| List ofdigital radio broadcast standards |
|---|
| DAB standards |
| 5G Broadcast |
| ISDB standards |
| AM bandin-band on-channel (AM IBOC) |
|
| FM bandin-band on-channel (FM IBOC) |
HD Radio (HDR)[1] is atrademark forin-band on-channel (IBOC)digital radio broadcast technology. HD radio generallysimulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily byFMradio stations in the United States, U.S. Virgin Islands, Canada, Mexico and the Philippines,[citation needed] with a few implementations outside North America.
HD Radio transmits the digital signals in unused portions of the same band as the analog AM and FM signals. As a result, radios are more easily designed to pick up both signals, which is why the HD in HD Radio is sometimes referred to stand forHybrid Digital, not "High Definition".[2] Officially, HD is not intended to stand for any term in HD Radio, it is simply part ofiBiquity's trademark, and does not have any meaning on its own.[3] HD Radios tune into the station's analog signal first and then look for a digital signal. The European DRM system shares channels similar to HD Radio, but the European DAB system uses different frequencies for its digital transmission.[4]
The term "on channel" is a misnomer because the system actually sends the digital components on the ordinarily unused channelsadjacent to an existingradio station's allocation. This leaves the original analog signal intact, allowing enabled receivers to switch between digital and analog as required. In most FM implementations, from 96 to 128 kbit/s of capacity is available. High-fidelity audio requires only 48 kbit/s so there is ample capacity for additional channels, which HD Radio refers to as "multicasting".
HD Radio is licensed so that the simulcast of the main channel is royalty-free. The company makes its money on fees on additional multicast channels. Stations can choose the quality of these additional channels; music stations generally add one or two high-fidelity channels, while others use lower bit rates for voice-only news and sports. Previously these services required their own transmitters, often on low-fidelity AM. With HD, a single FM allocation can carry all of these channels, and even its lower-quality settings usually sound better than AM.
While it is typically used in conjunction with an existing channel it has been licensed for all-digital transmission as well. FourAM stations use the all-digital format, one under an experimental authorization, the other three under new rules adopted by theFCC in October 2020. The system sees little use elsewhere due to its reliance on the sparse allocation of FM broadcast channels in North America; in Europe, stations are more tightly spaced.
This standard was meant to supersede otherexisting stereophonic standards on AM.
iBiquity developed HD Radio, and the system was selected by theU.S. Federal Communications Commission (FCC) in 2002 as a digital audio broadcasting method for the United States.[5][6] It is officially known as NRSC‑5, with the latest version being NRSC‑5‑E.[7]
iBiquity was acquired byDTS in September 2015 bringing the HD Radio technology under the same banner asDTS's eponymous theatersurround sound systems.[8] The HD Radio technology and trademarks were subsequently acquired byXperi Holding Corporation in 2016.
HD Radio is one of several digital radio standards which are generally incompatible with each other:
By May 2018,iBiquity Digital Co. claimed its HD Radio technology was used by more than 3,500 individual services, mostly in the United States.[9] This compares with more than 2,200 services operating with theDAB system.
A 400 kHz wide channel is required for HDFM analog-digital hybrid transmission, making its adoption problematic outside of North America. In the United States,FM channels are spaced 200 kHz apart as opposed to 100 kHz elsewhere. Furthermore, long-standingFCC licensing practice, dating from when receivers had poor adjacent-channel selectivity, assigns stations in geographically overlapping or adjacentcoverage areas to channels separated by (at least) 400 kHz. Thus most stations can transmit carefully designed digital signals on their adjacent channels without interfering with other local stations, and usually withoutco-channel interference with distant stations on those channels.[10] Outside the U.S., the heavier spectral loading of the FM broadcast band makes IBoC systems like HD Radio less practical.
The FCC has not indicated any intent to end analog radio broadcasting as it did withanalog television,[5] since it would not result in the recovery of anyradio spectrum rights which could be sold. Thus, there is no deadline by which consumers must buy an HD receiver.
