HD Radio is simply ordinary radio broadcast as a digital signal instead of the old analog signal to which we are accustomed. Think of it as the difference between a vinyl record and a CD. The digital signal is able to pack much more information in the same bandwidth so the broadcaster has the option of increasing the fidelity of the sound or sending more information over the same radio station. A company called Ibiquity developed the digital protocol and licenses HD Radio technology to radio stations and to manufacturers of HD radio receivers. HD radio signals can only be received and decoded by a digital HD radio receiver. This link, from Ibiquity’s HDradio.com, you can hear a sample of the difference between HD Radio and traditional analog radio.
Improved Audio Quality with HD Radio
For AM radio, HD radio promises to allow FM quality music and sound on the AM band. This means that as HD radio becomes the mainstream standard, we may see a resurgence of music programming on AM radio stations. Because the HD radio receiver is decoding a digital signal, there is no opportunity to introduce static into the signal. The receiver reproduces only the same crisp, clear audio that was encoded and broadcast from the radio station. To find a list of radio stations that are broadcasting in HD, click here.
Turning One Radio Station into Three
The extra efficiency of digital encrypted FM stations can be used to deliver CD quality sound. Alternately, the broadcaster can use the excess bandwidth to transmit other information. Some radio broadcasters view this as an opportunity to compete with the hundreds of niche stations offered by satellite radio. HD Radio allows them to broadcast two or three distinct and separate radio programs simultaneously. So if you are listening to 96.1 on the FM dial on a digital or HD Radio, then you can choose between their A, B, or C programming with an HD Radio receiver. These secondary and tertiary stations are called HD2 and HD3 stations.
Alternate Programming Options with HD Radio
While 96.1 might ordinarily feature today’s country music favorites, the HD2 and HD3 programming channels might feature bluegrass or rockabilly music, or even a genre completely unrelated to the main station’s programming. They might even choose to offer an all talk format on one of the secondary channels. Of course, if the bandwidth is used for additional stations, then it cannot also be used to increase the audio fidelity.
More Commercial Sales Opportunity
From the broadcaster’s perspective, the additional stations allow the opportunity to sell commercials on all three stations. Of course, that’s only profitable so long as the listeners of all three channels number more than those of the single station. Simply splitting the existing audience over more stations doesn’t help increase revenue.
Text Embedded in HD Radio Signal
With the digital broadcast, it is also simple to add basic information along with the audio to be displayed as text on an HD Radio display. This can include the radio station’s call letters, the title of the song that’s being played, the artist, remaining time in the song, or unrelated information like contests and trivia. The few bits of digitally encoded text use only negligible bandwidth and have no effect on the audio being transmitted.