HD Radio technology works much like traditional analog transmissions (AM and FM are both analog signals).The difference is that the station broadcasting HD Radio technology transmits an extra digital radio signal, along with its normal analog signal. It can also broadcast a third signal for text data (click here to learn more about text data).
Your radio receiver receives the signal – just as it does an AM or FM signal. If you have a HD Radio receiver, it will decompress and translate the signal and viola! You get bright, clean, near-CD quality sound.
What happens if you don’t have one of these receivers? It’s simple. You hear your normal analog radio– AM or FM.
What to expect from digital AM and FM radio
AM radio has smaller sections of bandwidth than FM radio. This means there is not enough “space” to give AM stations the same near-CD quality as FM stations. But there is enough bandwidth that AM stations will be able to broadcast with the same clarity of signal as one of today’s analog FM stations. This performance boost is expected to make AM radio a better alternative to FM than it has been – to give you more listening choices.
Digital FM radio is less vulnerable to reception problems. Your HD Radio tuner’s digital processors will eliminate all those annoying pops, hisses, fades and static caused by interference.
What happens if you lose the digital signal for some reason? Really nothing. HD Radio technology defaults back to analog mode in much the same way as conventional radios switch from stereo to mono mode when the signal is weak. Then, when the digital signal again becomes available, your HD Radio automatically switches back.
If you just have to know “what’s behind the curtain”
Here’s a technical description of HD Radio as written by Larry Loeb, Principal, PBC Enterprises.
“Digital radio has been in development in the US since 1991. Digital Audio Broadcasting (DAB) is a system that has been in use around the rest of the world for years now. But US broadcast spectrum is different, and the VHF frequencies of 174 MHz to 240 MHz(or 1450 MHz to 1490 MHz) that DAB uses aren’t available.
“It wasn’t until 2002 that the FCC blessed a single method of doing digital radio for the US: iBiquity DigitalCorp’s IBOC, which stands for in-band on-channel. (iBiquity, by the way, wasformed by Lucent and Westinghouse as a spin-off.) The system uses the same radio spectrum that a station currently uses for broadcast, and (unlike HD TV) can allow a station’s content to be received by analog and digital radios with the same signal (in the “hybrid” mode). Of course, the digital signal will sound better, but the analog radio won’t sound any worse.
“If HD takes off, broadcasters can eventually go all-digital. But the IBOC signal fits into the power level/frequency spectrum mask that the FCC wants to see from a broadcaster right out of the gate, so no frequency reassignments will be necessary to implement the scheme. Use of existing broadcast spectrum is such a powerful advantage for the IBOC system that many European countries using DAB (except for Britain, where DAB seems to be entrenched) are now considering changing over to IBOC.
“Source material is provided by a broadcaster in layer 5, source encoded in layer 4, multiplexed into logical channels by layers 3 and 2, and finally formatted for RF transmission in layer1.
An AM IBOC broadcast can be either hybrid (which retains the mono AM signal in analog form) or all-digital. In the hybrid waveform, the OFDM (orthogonal frequency division multiplex) sub carriers are located in primary and secondary sidebands on either side of the host analog signal, as well as underneath the host analog signal in tertiary sidebands. In the AM system, due to the narrow bandwidth available, Quadrature Amplitude Modulation (QAM) is used on each of the OFDM sub carriers. Each sideband has both an upper and lower component. Status and control information is transmitted on reference sub carriers on either side of the main carrier. Figure 2 shows these relationships.
Two additional sub carriers exist between the primary and secondary and the secondary and tertiary sidebands on either side of the main carrier. These are called the IBOC Data System (IDS) sub carriers and are primarily used for low latency, low data rate applications such as SIS. The power level of each OFDM subcarrier, in the primary sidebands, is fixed relative to the unmodulated main analog carrier. However, the power level of the secondary, IDS, and tertiary sub carriers is adjustable.
Things change if the AM broadcast is all-digital. Figure 3 shows what the waveform spectrum would look like in this case.
The FM IBOC system shares the same protocol layers as the AM system. There are differences due to the wider bandwidth available in the FM system. Three waveform types can be created: hybrid, extended hybrid, and all-digital.
