only in XM for home. Anyone know if a repeater is planned for the St. John's area? Also, what are the possibilities for using a larger antenna on the roof of the house in order to compensate for a weaker signal?

Hugh,

Both services have "home kits" for their units or componet style receivers (Polk for XM, Kenwood for Sirius) and small home antennas (about 2x a pack of playing cards) that can even be mounted indoors (with some luck) or outdoors. I have my antenna near a south facing window and get 100% signal. I have connected my XM radio to my stereo system and it worked fine. I use a 900mhz wireless speaker system so I can "broadcast" to speakers anywhere in my house, yard, pool (I live on 5 acres so music volume is not a problem).

Both services will work fine at home in most of Canada, so select the service that offers the programming you like. The cavet for satellite radio...it is not CD quality and almost all of the radios only offer analogue hook up (i.e no direct digital connection to your system) so if you have a really high end audiophile set up, you might be disappointed with the sound quality.

Hugh,
almost all of the radios only offer analogue hook up (i.e no direct digital connection to your system) so if you have a really high end audiophile set up, you might be disappointed with the sound quality.


I believe Polk audio sells a seperate component(the XRt12) that is designed for home audio systems and it has digital outputs(both optical and coaxial). It retails for between $250 and 300US.

Just a couple corrections on the previous post.

close but not quite. The Apogee of the Sirius satellites is actually located near Hudson Bay in Northern Manitoba, although at that altitude of apogee the look angle is still pretty much 90 degrees anywhere in Manitoba.


You are correct about the apogee. I was referring to the location where the satellites cross in their "figure eight orbits". This is just south of Winnipeg. There is an animated map of the orbits at:

http://www.siriusbackstage.com/forum/viewtopic.php?t=25580

Sirius apparently has plans for a fourth satellite. It will be interesting to see the animated map after that bird goes up.

Bryston is indeed correct about the Polk Reference Receiver XRt-12

From myradiostore.com

"The XRt12 also offers direct digital outputs (both optical and coaxial) so you can plug it directly into any receiver or processor equipped with digital inputs."

So I stand corrected !...looks like a new toy to add to my list :cool:

Give us a full review after you've tried it, please.

You are correct about the apogee. I was referring to the location where the satellites cross in their "figure eight orbits". This is just south of Winnipeg. There is an animated map of the orbits at:

http://www.siriusbackstage.com/forum/viewtopic.php?t=25580

Sirius apparently has plans for a fourth satellite. It will be interesting to see the animated map after that bird goes up.

Yup. That point that you refer to where the satellites cross is at an altitude of 35,000 km, exactly where geostationary orbit would be if the Sirius satellites were in circular orbits. The satellites themselves don't travel in "figure 8's", it just appears that way from the perspective of a ground observer or a fixed point on the surface of the earth. What's actually happening is that the satellite precesses as it gains altitute on it's journey towards apogee on each orbit. During the portion of the orbit which is below 35,000km above the earth the satellites are moving in their orbit at a rate which is faster than the rotation of the earth so from the perspective of a ground observer the satellites appear to move westward. With orbital mechanics the further out an orbit is the slower the velocity. So once the satellites reach 35,000 km on their journey towards apogee (the "cross" in the figure eight orbit) the rotation of the earth is faster than the linear velocity of the satellite relative to the earth so that the satellite appears to "back-up" in the sky and move eastward, creating the cross. After hitting apogee which is way up at > 40,000km, the process is reversed and the satelite starts gaining velocity until it again crosses the 35, 000km altitiude in which case then the satelite starts gaining on the earth and therefore from the perspective of the ground, the satellite appears to once again move westward, this is what creates the figure 8 pattern we see. This is essentially the same phenomenon we see if we observe planets like Mars which seem to create loops in the sky as they move in their orbits. The planets don't really loop it just appears that way from our perspective due to the combined movements of both the earth and mars. The same idea applies here, the Sirius satellites "appear" to move in figure-8 orbits due to the combined effects of both the earth's rotation and the highly elliptical orbits of the Sirius satellites. The design of the orbit is pretty ingenius, the key is that each Sirius satellite is able to acheive a high look angle for a long-period of time each day by virtue of the fact that it takes advantage of the geostationary orbital period by having a trajectory which gives the illusion that it is moving in one direction and then backing up later on, resulting in high availability over a relatively small spot in the sky for a long time.

I have had XM since March of this year. I chose XM over Sirius is because XM provides slightly better sound quality and has a much wider range of hardware to purchase. I have the Delphi MyFi which can store 5 hours of music and comes with the complete home and car kits. It also has a built-in antenna for portability. I have been up to Cochrane, ON with no degradation of signal.

Here is a review of both services from Cnet - http://reviews.cnet.com/4520-6466_7-5068442.html

Both services are comparable but there are a few key genres that are better/worse on one service or the other. For instance I'd say if you are a fan of Rave/dance music Sirius is definatly ahead of XM especially with the recent addition of BBC Radio 1 in addition to the other excellent channel Remix 62. There is also a slighter larger selection of Talk Radio content on Sirius. XM however has it over Sirius in terms of New Age music, Country music, Pop music, Audiobooks. I also think that Sirius has significantly better sports coverage than XM. Of course this is because I don't like baseball but I like Football and Hockey both of which are on Sirius.

Personally of course I'm a little biased in favor of Sirius because it excels in the type of content I like (ie Rave music, talk radio, sports NFL and NHL) whereas XM excels in the content i don't much care for except New Age (Country, Pop, Audiobooks, Baseball)

Also XM has a much better selection of Jazz and Alternative rock...I got rid of Sirius once I listened to XM for a week or so. Both services are slightly different but not really enough to say one is vasty superior to the other...it is just a matter of personal tastes...

I like jazz, rock and baseball, hence XM, where as mcpish likes rave, dance and hockey which he better on Sirius....the cool thing is there is the choice :cool:

There is also a difference in the content. XM has music channels, but they are not commercial-free. That would stop it for me. Why would I pay to listen to commercials?

The channels I have listened to don't have commericials. The only commercials that appear is touting other xm channels. I have heard of commercials on the Dr. Laura show but is only because they are getting the same feed as regular radio stations. These radio stations do advertise so XM has to fill the dead-air with something...

That would stop it for me. Why would I pay to listen to commercials?

Here is a (bit dated) 12 Step program for choosing between XM and Sirius, at least for Americans.

http://www.visi.com/~jweeks/steps/siriusvrsxm12step.html

One observation (Note the old date) is:

"Update—as of Feb 1, 2004, XM has gone commercial free on a majority of its music stations. Sirius has announced a pending change, but hasn’t said what will be changing yet. At this time, XM now has the edge in being commercial free on the music side. In the case of XM, commercial free does not mean interruption free, they still run a lot of ads for XM and promo spots for other XM channels."

I believe the Sirius change was to having all 60 music streams be commercial free. Like XM, Sirius does have short "bumpers" referring listeners to other in-house channels.

One other correction, from Step #5- XM attempts to give their channels the feel of a live DJ from a broadcast station, while Sirius keeps the DJ off the air, other than naming the songs on some channels.

On the few channels I listen to on Sirius, they have DJ's. One of the funniest had to be on the 80's channel, they were talking to a trucker who had called in. The trucker had a thick Texas accent, and was talking the talk, about working long days hauling heavy loads; very "manly" stuff. Then the DJ asked if there was something the trucker wanted to hear, and he replied: "Ya, can y'all play 'I want your sex', by that George Michael fellow?" :o

I nearly bust a gut laughing. :D