Satellite radio

Satellite radio is just what its name suggests: a radio service that uses satellites circling Earth to broadcast its programming. In 1992, the Federal Communications Commission (FCC) allocated a satellite spectrum (the "S" band, 2.3 GHz) for the broadcasting of satellite-based digital audio radio service (DARS). It eventually granted two licenses, one to Sirius Satellite Radio (formerly CD Radio) and one to XM Satellite Radio (formerly American Mobile Radio Corporation). The world's biggest satellite radio provider, 1worldspace, is available in Europe and several other countries but not in the United States.

As the satellites orbit the earth, programs are beamed to them from broadcast stations. The satellites then transmit the signal to special antennas on homes, cars and portable radios. Terrestrial repeaters throughout the country also receive the signal and help ensure that it's transmitted to receivers, especially in areas with tall buildings that might block the signal.

There are two big pluses for satellite radio listeners. First, every channel, whether it's on XM or Sirius, is largely commercial-free, which should appeal to radio listeners tired of having advertisements screamed into their ears while they sit in traffic. Most music channels have no advertising at all. Second, no matter where you are in the continental United States, you get the same reception as long as the skies are relatively clear. Unlike traditional radio, which loses reception once you're too far away from a certain station, satellites ensure you receive a signal no matter where you are in America. A driver could trek all the way from New York City to Los Angeles and never have to change the channel.

For about $13 a month, plus the cost of equipment and a small activation fee, both Sirius and XM listeners can receive more than 100 channels of satellite radio, including music ranging from classical to heavy metal, plus news, sports, talk and entertainment. But there are some notable differences between the two services, too.

The type of technologies used by XM and Sirius differs slightly, and the specific programming offered by both companies can vary, especially when it comes to news, sports and celebrities with contracts for their own shows. On the next two pages we'll take a look at those differences.