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Broadcast Technology Broadcast DXing IBOC Digital Radio Update by Bruce Conti
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In-Band On-Channel (IBOC) digital radio is moving closer to reality, albeit a little more slowly than expected. The FCC application process was streamlined for rapid approval of radio stations to begin digital broadcasting, and many stations have already gained approval (see Pop’Comm, July 2003). While FM IBOC digital broadcasting is poised to go on the air, a couple of key issues on the AM side have broadcasters holding their breath. The limited bandwidth of AM and nighttime skywave propagation is proving to be a challenge. The limited bandwidth of AM results in a lower data rate than FM. That means there’s less overall space in which to contain digital information on AM. This has lead to some objectionable artifacts being detected in the AM IBOC digital audio. As a result, the National Radio Standards Committee (NRSC) has suspended IBOC standard setting efforts. The following statement was issued by iBiquity: Due to some specific concerns about the current state of the AM audio quality, the NRSC has temporarily suspended standard setting efforts for IBOC digital broadcasting. At this time, we concur with their decision to temporarily delay these efforts until the issue is resolved. The NRSC has not expressed any concerns about the core system architecture or implementation of IBOC. There are no issues with coverage, reception, or functionality. This issue is in the audio coder and has to do specifically with AM audio quality. The resolution will be a software upgrade, and no other changes to the system will be necessary. As such, we have an on-going improvement plan and anticipate resolution of the AM audio quality issue as soon as possible. iBiquity and its partners continue to support radio’s transition to digital broadcasting and look forward to capitalizing on the potential for HD Radio. Regarding the status of nighttime AM IBOC testing, David Salemi, Vice President, Marketing, at iBiquity Digital reports, “We are near completion of the AM nighttime testing. We have just completed our subjective evaluation testing and the complete report should be sent to the NAB (National Association of Broadcasters) shortly.” AM IBOC has at least initially been limited to daytime only operation due to interference concerns involving nighttime skywave propagation. Nighttime operation of AM IBOC has been under test at 700 WLW Cincinnati and 710 WOR New York.
During the NAB Show in Las Vegas, there was
some speculation that digital programming would be separate from analog,
abandoning digital/analog blending in the hybrid IBOC mode of operation.
Hybrid IBOC was designed to provide an analog fallback when digital lock
is lost by simulcasting analog programming in digital. At the show,
however, 840 KXNT demonstrated IBOC with separate analog and digital
programming. Salemi says the digital/analog blending feature will be
implemented as planned. “For purposes of demonstrating high quality AM
digital music programming at the NAB show, we needed to transmit separate
programming on the digital sidebands,” explained Salemi. “There are no AM
music stations in Las Vegas. The broadcast of separate programming was
unique to this situation and does not reflect the designed commercial
operation of the HD Radio System (IBOC). The system will work as designed
with a simulcast of the digital and analog programming, with a blend
feature for the transition between analog and digital.” The hybrid IBOC
mode is considered temporary, until analog is phased out and replaced
entirely by IBOC digital.
1020 KINF Roswell, New Mexico, partial-data
letter, embroidered emblem, business card, t-shirt, and returned postage
received in 10 days, signed Tracye Nelson, Promo Mgr. Address: P.O. Box
670, Roswell, NM 88202. (Griffith, CO) |
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