Satellite Radio Technology

Satellite Radio Technology has revolutionised the radio industry. The ground based radio stations had a limited coverage and their signals dropped off as the distance increased. Satellites gave a totally new dimension to radio coverage. A satellite radio service can now cover a whole country or even a whole continent. The two major Satellite Radio services in United States, XM and Sirius, are able to cover the whole of mainland United States from coast to coast.

Satellite Radio Technology seems to be very simple, but is quite complex when we actually see the whole process of how it works. Initially to give a brief outline; the radio service broadcasts either recorded or live programming. This programming is encoded in the radio studios on the ground and beamed up to the company's satellites, via satellite dish. The satellites beam this signals back to earth where its received by the satellite radio antenna and then into your radio unit. In urban areas where it is difficult to receive a direct signal, there are terrestrial repeater stations which rebroadcast the programming. In your satellite radio unit usually there will be a buffer for a few seconds, so that even if a direct signal is lost, the unit can pick it up from a repeater station, and you can enjoy a continuous broadcast.

The programming which has to be beamed up to the satellite, goes through a process of encoding. For example, a song which has to be broadcasted will first be recorded in a specific format on a storage medium. Usually it is encoded at a high rate, maybe at 384kb/s, as this will preserve the quality of audio and also be efficient in meeting drive space requirements. The encoding process is nothing but the digitization of the stored audio file. This encoded file now will go to a device called the multiplexer where it is combined with a group of other programming of the other channels. Multiplexing is convenient as it enables the broadcaster to combine many channels into one massive digital stream, that can be beamed up to the satellite. This multiplexed data is sent via a satellite modem device which modulates the data onto an RF carrier. This is then transported to the transmitter dish through a hollow metal tube.

Satellite Radio Technology involves the use of satellites placed in geo-stationery orbit, about 23,000 miles above the earth. Geo-stationery means that the satellites are orbiting the earth, at the same speed as the planet is rotating, and from the ground it will seem as the satellites are in a fixed point in the sky. Geo-stationery satellites are commonly used by Satellite radio companies, as they enable the use of inexpensive fixed antennas.

The satellite's only major function is to transmit back the signal that it is sent to it. Usually higher frequencies are used to uplink to the satellite and lower frequencies are used for down-linking. The antenna connected to your satellite radio will pick up the signal transmitted by the satellite and you will enjoy digital quality programming in an excellent audio.