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June 1, 2009

What is HD Radio?

Filed under: Question of the Month — Tags: , , — Alan @ 12:24 pm

Q. I’m familiar with HDTV and satellite radio, but I keep hearing about HD Radio. What is it? – G.S.

A. HD Radio has nothing to do with “High Definition” or HDTV or satellite radio from XM or Sirius. HD Radio is a proprietary hybrid analog-digital radio system developed by iBiquity Corporation in which a low-level digital signal with the same content as the analog FM and AM signal is piggybacked and simulcast with a broadcaster’s analog radio signal, a system known as IBOC (In-Band On-Channel). This enables the millions of analog radio owners who have not purchased a new HD-ready radio to continue to receive the conventional FM or AM signals. However, owners of a new HD-ready radio will receive the much higher sound quality digital radio signal when the radio detects the low-level HD signal that is carried in the sidebands of the analog signal. The HD radio will switch instantly to the digital signal for FM or AM. If the digital signal fades, the HD radio then automatically (and seamlessly, according to iBiquity) reverts to the station’s analog FM or AM signals.

Unlike subscription-based XM/Sirius satellite radio, HD radio is free and is a terrestrial radio service selected and approved by the FCC as the terrestrial digital radio system for the USA. Launched in 2002, it’s now available on nearly 2,000 US stations (Canada has approved testing and installation of HD Radio but only a few stations in big urban centers have converted.) Public acceptance in the US has been very slow with many consumers confused by the “HD” name and existing subscription satellite radio services.

A “lossy” compression algorithm similar to but not compatible with MPEG-4 developed by iBiquity is used, and sound quality on FM is claimed to approach that of CD. AM radio quality is much improved, but reports of adjacent channel interference (other radio stations close in frequency to the HD radio broadcaster) have surfaced as well as complaints of poor HD radio sensitivity (the digital signal is broadcast at only 1% of the power of the broadcaster’s analog signal). Nevertheless, prices of HD radios have come down and various car companies (Ford and others) are also offering HD-ready radios as an option or standard accessory. In addition to much-improved sound quality and resistance to interference, HD radio has the capability to carry a text data-stream with the artist or album names, or subsidiary radio services, even including 5.1-channel surround sound. The FCC in the US has not indicated that it intends to end analog radio services as it has with TV broadcasting, as there is no potential benefit for the government in selling recovered spectrum space. Rest assured, then, that your existing home, car or portable radios will continue to receive good ol’ analog FM and AM radio for many years to come.

Alan Lofft was, for 13 years, Editor in Chief of Sound & Vision, Canada’s largest and most respected audio/video magazine. He edited Sound & Vision (Canada) until 1996, when he moved from Toronto to New York to become Senior Editor at Audio magazine.
Lofft has been writing about hi-fi and video professionally for over 20 years, ever since his first syndicated newspaper column, “Sound Advice”, began appearing weekly in The Toronto Star, Canada’s largest-circulation daily newspaper. In the late 1970s, he became a contributing editor, columnist, and equipment reviewer at AudioScene Canada, the leading national consumer electronics magazine at the time. Find out more about Alan in his bio.

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  • Gregory
    July 15, 2010 at 6:35 am

    Q? I bought the Onkyo S5300 HD Raidio receiver and simple plugged it in.
    Then hit the FM button, then Port button on the remote. No responds…
    Q? Does Kuwait have the capablity to receive HD raidio?


  • July 15, 2010 at 11:21 am

    Hello Greg,

    Thanks for your question. I doubt if the HD radio system from Ibiquity has been adopted in Kuwait or anywhere outside of North America. However,the conventional FM receiver on your Onkyo should work OK there. The FM band outside of North America is slightly different but you should be able to receive some FM stations if they exist. Have you attached an antenna to the terminals on the back of the Onkyo?

    Other digital radio systems exist in Europe and in the United Kingdom, but they wouldn’t be compatible with North America’s HD Radio system.

    Alan Lofft

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