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HD Radio (HDR) is a
trademark A trademark (also written trade mark or trade-mark) is a form of intellectual property that consists of a word, phrase, symbol, design, or a combination that identifies a Good (economics and accounting), product or Service (economics), service f ...
for
in-band on-channel In-band on-channel (IBOC) is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency. The name refers to the new digital signals being broadcast in the same AM or FM band (in-band), ...
(IBOC)
digital radio Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services. This should not be confused with In ...
broadcast technology. HD radio generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily by FM
radio station Radio broadcasting is the broadcasting of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based rad ...
s in the United States, U.S. Virgin Islands, Canada, Mexico and the Philippines, 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 for "hybrid digital", not "high definition". Officially, HD is not intended to stand for any term in HD Radio, it is simply part of
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
's trademark, and does not have any meaning on its own. 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. The term "on channel" is a misnomer because the system actually sends the digital components on the ordinarily unused channels ''adjacent to'' an existing
radio station Radio broadcasting is the broadcasting of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based rad ...
'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. Four AM stations use the all-digital format, one under an experimental authorization, the other three under new rules adopted by the FCC 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.


History

This standard was meant to supersede other existing stereophonic standards on AM.
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
developed HD Radio, and the system was selected by the
U.S. Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains ju ...
(FCC) in 2002 as a digital audio broadcasting method for the United States. It is officially known as NRSC‑5, with the latest version being NRSC‑5‑E.
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
was acquired by DTS in September 2015 bringing the HD Radio technology under the same banner as DTS's eponymous theater
surround sound Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener ( surround channels). Its first application was in movie theaters. Prior to ...
systems. The HD Radio technology and trademarks were subsequently acquired by Xperi Holding Corporation in 2016. HD Radio is one of several digital radio standards which are generally incompatible with each other: *
FMeXtra FMeXtra is a deprecated in-band on-channel digital radio broadcasting technology created by Digital Radio Express. It was intended to allow a second all-digital signal to be simulcast with an existing analog FM radio station, offering a less noisy ...
was a competing U.S. standard, but has been stagnant since the 2010s. * Compatible AM Digital (CAM‑D) for AM stations. *
Digital Audio Broadcasting Digital Audio Broadcasting (DAB) is a digital radio international standard, standard for broadcasting digital audio radio services in many countries around the world, defined, supported, marketed and promoted by the WorldDAB organisation. T ...
(DAB), a.k.a. Eureka 147, is the most common standard in Europe. *
Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—p ...
( DRM‑30 and DRM+ configurations) was intended mostly for
shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...
radio. 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. This compares with more than 2,200 services operating with the DAB system. A 400  kHz wide channel is required for HD FM 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-standing FCC licensing practice, dating from when receivers had poor adjacent-channel selectivity, assigns stations in geographically overlapping or adjacent coverage 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 without
co-channel interference Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel. Co-channel interference can be caused by many factors from weather conditions to administrative and design issues. Co-channel interferen ...
with distant stations on those channels. 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 with
analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, instantaneous phase and frequency, ...
, since it would not result in the recovery of any
radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3  Hz to 3,000 GHz (3  THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...
rights which could be sold. Thus, there is no deadline by which consumers must buy an HD receiver.


Technique

Digital information is transmitted using
OFDM In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission used in digital modulation for encoding digital (binary) data on multiple carrier frequencies. OFDM has developed into a popular scheme for ...
with an audio compression format called HDC ( High-Definition Coding). HDC is a proprietary
codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...
based upon, but incompatible with, the
MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...
standard HE-AAC. It uses a
modified discrete cosine transform The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where s ...
(MDCT)
audio data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...
algorithm. HD equipped stations pay a one-time licensing fee for converting their primary audio channel to
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
's HD Radio technology, and 3% of incremental net revenues for any additional digital subchannels. The cost of converting a radio station can run between $100,000 and $200,000. Receiver manufacturers who include HD Radio pay a royalty, 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 In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
stream, although the sound quality is then reduced to conventional AM-level.
Datacasting Datacasting (data broadcasting) is the transmission of data over a wide area using radio waves. It typically refers to supplemental information sent by television stations alongside digital terrestrial television (DTT) signals. However, datacas ...
is also possible, with
metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...
providing song titles or artist information. iBiquity Digital claims that the system approaches CD quality audio and offers reduction of both interference and static. However, the data rates in HD Radio are substantially lower than from a CD, and the digital signals sometimes interfere with adjacent analog
AM band Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM broadcasting, AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. Duri ...
stations. (see §  AM, below).


