A VERY SHORT HISTORY
HDRadio is a term coined by iBiquity Digital Corporation.
iBiquity was created in the year 2000 by the merger of the two leading developers of AM and FM digital
broadcasting, Lucent Digital Radio and USA Digital Radio. Early in its development, the format was
called IBOC or "In Band On Channel" which described the ability to add digital audio channels,
not only in the same band (AM or FM), but also within the same channel space already occupied
by the existing station. iBiquity now holds the patent on In-Band-On Channel broadcasting in the United States.
The Federal Communications Commission (FCC) and some innovative broadcasters were very interested in introducing
"digital-quality" radio to existing AM and FM listeners but did not want to allocate more spectrum or move the
existing stations to new frequencies. They also wanted the system to be initially "backwards compatible" since
there are an estimated 700 million broadcast receivers in the United States!
Another reason broadcasters were interested in a digital radio service was the growing popularity of
satellite radio (XM and Sirius) and internet streaming or "webcasting". They saw both technologies as
long-term threats to the existence of over-the-air commercial and public broadcasting.
THE ADVANTAGES OF HDRADIO
HDRadio or "In Band On Channel" allows the addition of digitally-produced channels to be added to existing
AM and FM stations within their own existing channel space. It gained popularity in the US because:
- It uses no new spectrum so current licenses remain the same.
- Every station keeps their current power and class status.
- It’s compatible with existing stations, services and (initially) receivers.
- It has lower implementation costs because much of the existing analog equipment can (usually) be re-used.
- It can be introduced in stages - first a hybrid service (compatible with existing analog receivers) then later
a "pure digital" service offering more features and channels (using new digital receivers).
- In the FM/HD version, the main digital channel can "blend to analog" if the digital reception is
- The FM/HD main channel signal sounds almost CD-quality, drastically reduces "popping" (aka multipath) and
increasing the station's "dynamic range".
- The AM/HD version is stereo and sounds similar to today's FM stations with greatly increased frequency
- Both the AM and FM band systems have other data carrying capabilities and options such as Program
Associated Data (PAD) which can display the station's call letters, program or song titles, artist or guest
names, news, weather, and even sports scores on the listener's radio.
- Because of their additional bandwidth, FM/HD stations can carry Secondary Audio Channels (SAC) using a
system called "multicasting". One FM station could have as many as two or three audio channels in addition
to their "main channel".