Introduction To XM Satellite Radio

XM satellite radio is a digital radio which provides digital programming directly from two high-powered satellites in which are placed in the geostationary orbit above the equator. The two satellites named Rhythm and blues are placed at one hundred and fifteen degrees west and at eighty five degrees west longitude respectively. They are kept in addition to a network of ground-based repeaters. This collection of two satellites and a ground-based repeater network is designed to provide gap-free coverage anywhere within the continental U.S., its southern tip of Alaska, and in the southern part of Canada. Signals from these satellites can also be received in the Caribbean Islands and most of Mexico. Initially the two satellites were named as rock and roll. But because of some technical problems the third satellite rhythm was launched. It was placed at 85 degrees west longitude just like the earlier placed satellite.

The initially kept satellite was moved to be co located with the other satellite where each satellite operated only one transponder. Because of this only half of the bandwidth was broadcasted. T5his was done to conserve energy and reduce the power consumption to half. In the meantime the blues satellite was made ready for launching. XM satellite radio’s head office is in Washington. Satellite radio signals die out at places of where there are high buildings, tunnels and bridges. At such places there is requirement of terrestrial repeaters. The terrestrial repeaters do not allow the signal to fade out. These repeaters are installed in United States as well as in Canada. The required number of repeater sites varies as the signal is regularly tested and monitored for optimal performance.

The terrestrial repeaters transmit signals in the same frequency band as the satellite does. On a general note we can say that a city contains round about twenty or more terrestrial stations. A signal receiver owner is not aware of the fact when a terrestrial station is being used, until and unless he or she checks antenna information from the receiver being used. Nowadays Unites State’s terrestrial repeater network is available to the public. Signals from XM satellite radio lie in the S band of the frequency spectrum. These signals use twelve and a half mega hertz of the S band. The signals are digitally compressed using a special technique namely the AAC Plus. This technique of coding is for audio signals while the voice signals use AMBE coding technique. These include the traffic and weather channels. The radio signals of XM are broadcasted on six separate radio carriers within the twelve and a half megahertz allocation. The whole content of the radio service that is both data and audio content is represented by only two carriers.