AM

The AM hybrid mode ("MA1") uses 30  kHz of bandwidth (±15  kHz), and overlaps
adjacent channel Adjacent or adjacency may refer to: *Adjacent (graph theory) in a graph, two vertices that are both endpoints of the same edge, or two distinct edges that share an end vertex * Adjacent (music), a conjunct step to a note which is next in the scale ...
s on both sides of the station's assigned channel. Some nighttime listeners have expressed concern this design harms reception of adjacent channels with one formal complaint filed regarding the matter: WYSL owner Bob Savage against WBZ in Boston. The capacity of a 30  kHz channel on the AM band is limited. By using spectral band replication the HDC+SBR codec is able to simulate the recreation of sounds up to 15,000 Hz, thus achieving moderate quality on the
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
-tight
AM band Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM broadcasting, AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. Duri ...
. The HD Radio AM hybrid mode offers two options which can carry approximately 40~60 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
of data, with most AM digital stations defaulting to the more-robust 40 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
mode, which features redundancy (same data is broadcast twice). The digital radio signal received on a conventional AM receiver tuned to an adjacent channel sounds like
white noise In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used with this or similar meanings in many scientific and technical disciplines, i ...
– the sound of a , or a large waterfall, or a strong, steady wind through a dense
forest canopy In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, the canopy is the upper layer or habitat zone, formed by mature tree crowns and includ ...
, or similar.


All-digital AM

All-digital AM ("MA3") allows for two modes: "Enhanced" and "core-only". * In enhanced mode, the primary, secondary and tertiary carriers are transmitted, allowing for a maximum throughput of 40.2 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
while using 20  kHz of bandwidth out to the station's 0.5  mV/m
contour Contour may refer to: * Contour (linguistics), a phonetic sound * Pitch contour * Contour (camera system), a 3D digital camera system * Contour Airlines * Contour flying, a form of low level flight * Contour, the KDE Plasma 4 interface for tab ...
. Inside this contour, stereo audio along with graphics (station logo and "artist experience" album artwork) and text information (the station's call sign, title, album, and artist) can be decoded by the receiver. : Beyond the station's 0.5  mV/m
contour Contour may refer to: * Contour (linguistics), a phonetic sound * Pitch contour * Contour (camera system), a 3D digital camera system * Contour Airlines * Contour flying, a form of low level flight * Contour, the KDE Plasma 4 interface for tab ...
, typically only the primary carriers can be received, which restricts the maximum throughput to 20.2 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
while only requiring 10  kHz of bandwidth. * In core-only mode, the station only transmits the primary carriers. 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. 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. * WWFD (WSHE since June 2024) was granted
special temporary authority Special Temporary Authority (STA) in U.S. broadcast law is a type of broadcast license which temporarily allows a broadcast station to operate outside of its normal technical or legal parameters. In the Federal Communications Commission (FCC) st ...
from the FCC in July 2018 to broadcast all-digital. It continues broadcast in digital-only mode under regular authorization. * WMGG broadcast in all-digital mode from January 2021 until a new owner returned it to analog-only mode following a station sale in November 2021. * WFAS broadcast in digital-only mode from May 2021 until its license was deleted in October 2024. * WSRO broadcast in digital only-mode from December 2021 until the station went silent in March 2023. After a brief return to the air in 2024, its license was cancelled in March 2025. * WYDE has broadcast in all-digital mode since September 2023. The FCC requires stations that wish to multiplex their digital AM signals to request and receive permission to do so. WWFD experimented with using a
digital subchannel In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compress ...
, operating a second channel (HD2) at a low data rate while reducing the data rate of the primary channel (HD1). In October 2020, the FCC concluded from WWFD's experiments: : "The xperimentalrecord does not establish that an audio stream on an AM HD-2 subchannel is currently technically feasible". In early 2020 the FCC rejected a multiplex request from WTLC.