Digital information istransmitted usingOFDM with anaudio compression format called HDC (High-Definition Coding). HDC is a proprietarycodec based upon, but incompatible with, theMPEG-4 standardHE-AAC.[11] It uses amodified discrete cosine transform (MDCT)audio data compression algorithm.[12]
HD equipped stations pay a one-time licensing fee for converting their primary audio channel toiBiquity's HD Radio technology, and 3% of incremental net revenues for any additional digital subchannels.[13] The cost of converting a radio station can run between $100,000 and $200,000.[14] Receiver manufacturers who include HD Radio pay a royalty,[15] which is the main reason it failed to be fully-adopted as a standard feature.
If the HD receiver loses the primary digital signal (HD‑1), it reverts to the analog signal, thereby providing seamless operation between the newer and older transmission methods. The extra HD‑2 and HD‑3 streams do not have an analog simulcast; consequently, their sound will drop-out or "skip" when digital reception degrades (similar to digital television drop-outs). Alternatively the HD signal can revert to a more robust 20 kbit/s stream, although the sound quality is then reduced to conventional AM-level.Datacasting is also possible, withmetadata providing song titles or artist information.
iBiquity Digital claims that the system approachesCD quality audio and offers reduction of both interference and static.[16] However, the data rates in HD Radio are substantially lower than from a CD, and the digital signals sometimes interfere with adjacent analogAM band stations. (see § AM, below).
The AM hybrid mode ("MA1") uses 30 kHz of bandwidth (±15 kHz), and overlapsadjacent channels on both sides of the station's assigned channel.[17] Some nighttime listeners have expressed concern this design harms reception of adjacent channels[18][19] with one formal complaint filed regarding the matter:WYSL owner Bob Savage againstWBZ in Boston.[citation needed]
The capacity of a 30 kHz channel on the AM band is limited. By usingspectral band replication the HDC+SBR codec is able to simulate the recreation of sounds up to 15,000 Hz, thus achieving moderate quality on thebandwidth-tightAM band.[20] The HD RadioAM hybrid mode offers two options which can carry approximately 40~60 kbit/s of data, with mostAM digital stations defaulting to the more-robust 40 kbit/s mode, which features redundancy (same data is broadcast twice).
The digital radio signal received on a conventionalAM receiver tuned to an adjacent channel sounds likewhite noise – the sound of a"hiss", or a large waterfall, or a strong, steady wind through a denseforest canopy, or similar.
All-digital AM ("MA3") allows for two modes: "Enhanced" and "core-only".[21]
When the receiver can only decode the primary carriers in either mode, the audio will be mono and only text information can be displayed. The narrower bandwidth needed in either all-digital mode compared to hybrid mode reduces possible interference to and from stations broadcasting on adjacent channels.[22] However, all-digital AM lacks the analog signal for "fallback" when the signal is too weak for the receiver to decode the primary digital carrier.
Five AM stations have operated as all-digital / digital-only broadcasters, either on an experimental basis or under new rules adopted by the FCC on 27 October 2020 that allow any AM station to voluntarily choose to convert to all-digital operation.[23]
The FCC requires stations that wish to multiplex their digital AM signals to request and receive permission to do so.[27]WWFD experimented with using adigital subchannel, operating a second channel (HD2) at a low data rate while reducing the data rate of the primary channel (HD1).[28] In October 2020, theFCC concluded fromWWFD's experiments:
TheFM hybrid digital / analog mode offers four options which can carry approximately 100, 112, 125, or 150 kbit/s of data carrying (lossy) compressed digital audio depending upon the station manager's power budget and desired range of signal. HD FM also provides several pure digital modes with up to 300 kbit/s rate, and enabling extra features like surround sound. LikeAM, purely-digitalFM provides a "fallback" condition where it reverts to a more robust 25 kbit/s signal.
