Q: What is HD Radio?

A: The term "HD Radio" is iBiquity Digital Corporation's trademarked name for their digital audio broadcasting technology, which has become the IBOC standard adopted for the United States.

Q: What's IBOC?

A: IBOC — In Band On Channel — derives its name from the kind of digital signal being broadcast. IBOC signals use the same AM and FM bandwidth as a station's analog signal ("in band"). The digital information is contained within the station's signal ("on channel").

Q: Is HD Radio technology the same as HDTV?

A: Only in the sense that they're both digital signals. Television's move to HDTV was mandated by the federal government. On the other hand, radio stations are voluntarily adding HD Radio technology to their regular broadcasts. Stations will continue using the same AM and FM frequencies they do now.

Q: What does "HD" stand for?

A: Originally, the initials stood for "hybrid-digital," because the digital signals were carried with the analog wave. According to iBiquity Digital Corporation, that's been changed, and the letters "HD" now don't stand for anything. Some articles and news stories have erroneously assumed that "HD" stands for "high definition," which has contributed to the confusion between HD Radio technology and high-definition TV.

Q: My favorite station says they're now broadcasting in HD Radio, but I don't hear a difference. What gives?

A: Many radio stations promote their HD Radio capability in their analog broadcasts. This sometimes leads to a little confusion, as the listener can assume that "now broadcasting in HD Radio" refers to a signal upgrade that only needs to happen at the station's end. It's not.

Unless you have an HD Radio tuner, you won't receive the digital HD Radio signals. So when you hear a station talking about HD Radio on your old receiver — and you don't hear a difference in sound quality — you're probably still just receiving the analog signal. Only after you've purchased an HD Radio tuner can you hear the difference.

Q: How is HD Radio different than current FM and AM radio?

A: Because they're digital, HD Radio signals aren't subject to atmospheric interference the way current FM and AM signals are. Background crackle and hiss are eliminated. The effect is similar to the difference between CDs and vinyl records. The digital CD signal is free of the surface noise that's always present on LP playback.

Q: How can I find out if my local station is broadcasting digitally?

A: As stations add HD Radio capability to their service, they generally publicize the fact. iBiquity Digital also maintains a site that lists which stations are broadcasting with HD Radio signals. Go to hdradio.com to find stations broadcasting in HD Radio in your area.

Q: My radio isn't compatible with HD Radio broadcasts. Will it become obsolete?

A: At this point, no. Unlike the conversion to digital television a few years back, analog AM and FM radio will remain on the air. Stations broadcasting with HD Radio technology will continue to simulcast their AM or FM analog signals, so you'll be able to enjoy the same stations as before. Without an HD Radio tuner, though, you'll miss out on the digital-only multicast channels some stations now offer.

Q: What is multicasting?

A: An HD Radio signal can be subdivided to send out two or more different kinds of programming simultaneously. When a station does this, it is multicasting.

Q: What is HD2?

A: HD2 is the term multicasting stations are using for their secondary digital-only channel. Some stations are using this second channel to offer more specialized programming, such as Latin Hits, Classical Opera, and Electronica.

Q: Can all HD Radio tuners get these extra channels?

A: Multicasting was developed after the first generation of HD Radio tuners hit the market. While all HD Radio tuners will pick up the station's primary digital channel, only radios that are designated multicast-capable will be able to pick up HD2 and any additional subchannels. Multicasting capability has since become a standard feature on HD Radio tuners. At this point, virtually all HD Radio tuners on the market can receive multicast channels.

Q: Satellite radio requires a monthly subscription fee for their digital broadcasts. What do HD Radio broadcasts cost?

A: Like current FM and AM radio, HD Radio broadcasts are free to the public. Your only expense is the purchase of an HD Radio tuner.

Q: Is the coverage area of my station's HD Radio signal identical to that of their current signal?

A: Currently, the FCC requires that stations' digital transmitters operate at lower power levels than their older analog counterparts. Because terrain obstacles affect analog and digital signals in slightly different ways, there's no sure-fire way to predict reception. For many stations, though, the coverage area for HD Radio seems to be about 60% of the analog coverage area. The FCC is expected to raise the limits for digital broadcast power in the near future. This should make the HD Radio coverage area for a station similar to — but not exactly the same as — its analog coverage area.

Q: What happens if I lose the HD Radio signal?

A: If your HD Radio tuner loses the station's digital signal, it will automatically switch over to the analog signal broadcast at the same frequency. There may be a slight break in the sound when this happens. When the tuner is back in range of your station's HD Radio signal, it will automatically go back to the digital broadcast.

Q: I see older car radios use the term "HD Radio ready." What does that mean?

A: An HD Radio ready car radio — or "head unit" — can play HD Radio signals, but requires a connection to a separate HD Radio tuner. Current car radios that offer HD Radio include a built-in tuner.

Q: Can I only hear HD Radio in the car?

A: No. Several manufacturers offer home theater receivers that have built-in HD Radio tuners.

Q: What is "tagging"?

A: "Tagging" or "Tag" was short for either iTunes® Tagging (if you had an iPod), or Song Tagging (if you were using a Zune HD). Tagging was a process that let you select the song you're listening to on an HD Radio station and create a reminder on your portable player to purchase it at a later time. This feature has been discontinued.