The hybrid contains digital information transmitted in sidebands on either side of the analog FM signal, which can be mono or stereo. This is shown in Figure 4, with the sub carrier numbers and the frequency offset.
The extended hybrid adds more digital information to the analog signal with upper and lower digital sidebands. This is shown in Figure 5.
The all-digital waveform shown in Figure 6 takes the frequency space previously used by the analog waveform and expands the bandwidth of the primary digital sidebands while adding lower-power secondary sidebands. All four of the extended frequency partitions are present in each primary sideband of the all-digital waveform.
Performance and power
There are seven primary service modes in FM waveforms (rather than the four of AM), due to the addition of the extended hybrid mode. Additionally, there are four secondary service modes that only come into play with the all-digital waveform. These serve to set up the performance and power level configuration of the logical channels used to get the content through the first protocol layer. By allowing different combinations, a broadcaster can configure the system for signal robustness.
The first protocol layer has several functions in it. The data is first scrambled (randomized) in each of the logical channels to avoid signal periodicity’s that can cause degraded reception. The channels are then encoded with forward error-correction algorithms that add error correction bits that the receiver can use to correct a signal when it processes it. Interleaving will reorder the transmitted bits to minimize burst errors that can occur in a fading channel. The service mode will affect how the interleaving is done. System control mapping, and OFDM subcarrier mapping are the next to occur. The output of these steps is a frequency-domain representation of the input signal. The shaped time-domain OFDM signal is then generated and transmitted. In the transmission step, the analog signal (if present) is modulated and combined with the digital signal to form the final composite signal that is transmitted.
Simulcasts for podheads
FM bandwidths let a broadcaster carry simultaneous programs along with the main one. Simulcast programs are one of the primary business attractions of using IBOC, because the additional content can differentiate one station from another. The prospect of selling ads on alternate programs doesn’t hurt, either.
Of course, someone’s going to eventually figure out that this is a great distribution channel for podcasts (that is, user-generated audio that the broadcaster can get for free). Broadcasters can stuff the side-channels with “hip” content that will market well to people who already get their music from the ‘net. They can also play wireless content aggregator to all the stuff that’s out there. All those sites with user MP3 compositions? Content. IBOC gives the radio crowd a chance to compete with the ‘net by co-opting it, embracing it, and distributing it.
This kind of thing isn’t as far off as you would think. Texas Instruments (TI) is a primary supplier of DSP chips used in HD radios for most of the grunt work. TI’s TMS320DRI300 provides both MP3 and Windows Media Audio support. The hipsters looking for a new electro-toy are more likely to be early adopters if their tastes in entertainment follow them. Why download a podcast if someone is streaming if for you?
Or, just do a timed record onto your hard disk. There are a lot of possibilities here, and I’ve only skimmed the very top of the lot.
HD radio is coming soon. The first real receivers are out, and more are coming. Expect a steady stream of content gimmicks in the near future, as broadcasters try to jump-start consumer acceptance and spur the sale of HD radios. They’ve learned their lesson from the satellite guys, and are ready to start fighting back.
My big question is, who will be the Howard Stern of HD radio?
HD Radio Signal Coverage
It’s here, but can you hear it?
One of the most frequent questions we got has to do with HD Radio’s signal coverage.
From what we have been able to learn to date, a station’s HD Radio signal should be just about identical to its conventional, analog AM or FM coverage. There will be areas where you will be able to hear only the analog signal and areas where you will be able to hear only the HD Radio signal.
Notice I said “should be just about identical.” This is because some sources say this just isn’t true. “We were told back in the beginning that the HD coverage would be equal to the analog signal,” says Robert Conrad, respected owner of WCLV-FM. “Unfortunately, the industry is now finding out this is not the case, that the HD coverage is considerably less, something like 60% of the analog coverage. We’ve also found that even in a strong HD signal area, a dipole antenna is required.”
On the other hand, Radiosophy, a manufacturer of HD Radios says this about signal coverage.
“Determining the useful coverage area for a radio station is somewhat complicated. Local terrain, other radio signals in the area and man-made interference can all affect how well you receive a given station. Plus, a radio signal will travel for a very long distance past the area where we, as listeners, think it sounds acceptable.
