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How Does Satellite Radio Work?
Satellite radio works quite simply. The radio
providers broadcast a digital signal to a satellite orbiting the earth.
The signal bounces off the satellite and is reflected to your satellite
radio receiver. Your satellite receiver decodes the signal and you have
your radio programming. While the concept is quite simple, there are many
details that go in to providing you with satellite radio and the two major
satellite radio providers go about it differently.
XM Radio
XM radio uses two satellites made by Boeing.
They are in orbit 22,000 miles above the earth and they have a third
satellite built and ready to be placed in orbit if something happens to
the other 2. The two satellites are in a geostationary orbit which means
they orbit the earth at the same speed as the earth is turning. This keeps
them the same distance from the earth at all times.
Sirius Radio
Sirius radio has three satellites placed in an
inclined elliptical constellation. This means that at least two satellites
are over the US at any given time. The satellites which are Loral
FS1300's, spend 16 hours a day over the United States. They spend the
other 8 hours whipping around the earth to repeat the process.
Repeaters
Both Sirius and XM use repeaters. The
repeaters pick up the satellite signal and rebroadcast it. This is useful
in congested cities and areas where the satellite signal might get blocked
by buildings.
Frequency
Both providers broadcast using the 2.3 GHz
frequency. This frequency was allocated for satellite radio use by the FCC
back in 1992.
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