FM

The FM hybrid digital / analog mode offers four options which can carry approximately 100, 112, 125, or 150 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
of data carrying (
lossy In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...
) 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 In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
rate, and enabling extra features like surround sound. Like AM, purely-digital FM provides a "fallback" condition where it reverts to a more robust 25 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
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 the
digital subchannel In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compress ...
s found in ATSC-compliant
digital television Digital television (DTV) is the transmission of television signals using Digital signal, digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an ...
using
multiplexed In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource— ...
broadcasting. For example, some
top 40 In the music industry, the Top 40 is a list of the 40 currently most popular songs in a particular genre. It is the best-selling or most frequently broadcast popular music. Record charts have traditionally consisted of a total of 40 songs. "To ...
stations have added
hot AC Adult contemporary music (AC) is a form of radio-played popular music, ranging from 1960s vocal and 1970s soft rock music to predominantly ballad-heavy music of the 1980s to the present day, with varying degrees of easy listening, pop, soul, ...
and
classic rock Classic rock is a radio format that developed from the album-oriented rock (AOR) format in the early 1980s. In the United States, it comprises rock music ranging generally from the mid-1960s through the early-1990s, primarily focusing on comm ...
to their
digital subchannel In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compress ...
s, to provide more variety to listeners. 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 In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
. 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 requires
synchronization Synchronization is the coordination of events to operate a system in unison. For example, the Conductor (music), conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are sa ...
of the two, with a significant delay added to the analog service. In some cases, particularly during
tropospheric ducting Tropospheric propagation describes electromagnetic propagation in relation to the troposphere. The service area from a VHF or UHF radio transmitter extends to just beyond the optical horizon, at which point signals start to rapidly reduce in st ...
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 the same 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. The listener can possibly turn HD reception off (to listen to the local station, or avoid random flipping between the two stations), or listen to the distant stations and try to get a station 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. Stations can transmit HD through their existing antennas using a diplexer, as on AM, or are permitted by the FCC to use a separate antenna at the same general location, or at a site licensed as an analog
auxiliary Auxiliary may refer to: In language * Auxiliary language (disambiguation) * Auxiliary verb In military and law enforcement * Auxiliary police * Auxiliaries, civilians or quasi-military personnel who provide support of some kind to a military se ...
, 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 same
broadcast range A broadcast range (also listening range or listening area for radio, or viewing range or viewing area for television) is the service area that a broadcast station or other transmission covers via radio waves (or possibly infrared light, which i ...
, and that they maintain the proper
ratio In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
of
signal strength In telecommunications, particularly in radio frequency engineering, signal strength is the transmitter power output as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those used i ...
to each other so as not to cause
destructive interference In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater amplitude (constructive in ...
at any given location where they may be received.


Artist Experience

HD Radio supports a service called "Artist Experience" 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 the
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
certification, which includes displaying the artwork properly.


EAS alerts

Since 2016, newer HD Radios support
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is li ...
and
Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...
(EAS) alerts in which the transmission of traffic, weather alerts,
AMBER Amber is fossilized tree resin. Examples of it have been appreciated for its color and natural beauty since the Neolithic times, and worked as a gemstone since antiquity."Amber" (2004). In Maxine N. Lurie and Marc Mappen (eds.) ''Encyclopedia ...
, 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.