“Because of these factors, each radio station has a coverage area that is broken into 3 different levels: local coverage, distant coverage and fringe coverage.
Local coverage is the area where the radio signal is strong and almost any radio should get good reception.
Distant coverage often requires a radio with a good antenna, and smaller portable radios may not receive the signal.
Fringe coverage is the area where reception is possible only with a good external antenna, if at all.
An HD capable radio should get reliable digital signals in the local coverage area, and may get digital signals in distant coverage areas, depending on the environment. Radios in fringe areas usually don’t receive digital signals, because unlike a traditional analog signal that fades out as you travel away from it, digital will simply disappear when the signal isn’t strong enough.
Finally, one of my visitors who works for an HD Radio manufacturer, basically said, “it depends.” He also pointed out that there are a number of factors that go into an HD Radio signal, including interference, the height of the station’s antenna, the transmit power level, etc. He went on to write, “For FM, digital is generally received out to the 45-50 dBu field strength contour.” This means, you would have to get a coverage map of the station to translate that into miles. Click here to find a list of stations within a given zip code that have a field strength of more than 50 dBu.
The Good News
The good news is that if your HD Radio signal disappears, your HD Radio will automatically switch back into analog mode.
I believe that signal coverage will not be a problem if you live in a metropolitan area or an area close to your favorite HD Radio stations. However, if you live rural and have problems picking up conventional analog stations, than HD Radio could be a problem, too.
Also, keep in mind that HD car radios will show more variance in station reception than a tabletop radio or component receiver which basically sits stationary in your home.
HD Radio Texting
Wait, wait. Is that a text message on my radio?
One of the most exciting things about HD Radio technology – besides the fact that it just sounds so darn good – is the fact that it makes it possible for stations to broadcast text messages.
HD technology’s text messages can be as simple as the name of a song and the artist or weather information.
HD Radio stations could also broadcast commercials or important news as text messages. Some may elect to provide traffic alerts. either as text messages or as digital information — free or for a monthly fee. Other stations may decide to stay with the name of the song playing and the artist. Still other stations may elect to give away the weather updates but with short text commercials – to offset the cost of the free texting. Ultimately, it will be up to each individual station to decide what they want to do with text messaging and digital services.
As one example of texting, Amy Gilroy recently reported in TWICE (This Week in Consumer Electronics) that by the end of the year, Clear Channel will be delivering Real-time traffic information over HD Radio. Moreover, HD technology will allow Clear Channel to deliver the data almost twenty time faster than the RDS network via which Clear Channel is now running a real-time traffic service.
According to Clear Channel, the new HD radio service will launch in 48 markets this year with about 100 stations broadcasting HD traffic information. The company will eventually roll out this service to all its HD stations. HD technology-based traffic modules will have a built-in HD Radio receiver.
The greater bandwidth in the HD signal is expected to enable enhanced services including weather forecast updates and point of interest (POI) updates. Clear Channel says a significant number of suppliers are already offering real time traffic information, including Audiovox,TomTom, Garmin and Cobra.
HD technology radios are now more expensive than conventional radios. One reasons for this is because they have to be designed to display the text messages and because some of the digital components are more expensive than the analog parts found in conventional radios.. However, as manufacturers such as Sony ramp up production, the cost of these radios is expected to become much more competitive — with prices of $100 or less.
HD2 Channels or Multicasting
In HD Radio technology, compressed digital signals can be subdivided. This allows a station to multi-cast. meaning it could broadcast two or more programs at the same time. So, its listeners might be able to choose between a sports program and easy listening music – on the same station at the same time.
This gets exciting because it allows stations to do more niche broadcasting, just as cable as brought niche channels to television.
For example, the radio station you’ve always tuned to for classic rock, might subdivide into classic rock, and reggae, or classic rock and old school hip-hop.Naturally, you would be able to hear these stations only if you have an HD receiver. If you don’t, you’ll still hear the same AM or FM station you’re used to.
There are stations that are trying to increase their listening audience with some very different formats. WLIT which has adult contemporary on its main channel and disco on its HD2 outlet. WOJO has gone an entirely different direction with its two channels broadcasting reggaeton and Latin American dancehall.
