What is HD Radio?

HD Radio is a digital signal that is transmitted by certain radio stations to radios equipped with an HD Radio tuner. You can't get HD Radio on a radio that doesn't have HD Radio tuning circuitry, despite some radio stations telling the listener that their signal is broadcast in HD. This HD does the listener no good unless they own a radio that has an HD Radio tuning circuitry built-in, or an HD Radio tuner attatched to a car radio.

What we all grew up with was analog radio, the old fashioned way of transmitting radio signals from the radio station to every radio ever built. HD Radio is digital. You can't receive digital radio signals on a radio that doesn't have HD Radio tuning circuitry or else all you will hear is just the analog signal.

HD Radio is a digital way of transmitting a radio signal to an HD Radio receiver. With analog, you can get a perfect signal if you're close enough to within the signal's contours, but as you drive farther away, the signal gets weaker and fades gradually until all you hear is static. With digital, you get either the signal, which is perfect, or nothing if you're too far or if something else is blocking the signal from you.

With analog, your reception is subject to interference such as pops, hiss, static, hash, electrical noise, or fading in and out. With digital, you get a perfect signal as long as your radio is within a line of sight from the radio station's transmitters.

Many radio stations all over the country have or are having their broadcast signals upgraded to broadcast not only the original analog signal, so that all radios will continue to receive the station, but also anywhere from one HD Radio digital signal, which is essentially the duplication of its originating broadcast that is also heard on its analog signal, to as many as three called multicasting. You can't get any multicasted signals with an analog radio. The multicast channels are often called HD2 or HD3.

The current restriction for AM radio is that they cannot broadcat multicast digital signals. They can broadcast the analog and the lone duplicating digital signal on one frequency. The upside of digital AM is that they can broadcast their programming in stereo. Remember back in the 1980s when there were two competeting stereo AM analog broadcasts competeting to become the standard? Needless to say, they're both history.

I read somewhere else that theoritically, there can be as many as eight multicast stations alongside the analog and HD1 digital signal called HD2 through HD9, but those could be for services that don't require high-fidelity stereo signals.

In addition to the digital signals, the wireless data feature enables text information such as titles, artists, weather or traffic alerts to be broadcast directly to the HD Radio receiver's display screen.

Approved by the Federal Communications Commission in October 2002 as the only system for digital AM and FM broadcasting in the U.S., HD Radio technology is developed and licensed by iBiquity Digital Corporation and supported by the leaders of the broadcasting, consumer electronics and automotive industries.

Ibiquity claims that digitized AM sounds like FM and digitized FM sounds like CD quality. I can't vouch for those claims, but let's say that AM would sound cleaner if not like FM.

As time goes on, it's possible that with HD Radio, the text information could display alerts such as traffic reports, missing child alerts, stolen car bulletins, emergencies, and more, displacing other information as warranted.

Theoritically, it's possible to broadcast digital 5.1 surround sound programming.

As long as the RIAA doesn't cry foul, a store-and-replay feature could be developed to allow listeners to rewind a song they have just heard or record a program to play back at a later time.

A "Buy Button" feature could be implemented to allow listeners to purchase products advertised or to print coupons with a printer.

The ads you hear on the radio tout the few facts that are accurate about HD Radio such as that they're free and that they offer more choices. What the ads don't tell you is that the number of additional choices you get with HD Radio range from one multicast signal for a smaller market to over two dozen for a big city like New York. If you want to hear your favorite radio signal cleaned-up digitally, first, make sure that your station is broadcasting in HD before you buy an HD Radio or else you will be disappointed if you like to listen to your station that hasn't upgraded its broadcast facilities to send out digital programming to an HD Radio.

Yes, HD Radio is free, but will yield you a fraction of the additional signals you could get if you subscribed to satellite radio and paid $13 a month after shelling out $100-200 for either the XM or Sirius receivers. If you want satellite and HD radio at the same time, there's nobody stopping you from doing that!

More stations are converting to HD Radio technology all the time and most major cities now have a wide selection of broadcasts. Eventually, more of the HD2 and HD3 channels will come into your city offering some niche programming you can hear on satellite and some that you won't.

For a complete list of HD Radio broadcasters, visit the website http://www.hdradio.com/