Bandwidth and power

FM stereo FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high-fidelity sound ...
stations typically require up to 280 kilohertz of
spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
. 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 when
RBDS Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identificat ...
is used). Only 15  kHz of the baseband bandwidth is used by analog
monaural Monaural sound or monophonic sound (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce so ...
audio (baseband), with the remainder used for
stereo Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
,
RBDS Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identificat ...
,
paging In computer operating systems, memory paging is a memory management scheme that allows the physical Computer memory, memory used by a program to be non-contiguous. This also helps avoid the problem of memory fragmentation and requiring compact ...
, radio reading service, rental to other customers, or as a transmitter/studio link for in-house
telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', 'far off', an ...
. 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. Extended hybrid provides up to approximately 50 kbit/s additional capacity. Any existing
subcarrier A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio bro ...
services (usually at 92  kHz and 67  kHz) that must be shut down to use extended hybrid can be restored through use of
digital subchannel In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compress ...
s. However, this requires the replacement of ''all'' 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 total
baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into ...
modulation Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...
is reduced, there is no reduction to the analog carrier power. The
National Association of Broadcasters The National Association of Broadcasters (NAB) is a Industry trade group, trade association and lobbying, lobby group representing the interests of commercial and non-commercial over-the-air radio and television broadcasting, broadcasters in th ...
(NAB) requested a 10 dB (10×) increase 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 National Public Radio (NPR) is an American public broadcasting organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It serves as a national Radio syndication, syndicator to a network of more ...
was opposed to any increase because it is likely to increase interference to their member stations, particularly to their broadcast 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. North American FM channels are spaced 200  kHz apart. An HD broadcast station will not generally cause interference to any analog station within its 1  mV/m
service contour In US broadcasting, service contour (or protected contour) refers to the area in which the Federal Communications Commission (FCC) predicts coverage. The FCC calculates FM and TV contours based on effective radiated power (ERP) in a given direct ...
– 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/m
contour Contour may refer to: * Contour (linguistics), a phonetic sound * Pitch contour * Contour (camera system), a 3D digital camera system * Contour Airlines * Contour flying, a form of low level flight * Contour, the KDE Plasma 4 interface for tab ...
. On 29 January 2010, the U.S. FCC approved a report and order to voluntarily increase the maximum digital
effective radiated power Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would ha ...
(ERP) to 4% of analog ERP (−14 dB c), up from the previous maximum of 1% (−20 dBc). 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 ongoing RF interference to another station come from locations within the other station's licensed service 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. The station to which the interference is caused bears the burden of proof and its associated expenses, rather than the station that causes the problem. For grandfathered FM stations, which are allowed to remain over the limit for their
broadcast class This is a list of broadcast station classes applicable in much of North America under international agreements between the United States, Canada and Mexico. Effective radiated power (ERP) and height above average terrain (HAAT) are listed unless ot ...
, these numbers are relative to that lower limit rather than their actual power.


Comparison to other digital radio standards


HD versus DAB

Some countries have implemented Eureka-147 Digital Audio Broadcasting (DAB) or the newer
DAB+ Digital Audio Broadcasting (DAB) is a digital radio international standard, standard for broadcasting digital audio radio services in many countries around the world, defined, supported, marketed and promoted by the WorldDAB organisation. T ...
version. DAB broadcasts a single multiplex that is approximately 1.5 
megahertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base ...
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 the ITU Region 2 (including the United States) – with capability of 300 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
in digital-only mode. The gradually phased out first generation DAB uses the
MPEG-1 Audio Layer II MP2 (formally MPEG-1 Audio Layer II or MPEG-2 Audio Layer II, sometimes incorrectly called Musicam) is a lossy audio compression format. It is standardised as one of the three audio codecs of MPEG-1 alongside MPEG-1 Audio Layer I (MP1) and M ...
(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. Many DAB stations also broadcast in mono. In contrast, DAB+ uses the newer AAC+ codec and HD FM uses a codec based upon the
MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...
HE- AAC standard. Before DAB+ was introduced, DAB's inefficient compression led in some cases to "downgrading" stations from
stereophonic Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
to
monaural Monaural sound or monophonic sound (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce so ...
, in order to include more channels in the limited 1 
Mbit/s In telecommunications, data transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multi ...
bandwidth. 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 the VHF band II ( FM) or
medium wave Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytim ...
band. DAB better suits national broadcasting networks that provide several stations as is common in Europe, whereas HD is more appropriate for individual stations.


HD versus DRM

Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—p ...
(DRM 30) is a system designed primarily for
shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...
,
medium wave Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytim ...
, and
longwave In radio, longwave (also spelled long wave or long-wave and commonly abbreviated LW) is the part of the radio spectrum with wavelengths longer than what was originally called the medium-wave (MW) broadcasting band. The term is historic, dati ...
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 hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...
. The two standards also share the same basic modulation scheme (COFDM), and HD AM uses a proprietary codec. DRM 30 operates with xHE-AAC, historically with any of a number of codecs, including AAC, Opus, and HVXC. 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 and DRM+, 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: * Hybrid mode (digital/analog) - 10 kHz analog plus 5 kHz digital bandwidth allows 5–16 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
data rate; * 10 kHz digital-only bandwidth confined to ±5 kHz of the channel center allows 12–35 kbit/s; * 20 kHz digital-only bandwidth using ±10 kHz (including half of the adjacent channels) allows 24–72 kbit/s. On the medium wave, actual DRM bit rates vary depending on day versus night transmission (
groundwave Ground wave is a mode of radio propagation that consists of currents traveling through the earth. Ground waves propagate parallel to and adjacent to the surface of the Earth, and are capable of covering long distances by diffracting around the ...
versus
skywave In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvatur ...
) and the amount of bits dedicated for error correction (signal robustness). Although DRM offers a growth path for AM broadcasters, it shares some issues with HD Radio in the AM: * Shorter broadcast distance in hybrid mode compared to an analog AM signal * Interference with adjacent channels when using the 20  kHz mode though in all-digital mode the signal fits inside the designated channel mask. DRM+, a different system based upon the same principles of HD Radio on the FM band, but can be implemented in all the VHF bands ('' 1'', '' 2'', and '' 3''), 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 (compared to HD FM with 0.4 MHz allowing 300 kbps.) Digital Radio Mondiale is an
open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a common prerequisite that open standards use an open license that provides for extensibility. Typically, anybody can participate in their development due to ...
s system, albeit one that is subject to
patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...
s and
licensing A license (American English) or licence ( Commonwealth English) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another par ...
. HD Radio is based upon the intellectual property of iBiquity Digital Co. / Xperi Holding Co. The United States uses DRM for HF /
shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...
broadcasts.