Some of the other HD2 channels in Chicago are WKSC’103.5’s “Gay Pride Radio; “WGCI 107.5’s Old School Hip Hop; WUSN 99.5’s Future Country; and WBBM 96.3’s all-dance music format.
Here in my area, the broadcasters have not shown much imagination; most are just programming variations of a theme, i.e. if the main format is modern C&W, the HD2 channel might be classic C&W. However, we do have one easy listening station here that is using its HD2 channel to broadcast all blues.
Cox Broadcasting has launched seven high-definition subchannels (HD2 channels). These subchannels can be heard on the company’s stations in Atlanta and Tampa.
In Atlanta, WSB-FM, an Adult Contemporary station, will broadcast a new Soft Standards HD2 sub-channel; WBTS-FM, a Rhythmic Top 40 station, will broadcast a PopTop 40 HD2 sub-channel; WALR-FM, an Urban Adult station, will broadcast an Adult Hip Hop HD2 sub-channel; and WSRV-FM, a Classic Hits station, will simulcastCox Radio’s AM750 News/Talk format on its HD2 sub- channel.
In Tampa, WSUN-FM, an Alternative Rock station, will broadcast an All Grunge Rock HD2 sub-channel; WPOI-FM, an 80’s Hits station, will broadcast a Modern Adult HD2 sub-channel; and WWRM-FM, an Adult Contemporary station, will broadcast a Contemporary Christian HD2 sub-channel.
And look, Ma. No commercials!
Just as important, these HD2 channels are commercial free. In fact, the nation’s broadcasters have pledged to keep HD2 channels commercial-free at least through 2007.
From what we have heard this is both good news and bad news. The good news is obvious – no annoying commercials. The bad news is that some of the HD2 channels are just one song after another with no announcer at all. We suppose this could get a bit boring after a bit.
Where to Buy HD Radios
Buying an HD technology radio is already easy. You may be able to find one at your neighborhood Best Buy, Circuit City and Wal-Mart.
This is especially true of HD car radios. There are also several sites on the Internet where you cannot only buy HD technology radios, you can compare prices for several different sources. Among these are NexTag, and Buy.com.
As of this writing, there are seven manufacturers offering compact, portable, tabletop radios with HD technology that offer amazingly clear, room-filling sound. These manufacturers are Radiosophy, RadioShack, Sangeon, Polk Audio, Boston Acoustics, Sony and Cambridge Soundworks. More manufacturers are expected to announce portable, tabletop radios soon.
At least seven manufacturers offer HD car radios, including JVC, Panasonic, Kenwood,Sanyo, Sony, Alpine and Eclipse. Again, more manufacturers, including Sony, are expected to soon announce HD Technology car radios.
Finally, three companies have component-type HD technology receivers available. They are Yamaha, Audio Design Associates (ADA), and Day Seguerra. All three of these HD technology-compatible receivers are designed to be used in conjunction with home theater systems. You may find one of the HD Technology receivers at your local home theater retailer or high-end sound components store.
The Sony XDR-S3HD Radio
The Sony XDR-S3HD radio comes in a stylish wood cabinet and features FM Multicasting, which is the the ability to receive multiple program streams over a single FM frequency. It can also handle Data services or text based information – artist name, song title, etc. that scroll across the receiver display.
The Sony XDR-S3HD Radio has an easy to see large, full-dot backlit LCD display has brightness, contrast and display mode adjustments and digital tuning for accurate tuning of radio stations. In addition, the unit boasts stereo speakers with bass reflex sound system, and treble, bass tone control and surround sound functions. There are 20 FM and 20 AM presets. As of this writing (7/9/07), Sony had not published the XDR-S3HD radio’s size nor its weight.
Sanyo HD Car Radio
The Sanyo HD car radio (ECD-HD1990M) is an in-dash HD radio and WMA/MP3 CD Player with front AUX in. It features a detachable front panel and full-function, credit-car sized remote. The power output is 50W x 4.
The Sanyo EC-HD1990M’s CD deck features motorized CD loading, and playback of both CD-Rs and CD-RWs. The display is a Vacuum Fluorescent Display (VFD) and there are rotary volume and tone controls.
