Posted on May 2, 2012 in Entertainment, Tech & internet
How does satellite radio work? It seems kind of like magic. There are no commercials, the sound quality is pretty good, I’m never out of range, and it comes right into my car stereo for a few bucks a month. How does it all happen?
(Apologies for that headline to Arthur C Clarke and Stanley Kubrick.)
Practically every new car today offers built-in satellite radio capability right from the factory, plus there are all kinds of aftermarket add-on receivers — and for a couple bucks a month you can get practically commercial free radio that works from coast to coast. It’s almost like magic.
From the beginning end of it, satellite radio isn’t much different from AM or FM radio — a guy/girl sits in a room with a microphone, talking and playing music. This audio is sent to a transmitter somewhere, either on site or via a microwave link to a remote transmitter.
Here’s where things get a little different.
In the case of FM radio, that signal from the transmitter goes directly to your radio. If the station runs enough power and has a decent transmitter site, you might be able to hear the broadcast from 50-60mi away. Once you get outside of that range? No dice. Better find another station.
Satellite radio also beams a signal from a transmitter — in the case of Sirius/XM, the primary uplink facility is located in Vernon, New Jersey — but instead of going directly to your radio, it goes to a series of satellites orbiting the earth. The satellites then beam the signal towards Earth — specifically the southern bit of Canada, all of the lower 48 states, and a bit of northern Mexico — where your satellite radio receiver picks up the signal and plays it through your stereo. And since the satellites cover the entire (contiguous) United States, you can drive from coast to coast and listen to the same station the whole way there.
If that’s good enough explanation for you, and you’d rather skip the techy bits, then you might want to skip the next section. If you’d like to hear about orbits and the like, then keep reading.
Before the merger of Sirius and XM, each company launched its own satellites, with different ideas about how they should operate. Sirius (originally) opted for a geosynchronous highly elliptical orbit, with a 24-hour period (I warned you this was going to get techy).
With three different satellites in orbit, each one spent roughly 16 hours a day over the continental United States, guaranteeing at least one satellite over the country at all times.
There’s nothing inherently wrong with this setup, except for one little glitch: people using fixed receivers, at home or in the office, sometimes noticed they had to move the antenna to regain reception from time to time. As the satellites would make their passes over the US, sometimes the signal would go out of line-of-sight to fixed antennas.
XM opted to put their satellites in geostationary orbits, meaning they are orbiting the Earth at a fixed point overhead — they’re always in the same place. This made for better fixed reception, at the cost of — at times — losing reception in a car as you drove under an overpass, as the signal is always coming from directly overhead.
Since the merger, Sirius has opted to move to launching new satellites into geostationary orbit, as newer satellite receivers have a “buffer,” as well as there being a terrestrial repeater network, allowing for seamless audio when passing under obstructions or through large downtown areas with tall buildings in vehicles.
As you can imagine, launching a series of satellites into space isn’t exactly pocket change. According to one source, the entire cost of launching a satellite service is in the neighborhood of $1.5 billion. That’s billion with a “B.” The average cost to launch a single satellite is in the ballpark of $150 million.
So herein lies another one of the big differences between regular FM (or “terrestrial”) radio and satellite radio. Terrestrial radio pays for almost all of their operating expenses through advertising — commercials. Satellite radio, for the large part, sells no advertising on its programming and runs almost no commercials — part of the selling point of satellite radio. So in order to fund the (pun intended) astronomical costs of running a satellite radio service, you’ve got to pay to play — that is, pay a monthly subscription fee.
Really, satellite and terrestrial radio aren’t terribly different. They both send broadcast music and talk out via radio waves — they just take different paths to get to you. And, of course, one costs a little more money out of pocket than the other, since one you pay for with real dollars, and the other you “pay” for by listening to lots of ads.
Satellite in space photo: One in the constellation of 24 GPS satellites that transmits radio signals to Earth from 11,000 miles in space, courtesy NOAA. Yes, it’s not the Sirius/XM satellite, but it’s a satellite. In space and everything.
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