This is the IBOC Section of
The Broadcast Archive
Barry Mishkind - The Eclectic Engineer
last updated 12/26/08
2002 appears to be the year IBOC (In Band On Channel)
Digital radio made its first "mark."
KROQ-FM (Los Angles) became the first station to
"Officially" run IBOC 24/7 on September 29, 2002. KROQ chose the Orban
Optimod 8400 with digital options to drive the processing. (Some stations,
including one in Seattle had been running more or less consistent IBOC since
mid/late 2002, but essentially in an "experimental" mode. Updated
information will appear if available.)
The tests conducted in Seattle, along with other cities gave
Ibiquity the strength to head toward a nationwide rollout in early 2003. What is
IBOC (or IBAC - In Band, Adjacent Channel)? Let's take a look.
IBOC for AM and for FM.
IBOC impresses digital information on top of the regular
analog signal. In general, you could say it "increases the sidebands"
of the station, hence some complaints from the DX crowd about making the band
Among the "pluses" claimed for IBOC:
1. Reduced multipath on FM
2. The ability to run more than one program at a time.
3. The ability to send digital text at the same time.
Phil Alexander writes: "... the
history of IBOC is a very ugly chapter that begins in the 1960's with FM stereo.
In hindsight, that was the time to move from VHF FM analog
to UHF digital, but with the existing FM service mired in
a battle for survival, it was a full generation too early even though the
techniques and hardware were not unknown in some circles.
Twenty years later, FM had won dominance over AM because the
FCC did not act in the '70's to move the medium forward into the stereo era. The
FCC induced AM stereo debacle is too well known to waste bandwidth recounting
here, so I'll skip that part.
However, the FCC/industry AM stereo failure combined with
years of FCC non-enforcement of electronic noise radiation rules have left AM at
the low point of its history in many ways. The IBOC conversion was the FCC's
effort toward AM band salvation after the broadcast industry turned down the
idea of moving to UHF (the same frequencies later allocated for Sirius/XM)
possibly using a scheme like Eureka, or Eureka itself. The reason for rejection
was this move would have upset the coverage applecart by equalizing the audience
coverage of all stations in a transmitter group.
Needless to say, the idea was a nonstarter with the dominant
50 kW owners, so the IBOC rulemaking began with a specific requirement for In
Band On Channel proposals that would be evaluated. The intent was a hybrid
transition period during which both digital and analog signals would be
transmitted together to build receiving sets in the market after which stations
could elect to discontinue analog and increase digital power levels. And, by the
way, make sure the same system will work for FM (i,e., VHF) so all stations will
have technical parity.
One of the entrants was the old, original AT&T
Laboratories. Alas, AT&T was split and the part involved in IBOC became a
Lucent asset. Lucent DR Operations and a company called USA Digital Radio were
the two finalists remaining in the FCC contest when Lucent determined DR Ops did
not fit within their future business plan and placed it on the block.
USADR won the FCC battle by buying their only remaining
competitor and withdrawing the Lucent entry. At that point they named themselves
Ibiquity. Some wags have opined it was more a play on inequity than ubiquity,
but whichever it was, the rest, as they say, was history.
The reality is the Ibiquity/USADR system is not well regarded
in a large segment of the broadcast engineering community, especially the
"AM" part. Because they have not been open with the engineering
community and have generally pursued a non-disclosure/trade secrets strategy,
Ibiquity, itself, has not won many friends either. The general consensus seem to
be one of false promises and under performance, both in engineering and
marketing. However, they seem to have excellent lobbyists and have forged
relationships with the NAB, their licensed equipment manufacturers and early
adopting groups including Clear Channel.
You may wonder how they have managed to maintain a closed
strategy with the FCC, however IBOC is optional, not mandatory. In a mandatory
situation it appears full disclosure would be inevitable. My own view, which I
have publically stated for several years, is that IBOC is a terrible system, but
it has been approved by the FCC, thus it is the only one we will get. However,
it may be interesting to see if DRM which I believe is superior can gain a
significant foothold in the western hemisphere.