FM stations can divide their datastream into sub-channels (e.g., 88.1 HD‑1, HD‑2, HD‑3) of varying audio quality. The multiple services are similar to thedigital subchannels found inATSC-compliantdigital television usingmultiplexed broadcasting. For example, sometop 40 stations have addedhot AC andclassic rock to theirdigital subchannels, to provide more variety to listeners.[30] Stations may eventually go all-digital, thus allowing as many as three full-power channels and four low-power channels (seven total). Alternatively, they could broadcast one single channel at 300 kbit/s.
FCC rules require that one channel be a simulcast of the analog signal so that when the primary digital stream cannot be decoded, a receiver can fall back to the analog signal. This requiressynchronization of the two, with a significant delay added to the analog service. In some cases, particularly duringtropospheric ducting events, an HD receiver will lock on to the digital stream of a distant station even though there is a much stronger local analog-only station on thesame frequency. With no automatic identification of the station on the analog signal, there is no way for the receiver to recognize that there is no correlation between the two.[a] The listener can possibly turn HD reception off (to listen to the local station, or avoid random flipping between the two stations), orlisten to the distant stations and try to get astation ID.
Although the signals may be synchronized at the transmitter and reach the receiving equipment simultaneously, what the listener hears through an HD unit and an analog radio played together can be distinctly unsynchronized. This is because all analog receivers process analog signals faster than digital radios can process digital signals. The digital processing of analog signals in an HD Radio also delays them. The resulting unmistakable "reverb" or echo effect from playing digital and analog radios in the same room or house, tuned to the same station, can be annoying. It is more noticeable with simple voice transmission than with complex musical program content.[b]
Stations can transmit HD through their existing antennas using adiplexer, as onAM, or are permitted by the FCC to use a separate antenna at the same general location, or at a site licensed as an analogauxiliary, provided it is within a certain distance and height referenced to the main analog signal. The limitation assures that the two transmissions have nearly the samebroadcast range, and that they maintain the properratio ofsignal strength to each other so as not to causedestructive interference at any given location where they may be received.
HD Radio supports a service called "Artist Experience"[31] in which the transmission of album art, logos, and other graphics can be displayed on the receiver. Album art and logos are displayed at the station's discretion, and require extra equipment. An HD Radio manufacturer should pass theiBiquity certification, which includes displaying the artwork properly.
Since 2016, newer HD Radios supportBluetooth andEmergency Alert System (EAS) alerts[32] in which the transmission of traffic, weather alerts,Amber and security alerts can be displayed on the radio. As with "Artist Experience", emergency alerts are displayed at the station's discretion, and require extra equipment.
FM stereo stations typically require up to 280 kilohertz ofspectrum. The bandwidth of an FM signal is found by doubling the sum of the peak deviation (usually 75 kHz) and the highest baseband modulating frequency (around 60 kHz whenRBDS is used). Only 15 kHz of the baseband bandwidth is used by analogmonaural audio (baseband), with the remainder used forstereo,RBDS,paging,radio reading service,rental to other customers, or as atransmitter/studio link for in-housetelemetry.
In (regular) hybrid mode a station has ±130 kHz of analog bandwidth. The primary main digital sidebands extend ±70 kHz on either side of the analog signal, thus taking a full 400 kHz of spectrum. In extended hybrid mode, the analog signal is restricted to ±100 kHz. Extended primary sidebands are added to the main primary sidebands using the extra ±30 kHz of spectrum created by restricting the analog signal.[33] Extended hybrid provides up to approximately 50 kbit/s additional capacity.[34] Any existingsubcarrier services (usually at 92 kHz and 67 kHz) that must be shut down to use extended hybrid can be restored through use ofdigital subchannels. However, this requires the replacement ofall related equipment both for the broadcasters and all of the receivers that use the services shifted to HD subchannels.
