Cool beans - Competition coming for XM

Hi ya'll,

It seems that Sirius is launching an aviation weather product to compete with XM. See this bit of PR

I was a bit disappointed in the audio offerings from both XM and Sirius, but I really want to purchase some sort of in flight weather before next winter...

Now for the little known secrets

I wonder how Sirius and WSI are going to get around this problem. Sirius uses a bunch of terrestrial stations that simulcast with the satellites (ever driven under a bridge, overpass, tunnel in a sirius coverage area - the radio keeps playing).

Now this works great for Automobiles and Homes (homes have to have it so they don't have to have line of sight to the satellites). But airplanes being up in the air will have a problem. They will have line of site to the sat *and* to the ground based system. This will cause interference and I"m not sure how they are going to deal with that.... Will be interesting.

Also, I wouldn't get too excited about it. WSI is available today with similar coverage to XM and a similar product - However, have you looked at their pricing models. They are astronomical to what you get from XM.

So, they'll have to fix the interference issues that they will have based upon their system design and they will have to fix their pricing model before they pose much of a thread to XM. They also just announced that if you own an AV100 or 200, the current generation receivers, they will stop working in 2007 and you have to pay money to upgrade.

I've never heard of any problems with ground repeaters. Since a car can be in site of the satellite and a ground repeater at the same time, I can't see how a plane would be any different. Plus XM supposedly has many more ground repeaters than Sirius, so I'd think the problem would be worse with XM.

More competition is a good thing. Maybe WSI was more expensive because of the satellite network they were using. Hopefully with Sirius they'll be able to bring the price down.

aadamson said:

I wonder how Sirius and WSI are going to get around this problem. Sirius uses a bunch of terrestrial stations that simulcast with the satellites (ever driven under a bridge, overpass, tunnel in a sirius coverage area - the radio keeps playing).

Click to expand...

This shouldn't be a problem, right? I mean..unless you're flying your airplane through a tunnel or something.

As I understand it, the terrestrial repeaters only exist around heavily populated areas to provide continuous coverage. Driving on the freeway under a bridge doesn't cut out...not because of repeaters...but because of the redundancy in the compression algorithm and signal. If you look at your display (carefully) as you drive under an overpass, you'll see the 'signal bars' go down as you pass under the bridge. A friend of mine who works in the industry explained it to me like this. The 'signal bars' on the primary display of XM's receivers is not a signal at all. It's the buffer sizes. There are basically three simultaneous buffers of data being sent from the satellites, slightly staggered in time. This gives your receiver time to get each requisite packet of data. If some interference causes the loss of one packet of data, the packet can be captured from subsequent streams. This is basically what the three signal bars mean. If the data is being captured from all three streams, all three bars will be indicated. If on average two of three buffers are being dropped, only one bar will appear on the display.

If you're in the air I don't think you'll have any problems. They broadcast nationwide (and then some). The only problems with reception are caused by factors like physical obstructions.

Note: Just thought of something else: The three Sirius satellites are elliptical LEO (as in not geosynchronous) which means that they must be timed just right to provide continuous coverage. XM, however, uses geosync satellites. I guess it's possible that if the Sirius satellites aren't timed just right there could be some areas with minimal coverage at one point and optimal coverage several hours later, whereas XM provides consistant coverage to the entire country (and beyond).