HD Radio technology has been around since 2002, but American radio stations and manufacturers are finally pushing it. You may have heard the advertisements. If you're considering HD Radio, there are some things you should know.

CLEARER SOUND

Many people assume that the HD stands for "high definition." In reality, though, HD Radio is simply a trademarked brand name of iBiquity Digital Corp., which invented and manufactures the broadcast equipment.

HD Radio does deliver clearer sound than traditional radio. With HD Radio, FM stations are broadcast in CD quality and AM stations are broadcast in FM quality.

HD Radio is transmitted with a digital signal. It is carried within the existing AM or FM signal, much as FM stereo is carried with the original FM mono signal. The HD Radio signal is free of static, pops, fades and crackles. Also, HD Radio is less prone to drops and reflections from interference.

SATELLITE VS. HD RADIO

Satellite radio requires a subscription, but with HD Radio programming is free.

Satellite radio offers hundreds of stations. HD Radio, on the other hand, is broadcast by regular local over-the-air stations. And, unlike satellite radio, HD Radio stations are subject to FCC indecency regulations.

HD Radio allows FM stations to add lots of programming because it gives them two digital audio channels along with their regular analog channel. AM stations have their current analog channel and a new digital audio channel. This means that an FM station could have a top 40 broadcast on one audio channel and an all-news or sports broadcast on the others. The broadcasts would occur simultaneously. The frequency of the FM station might be 98.1. The station's new HD channels would appear on the HD radio as 98.1-1 and 98.1-2.

ANALOG BROADCASTS

With an HD Radio, you can still pick up traditional analog broadcasts. That's because many broadcasters have not yet converted their stations to HD Radio.

When a station adds HD Radio, the digital signal is automatically received by your HD Radio receiver. The station's dial position remains the same.

NOT ALL ARE HD

Eventually, there will be thousands of HD Radio signals across America. Already there are hundreds in Mainland states.

The HD Radio Web site, www.hdradio.com, says no stations in Hawai'i are currently broadcasting HD Radio, but promises that eight Clear Channel-owned stations in Hawai'i, including KSSK, soon will be broadcasting it.

NEW EQUIPMENT

The HD Radio Web site also lists HD Radio receivers available. Expect to pay about $200 for a car unit. Eventually, HD Radio receivers will probably be standard in most vehicles.

Expect to pay $300 or more for a home receiver. Some include docks for your Apple iPod.

Polk Audio, Boston Acou-stics and Cambridge Sound Works make HD Radios.

E-mail Kim Komando at gnstech@gns.gannett.com.