The ratio of power of the analog signal to the digital signal was initially standardized at 100:1 (−20 dBc), i.e., the digital signal power is 1% of the analog carrier power. This low power, plus the uniform, noise-like nature of the digital modulation, is what reduces its potential for co-channel interference with distant analog stations. Unlike with subcarriers, where the totalbasebandmodulation is reduced, there is no reduction to the analogcarrierpower. TheNational Association of Broadcasters (NAB) requested a 10 dB (10×) increase[35] in the digital signal from the FCC. This equates to an increase to 10% of the analog carrier power, but no decrease in the analog signal. This was shown to reduce analog coverage because of interference, but results in a dramatic improvement in digital coverage. Other levels were also tested, including a 6 dB or fourfold increase to 4% (−14 dBc or 25:1).National Public Radio was opposed to any increase because it is likely to increase interference to their member stations, particularly to theirbroadcast translators, which are secondary and therefore left unprotected from such interference. Other broadcasters are also opposed (or indifferent), since increasing power would require expensive changes in equipment for many, and the already-expensive system has so far given them no benefit.
There are still some concerns that HD FM will increase interference between different stations, even though HD Radio at the 10% power level fits within the FCC spectral mask.[36] North AmericanFM channels are spaced 200 kHz apart. An HD broadcast station will not generally cause interference to any analog station within its 1 mV/mservice contour – the limit above which the FCC protects most stations. However, the IBOC signal resides within the analog signal of the immediately adjacent station(s). With the proposed power increase of 10 dB, the potential exists to cause the degradation of the second-adjacent analog signals within its 1 mV/mcontour.[37][38][39]
On 29 January 2010, the U.S. FCC approved areport and order to voluntarily increase the maximum digitaleffective radiated power (ERP) to 4% of analogERP (−14 dBc), up from the previous maximum of 1% (−20 dBc).[40] Individual stations may apply for up to 10% (−10 dBc) if they can prove it will not cause harmful interference to any other station. If at least six verified complaints of ongoingRF interference to another station come from locations within the other station's licensedservice geographic region, the interfering station will be required to reduce to the next level down of 4%, 2% (−17 dB), or 1%, until the FCC finally determines that the interference has been satisfactorily reduced.[41] The station to which the interference is caused bears theburden of proof and its associated expenses, rather than the station that causes the problem. Forgrandfathered FM stations, which are allowed to remain over the limit for theirbroadcast class, these numbers are relative to that lower limit rather than their actual power.
In May 2025 the FCC confirmed it would permit asymmetric sideband levels to be used.[42] The total power in the asymmetric side bands must not exceed that which would be permitted when the sidebands are symmetrical. The use of asymmetrical sidebands can reduce interference to an adjacent FM channel.
Some countries have implementedEureka-147 Digital Audio Broadcasting (DAB) or the newerDAB+ version. DAB broadcasts a single multiplex that is approximately 1.5 megahertz wide (≈1 megabit per second). That multiplex is then subdivided into multiple digital streams of between 9~12 programs (or stations). In contrast, HD FM requires 400 kHz bandwidth – compatible with the 200 kHz channel spacing traditionally used in theITU Region 2 (including the United States) – with capability of 300 kbit/s in digital-only mode.
The gradually phased out first generationDAB uses theMPEG-1 Audio Layer II (MP2) audio codec which has less efficient compression than newer codecs. The typical bitrate for DAB stereo programs is 128 kilobit per second or less and as a result most radio stations on DAB have a poorer sound quality than FM does under similar conditions.[43] Many DAB stations also broadcast in mono. In contrast, DAB+ uses the newerAAC+ codec and HD FM uses a codec based upon theMPEG-4HE-AAC standard.
Before DAB+ was introduced, DAB's inefficient compression led in some cases to "downgrading" stations fromstereophonic tomonaural, in order to include more channels in the limited 1 Mbit/s bandwidth.[44]
Digital radio allows for more stations and less susceptibility for disturbances in the signal. In the United States, however, other than HD Radio, digital broadcast technologies, such as DAB+, have not been approved for use on either theVHF band II (FM) ormedium wave band.
DAB better suits national broadcasting networks that provide several stations as is common in Europe, whereas HD is more appropriate for individual stations.
