OTHER TECH

Making Stations StickierLike other digital audio systems, HD Radio will carry digital subcodes along with the audio. Codes that tell when programs and songs begin and end could trigger TiVo-like features that would let your HD Radio receiver record the end of a program or song you couldn't stay to hear, or even record shows you can't be around to hear when they're broadcast. Other codes could let your radio display the artist, title, and album source of the current song, and maybe even show the album cover. Information on traffic and weather or emergency alerts could be displayed as well.

Broadcasters hope goodies like these will make their stations "stickier," improving the listeners' experience so they stay tuned in longer. Song and artist identification will be a major draw. "That's the main thing that drives people to stations' Web sites," said Mike Lyons, iBiquity's director of aftermarket business development. Unrelated information has its uses, too. A music station could, for instance, display updated sports scores so team fans don't tune away to a news station.

While HD Radio hardware and digital listeners are scarce at the moment, the stations' biggest benefit will be the chance to hype themselves as "digital" to listeners who can't yet hear it that way. That alone will make some listeners think a station's sound has improved, and some stations actually will improve their analog sound quality by upgrading their audio equipment for the digital era.

Analog AM listeners, however, may note a slight change for the worse. To fit both analog and digital signals into AM's narrow channels (about a tenth the size of FM's), broadcasters will have to cut off their audio high frequencies at 5 kHz instead of 10 kHz. However, because of noise in the AM band, few radios now reproduce the upper frequencies anyway, and some stations no longer broadcast them, preferring to put more power into a smaller bandwidth to make their programs sound louder. For HD listeners, the frequency range of digital AM would be about equal to analog FM's-60 Hz to 15 kHz-and the sound would be in stereo.

Stations hope that giving these benefits to listeners will result not only in increased loyalty but also extra cash. Some of that extra money could come from onscreen ads coordinated with the program, such as for record stores when music is playing. Stations could also charge to display Web addresses and phone numbers during commercials that mention them. Alpine has demonstrated an HD Radio receiver with a built-in printer to spit out store coupons and maybe even concert or movie tickets.

But most of the money is expected to come from subscription services for things like stock-market reports or real-estate listings. And none of this, says iBiquity, will interfere with the SCAs (Subsidiary Communications Authorizations) that FM stations use to transmit background music, paging signals, or other services that bring in revenue.

There's also talk of splitting up HD Radio's data space, which can carry 150 kilobits per second (kbps) on FM, to hold one free and one subscription audio channel. That would work better for speech than music, of course.

FCC ApprovedHD Radio also appeals to broadcasters because its in-band, on-channel (IBOC) system uses existing frequencies and stations. With IBOC, stations can minimize the cost of new transmitters and the real estate to hold them, avoid costly auctions of new frequencies, and ease the transition for themselves and their listeners.

The technology, though, is complex, and to gain FCC approval, which came late last year, HD Radio had to prove it wouldn't cause interference problems for the millions of people who listen to analog AM and FM. Early testing revealed some potential for interference, mainly with older stations whose analog signals already overlap and interfere with one another, but the system was redesigned to deal with that. Currently, AM stations aren't allowed to broadcast HD Radio at night, when their signals and those of other stations carry farther, but that might change if further tests show that interference from the digital signal is not significant.

Even before the FCC's decision, HD Radio gained approval by the International Telecommunications Union (ITU), which coordinates telecommunications standards and development throughout the world. As a result, "I've been getting inquiries in languages I'd never even heard before," said iBiquity's Mike Lyons. Interest from other countries increased after FCC approval because the size of the U.S. market is expected to encourage rapid development of HD Radio broadcast equipment and receivers and, in turn, lower the prices.

Eureka 147, the digital radio system now used in other countries, including Canada, was considered for the U.S. but ultimately rejected because of the expense and complexities of changing over to a completely new system and because it uses frequencies reserved for the military. The Eureka system is intriguing because one station can carry several programs at once, the number depending on program bandwidth. A single station can choose to carry either five CD-quality programs, six FM-quality programs, 12 AM-quality programs, 30 voice channels, or various combinations of these. All stations in a network can share a single frequency, so listeners don't need to retune when going from one station's coverage area to another's.

Another alternative to HD Radio is digital satellite radio, which can cover entire continents without dotting the landscape with new transmitters. But that cross-continental coverage makes it impractical for satellites to deliver local programming. From the perspective of local broadcasters, that makes it no alternative at all.