Acceptance and criticism


Awareness and coverage

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"''. Some broadcast engineers have expressed concern over the new HD system. A survey conducted in September 2008 saw a small percentage of participants that confused HD Radio with
satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a '' broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than te ...
. 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. 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. There are an increasing number of stations switching to HD or adding subchannels compatible with digital radio, such as St. 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.


Different format and compatibility standards

Even though DAB and DRM 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 in
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
,
Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
,
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
,
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
,
Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
, and a few other countries). DAB and DRM receivers cannot receive HD signals in the U.S. The HD system, which enables AM and FM 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 the
Advanced Audio Coding Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. It was developed by Dolby, AT&T, Fraunhofer and Sony, originally as part of the MPEG-2 specification but later improved under MPEG-4.ISO (2006ISO/ ...
(AAC) family of codecs are publicly documented standards, the HDC codec exists only within the HD system, and is an
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
trade secret A trade secret is a form of intellectual property (IP) comprising confidential information that is not generally known or readily ascertainable, derives economic value from its secrecy, and is protected by reasonable efforts to maintain its conf ...
. Similarly DAB or DRM are open specifications, while iBiquity's HD specification is partly open, but mostly private. HD Radio does not use ATSC, the standard for digital 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 the
FM broadcast band The FM broadcast band is a range of radio frequencies used for FM broadcasting by radio stations. The range of frequencies used differs between different parts of the world. In Europe and Africa (defined as International Telecommunication Union ( ...
(87.7–87.9 
MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...
) overlapped with the FM audio carrier of U.S. analog television's channel 6; because the
NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...
analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, instantaneous phase and frequency, ...
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 and operated as radio stations. Full-powered television stations were forced 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...
frequency, eliminating the former dual-medium compatibility of channel 6 television stations. Current low-power ATSC 3.0 channel 6 stations that broadcast an audio carrier on 87.75 do not have HD Radio.


Reduced-quality concerns

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 allows
multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource� ...
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 : "one free over-the-air digital stream ust beof equal or greater quality than the station's existing analog signal". If the FCC disallows analog simulcasting, each station will have over 300 
kbit/s In telecommunications, data transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...
bandwidth available, allowing for good stereo quality or even
surround sound Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener ( surround channels). Its first application was in movie theaters. Prior to ...
audio, together with multiple sub-channels, and to a lesser extent more freedom for low-power, personal FM transmitters, to pair modern
smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...
s,
computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s, and other devices to legacy analog FM receivers. The broadcasting industry is seeking FCC approval on future HD receiver models, for
conditional access Conditional access (CA) is a term commonly used in relation to software and to digital television systems. Conditional access is an evaluation to ensure the person who is seeking access to content is authorized to access the content. Access is man ...
; that is, enabling the extra subchannels to be available only by paid
subscription The subscription business model is a business model in which a customer must pay a recurring price at regular intervals for access to a product or service. The model was pioneered by publishers of books and periodicals in the 17th century. It ...
. NDS has made a deal with
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
to provide HD Radio with an encrypted content-delivery system called "RadioGuard". 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 internal filters or the addition of a post-detection filter to prevent degradation of the analog signal quality on stations broadcasting HD Radio.


