The stage is set
At the 2004 Consumer Electronics Show (CES), iBiquity Digital Corporation showed several practical applications for HD Radio, the digital broadcasting technology that could revitalize terrestrial radio. HD Radio is iBiquity?s name for IBOC (In Band On Channel) technology. It creates a digital signal that's broadcast alongside the analog signal radio stations currently send out. For the listener, the benefit is immediately audible. Unaffected by the atmospheric conditions that distort analog signals, digital FM radio has near CD-quality sound, while digital AM sounds like FM.

National Public Radio (NPR), in conjunction with Kenwood USA and Harris Corporation, demonstrated its Tomorrow Radio project at the 2004 CES. The project uses HD Radio technology in a different way to address the unique needs of non-commercial radio. The success of Tomorrow Radio could have a profound impact on the way public radio is used in the future.

Digital radio 101
In order to appreciate the impact of Tomorrow Radio, it's important to understand what HD Radio technology is, and what digital broadcasting offers to the radio listener.

HD Radio technology isn't as familiar to the general public as HDTV, and there's some confusion about the two terms. HDTV is coming because TV stations have been required by law to make the switch to digital broadcasting by 2006. At that time the government will reclaim the frequencies currently used by stations for analog broadcasts. HDTV signals will be broadcast on a new band of frequencies, meaning older TVs without some kind of HD converter won?t be able to get any signal at all.

There?s been no similar federal mandate for digital radio. Unlike television, where digital signals will be broadcast at an entirely new bandwidth, radio stations will keep their assigned frequencies. Basically, the conversion to HD Radio technology means stations will be broadcasting a digital signal at the edge of their allowed frequency in addition to their current analog signal. Older radios won?t become obsolete — they just won?t be able to pick up the newer signal (although they?ll continue to receive the analog transmission).

The station at 91.3 FM is broadcasting a normal signal. The station at 91.1 FM has added an HD Radio signal. The width of the signal increases slightly, but not enough to interfere with neighboring frequencies.

Along with this near CD-quality digital audio signal, or Main Audio Program (MAP), there?s also a text stream embedded in the carrier wave. This Program Associated Data (PAD) gives land-based stations capabilities similar to satellite radio services. Text scrolls across the front of the receiver?s LCD panel. Song and artist information and station ID are standard content, but the PAD can also include traffic and weather updates or other information the station provides — even commercials.

Tomorrow Radio
Commercial broadcasters see digital radio's sound quality and PAD features as a way to compete with satellite radio. NPR saw something different: a possible application of HD Radio technology that solves one of public radio's more pressing problems. Public broadcasting, collectively, embodies several different formats: classical music, jazz, world music, Americana, news, talk, entertainment programming and more. Each genre has its own loyal audience, in some cases with little overlap.

When your local public station switches from "Morning Edition" to "Midday Classics," for example, the news audience tunes out and the classical music audience tunes in. Stations struggle to serve a diverse audience with a single signal that at best represents programming compromises their audiences are willing to put up with. Towards that end, the Tomorrow Radio Project explored the possibility of subdividing IBOC's 96kbps digital signal into two or more viable audio streams, giving stations the opportunity to broadcast different formats simultaneously.

The project was undertaken with some important partners. Kenwood USA, one of the nation?s largest manufacturers of audio gear, developed the HD Radio receivers used to test Tomorrow Radio. Kenwood is bringing HD Radio receivers to the marketplace in 2004. The Harris Corporation, a major supplier of broadcast equipment, created transmission equipment capable of splitting the digital signal that was used for the tests.

The promise of no compromise
According to Mike Starling, NPR's vice president of engineering and operations, nine of the top twenty-five radio markets only have one NPR affiliate station. Most smaller markets are served by a single public radio station. These stations have the difficult task of deciding what combination of formats they'll carry — knowing that each format only serves a fraction of their total potential audience. In some cases, there are simply not enough broadcast hours to adequately provide all the kinds of programming listeners desire. Since a significant part of a public radio station?s funding comes from listener contributions, reaching that under- or unserved potential audience is a major problem stations are desperate to address.

At CES, Tomorrow Radio successfully demonstrated that stations could broadcast two discrete streams of programming, both with sound quality that matches or exceeds current FM broadcasts. Each stream has its own PAD (or text information) — now an expected part of any digital radio broadcast. According to Starling, the 96kbps signal can be further subdivided, and as compression technology continues to improve, this capability will enable stations to provide even more program options.

So what?s it to me?
You?re driving the morning carpool. Coming through your car system is the signal from your local public radio station, WXYZ — classical music. Although you tuned in fifteen minutes after it started, you know the music is Mozart?s Symphony No. 40, because that information scrolled across your car radio, as well as the names of the performers, and the record label. The music sounds great because it?s a digital broadcast — no static, no fading in and out. The soft passages are perfectly audible, the loud sections full-sounding and clean.

You pick up your first passenger who prefers news. With a press of a button, you abandon the main audio programming and Mozart. You?re now listening to NPR?s Morning Edition on WXYZ's Supplementary Audio Program (SAP). Although you've tuned into the middle of an interview, you know (according to its PAD) that Bob Edwards is talking with the new director of the Smithsonian. The signal is still digital, the sound still clear and static-free.

An HD radio broadcast from hypothetical WXYZ — WXYZ splits its digital signal into the Main Audio Program (MAP) and Subsidiary Audio Program (SAP). The MAP duplicates the programming going over the analog FM. The SAP is further subdivided, allowing WXYZ to digitally broadcast three different formats simultaneously.

Your next passenger likes bluegrass — something commercial country stations won?t touch. No problem — WXYZ has subdivided its SAP and provides bluegrass programming as well. Because its been allocated fewer kbps then the MAP, the sound isn't quite as full as the classical program. Nevertheless, it is still free of static and interference.

Without digital radio, WXYZ can broadcast but one of these programs at a time. Only one of the people in our hypothetical carpool would have been a regular WXYZ listener — or a financial supporter of the station.

Here and now
While still in the future for most listeners, HD Radio conversion is already happening at stations across the country. Although not involved with Tomorrow Radio, public radio station WGUC in Cincinnati has been broadcasting HD Radio signals since July 2003 and has been following the project's developments. According to Chris Phelps, WGUC?s vice president for marketing, the technology's sound quality is perfectly suited to the station's classical music format, and the potential of using the SAP to better serve a news audience is very exciting.

In the spring of 2004, WGUC will aggressively promote its digital radio capability, coinciding with the anticipated arrival of HD Radio receivers in the marketplace. In addition to educating the public through on-air spots, and detailed information on their website, WGUC will also have a demonstration car at their public events so the station can offer listeners the opportunity to experience digital radio for themselves.

What next?
At the moment, the industry is waiting on the FCC for approval to subdivide the MAP. If it passes, Starling posits public radio will be completely transformed within 10 years. Reports from CES suggest attending FCC officials responded positively to the demonstration, which has proponents hopeful for quick approval.

Once they're able to offer multiple channels, public radio stations will dramatically increase their ability to serve more listeners with differing interests simultaneously. With HD Radio, public stations can better fulfill their mission to entertain, enlighten and inform — with digital quality sound.