Washington – The Federal Communications Commission (FCC)
might be able within a few weeks to approve the compromise proposal by iBiquity
and National Public Radio (NPR) to boost the digital output of digital FM
stations, said NPR Labs executive director Mike Starling.
If the FCC delegates the issue to its media bureau, as seems
likely, the issue won’t have to wait for a vote by the FCC commissioners, he
said.
Once the bureau acts, a small minority of FM stations
currently broadcasting a digital signal could use their existing gear to boost
digital power output, but many others — probably a majority of digital FM
stations — would need to purchase a new transmitter, he said.
The compromise will extend the range of digital FM stereo signals
and improve in-building penetration of digital stereo signals while minimizing
a digital broadcast’s potential interference with the analog signals of first-adjacent stations, or those
operating on an adjacent frequency in “nearby but somewhat-distant markets,”
Starling said. The compromise includes
technical criteria, based on NPR field research, to manage a station’s power
increases to limit such interference.
The compromise, Starling added, “will preserve and energize
the momentum behind the digital radio transition by helping ensure American
listeners have the same ubiquitous relationship with digital service as they
have with analog service.”
Under the compromise, all FM stations will be allowed to boost
the output of their digital broadcasts from the currently allowed 1 percent of authorized
analog-signal output to 4 percent, or a gain of 6dB. These stations could
supplement gaps in digital coverage with low-power digital boosters, which are
small enough to be installed on rooftops like small cellular base stations.
Such boosters could be available in one to two years following development work
by iBiquity and NPR, Starling said.
Also under the compromise, a small minority of FM stations
would be able to boost their digital signal to 10 percent of currently
authorized analog-signal output because, based on distance and terrain, they
wouldn’t interfere with the analog signals of first-adjacent-channel stations,
Starling said.
About two-thirds of FM stations under could enjoy an
additional improvement in digital reception by implementing a so-called “asymmetrical
power increase,” an approach that iBiquity and NPR have pledged to co-develop. These
stations could increase the power of one of their two redundant digital signals
to 4 percent of analog output and the other digital signal by anywhere up to 10
percent of analog output, Starling explained. Each of these redundant signals operates
on a different sideband frequency. An asymmetrical 10 percent increase would
improve digital reception but not as much as a 10 percent increase on both
sidebands.
If stations boost both of their digital sideband signals to 4
percent of analog strength, the range of their digital stereo signal would exceed
the range of their analog FM stereo signal, Starling said. Currently, at an
output level of 1 percent of analog output, digital FM stereo signals cover only
about 89 percent of the footprint of an analog FM stereo signal, Starling said.
With a 4 percent boost to both digital signals, he noted, digital
stereo range would be comparable to the range of “a good listenable mono analog
signal,” whose range exceeds the range of an analog stereo signal, Starling added.
NPR’s estimates of current digital stereo range are more
conservative than those of digital-radio developer iBiquity.
In a past filing with the FCC, iBiquity said automakers and
receiver manufacturers have expressed “concern about digital coverage and
consumer reactions to products that may not have the same coverage as analog
radio receivers.” These issues “continue to provide impediments to the
successful rollout of HD Radio broadcasting.” In addition, a more-than-year-old
dispute between NPR and iBuqity over allowable power boosts has “slowed station
conversions due to unwillingness to invest in transmission equipment that may
be insufficient for high-power operations,” iBiquity said. At the same time, “broadcasters
are unwilling to invest in higher power equipment that may never be authorized
for use.”