Reduced analog signal

Radio stations are licensed in the United States to broadcast at a specific
effective radiated power Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would ha ...
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 increase RF 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.


High costs

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 plus per-channel annual fees (3% of the station's annual revenue) to be paid to Xperi for HD‑2 and HD‑3 (HD‑1 has no royalty charge). Large companies in larger
media market A media market, broadcast market, media region, designated market area (DMA), television market area, or simply market is a region where the population can receive the same (or similar) television station, television and radio broadcasting, ra ...
s – such as
iHeartRadio iHeartRadio (often shortened to just "iHeart") is an American freemium broadcast, podcast, radio streaming and Music Streaming platform owned by iHeartMedia. Founded in August 2008, iHeartRadio serves as the national umbrella brand for iHeart ...
or Cumulus Broadcasting – can afford to implement the technology for their stations. However,
community radio Community radio is a radio service offering a third model of radio broadcasting in addition to commercial broadcasting, commercial and public broadcasting. Community broadcasting, Community stations serve geographic communities and communities o ...
stations, both commercial and noncommercial, in many cases cannot afford the
US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
1,000 yearly Xperi fee assessed to LPFM stations. During mid-2010 a new generation of HD Radio broadcasting equipment was introduced, greatly lowering the startup costs of implementing the system. HD Radio receivers cost anywhere from around
US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
50 to several hundred dollars, compared to regular FM radios which can sometimes even be found at dollar 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.


Power consumption

Conventional analog-only FM
transmitter In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna (radio), antenna with the purpose of sig ...
s normally operate with " class C"
amplifiers An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power suppl ...
, which are efficient, but not linear; HD Radio requires a different amplifier class. A class C amplifier can operate with overall transmitter efficiency higher than 70%. 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.


