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 system operators provide digitized and compressed audio over their networks, both because of its programming and because SDARS can be received in a moving car, where much of today's radio listening takes place; existing digital audio services cannot. (A different form of satellite digital radio, from WorldSpace Corp., Washington, D.C., is currently serving parts of Africa and Asia. It started service in 1999, and is less optimized for mobile use.) Meanwhile, the free, over-the-air terrestrial broadcasters are expected to choose digital audio broadcasting technologies for both the AM and FM bands by year-end.( Martin R. Davidoff 6-12)Why go digital Just as was true for other media, the conversion to digital offers radio a wealth of benefits not available from current AM or FM analog systems. Radio is an audio service, so consumers naturally compare it to the most pervasive high-quality audio technology, the compact disk (CD). A good FM signal played by a high-quality, stationary receiver compares favorably to a CD's sound. But put the FM receiver in a moving vehicle (typical for radio listening), and channel imperfections experienced by FM quickly lower the sound quality. The problems include environmental noise and RF signal reflection...
