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Hi Definition (HD) Radio explained
 
Submitted for inclusion by Garrett
HOW DOES IT WORK:

For an upgrade cost of about 75,000$, a radio station can take its existing analog broadcast and create 2 additional components: the analog source is run thru a compressor to create a new digital feed, and lastly, you'll need some text info to describe the broadcast content (similar to how ID3 tags are used to describe the artist, song and album information on your MP3 files). This new digital feed and text info is then broadcast on the subcarriers of the stations current analog frequency...

Without getting overly technical, I'll give you and example: your station, 3WBC, broadcasts on 94.1 FM, but in reality, your station owns the space from just above 93.9 and just below 94.3. This area above and below the actual channel is where the digital signal is broadcast at lower power.The process is called I.B.O.C or In-Band On-Channel.

Then, you'll take your HD Radio receiver and tune it to a station that has a digital feed, it will first pull the Analog signal and after a brief moment, it will switch to the digital signal. Since it takes a receiver a few moments to decode the digital information, rather than having you sit and listen to just silence, it will play the analog program and when it has all its digital ducks in a row it will cross-fade into the better digital broadcast. Program information such as artist and song information or program name and host will scroll across a display on the front of the receiver.

As far as AM Radio concerned, it will work in basically the same fashion (although technically it operates on sideband instead of sub-carrier frequencies), and oh yeah... one more thing, because of the nature of how AM tends to increase its broadcast distance quite a bit after the sun goes down, digital AM radio has ben restricted to daylight hours.

HOW/WHAT DO I LISTEN:

It seems that most of the car stereo manufacturers have a product currently on the market or have plans to release ones in the not-to-distant future. Both Kenwood and Panasonic have car stereos that are HD-Radio READY (which means they are set up to add a HD Radio module to them for an additional $399 on top of the cost of the head unit itself.) Only one unit from Panasonic had the HD radio built-in and it goes for about $499. Doesn't this sound a little like HD-Ready TV receivers - where if you wanted to actually watch HD programming, you still needed to buy the separate tuner... it's funny how that works.

Two companies offer table-top HD radios starting at 450$.So you've had your old car stereo ripped out and spent anywhere from 500 to 1000$, is anyone actually broadcasting in digital?

Well, since 2003, when the first radio station WOR in New York went online, 494 other stations have joined the digital club, with another 422 stations licensed, but they haven't started transmitting in digital. That may seem like a lot, but let me give you some numbers:

In the US alone we have 4761 AM stations and 8756 FM stations... thats over 13,500 stations, Thats only 3% of the total market in a little over a year and a half. Most the early adopters are college and public radio stations.

A recent New York Times article mentions that Clear Channel (one of the larger commercial radio conglomerates here in the US) which owns 1,200 stations, says it is committed to taking 95 percent of its stations in the top 100 markets digital within three years.

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