Monday, January 23, 2012

Satellite Radio Technology

By Owen Jones


Satellite radio technology is similar to cable or satellite television and it is certainly here to stay. There are a number of reasons for this: the quality of the transmissions is higher, the quality of the apparatus's reception is higher and the general coverage of the station, that is to say the so-called satellite's footprint is much greater too.

This means that if you drive long distances, you will be able to stick with the same station without having to look for a new one every forty or fifty miles as you need to do with AM or FM radio channels.

In order to reach this quality, the recording and playback speed needs to be around the 384 kbps level. The music tracks are catalogued in a similar way to the MP3 system, which uses names called ID3 tags.

Each station on satellite radio attempts to establish its own identity. A music station may try this by playing music only of one type or from only one period or decade. This means that you may get a satellite radio station called 1970's Punk music or Twentieth Century Classical Music.

On some channels, the music controller or disc jockey will choose, say, fifty minutes worth of music, will listen to it in order to ascertain that the quality and the order are correct and then let the computer play it over the airwaves. This leaves ten minutes every hour for the news and then the sequence can be repeated automatically.

Satellite transmission uses digital recordings and each channel is encoded on a different frequency. Similarly, each decoder, say, in your car or your home has to recognize and decode each channel separately as well. This coding and decoding is done very quickly, in fact in what is called 'real time'.

The resulting binary or digital code is then turned into into analogue signals so that your speakers can replay it. This process creates sound which is just about of CD quality.

The transmitting satellites are in a geo-stationary orbit at 23,000 miles above the Earth and have a large footprint which is the name given to the area of ground that is capable of receiving their transmissions.

In America, for example, the two regions concentrated on at first were the densely populated east and west coasts in order to maximize potential income. One satellite would be incapable of covering the entirety of the United States in that orbit.

In order to receive satellite transmissions, you will have to use a special antenna on your decoder. This antenna must be capable of receiving L-band transmissions for it to be of use.

These new antennas are a huge improvement on the satellite dishes (comparable to those used for satellite TV) that one used to have to have in order to take advantage of satellite radio technology




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