There is a 6 mode preset EQ and 36 station presets – 6 AM, 18FM, 12ATP.The CD changer controls also operates the Sanyo EAX-516 CD changer. In addition, the Sanyo EC-HD1990M has two pairs of RCA line outputs, RCA input in the rear and sub-woofer output.
Sangean HDR-1 Tabletop Radio
The Sangean HDR-1 tabletop radio gives you everything you’d expect in an HD radio – AM sound as clear as today’s FM and FM as clear and clean as if you were listening to a CD. Thanks to my special price, it’s just about the most affordable, top-quality HD tabletop radio available and represents a great price value.
As you would expect, the Sangean HDR-1 tabletop radio lets you hear all those “invisible” HD2 channels between the regular frequencies – where broadcasters have put different and, in some cases, very non-conventional programming.
Plus, the Sangean HDR-1 tabletop radio displays text information, such as station IDs, artist names, and song titles on its large, easy-to-read LCD screen.
In addition, the Sangean HDR-1. has two 2-1/2″ speakers set in the acoustically tuned cabinet that deliver rich, detailed highs and mids, with nice, round bass. You’ll also like the sort of hip, retro look of its nicely finished wood cabinet.Letting the HDR-1 wake you up almost makes the morning fun with its built-in digital clock that displays both time and date, and includes dual alarms with snooze, as well as a sleep timer. Adjust the sound with the bass and treble control, or just use one of the EQ presets. And you can operate the radio from across the room with its provided remote.
Sangean’s suggested retail price of this tabletop radio is $249.95.
The HDR-1’s complete specifications
- Auto Tuning System (ATS)
- Auto preset system
- 20 Memory presets (10 FM, 10 AM)
- Frequencies:o FM 87.5-108o AM 520-1710
- Backlit LCD display• Displays information such as: channel No., channel frequency, ensemble label, service label, dynamic label, transmission mode, data rate, secondary service availability
- Automatic multiplex re-configuration
- Tone and bass control
- EQ presets
- Alarm w/ Humane wake system
- Snooze function
- Adjustable sleep timer
- Multicast capability
- Program Associated Data service (PAD)
- Hybrid and full digital radio reception
- IR Remote control
- Weight: approx 6 lb. 9 oz.
- Dimensions (W x H x D): 11″ x 4.5″ x 7.5″
Panasonic CQ-CB890IU HD Car Radio
The Panasonic CQ-CB890IU HD Radio is a fully-featured, in-dash unit that includes HD Radio technology and is XM Satellite ready.
Measuring a sleek 1.94” x 7” x 6.125”, this Panasonic deck features playback of both MP3/WMA files and accommodates CD-R/CD-RW disks. It has bass, treble and balance fader controls, and a maximum power output of 50W x 4. Pre-amp outlets include front, rear and subwoofer, and the subwoofer is SBC-SW (Super Bass Controlled Subwoofer).
The Panasonic CQ-CB890IU’s sound quality is rated SQ7 and its speaker impedance is 4-8 ohms. The subwoofer output level/impedance is 50/60 ohms and it has 18 FM presets and 6 AM presets. The CD deck features a multi-stage noise shaping 1 bit DAC, 3-beam hologram pickup, and scan, search, repeat and random play.
Because the The Panasonic CQ-CB890IU is an HD technology radio, there is a text display for XM, CD and HD text. This super-bright display is a high definition, 3D dot matrix LCD. The LCD illumination color is blue and button illumination is light blue. The front panel is fully motorized, the faceplate is removable, and the CD acccess is open face. The unit comes with a wireless remote control and weighs just 5.73 lbs.