Programming

Until 2013, the HD Digital Radio Alliance, acted as a liaison for stations to choose unduplicated formats for the extra channels (HD‑2, HD‑3, etc.). Now,
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
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 regular FM (and some AM) 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 iHeartRadio (often shortened to just "iHeart") is an American freemium broadcast, podcast, radio streaming and Music Streaming platform owned by iHeartMedia. Founded in August 2008, iHeartRadio serves as the national umbrella brand for iHeart ...
is selling programming of several different
music genre A music genre is a conventional category that identifies some pieces of music as belonging to a shared tradition or set of conventions. Genre is to be distinguished from musical form and musical style, although in practice these terms are sometim ...
s to other competing stations, in addition to airing them on its own stations. Some stations are
simulcast Simulcast (a portmanteau of "simultaneous broadcast") is the broadcasting of programs or events across more than one resolution, bitrate or medium, or more than one service on the same medium, at exactly the same time (that is, simultaneously) ...
ing their local AM or lower-power FM broadcasts on sister stations' HD‑2 or HD‑3 channels, such as KFNZ-FM in
Kansas City The Kansas City metropolitan area is a bi-state metropolitan area anchored by Kansas City, Missouri. Its 14 counties straddle the border between the U.S. states of Missouri (9 counties) and Kansas (5 counties). With and a population of more t ...
simulcasting 610  AM KFNZ'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 the
smooth jazz Smooth jazz is commercially oriented crossover jazz music. Although often described as a "genre", it is a debatable and highly controversial subject in jazz music circles. As a radio format, however, smooth jazz radio became the successor to e ...
format from the analog radio dial in many markets, stations such as WDZH‑FM in
Detroit, Michigan Detroit ( , ) is the List of municipalities in Michigan, most populous city in the U.S. state of Michigan. It is situated on the bank of the Detroit River across from Windsor, Ontario. It had a population of 639,111 at the 2020 United State ...
, (formerly WVMV),
WFAN-FM WFAN-FM (101.9 FM) is a commercial radio station licensed to New York, New York. Owned by Audacy, Inc., the station simulcasts a sports radio format known as "Sports Radio 66 AM and 101.9 FM", or "The FAN", along with co-owned WFAN (660 AM) ...
in
New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
, and WNWV-FM in
Cleveland, Ohio Cleveland is a city in the U.S. state of Ohio and the county seat of Cuyahoga County, Ohio, Cuyahoga County. Located along the southern shore of Lake Erie, it is situated across the Canada–United States border, Canada–U.S. maritime border ...
, program smooth jazz on their HD‑2 or HD‑3 bands. Some HD‑2 or HD‑3 stations are even simulcasting
sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...
AM stations. In St. Louis, for example, clear-channel KMOX‑AM (1120  kHz analog and HD) is simulcast on KEZK-FM 102.5  FM‑HD3. KBCO‑FM in
Boulder, Colorado Boulder is a List of municipalities in Colorado#Home rule municipality, home rule city in Boulder County, Colorado, United States, and its county seat. With a population of 108,250 at the 2020 United States census, 2020 census, it is the most ...
, uses its HD‑2 channel to broadcast exclusive live recordings from their private recording studio. CBS Radio is implementing plans to introduce its more popular
superstation ''Superstation'' (alternatively rendered as "super station" or informally as "SuperStation") is a term in North American broadcasting that has several meanings. Commonly, a "superstation" is a form of distant signal, a broadcast television sign ...
s into distant markets (
KROQ-FM KROQ-FM (106.7 MHz) is a commercial radio station licensed to Pasadena, California, serving Greater Los Angeles. Owned by Audacy, Inc., it broadcasts an alternative rock format known as "The World Famous KROQ" (pronounced "kay-rock"). The sta ...
into New York City, WFAN‑AM into Florida, and KFRG-FM and KSCF‑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 WJFK-FM (106.7 Hertz, MHz "106.7 The Fan") is a commercial radio, commercial radio station licensed to serve Manassas, Virginia, and serving the Washington metropolitan area. WJFK-FM airs a sports radio, sports radio format and is owned and opera ...
in
Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...
, a
sports radio Sports radio (or sports talk radio) is a radio format devoted entirely to discussion and broadcasting of sport, sporting events. A widespread programming genre that has a narrow audience appeal, sports radio is characterized by an often-low comed ...
station which also carries sister sports operations WJZ-FM from
Baltimore Baltimore is the most populous city in the U.S. state of Maryland. With a population of 585,708 at the 2020 census and estimated at 568,271 in 2024, it is the 30th-most populous U.S. city. The Baltimore metropolitan area is the 20th-large ...
;
Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
's WTEL‑AM and
WIP-FM WIP-FM (94.1 MHz) is a commercial radio station licensed to serve Philadelphia, Pennsylvania. The station is owned by Audacy, Inc. and broadcasts a sports radio format. The WIP-FM offices and studios are co-located in Audacy's corporate headq ...
; and WFAN‑AM from New York. 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. Public broadcasters are also embracing HD Radio.
Minnesota Public Radio Minnesota Public Radio (MPR) is a public radio network for the state of Minnesota. With its three services, KNOW-FM, News & Information, KSJN, YourClassical MPR and KCMP, The Current, MPR operates a 46-station regional radio network in the upper ...
offers a few services:
KNOW-FM KNOW-FM (91.1 MHz) is the flagship radio station of Minnesota Public Radio's news and information network. It is licensed to Saint Paul and serves the Minneapolis-Saint Paul radio market. The station is non-commercial and listener-supported. ...
, the MPR News station in the
Twin Cities Twin cities are a special case of two neighboring cities or urban centres that grow into a single conurbation – or narrowly separated urban areas – over time. There are no formal criteria, but twin cities are generally comparable in stat ...
