HD Radio power increase?

There has been an email conversation within the public radio community about whether or not to increase the power of the digital ("HD Radio") service of those radio stations which provide both analog and digital services.  Unlike digital television, which completely replaces analog television next February and for which digital operates on a completely different channel, digital radio operates on the same channel, magically intertwining with the analog signal.  It's not likely that analog radio will go away any time soon, or perhaps ever. 

So the fact that these two technologies have to co-exist has led those who set conditions for such things to provide for a very low power level for the digital component.  But that has caused HD Radio coverage to be, in many cases, less than for the analog part of the signal.  In public radio, some stations, such as the ones I managed out in the Northwest, take advantage of nearby mountaintops for transmitter sites, but that often means they're not as closely located to the metropolitan population center as is desirable in a low-power digital situation. 

The FCC has been looking into this and is considering permitting stations to increase the digital power level.  NPR has conducted tests on this and it has revealed some concerns.  The Executive Director of NPR Labs, Mike Starling, takes over from here in a note he posted yesterday to the public radio system:

Regarding the recent messages about HD Radio coverage and the proposed power increases, our studies show we need to balance the need for digital coverage improvement against potential interference to your analog signals.

While improving HD Radio indoor coverage is essential, NPR supports a managed power increase, on a voluntary basis, where needed. We do not support iBiquity’s unconditional, proposed 10 dB power increase at the minority of stations where our studies predict interference can occur to more than 20% of the listeners INSIDE of the protected 60 dBu contour of neighboring first-adjacent stations.

Please join us next week for an interconnect to go over this issue and why we feel so strongly that a managed increase is necessary. We’ll be providing audio samples of the interference we found in our study -- so you can actually hear the interference effects for yourself.

[Here, I take out the interconnect info, but if you're in public radio, please check for the details with your A-Rep and join the discussion. --Dennis]

The FCC has put both the NPR Labs DRCIA report and the “Joint Parties” filings out for public comment, with a comment deadline of November 28 (yes, the day after Thanksgiving). We are eager to hear from you so that your views will inform our comments in this proceeding - and to hopefully achieve a common public radio position on this filing.

Helpful resources:

• DRCIA Report - Executive Summary http://www.nprlabs.org/publications/reports/200807151044-DRCIAFullReport-ExecSummary.pdf

• HD Interference Maps showing expected FM interference coverage for 49 stations: http://www.nprlabs.org/research/drcia_maps_index.php

While adjacent channel IBOC interference does not obliterate the signal or fundamentally alter basic intelligibility, it increases the noise level of reception, which is most noticeable on voice programs such as news and public affairs. In our report, a consumer listener panel determined our protection criteria for the FM signal at not less than “good” audio quality. While it is still a listenable signal for committed listeners, it is audibly noisier than interference at the present 1% IBOC power. And outside your protected coverage area (which the FCC has recently reminded us they do not protect against such effects) it would be worse. We are especially concerned in situations where adjacent channel spacing is insufficient in our view to support a full 10dB power increase among spectrum neighbors (which could include your station!).

Even in close-spaced instances, we believe alternative solutions such as unequal sideband power, directional IBOC antennas, and single frequency network boosters can provide the needed improvement in indoor signals without generating the interference levels that listeners judge as degraded signals. To our favor, iBiquity announced at the September NAB Radio conference that they will fully support the development and deployment of these recommended alternative strategies.

Just as our DTV colleagues faced significant challenges a few years back with the need for increased power, we hope this chapter in HD’s rollout will be chronicled under “early lessons learned” about the robustness and indoor penetration limits of digital signals.

Hopefully, this too will turn out to have been an important, but ultimately successful turn of events to optimize the digital deployment for the future. We look forward to hearing from you during the interconnect.

Some very interesting trade-off decisions to be made.

Update 14 November 2008:
Recommend you also read the comment from PocketRadio below, from which this link to Cost considerations for increasing HD Radio another 10 dB comes.   --Dennis

Comments

[NervousCat]

I'm one of those "deaf consumers" who bought one of these radios. I couldn't return it because I bought it on eBay - USED! Yes, I am soured on the idea of HD radio - but my SONY table radio is still a great little AM/FM ANALOG radio. HD Radio reception is nonexistent after I spent hours fiddling with the NPR labs recommended FM Reflect indoor dipole antenna. More power is welcome, but not at the expense of more FM hiss. HD Radio is stuck between a rock and a hard place. It's sink or swim, and it's been sinking for years. Oh yes, lots of old folks listen to the radio. My aunt bought a Tivoli Audio Model One AM/FM radio because it is simple to operate. One large tuning knob and two smaller volume and band selector knobs. I have yet to see an HD radio with simple controls like that. LCD menus? Forget it.

[Warren Shulz Chief Engineer WLS-AM / WLS-FM Radio Chicago]

By iBiquity's own admission 1% power was choosen to minimize interfence to analog recivers and adjacent channels. With less that 1% IBOC receivers in place at this time it not should be no 10% power increase but HELL NO to 10% IBOC power. IBOC is bad science and increasing the power level won't change that. We need to preserver analog FM broadcast. In Chicago listening to the FM dial with an analog tune the hiss of iBOC saturates the dial. Because the hiss appears as interstation noise it goes unnoticed at 1%; going to 10% will be intolerable. Stop the insanity and say HELL NO. The NPR report should be heeded as netural party to preserve FM analgo service until such time the IBOC receivers reach 80% penetration. iBiquity has ran more promotional announcements than GIECO. The public has voted 'no thanks" to IBOC radio.

[PocketRadio]

"Upping HD Radio signal strengths"

"The short math given what we know today is that it will cost roughly double on the transmission end to increase HD Radio FM power tenfold. There are likely to be additional costs for cooling and air handling as well, in order to dissipate the excess energy required to get out another 10 dB in HD Radio signal. And, for some higher powered stations, existing HD Radio configurations may not be able to handle the power load, which could add to the cost and complexity of increasing HD Radio beyond its current power level... Also worth considering is existing transmitter combiner technology and whether or not it can support the added demands of increasing HD Radio broadcasts another 10 dB. If not, then it’s very likely that stations at the higher power levels will need to factor in a new antenna system that can support HD Radio, rather than piggyback onto their existing FM antenna system. At the higher powers, especially, an immediate 10 dB increase in HD Radio signal may be cost prohibitive... This will typically mean the addition of another similarly rated transmitter (using a combining technique) or the purchase of a new transmitter of roughly twice today’s power level."

http://www.rbr.com/features/intel_briefs/hd_radio_signal_bealor_cavell.html

Do you really think that most station chains are going to be able to afford this upgrade, with the state of the economy, and many of their stocks in the penny-stock range? Doubtful. Besides, first-impressions are everything with consumers, as those few consumers that purchased these "deaf" radios, that did not deliver on programming either, ended up returning them. The FCC just authorized the white-space TV channels for Internet-related mobile devices - HD Radio is antiquated right out of the box.