Travelers have always been a non-issue for radio stations, but good radio reception for long periods of time has always been an issue for those on the go. Finally, two companies have developed a solution to this dilemma – satellite radio. No longer does a hip-hop fan have to scan the dial simply to find that a big band format is the only signal available in the area. A person can travel from Washington State to Washington, DC while listening to the same station the entire trip…or they can choose to go nowhere at all. The concept is simple: beam your favorite music from the space.
The question remains, if mobile phone companies can complete calls around the world – from the ground, why can’t a radio signal be heard from coast to coast? Cellular phones work using many towers, as you travel out of the reach of one, another picks up your call. Radio works much the same way, but within particular areas, a frequency (the number on your dial) is licensed by the Federal Communications Commission (FCC) for use by a certain station at a licensed power, therefore the signal does not “jump” from transmitter to transmitter as you move. For example, KCYY in San Antonio, TX sits at the 100.3 FM frequency. It has a license for broadcasting at a power of 100,000 watts (highest allowed by federal law). However, in Tahoka, TX, KMMX calls 100.3 FM home. If a person begins driving northwest from San Antonio while listening to KCYY and talking on a mobile phone, the call will continue while the station format will change from Country to Mix as they travel from one coverage area to another (although it is unlikely that this transition will be seamless – resulting in static). If the driver were listening to satellite radio, both the call and the music would continue uninterrupted.
BUT HOW???
The two competitors jockeying for market share in the United States are Sirius and XM Radio. Each has developed different methods of delivering their programming to subscribers.
Several forms of programming are suitable for use by satellite radio. Most is amassed digitally at the companies’ headquarters for instant play either by pre-programming or a simple point and click. In the rare case that a song is not available on the massive storage servers (Sirius has 7 terabytes of storage capacity and XM has 22) - the “antiquated” CD is also an option. Additionally, live performances are offered by both providers so there is never a lack for original material. Any of these may be sent from the company’s headquarters in either New York City (Sirius) or Washington, DC (XM Radio) to a ground station located near the studio. The information (music, news, etc.) is then passed on to the company’s satellites. Simply put, the ground unit is a large satellite dish capable of “beaming” programs to the satellites thousands of miles above Earth.
HOW MANY AND WHAT ORBIT?
Sirius and XM Radio put many years into research and development of their respective products and as would be expected, they chose vastly different paths from the satellite perspective.
Though it is of relatively little excitement to the lay person, Sirius opted to use Loral FS1300 satellites while XM uses Boeing HS 702 satellites. What is interesting is the number of satellites and orbit they each chose to use.
Sirius has three satellites in orbit and one on the ground ready for transport into space in the event of a malfunction. They orbit in an elliptical pattern. Two satellites are over the country at any given time. They spend 16 hours over the United States and then fly around to the other side of the globe only to return 8 hours later. XM’s two satellites (like Sirius, a back-up is ready to go if needed) - aptly named “Rock” and “Roll” - orbit in a geostationary pattern directly above the equator, moving at the same rate as the Earth. By doing this, they are always above the listening area.
Once a program reaches the satellites, the signal is broadcast back to Earth where it can be intercepted by receiver units or in many cases, repeaters. Repeaters are placed in heavily built-up areas due to the interference caused by overpasses, buildings, terrain, and the like. A receiver buffers the program for a few seconds in the case that a drop-out should occur, likely due to these obstacles. Due to this method, a listener never knows that a signal has been lost. Plus, a listener can not differentiate between a signal that they are receiving directly from a satellite or one they are receiving from a repeater. This is true regardless of where a subscriber is listening – in the car, at home, at the office, etc.
Perhaps the days of scanning the dial every hour while on a long trip are over. A big problem for some has been solved through the use of satellite technology.