Digital Radio Mondiale (DRM 30) is a system designed primarily forshortwave,medium wave, andlongwave broadcasting with compatible radios already available for sale. DRM 30 is similar to HD AM, in that each station is broadcast via channels spaced 10 kHz (or 9 kHz in some regions) on frequencies up to 30 MHz. The two standards also share the same basic modulation scheme (COFDM), and HD AM uses a proprietary codec. DRM 30 operates withxHE-AAC, historically with any of a number of codecs, including AAC, Opus, andHVXC. The receiver synchronization and data coding are quite different between HD AM and DRM 30. As of 2015 there are several radio chipsets available which can decode AM, FM,DAB, DRM 30 andDRM+, and HD AM and HD FM.
Similar to HD AM,DRM allows either hybrid digital-analog broadcasts or pure digital broadcasts, DRM allows broadcasters to use multiple options:
On the medium wave, actual DRM bit rates vary depending on day versus night transmission (groundwave versusskywave) and the amount of bits dedicated for error correction (signal robustness).
Although DRM offers a growth path forAM broadcasters, it shares some issues with HD Radio in the AM:
DRM+, a different system based upon the same principles of HD Radio on the FM band, but can be implemented in all theVHF bands (1,2, and3),[45] either as a hybrid analog-digital or digital only broadcast, but with 0.1 MHz digital-only bandwidth, it allows 186.3 kbit/s data rate[46][47] (compared to HD FM with 0.4 MHz allowing 300 kbps.)
Digital Radio Mondiale is anopen standards system, albeit one that is subject topatents andlicensing. HD Radio is based upon the intellectual property ofiBiquity Digital Co. /Xperi Holding Co. The United States uses DRM forHF /shortwave broadcasts.[48]
According to a survey dated 8 August 2007 by Bridge Ratings, when asked the question,"Would you buy an HD Radio in the next two months?", only 1.0% responded"yes".[49]
Somebroadcast engineers have expressed concern over the new HD system.[50] A survey conducted in September 2008 saw a small percentage of participants that confused HD Radio withsatellite radio.[51]
Many first-generation HD Radios had insensitive receivers, which caused issues with sound quality. The HD Radio digital signal level is 10–20 dB below the analog signal power of the station's transmitter. In addition, commentators have noted that the analog section of some receivers were inferior compared to older, analog-only models.[52]
However, since 2012, HD capable receiver adoption has significantly increased in most newer cars, and several aftermarket radio systems both for vehicles and home use contain HD Radio receivers and special features such as Full Artist Experience. iBiquity reports that 78% of all radio listening is done on stations that broadcast in HD.[53] There are an increasing number of stations switching to HD or adding subchannels compatible with digital radio, such asSt. Cloud, Minnesota, where many local radio outlets find a growing number of listeners tuning in to their HD signals, which in turn has benefited sales.[54]
Even thoughDAB andDRM standards are open standards and predate HD Radio, HD receivers cannot be used to receive these stations when sold or moved overseas (with certain exceptions; there are HD stations inSri Lanka,[55][needs update]Thailand,Taiwan,Japan,Romania, and a few other countries).
DAB and DRM receivers cannot receive HD signals in the U.S. The HD system, which enablesAM andFM stations to upgrade to digital without changing frequencies, is a different digital broadcasting standard. The lack of a common standard means that HD receivers cannot receive DAB or DRM broadcasts from other countries, and vice versa, and that manufacturers must develop separate products for different countries, which typically are not dual-format.
Whereas theAdvanced Audio Coding (AAC) family of codecs are publicly documented standards, the HDC codec exists only within the HD system, and is aniBiquitytrade secret.
