Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now


Power Boost or Bust for HD Radio

Improvement in Digital Coverage Area Necessary for HD Radio Success

This year marks the long-awaited shutdown of over-the-air analog TV in this country. It emphatically closes the book on television’s first 60 years.

TV’s transition to digital has had its own litany of twists and turns. But HDTV enjoyed widespread acceptance and had the blessing of a mandated conversion to digital by FCC rule. Radio, it seems, will not be so blessed.

In the beginning, almost everyone was impressed at how well digital radio performed using only 1 percent of the channel power carried by its analog host. The efficiency of OFDM modulation coupled with clever coding and decoding tricks blew away legacy analog schemes. As with every other electronic-based enterprise, digital technology gifted the broadcasting business a dramatically more powerful and effective set of tools to carry on its mission.

However, the past seven years of the HD Radio rollout has brought us to one painfully obvious conclusion: 1 percent power for the digital signal is not going to make this technology a winner. Impressive though it may be in some markets, it’s simply not enough to deliver consistent and reliable performance, particularly for indoor reception. Better receivers cannot get us there by themselves.


No matter how many more features or improvements HD Radio might deliver for the consumer, Joe Public is not going to buy a new HD Radio receiver unless it captures and holds his favorite stations as well as or better than his trusty old analog sets in all the venues he wants to use it. Too many episodes of signal dropouts, blends-to-analog or no HD Radio signal at all leave a horrible impression. Resorting to an external antenna is not an acceptable or realistic solution.

The inventors of HD Radio knew going in that the transition from analog to digital was going to be problematic. As early as 2004, Godfather Glynn Walden told many of us that more digital power would be needed to give consumers the same “radio experience” as analog. Blend-to-analog was only a crutch to allow HD Radio to walk. It eventually would have to start running on its own. But iBiquity was constrained to use a conservative approach during the initial rollout to protect the analog host from degrading hiss while trying to keep the primary contour reach roughly equivalent to the analog.

We all knew it would take a while for HD Radio to achieve critical mass on the transmission side in order to convince receiver manufacturers that receivers were worth making and marketing. For the most part, broadcasters have done their part, but even with more than 100 models of HD Radios now available, there is no real consumer demand.

Despite better marketing, receiver sales figures have been … shall we say, rather disappointing. Less than a million receivers have been sold since the technology’s introduction, according to iBiquity. That number pales in comparison to that of any other successful electronic innovation targeting a mass audience. Bob Struble can spin all he wants but this one issue has become a real and serious problem that iBiquity and its stakeholders know they have to solve. And they have to solve it sooner than later.


The obvious solution, and the only one we can see to turn around the fortunes of HD Radio, is the 10 dB digital power boost. IBiquity’s plan all along was to ramp up the power after HD Radio signals became widely available in all significant markets. Radio sales were expected to keep pace and enjoy a corresponding ramp-up so that analog interference issues would be less of a concern. Clearly that hasn’t happened.

People on broadcast listservs and in the trade press are reporting a small but growing number of stations that have turned off their HD Radio. Most of them appear to be AM, but it’s hardly an auspicious omen. The deepening recession and heavy cost-cutting puts pressure on owners and managers to suspend support for anything that is not producing revenue. Most FM-HD stations are hanging in there, but it appears HD Radio has arrived at that proverbial fork in the road a little sooner than it had planned. Should HD-R power be increased now or later, after it achieves more use and acceptance?

The 10 dB power increase proposal has been under careful review for almost two years. Field testing is being conducted in a number of major markets by several NPR affiliates, CBS Radio, Greater Media and a few other groups. NPR Labs launched a comprehensive HD Radio coverage and interference evaluation effort in late 2006 under the capable leadership of John Kean. With NCE stations tightly packed into their end of the band, using contour protection instead of distance protection, NPR understandably is more concerned about interference issues with such a large power increase on the table.

