NPR Study Suggests Concerns With Increase in HD Radio Power
A recent proposal to increase the power levels at which HD Radio stations operate - to improve coverage and, perhaps more importantly, building penetration so that people can receive digital channels inside buildings - has been the subject of a cautionary study released by National Public Radio. That study was summarized in a story in the NPR magazine Current (an executive summary can be found here, and the entire 280 page study is here). The study agrees that an increase in power suggested by the recent proposal would increase HD Radio coverage and significantly increase building penetration, but it would do so only at the cost of causing interference to existing analog stations - in some cases significant interference. Such interference would be especially troublesome in receivers in cars, where radio broadcasters have long concentrated some of their most important programming to capture people in the place where competing entertainment options are most limited.
The NPR study does suggest that there could be ways to limit the interference using directional antennas or lessening power but using digital boosters that could be tuned slightly off-center on their frequencies to protect adjacent channel stations. HD radio operates on the sides of a station's analog channel (thus its original name - "IBOC" for In-Band On-Channel), thus potentially causing interference to adjacent channel stations. By suppressing the signal on the side of the signal nearest to the adjacent channel station and sending the digital bits out of the other side of the channel, some of this interference could be minimized. Yet systems capable of such protections have not yet been fully developed.
NPR has been in the forefront of the development of digital radio, as it sees the vast opportunity for providing multiple streams of programming on a single FM channel, serving various constituents with varied programming. See, for instance, our post on the services offered by Washington DC NPR affiliate WAMU. Because of NPR's leadership on the issue, the caution reflected by this study may be given serious consideration. As noted in the Current article, this topic will be discussed at panels at the NAB Radio Show in Austin next week - panels that may well be worth attending to hear the differing viewpoints on this proposal.
"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
Yea, good-luck with this one!
Why not just turn HD off?
Does NPR's 'study' remind you of timid pyromaniacs trying to get Mrs. O'Leary's cow to kick over the lantern again but not burn down the Chicago - again?
What difference does it make? Chicago's toast - again. In radio's case debating how to safely jam adjacent competing stations with HD without jamming your own well illustrates HD's destructive, disingenuous, self-serving essence.
Haven't HD cheerleaders long angrily denied interference and insulted all who expressed concern about it?
So why debate minimizing HD jamming which they claim doesn't exist?
Is it because 'everything about HD is a lie' as one prescient observer noted, and anyone who co-signs the HD lie soon speaks nonsense?
When something destructive is promoted with vague, contradictory, shifting stories, don't people instinctively sniff a racket - and walk away?
Is that why the rejected HD?
Paul Vincent Zecchino
Manasota Key, Florida
08 September, 2008