Similarly DAB or DRM are open specifications, while iBiquity's HD specification is partly open, but mostly private.[56]
HD Radio does not useATSC, the standard fordigital television in the United States, and so fails to recover the former TV and FM radio compatibility enjoyed by TV channel 6 broadcasters. In the days of analog television, the lowest sliver of theFM broadcast band (87.7–87.9 MHz) overlapped with the FM audio carrier of U.S. analog television's channel 6;[d] because theNTSCanalog television standard used conventional analog FM to modulate the audio carrier, the audio of television stations that broadcast on channel 6 could be heard on most FM receivers. In earlier days of television and radio, several television stations exploited this overlap andoperated as radio stations. Full-powered television stations wereforced to cease their analog broadcasts in June 2009, and low-powered stations ceased analog broadcasts by July 2021. Because the digital television and all digital radio standards are incompatible, HD receivers are not able to receive digital TV signals on the 87.75 MHz frequency, eliminating the former dual-medium compatibility of channel 6 television stations. Current low-powerATSC 3.0channel 6 stations that broadcast an audio carrier on 87.75 do not have HD Radio.
Promotion for HD Radio often fails to make clear that some of its features are mutually incompatible with other features. For example, the HD system has been described as "CD quality"; however, the HD system also allowsmultiplexing the data stream between two or more separate programs. A program utilizing one half or less of the data stream does not attain the higher audio quality of a single program allowed the full data stream. The FCC has declared
If the FCC disallows analog simulcasting, each station will have over 300 kbit/s bandwidth available, allowing for good stereo quality or evensurround sound audio, together with multiple sub-channels, and to a lesser extent more freedom for low-power, personal FM transmitters, to pair modernsmartphones,computers, and other devices to legacy analog FM receivers.
The broadcasting industry is seeking FCC approval on future HD receiver models, forconditional access; that is, enabling the extra subchannels to be available only by paidsubscription.NDS[e] has made a deal withiBiquity to provide HD Radio with an encrypted content-delivery system called "RadioGuard".[58]NDS claims that RadioGuard will "provide additional revenue-generating possibilities".
Mostly all existing FM receivers tuned to a channel broadcasting a HD signal are prone to increased noise on the analog signal, called "HD Radio self-noise", due to analog demodulation of the digital signal(s). In some high fidelity FM receivers in quality playback systems, this noise can be audible and irritating. Most all existing FM receivers will require modifications to the internalfilters or the addition of a post-detection filter to prevent degradation of the analog signal quality on stations broadcasting HD Radio.
Radio stations are licensed in the United States to broadcast at a specificeffective radiated power level. In 2008,NPR Labs did a study of predicted HD Radio operation if the digital power levels were increased to 10% of the maximum analog carrier power as is now allowed by the FCC under certain circumstances, and found the digital signal would increaseRF interference on FM. However the boosted digital HD signal coverage would then exceed analog coverage, with 17% more population covered in vehicles but 17% less indoors.[59]
The costs of installing the system, including fees, vary from station to station, according to the station's size and existing infrastructure. Typical costs are at least several tens of thousands of dollars at the outset[f] plus per-channel annual fees (3% of the station's annual revenue[citation needed]) to be paid to Xperi for HD‑2 and HD‑3 (HD‑1 has no royalty charge). Large companies in largermedia markets – such asiHeartRadio orCumulus Broadcasting – can afford to implement the technology for their stations. However,community radio stations, both commercial and noncommercial, in many cases cannot afford theUS$1,000 yearly Xperi fee assessed toLPFM stations. During mid-2010 a new generation of HD Radio broadcasting equipment was introduced, greatly lowering the startup costs[f] of implementing the system.
HD Radio receivers cost anywhere from aroundUS$50 to several hundred dollars, compared to regular FM radios which can sometimes even be found atdollar stores. Although costs have historically been higher for HD hardware, as adoption has increased, prices have been reduced, and receivers containing HD Radio are becoming more commonplace – especially as more stations broadcast in HD format.[citation needed]
 | This sectionappears to contradict itself. Please see thetalk page for more information.(March 2023) |
Conventionalanalog-only FMtransmitters normally operate with "class C"amplifiers, which areefficient, but not linear; HD Radio requires a differentamplifier class. A class C amplifier can operate with overalltransmitter efficiency higher than 70%.[g] Digital transmitters operate in one of the other amplifier classes – one that is close to linear, and linearity lowers the efficiency. A modern hybrid HD FM transmitter typically achieves 50~60% efficiency, whereas an HD digital-only FM transmitter should manage just 40~45%. The reduced efficiency causes significantly increased costs for electricity and for cooling.
