The Emergence of Satellite Radio Essay

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The Emergence of Satellite Radio While the transition of television to a digital technology with its improved picture and sound quality has been a much publicized and controversial process, television's venerable ancestor, radio, has stayed in the background. But this year, in the United States, radio broadcasting is making its own digital leap. Two start-ups are introducing a new type of radio broadcast--subscription-based digital audio sent from satellites. With satellite digital audio radio services (SDARS), as they're called, listeners will be able to tune in to the same radio stations anywhere in the United States.

SDARS differs from so-called digital music services, in which direct broadcast satellite or cable
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The problems include environmental noise and RF signal reflections that give rise to multipath fading--variations in RF signal level due to signal reflections. The improved robustness of digital radio promises to remedy this, delivering near-CD sound for most listening conditions.

With AM radio, the transition will be even more marked. The new digital service will offer two-channel stereo sound and greatly increased frequency response, resulting in audio quality comparable to today's analog FM.

In addition, digital will greatly enhance terrestrial radio robustness, which is the ability to withstand factors such as multipath fading, environmental noise, and impulse noise interference due to automobile ignitions or home appliances. Digital's robustness also holds up well against interference from nearby radio broadcast signals and terrain blockage for FM, as well as signal attenuation due to grounded conductive structures like reinforced-concrete highway overpasses for AM.

With most radio listening done in a moving car, the signal degradation varies constantly with time, further complicating matters. To reduce or eliminate these problems, a variety of signal-processing techniques (described below) have been incorporated into digital radio systems.

While enhanced quality and robustness and new services entice broadcasters, and should bode well for a
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