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Two-channel digital FM ‘works great’

Originally published in Current, Jan. 19, 2004
By Mike Janssen

Technology that puts two distinct digital streams in one FM channel performed well in recent tests and — with FCC approval — will soon be publicly available.

The Tomorrow Radio technology developed and promoted by NPR, Harris Corp. and Kenwood USA "not only works, but works great," says Mike Starling, NPR's v.p. of engineering. Starling hopes the FCC will take the first step toward allowing stations to use Tomorrow Radio by beginning an additional rulemaking within the next few months.

NPR has spearheaded the development of Tomorrow Radio, which exploits digital radio's ability to divvy up a broadcast signal. Observers in public radio eagerly await the chance to double their FM real estate.

Commercial broadcasters, meanwhile, have shied away from a development that might not bring them many more ad dollars in markets where they believe viable formats are exhausted.

NPR unveiled Tomorrow Radio Jan. 8-11 at the annual Consumer Electronics Show in Las Vegas, where Starling says it drew heavy interest.

It builds on the flexibility of the digital radio standard developed by iBiquity Digital Corp., which is just now starting to hit the air. Nearly 300 stations have licensed iBiquity's technology, which the company markets as HD Radio. The first digital radio receiver was sold Jan. 5 [2004] in Iowa.

What makes Tomorrow Radio a boon to broadcasters is its ability to divide HD Radio's FM signal into two channels that can be programmed independently. Public radio programmers have a wealth of shows to choose from that might draw listeners but, in most cases, nowhere to put them. Starting or acquiring a new frequency is often impractical or even impossible.

Undivided, HD Radio's 96 kbps signal sounds almost as clean as a compact disc, according to Starling. Tests divided the data stream into two channels, 64 kbps and 32 kbps, but he says it could be split in different proportions. He wonders if the FCC will set a minimum bit rate for broadcasting.

With processing technology developed by the Seattle-based company Neural Audio, the 64 kbps channel sounds almost as good as a 96 kbps feed, and a 32 kbps channel sounds closer to today's analog FM, Starling says.

"There's definitely a tradeoff involved in splitting the channel," he says. "You do take a slight quality hit, but I think most people would probably not notice it."

Buttons on digital receivers will let listeners switch between channels.

On the road

NPR and its partners contracted with Hammett & Edison, a San Francisco-based engineering company, to test Tomorrow Radio in four major markets from August to December last year. A van outfitted with Kenwood receivers logged 7,500 miles in New York, Los Angeles, San Francisco and Washington, D.C.

Hammet & Edison finished the first round of testing in September but hit the road again when iBiquity adopted a new codec, a device that converts analog data into digital. Engineers found that the new codec, called HDC, improved Tomorrow Radio and allowed receivers to switch between channels more quickly--in just two seconds on a Kenwood receiver, says Mike Bergman, Kenwood's senior manager of digital broadcast products.

Each test station aired its main signals at 64 kbps and a tone on the 32 kbps supplemental channel. The van received the supplemental signal 95 percent of the time, usually almost as far out as the station's protected 60 dBu contour.

A difference between the two streams is that the main one still can be received--in analog--if the digital signal does not come through. HD Radio technology sandwiches digital channels around the analog signal received by regular FM radios and which also serves as a backup for digital receivers when digital reception drops out. A station's supplemental channel, however, lacks a backup.

FM stations with frequencies close to those of the test stations interfered with the supplemental channel at times, Hammett & Edison reported.

Testing cost $1 million. NPR has not yet determined its share of the costs, Starling says. CPB contributed $500,000 to the effort.

Will commercial get on board?

Tomorrow Radio's future depends on its reception among consumers, broadcasters and FCC commissioners. It may clear the regulatory hurdle with ease--some FCC commissioners expressed excitement about the supplemental streams when they made HD Radio the digital standard in October 2002.

Tomorrow Radio may cost stations relatively little. They will need special software from transmitter manufacturers, Starling says, which has already been developed and will not cost extra. Stations might still have to pay for a means to transmit the supplemental channel from studio to transmitter.
A CPB agreement with iBiquity exempts stations from paying additional licensing fees for the supplemental audio streams.

The prospect of supplemental audio has intrigued pubcasters for years. Some are depending on it to stoke interest among their listeners, possibly encouraging them to open their wallets and support radio's digital transition.
"It sounds good enough to make me want to go there," says Scott Hanley, g.m. of WDUQ in Pittsburgh, who heard the Tomorrow Radio demo in Las Vegas. "It sounds good enough to make me believe that it's only going to get better, and it's quite good now."

Programmers still have to decide how to use their newfound broadcast space. Some dual-format stations could split the problematic schedule into all-news and all-music channels. Hanley, however, is considering keeping WDUQ's dual format of jazz and news intact on its main channel, and programming a second channel that flip-flops the scheduling.

Receivers, the remaining puzzle piece, could hit the market as soon as the FCC gives the nod. Kenwood is prepared to equip most of its digital receivers with Tomorrow Radio, says Bergman, who would not discuss whether the feature would carry an extra cost.

Other receiver manufacturers had "very warm, positive conversations" with NPR in Las Vegas, Starling says: "They were uniformly focused on which button they would use to access [the second channel], as opposed to whether or not they would offer the feature."

But could weak interest among commercial broadcasters hamstring Tomorrow Radio? A Los Angeles commercial broadcaster told Starling that he could use the technology to program a Spanish-language version of his station, a strategy that could carry over to other Latino-heavy markets. But others in commercial radio are just starting to consider adopting HD radio, much less its offshoots.

"Digital broadcasting itself is in its infancy," says Charlie Morgan, senior v.p. at Susquehanna Radio Corp. in York, Pa. Nine of the company's 23 stations will soon be digital.

"All the people I know are aware of it; they're watching it," Morgan says of Tomorrow Radio. "I'm not aware of anyone making any pronouncements of what they'll do in the future."

Receiver manufacturers and the industry at large have so far shown unexpectedly strong interest in Tomorrow Radio, Starling says. "But there's no question that if a fair number of commercial stations, in addition to public radio stations, were to commit to this kind of service expansion, that it would help stimulate ubiquitous product in the marketplace," he adds.

The commercial response could bear on Tomorrow Radio's growth, concedes Kenwood's Bergman, but NPR's demographic holds enough promise to interest the company. "Right now, it's enough of a response that it is a market all by itself," he says.

Web page posted Jan. 19, 2004
Current: the newspaper about public TV and radio
in the United States
Current Publishing Committee, Takoma Park, Md.


Industry standards group gives the nod to digital radio, 2001.


HD Radio (digital radio) receivers debut at Consumer Electronics Show, Radio World reports.

iBiquity press release: first digital radio sold, Cedar Rapids, Iowa.

NPR announces Tomorrow Radio project a year ago.

Second channel could be a vital selling point for digital radio, says Skip Pizzi in Radio World.