Until 2013, theHD Digital Radio Alliance,[h] acted as a liaison for stations to choose unduplicated formats for the extra channels (HD‑2, HD‑3, etc.). Now,iBiquity works with the major owners of the stations to provide various additional choices for listeners, instead of having several stations independently deciding to create the same format. HD‑1 stations broadcast the same format as the regularFM (and someAM) stations, and many of these stations offer one, two, or even three subchannels (designated HD‑2, HD‑3, HD‑4) to complement their main programming.
iHeartRadio is selling programming of several differentmusic genres to other competing stations, in addition to airing them on its own stations. Some stations aresimulcasting their localAM orlower-power FM broadcasts on sister stations' HD‑2 or HD‑3 channels, such asKFNZ-FM inKansas City simulcasting 610 AMKFNZ's programming on 96.5 FM‑HD2. It is common practice to broadcast an older, discontinued format on HD‑2 channels; for example, with the recent disappearance of thesmooth jazz format from the analog radio dial in many markets, stations such asWDZH‑FM inDetroit, Michigan, (formerly WVMV),WFAN-FM inNew York City, andWNWV-FM inCleveland, Ohio, program smooth jazz on their HD‑2 or HD‑3 bands. Some HD‑2 or HD‑3 stations are even simulcastingsisterAM stations. InSt. Louis, for example, clear-channelKMOX‑AM (1120 kHz analog and HD) is simulcast onKEZK-FM 102.5 FM‑HD3.KBCO‑FM inBoulder, Colorado, uses its HD‑2 channel to broadcast exclusive live recordings from their private recording studio.CBS Radio is implementing plans to introduce its more popularsuperstations into distant markets (KROQ-FM into New York City,WFAN‑AM into Florida, andKFRG-FM andKSCF‑FM into Los Angeles) via HD‑2 and HD‑3 channels.
On 8 March 2009,CBS Radio inaugurated the first station with an HD4 subchannel,WJFK-FM inWashington, D.C., asports radio station which also carries sister sports operationsWJZ-FM fromBaltimore;Philadelphia'sWTEL‑AM andWIP-FM; andWFAN‑AM fromNew York.[i][60] Since then numerous other channels have implemented HD‑4 subchannels as well, although with nearly 100% talk-based formats, because of the reduced audio quality. For example,KKLQ‑FM in Los Angeles operates an HD‑4 signal and aired The Mormon Channel which was 99% talk.[61]
Public broadcasters are also embracing HD Radio.Minnesota Public Radio offers a few services:KNOW-FM, theMPR News station in theTwin Cities, offers music serviceRadio Heartland on 91.1 FM‑HD2 and additional news programming called "BBC News and More" on 91.1 FM‑HD3;KSJN-FM, the classicalMPR station in theTwin Cities, provides "Classical 24" service on 99.5 FM‑HD2; andKCMP-FM, on 89.3 FM in theTwin Cities, offers "Wonderground Radio", music for kids and their parents, on 89.3 FM‑HD2.[62]
KPCC‑FM (Southern California Public Radio), heard on 89.3 FM inLos Angeles, offers a digital simulcast of its analog channel on 89.3 FM‑HD1 andMPR's music serviceKCMP-FM on 89.3 FM‑HD2 in Los Angeles.[63]
New York Public Radio inNew York City,WNYC (AM) andWNYC-FM, (d.b.a.WNYC) re-broadcasts a locally programmed, all-classical service fromWQXR-FM called "Q2", on 93.9 FM‑HD2. The service launched in March 2006.[64] On 8 October 2009, the format was moved toWQXR‑HD2 (WXNY-FM) on 105.9 FM whenWQXR-FM was acquired byNew York Public Radio as part of a frequency swap withUnivision Radio for their former frequency. The programming on theWNYC-FM‑HD2 channel now is a rebroadcast ofWQXR-FM, in order to give full coverage ofWQXR-FM programming in some form, as the 105.9 FM signal is weaker, and does not cover the whole area.
