Think back to Dec. 21, 2000. On that day, President Clinton signed
into law an appropriations bill containing a requirement that the FCC
conduct an experimental program to determine whether low-power FM
(LPFM) radio stations would cause harmful interference to listeners of
existing full-power FM (FPFM) radio stations or FM translator stations
operating on third-adjacent channels. That's a mouthful to say, but it
raised some serious issues that should have shaped the plans for former
FCC Chairman William Kennard's great experiment to bring a radio voice
to the masses in the form of LPFM. Obviously, Kennard didn't wait for
the results. The study has finally been completed, and the results were
publicly announced in mid-July.
The saga of LPFM is old news to broadcasters today, but to LPFM
supporters, the struggle for a widespread LPFM service continues.
From the original bill, the program directed the FCC to select an
independent group to conduct field tests in various markets. The field
tests were to include an opportunity for the public to comment on
interference, as well as independent audience listening tests to
determine what is objectionable and harmful interference to the average
radio listener. These tests were to be conducted in more than nine FM
radio markets by waiving the minimum distance separations for
third-adjacent channels for the stations. The goal was to evaluate
whether minimum distance separations for third-adjacent channels are
needed for FM translator and FPFM stations.
The MITRE Corporation was selected by the FCC to provide technical
leadership and management by establishing and monitoring the
experimental program. MITRE contracted Comsearch to conduct the field
measurement and public comment data collection portions of the
experiment. The FCC will present the data in the final report to
So what did the report say? It took 203 pages, but the short answer
is that the amount of interference that a listener may experience
depends on the type of radio he uses. It took three years to determine
what most broadcasters already know. The measured results indicate the
receiver least susceptible to LPFM interference was the in-vehicle
receiver. Next was the home receiver, followed by the clock radio. The
boombox and Walkman were the worst performers. For the most part, the
less expensive the receiver, the more susceptible it is to
third-adjacent channel interference.
This sounds like a win for the FPFM stations, but the details of the
report state that interference to the FPFM occurred when the receiver
was close to the LPFM transmitter. How close? Try 50 feet.
The question remains as to what this study proves. The answer is
that it really proves nothing. The third-adjacent channel protection of
a full-power station from a low-power station is not really an issue.
In most cases, the FPFM signal will easily overcome the potential LPFM
I tried reading some of the respondent surveys to get a better
understanding of what the listeners heard. I'm not convinced that these
responses add anything to the study. Most of the comments describe
interference from multi-path, terrain and electro-magnetic sources. I
don't think most of the listeners could have identified the supposed
source of the interference without being prompted in some way. Some
respondents reported interference even when the LPFM transmitter was
not in operation.
Third-adjacent protection of FPFM stations from LPFM stations is not
an issue. To be honest, second-adjacent interference is probably not
much of an issue either. Who will win in the end? We all know that laws
and FCC rules have nothing to do with science and hard data. In the end
the loudest lobbyist will prevail.
The FCC seeks public comments on the report. Comments are due by
Read the entire MITRE report online through the FCC website at
this link: http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6514285088
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