Other features of the Panasonic CQ-CB890IU include:
- High & Low Pass Filters (cross-over)
- Subwoofer Output Level/Impedance 60/60 ohms
- High Pass Filter Frequency
- Low Pass Filter Frequency 80/120/160Hz
- Radio DSP
- Auto Present Memory with ScanFMO (FM Optimized)
- AFE (Adaptive FM Front End)
- INQ (Impulse Noise Quieting)
- AM Usable Sensitivity S/N 20dB 25dB/µV (17uV)
- FM Usable Sensitivity (75 ohms,S/N 30dB)
- -12.2dBf (1.12µV)
- MOS-FET Output stage
- Stereo Separation 40dB
- 50dB Quieting Sensitivity (75 ohms)1.5dBf (1.59 µV)
- S/N Ratio (FM mono)62dB
- Alternate Channel Selectvity 75dB
- One-chip digital circuit
- One chip digital circuit
- Frequency response (±1dB)20Hz – 20 Khz
- S/N Ratio 96dB
- THD (1kHz)0.01%
- Channel separation (1kHz)86dB
CD CHANGER CONTROLS
- Track/disc scan
- Track/disc repeat
- Search and Random Play
- Spectrum analyzer
- Day and night design
- AUX input
- Flashing warning light
- Built-in quartz clock
Kenwood EZ700SR HD Car Radio Tuner
The Kenwood EZ700SR is a slim, compact, powerful AM/FM/HD radio and CD player featuring a full dot matrix display with white LED backlight. It’s CD section can handle both CD-Rs and CD-RWs and it plays back both MP3 and WMA files. In addition, the CD deck has CD text with disc naming.
A large, rubber-coated, rotary knob controls the EZ700SR’s volume and the faceplate is both flip-down and removable. There is a matching, multi-function jog dial, a system Q EX equalizer with user memory, a powerful 50W x 4 MOSFET amplifier (200 total), and 3 sets of pre-amp outputs (front, rear and non-fading).
Additionally, the Kenwood EZ700SR offers red or green selectable illumination color, high-pass and low-pass electronic crossovers, dual zone / dual source output, and 24 AM / FM Presets. There is a rear auxiliary output, and 3 Sets of Preamp Outputs. It also has a built-in Sirius Satellite Radio (subscription required for any stereo operation) and comes with a Sirius Satellite Radio Antenna.
- Glossy Ebony Finish
- Internal Amplifier Mute
- Source Tone Memory
- Station Naming
- Programmable Security Code
- CD Changer & Music Keg™ Control
- Faceplate Carrying Case
- Grip Type Remote Control
- Glossy Ebony Finish
- CD Frequency Response 10-20,000 Hz
- 105 dB CD Signal to Noise Ratio
New ADA products
Audio Design Associates (ADA) has announced three, new, high-end HD tuners in rack-mountable chassis.
The first is a single tuner in a “black box.” The tuner must be remote controlled. All previous Quadritune and HTR-2400 units may be upgraded to HD status. ADA has also said it will soon introduce a Suite 8100 8×8, multi-room receiver which can have a single tuner installed in it. All ADA tuners are modular design.
ADA offers a total of four tuner modules which may be installed in any combination in any of their tuners.
Individual HD Radio Module
- HD Radio AM-FM and Weather Band
- Standard analog AM-FM and Weather Band
- XM satellite radio
- Sirius Satellite radio
Individual HD Radio Module for upgrades: $599
TSS-1 (single slot box) loaded with one HD Radio Module is: $999
- One U-mount chassis
- Up to two independently-controlled modules
- RCA audio output for each module
- Optical, digital audio output for each module
Duo Tuner loaded with one HD Radio Module and one Satellite Radio Module is: $2,199
Quadritune Tune Suite
- Two U-rack mount chassis
- Up to four independently-controlled modules
- RCA output for each module
- Optical, digital audio output for each module
Quadritune chassis loaded with one HD Radio Module and one Satellite Radio Module is: $3,199
HD Pro Tuner
- Two U-rack mount chassis
- Two HD tuners with AM, FM and Weather Band
- Balanced analog outputs
- Optical, digital audio outputs
- RCA Audio outputs
- Built-in front panel, 15-watt headphone amplifier with A/B switch and volume control
- Dual Stereo 20-step VU meters with peak hold indicator
- Split mode capability for simultaneous analog/digital comparison
- RS-232 OR Ethernet control
- Relay contact warning outputs for signal loss, HD loss and audio loss
The Duo Tuner, Tune Suite and HP Pro tuners display text feedback that can include station/channel number, station name, genre, artist, album and song. For HD FM, they also indicate the presence of multi-casting programming.
NOTE: All prices quoted herein are U.S. list and subject to change without notice.
For more information on ADA tuners, please go to www.ada-usa.com.