So Who Is Raising Digital Power?
image shows HD Radio reception performance of WHTZ(FM)’s digital
signal, 20 dB below carrier, via an OEM automotive antenna along
I-287 in Westchester County, N.Y. Comparisons are made to WLTW(FM)’s
digital signal at –14 dBc.
Radio stations are raising power levels; just how many are doing so
is the subject of a talk I’ll give on Sunday at the NAB Show.
2010, the Federal Communications Commission adopted new technical
rules to permit FM stations voluntarily to increase hybrid digital
power levels from –20 dBc to –14 dBc for most stations, and set a
system to allow some stations to achieve up to –10 dBc.
did some extensive research and digging into FCC records to find out
how widely high-level power levels have been adopted. I knew from
anecdotal evidence talking to engineers across the country that
stations were increasing HD Radio power, but nobody could quantify
that. I had asked the FCC and iBiquity the number of elevated HD
power stations in operation, but both entities only were able to
provide a partial picture.
sorted through some FCC records to try to get some hard numbers on
the increase. While the research I did does not offer the full count
of increased stations, the numbers available, I think, are
encouraging and show some significant progress. They were higher than
I personally was expecting. There are approximately 365 stations
running at some elevated digital power level as of early February.
The paper breaks the findings down further.
presentation also has a second part, exploring results of field
testing that I’ve done on behalf of Clear Channel.
the last year and a half, I have driven thousands of miles in various
markets, monitoring and logging the reception characteristics of
elevated digital signals. The stations I have had the opportunity to
study in depth have operated in the range between –14 dBc to –20
dBc. I focus on the differences of these two power levels in the
had been unable to locate any extensive performance studies of the
–14 dBc power level, the most common power level deployed. All of
the studies that were submitted on the record to the commission in
the 2007–2008 timeframe were based on the full power increase to
–10 dBc. The information in the paper could very well be the first
time data is shared publicly on –14 dBc performance. The tests
covered in the paper are in the New York and Los Angeles markets.
some of our testing is more indicative of “real-world” automotive
testing. I performed measurements using OEM “in glass” automotive
antennas and I compared the differences between standard quarter wave
antennas. This, too, has an impact on HD Radio reception performance
in the automotive environment. Generally speaking, the “in glass”
antennas do not perform as well as other antenna designs. In the
paper, I compare how these antennas perform at the –14 dBc and –
20 dBc power levels.
automotive manufacturers are including HD Radio in many of their
latest vehicles. Because of the increasing receiver base for HD
Radio, and the growing importance of data delivery via HD Radio
(Artist Experience, traffic data, etc.), I hope to add to the
technical record of tangible benefits of elevated digital power.
session is called “Field Observations of Elevated FM HD IBOC Power
Levels.” Radio World will report on the detailed findings after the
Jurison is a senior operations engineer for Clear Channel Media +
Entertainment’s Engineering and Systems Integration Group. He holds
several SBE certifications including CSRE, CBNE, AMD and DRB. His
opinions are not necessarily those of Clear Channel or Radio World.