Commercial-free digital radio via satellite from XM Satellite Radio (www.xmradio.com) and Sirius Satellite Radio (www.siriusradio.com). Each company has its own service and satellites and exclusive spectrum in the 2320-2345 MHz frequency band. However, in 2008, both companies merged to become Sirius XM Radio Inc.

For a monthly fee, satellite radio offers more than 120 channels of music, news, sports, weather and talk, and unlike terrestrial radio (AM, FM and HD), the signal stays tuned no matter where one travels within the U.S.

Home, Car and Portable
Tuners are available for home and car, and portable units can serve multiple venues. Although adapters are used to retrofit existing cars, both companies partnered with auto manufacturers to place their respective radios in new cars. Some portable units output an FM signal that is picked up by the car's FM tuner, which eliminates wiring into the car's audio system. See DAB and DARS.

Merged Radios
Launched respectively in 2001 and 2002, XM and Sirius competed for many years offering a package price for all their channels. As a single company, Sirius XM allows customers to choose their programming on a channel-by-channel basis; however, new radios are required.