Kean concludes that a digital power increase from –20 dBc to –10 dBc would significantly enhance digital performance, assuming all stations were operating in digital. NPR prefers to label HD Radio as IBOC DAB. Overall, mobile IBOC DAB coverage would jump from 85 percent to 117 percent of quality analog coverage, as measured by population, for 50 sample stations. Indoor and portable IBOC DAB covered population totals would increase from 38 percent to an average 82 percent of equivalent analog coverage.

This suggests the power boost actually would make digital coverage better than analog for car radios and almost as good for indoor and portable sets; indoor and portable reception more than doubles. These are critical and compelling enhancements.


There would be an interference penalty of at least some consequence, affecting short-spaced stations especially. Assuming all stations operated with digital and increased power from 1 percent to 10 percent, the mobile analog FM population would be reduced an average of 14 percent to 26 percent for the sample stations due to interference from IBOC DAB. Analog FM indoor covered population would be reduced by IBOC interference an average of 6 percent to 22 percent for the sample stations. Interference to portable analog service was judged minimal at 1 percent digital power but would increase to a coverage loss of 6 percent with a 10 dB digital power boost.

Interference would affect some stations severely in portions of their analog mobile service area. Forty-one percent could lose a third or more of their covered population and 18 percent would lose more than half of their population. These figures assume all stations would be operating in HD Radio with the full 10 percent increase in digital power, so they represent the worse-case scenario. Digital-to-digital interference considerations were not evaluated since first adjacencies potentially affected are already significantly degraded by analog interference.

The complete NPR report and summary conclusions can be reviewed at

The principle spokesmen for commercial broadcasters Greater Media and CBS Radio are saying that a digital power increase would be beneficial and appropriate for most all HD Radio stations in all markets. They’ve concluded that the overall service improvements clearly outweigh the modest interference increases and decidedly serve the greater good.

Photo by Leslie Stimson NPR’s Mike Starling is supportive about increasing the digital power level but is a bit more guarded and selective on how the full 10 percent increase should be authorized. He feels more study is needed to make sure those stations likely to receive the most interference are properly protected.


Radio World’s Dec. 18 webinar, “What to Watch for in 2009 — A Radio World TechCast: 360 Degree Industry Roundtable,” gives good insight on how NPR and Greater Media view the power increase proposal and what’s likely to happen next. You can watch and listen to the archived podcast at Register via the form for free access.

Participants Mike Starling and Milford Smith agreed that a 10 dB increase should be afforded to stations with no short-spacing or present interference constraints. A base increase of a lesser amount, probably around 6 dB, should be afforded to all other stations. Some stations may also find that a 6 dB power increase provides an acceptable tradeoff between increased digital coverage and digital self-interference to analog. Increases (or decreases) from that amount could then be granted on a station-by-station basis, pending evaluation of real interference to the protected contours of other stations.

All of the webinar participants agreed that this proposal deserves a fast track at the FCC and hopefully could be adopted later this year.

Considering the evidence produced by the studies and field testing done so far, this proposal is a measured and balanced approach to help save radio’s digital future. While many of us may have preferred an open-source and more flexible system design, iBiquity HD Radio is the hand we have been dealt.

Nobody who wants to see radio remain a valuable, competitive and successful service for 235 million Americans who use it every day should want to contemplate what would happen to our enterprise long-term if HD Radio fails. It would take years to resurrect and perfect another effort of implementing the benefits of digital to radio’s over-the-air delivery.

Time is beginning to run short. Receiver manufacturers are not going to keep making HD Radios and introducing new models unless consumers start buying a lot more of them. Even if iBiquity were to decide to reduce licensing fees radically it would not fix the performance problem. And all the marketing in the world won’t fix it either. For iBiquity and its stake holders, the digital power boost appears to be the last card in the deck they can play to win this game.

Guy Wire is the pseudonym for a veteran broadcast engineer. Read past articles under Columns at

Sorry. No data so far.