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How HD Radio Works

        Tech | Radio

HD Radio Receivers
An HD Radio Receiver
An HD Radio Receiver
Photo courtesy Amazon

So far, the number of HD Radio receivers currently in homes or cars is low -- about 100,000 units. iBiquity hopes to sell four times that many before the end of 2006. One reason for the low market penetration was that first-generation HD Radio receivers were extremely expensive, costing more than $1,000. Today, you can buy car stereos that support HD Radio for about $200, and home theater receivers that can pick up HD Radio don't cost much more than other high-end receivers. There are also reports of a Kenwood home receiver that costs $100.

As of October 2006, HDRadio.com reported 609 stations in the U.S. broadcasting some form of HD Radio. About half of those stations were multicasting, and very few were using data casting.

HD Radio has not had a smooth ride. In addition to compression method changes and cost issues, the technology has had to deal with controversy over the FCC's decision to name it the primary standard for digital radio in the United States, competition from other digital radio formats, complaints that the sound and reception quality don't live up to expectations and problems with interference with other signals.

Many people within the radio industry have voiced concerns that iBiquity's system was granted primary status by the FCC, because perhaps another digital radio format could perform better. Some claim that the people in charge of deciding that HD Radio should be the primary U.S. digital radio system are also the same people who have invested heavily in the technology, creating a conflict of interest [Source: Wired].

Eureka-147, a digital radio format popular in Europe, uses a separate frequency band for digital broadcasts instead of piggybacking the digital signal onto analog broadcasts. There have been attempts to get the FCC to open that band to digital broadcasting in the United States. Kahn Communications reported the development of a system to offer higher-bandwidth AM radio without many of the problems faced by HD Radio on the AM band, and without requiring new receivers to hear it.

While HD Radio is supposed to use the same amount of bandwidth as the original analog station, there have been complaints about interference, particularly with AM. AM waves travel much farther at night due to the bending of the waves within the ionosphere (See Why do you hear some radio stations better at night than in the day? for more.). Because of this, the FCC does not allow HD Radio broadcasts at night on AM stations. During the daytime, adjacent stations are not allowed to broadcast in HD because they create too much interference. Even on the FM band, the digital signal sometimes creates an audible sound on adjacent channels, particularly for hobbyists who try to tune in distant FM signals (known as DXing).

Those who have purchased HD Radio receivers have reported some problems. At times, the audio compression causes a noticable reduction in sound quality. Some radio stations are not properly processing their signal for digital transmission, causing distorted sound. At times, the volume level or timing of the digital signal is different from the analog version, resulting in problems when the receiver has to switch between the two [Source: Crutchfield Advisor]. Other users have found that digital signals are difficult to tune in, that multicasting seriously impacts audio quality, or that stations broadcasting in HD Radio suffer a loss in quality of the analog signal.

For lots more information on HD Radio and related subjects, check out the links on the next page.