WMIL-FM inMilwaukee has offered an audio simulcast ofFox affiliateWITI‑TV on their HD‑3 subchannel since August 2009 as part of a news and weather content agreement between iHeartRadio andWITI‑TV. This restoredWITI‑TV's audio to the Milwaukee radio dial after a two-month break, following the digital transition; as a channel 6 analogtelevision stationWITI‑TV exploited the87.7 FM audio quirk as an advantage, in order to allow viewers to hear the station's newscasts andFox programming on their car radios.
KYXY‑FM, operated byCBS inSan Diego on 96.5 FM and offers their HD‑2 channel as one of the few "subchannel only" independent Christian music based formats on HD Radio. Branded as "The Crossing", it is operated byAzusa Pacific University.
College radio has also been impacted by HD Radio, stations such asWBJB-FM which is a public station on a college campus offer a student run station as one of the multicast channels.WKNC-FM inRaleigh, NC, runs college radio programming on HD‑1 and HD‑2, andelectronic dance music onWolfBytes Radio onWKNC-FM‑HD3.
Some commercial broadcasters also use their HD‑2 channels to broadcast the programming of noncommercial broadcasters.Bonneville International uses its HD‑2 and HD‑3 channels to broadcastMormon Channel which is entirely noncommercial and operates solely as a public service from Bonneville's owner,The Church of Jesus Christ of Latter-day Saints. That network of eight HD‑2 and HD‑3 stations was launched on 18 May 2009 and was fully functional within two weeks. Also, in Detroit,WMXD-FM, anurban adult contemporary station, airs thecontemporary ChristianK-Love format on its HD‑2 band (the HD‑2 also feeds several analog translators around the metropolitan area – see below), due to an agreement between iHeartMedia andK-Love ownerEducational Media Foundation (EMF), allowingEMF to programWMXD-FM's HD‑2 channel. On a similar note,Los Angeles'KRRL 92.3 FM‑HD3 signal rebroadcastsEMF'sAir1, and in Santa BarbaraKLSB 97.5 FM airsK-Love on its primary frequency, and rebroadcastsAir1 on HD‑2 (though neither supports "Artist Experience"). In St. Louis, Missouri,WFUN 96.3-HD2 rebroadcastsK297BI for the classical music station Classic 107.3.
In July 2018, as part of a projected one year experiment,WWFD‑AM inFrederick, Maryland, became the firstAM station to eliminate its analog transmissions and broadcast exclusively in digital.[65]
Although FMbroadcast translators are prohibited from originating their own programming, theFCC allows translator stations to rebroadcast an HD Radio subchannel of the primary station it is assigned to, instead of the programming of that station's analog signal. Station owners in large markets have taken advantage of this rule to allow HD subchannels to be heard on analog FM, or take AM licenses with attached translators silent while continuing to feed the translator.
Translators can also be used in a more traditional manner to extend the range of the full content of the primary station, including the unmodified main signal and any HD Radio sub-channels, in areas where the station has poor coverage or reception. Translators are not required to transmit an HD Radio signal, and the vast majority of existing translators do not.
By 2012, there were several HD receivers available on the market. A basic model costs aroundUS$50.
Automotive HD receiver manufacturers include:
Most car manufacturers offer HD receivers as audio packages in new cars, including:
Home and office listening equipment is available from a number of companies in both component receiver and tabletop models, including:
Initially, portable HD receivers were not available due to the early chipsets either being too large for a small enclosure and / or needing too much power to be practical for a battery-operated device. However, in January 2008 at theConsumer Electronics Show (CES) inLas Vegas,iBiquity unveiled a prototype of a new portable receiver, roughly the size of a cigarette pack. Two companies made low-power chipsets for HD receivers:
At least five companies made portable HD receivers:
By 2012,iBiquity was trying to get HDR chipsets intomobile phones.
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