HD Radio technology allows AM/FM broadcasters to offer crystal-clear digital sound and scrolling text. Multiple channels can be offered from a single FM frequency, and advanced services such as traffic updates and location-based information, are possible…all subscription free. HD radio is a digital broadcast that offers CD-quality sound for FM stations. BMW has been offering it on its models for the past year, and now Mercedes-Benz will include it as an option on the 2009 E-, M-, R-, GL-, and G-class, all but the E-class being SUVs.

HD Radio already broadcasts to more than 80 percent of Americans. Its subscription-free service has more than 1,700 stations that broadcast in crystal-clear quality. HD Radio has now come up with some brilliant music packaging and other interesting programs.

I go out of my way to not listen to the local crap unless it's absolutely necessary for some news item while on the road and I don't need to listen to that in HD. HD radio allows FM stations to have CD quality sound, and lets AM stations be in stereo and sound like normal FM stations. It's pretty cool. HD Radio equipped stations must pay annual royalties to iBiquity, and costs paid by the manufacturers of HD transmitters that are passed along to the purchaser.

HD radios used to cost $100 or more, but the cost of some has gone down in recent months.HD radio will be really great when/if the FCC approve the proposal now under review for a 10dB (i.e. Also in the future when AM stations can go all digital, their digital signal will be 15dB (32 fold)higher without the need for the sidebands.

HD radio sounds remarkable but this is limited to the radio that you purchase to decode the signal. There are good ones and junk ones.

HD Radio does it all with a tremendous technological leap from the analog broadcasts of the past.

Experience more choices, crystal clear sound, and no subscription fees. HD radio gives you more channels to choose from so you can hear more of what you like. Enjoy music the way it was meant to be heard with AM stations that deliver FM sound quality and FM stations that sound like your favorite CDs. All you need is an HD radio receiver. HD Radio, Discover It.

Because they're digital, HD Radio signals aren't subject to atmospheric interference the way current FM and AM signals are. Background crackle and hiss are eliminated. The effect is similar to the difference between CDs and records. The digital CD signal is free of the surface noise that's always present on LP playback.

Sony HD Radio Add On Tuner - XT100HD

Experience more choices, crystal clear sound, and no subscription fees. HD radio gives you more channels to choose from so you can hear more of what you like. Enjoy music the way it was meant to be heard with AM stations that deliver FM sound quality and FM stations that sound like your favorite CDs. All you need is an HD radio receiver. HD Radio, Discover It.

Features:

• High-fidelity FM/AM Digital Radio with HD Radio Technology More choices, crystal clear sound, and no subscription fees. HD Radio has arrived.
• Compatible with most 2005 headunits and later that are SAT Radio Ready Check to see if your Sony headunit is compatible with the XT-100HD HD Radio Tuner.
• Built-in Sony Bus connectivity for external sources Yes 

Specifications:

• Tuner Frequency Range: FM Tuning range 87.5 ~ 107.9 MHz  
• Tuner Frequency Range-2: FM Intermediate frequency 10.7 MHz  
• Sensitivity: FM:Usable frequency 8 dBf  
• Selectivity: FM:Selectivity 75 dB at 400 kHz  
• S/N Ratio: FM:70 dB (stereo), 71 dB (mono), 80 dB (HD Radio broadcast)  
• Harmonic Distortion: FM:at 1 kHz - 0.04% (stereo), 0.04% (mono), 0.01% (HD Radio broadcast)  
• Frequency Response: FM: 20 - 15,000 Hz (conventional broadcast), 20 - 20,000 Hz (HD Radio broadcast)  
• Tuner Frequency Range-3: AM Tuning range 530 ~ 1,710 kHz  
• Tuner Frequency Range-4: AM Intermediate frequency 10.7 MHz  
• Sensitivity-2: AM:21 µV  
• Component Compatible: UniLink™ Control with CD-Text  
• Antenna Terminal(s): External antenna connector  
• Output(s): Sony BUS control output  
• Output(s)-2: Audio output  
• Output(s)-3: Antenna remote control  
• Input(s): Antenna input  
• Input(s)-2: Sony BUS control input  
• Input(s)-3: Audio input  
• Input Power: 12 V DC car battery (negative ground)