The transmission technology that will deliver to listeners compact disc-quality sound free of interference and noise is commonly called Digital Audio Broadcasting (DAB).
Digital radio is of equal or greater spectrum efficiency than its analog FM counterpart. Tests have shown that when operating the same transmitting frequency as the current FM band, DAB is more power efficient than FM, requiring as little as 1/1,000 the amount of transmitted power to cover the same area.
Digital conversion will enable public radio stations to produce and deliver programming using a far more efficient process than exists today. It will allow listeners and users to have a wide variety of new information services like radiotext (service for the hearing impaired, such as closed captioning for radio), format searching, selective news messaging (search by news topic), music lyrics and titles.
Not yet! But KQED is busy planning the conversion of our studio equipment to digital-based technology. In Europe and Canada, digital transmission is moving forward by use of Eureka-147 technology in the L-band. In 1992 the U.S. opted to allocate digital radio in the S-band, since the U.S. military and others were already using L-band frequencies. Satellite-delivered digital radio is the only authorized service for the S-band.
The holdup for digital radio transmission in the United States has been the lack of a vacant spectrum to allocate for the new digital radio services. U.S. broadcasters have been busy developing a technology that works in the existing AM and FM radio bands, hence, the name in-band on channel or "IBOC."
To receive digital signals, you will have to purchase a new digital radio. These radios will likely have the AM and FM reception as well. Just as most radios today are AM/fm, the new sets will likely be DAB/AM/fm. Once the transition from analog to digital transmission is complete, today's radio will be obsolete.
At present, there is not cost estimate for digital radios. The cost depends upon the final technology in place. For now, the numbers are highly speculative. As with the introduction of any new broadcast standard, the cost of initial sets will be at a premium until mass production reduces prices within a few months or years.
What will digital radio mean for public radio stations?
Digital compression will enable stations like KQED-FM to do more and better programming. For example, digital radio will provide more reliable FM transmissions that will be less subject to the effects of geography and electrical interference. (This is particularly important in rural areas.) Digital will also permit public stations to transmit "smart radio" signals that will deliver text messages along with the audio program. This digital text may be used to provide continuous specialized information, such as weather, traffic, music titles, program information or emergency warning information on a local basis. The scalability of digital technologies means that radio stations could have the ability to transmit one high fidelity CD-quality stereo signal or multiple signals of lower audio quality.
Will stations be able to provide multiple streams of programming?
Under an IBOC solution, full digital capacity will not be achieved until the analog FM station is turned off, leaving only the digital signal. At that point, ancillary services and the ability to scale the channel to transmit a single high quality service versus multiple lower quality signals should become operational.
IBOC DAB systems are being proposed to allow AM and FM broadcasters to transmit DAB on their existing frequency channels, along with their existing analog AM or FM signals — stations will stay where they are on the band. Technically, the wider band-width of the European-based Eureka system offers somewhat better transmission performance — but this approach requires a spectrum allocation that has not been successfully identified in the United States.
Digital conversion will allow public radio to maintain and improve its domestic programming content and move toward a concept of global telecommunications. Global telecommunications will remove the categories that now define and segregate video, audio and computers. With advanced telecommunications technology, video, audio, television, radio, telephone and all forms of data communications become defined by the amount of digital information (bits) required to transmit them. As universal standards become available, information exchange will become seamless from computer to telephone, from satellite to home, from subscriber cable to school.
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