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Saturday, April 22, 2006


HD Radio-Commentary: Has Anyone Thought This Through?

Economic and Political Considerations Can Trump Technical Ones at the FCC.
But while AM IBOC's appropriation of five channels is outrageous, FM IBOC's use of half of each adjoining, or "first-adjacent," channel is hardly innocuous.
Since Philadelphia lost its full-time classical station, I'd like to be able to hear WQXR (96.3) from New York. Until recently, that might have been possible.
But what good would the best possible tuner and antenna be when Beasley's CHR Rhythmic WRDW(FM) 96.5 in Philadelphia is running IBOC, with its lower side channel effectively jamming the upper half of WQXR(FM)'s weak 96.3 analog signal from New York?
And that's not the only problem with "HD FM." When two second-adjacent stations both use IBOC, each taking up half of the channel between them, they become in effect first-adjacents, at least with respect to their digital signals.
Want concrete examples?
WSTW(FM) 93.7 in Wilmington, Del., is a second-adjacent to both WMMR(FM) 93.3 and WYSP(FM) 94.1 in Philadelphia, both of which are running IBOC. IBOC signals from WSTW wreak havoc on those two Philadelphia stations' IBOC signals south of the city. And what about WPST(FM) 94.5 in Trenton, N.J.? That one would interfere with WYSP's IBOC north of Philadelphia, too. There are dozens of such situations around the country.
If nobody's noticed the problem yet, that's only because IBOC receivers automatically default to analog whenever the digital signal is too weak for adequate reception, provided there is an analog signal. Of course, once the stations pull the plug on analog to add more digital program streams - or switch their analog service to mono to extend their useable coverage area, as per Walt's suggestion - the problem will become immediately obvious.

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