, offers music service Radio Heartland on 91.1  FM‑HD2 and additional news programming called "
BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broad ...
and More" on 91.1  FM‑HD3; KSJN-FM, the classical MPR station in the
Twin Cities Twin cities are a special case of two neighboring cities or urban centres that grow into a single conurbation – or narrowly separated urban areas – over time. There are no formal criteria, but twin cities are generally comparable in stat ...
, provides " Classical 24" service on 99.5  FM‑HD2; and KCMP-FM, on 89.3  FM in the
Twin Cities Twin cities are a special case of two neighboring cities or urban centres that grow into a single conurbation – or narrowly separated urban areas – over time. There are no formal criteria, but twin cities are generally comparable in stat ...
, offers "Wonderground Radio", music for kids and their parents, on 89.3  FM‑HD2. KPCC‑FM (Southern California Public Radio), heard on 89.3  FM in
Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...
, offers a digital simulcast of its analog channel on 89.3  FM‑HD1 and MPR's music service KCMP-FM on 89.3  FM‑HD2 in Los Angeles.
New York Public Radio New York Public Radio (NYPR) is a New York City-based independent, publicly supported, Nonprofit organization, not-for-profit media organization incorporated in 1979. Its stated mission is "To make the mind more curious, the heart more open and t ...
in
New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
,
WNYC (AM) WNYC (820 kHz) is a non-commercial public broadcasting, public radio station, licensed to New York, New York. It, along with WNYC-FM, is one of the primary outlets for WNYC branded programming, provided by the non-profit New York Public Rad ...
and WNYC-FM, ( d.b.a.
WNYC WNYC is an audio service brand, under the control of New York Public Radio, a non-profit organization. Radio and other audio programming is primarily provided by a pair of nonprofit, noncommercial, public radio stations: WNYC (AM) and WNYC- ...
) re-broadcasts a locally programmed, all- classical service from WQXR-FM called " Q2", on 93.9  FM‑HD2. The service launched in March 2006. On 8 October 2009, the format was moved to WQXR‑HD2 ( WXNY-FM) on 105.9  FM when WQXR-FM was acquired by
New York Public Radio New York Public Radio (NYPR) is a New York City-based independent, publicly supported, Nonprofit organization, not-for-profit media organization incorporated in 1979. Its stated mission is "To make the mind more curious, the heart more open and t ...
as part of a frequency swap with Univision Radio for their former frequency. The programming on the WNYC-FM‑HD2 channel now is a rebroadcast of WQXR-FM, in order to give full coverage of WQXR-FM programming in some form, as the 105.9  FM signal is weaker, and does not cover the whole area. WMIL-FM in
Milwaukee Milwaukee is the List of cities in Wisconsin, most populous city in the U.S. state of Wisconsin. Located on the western shore of Lake Michigan, it is the List of United States cities by population, 31st-most populous city in the United States ...
has offered an audio simulcast of Fox affiliate WITI‑TV on their HD‑3 subchannel since August 2009 as part of a news and weather content agreement between iHeartRadio and WITI‑TV. This restored WITI‑TV's audio to the Milwaukee radio dial after a two-month break, following the digital transition; as a channel 6 analog
television station A television station is a set of equipment managed by a business, organisation or other entity such as an amateur television (ATV) operator, that transmits video content and audio content via radio waves directly from a transmitter on the earth's s ...
WITI‑TV exploited the 87.7 FM audio quirk as an advantage, in order to allow viewers to hear the station's newscasts and Fox programming on their car radios. KYXY‑FM, operated by CBS in
San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...
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 by
Azusa Pacific University Azusa Pacific University (APU) is a private evangelical research university in Azusa, California, United States. The university was founded in 1899 in Whittier, California, with classes first held on March 3, 1900, and degrees offered in 193 ...
. College radio has also been impacted by HD Radio, stations such as WBJB-FM which is a public station on a college campus offer a student run station as one of the multicast channels. WKNC-FM in Raleigh, NC, runs college radio programming on HD‑1 and HD‑2, and
electronic dance music Electronic dance music (EDM), also referred to as dance music or club music, is a broad range of percussive electronic music genres originally made for nightclubs, raves, and List of electronic dance music festivals, festivals. It is generally ...
on WolfBytes Radio on WKNC-FM‑HD3. Some commercial broadcasters also use their HD‑2 channels to broadcast the programming of noncommercial broadcasters.
Bonneville International Bonneville International Corporation is a media and broadcasting company, wholly owned by the Church of Jesus Christ of Latter-day Saints (LDS Church) through its for-profit arm, Deseret Management Corporation. It began as a radio and TV networ ...
uses its HD‑2 and HD‑3 channels to broadcast Mormon 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 The Church of Jesus Christ of Latter-day Saints, informally known as the LDS Church or Mormon Church, is a Nontrinitarianism, nontrinitarian Restorationism, restorationist Christianity, Christian Christian denomination, denomination and the ...
. 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, an
urban adult contemporary Urban adult contemporary, often abbreviated as urban AC or UAC, (also known as adult R&B,) is the name for a format of radio music, similar to an urban contemporary format. Radio stations using this format usually would not have hip hop music on ...
station, airs the
contemporary Christian Contemporary history, in English-language historiography, is a subset of modern history that describes the historical period from about 1945 to the present. In the social sciences, contemporary history is also continuous with, and related t ...
K-Love K-Love (stylized as K-LOVE) is an American Christian radio network. Owned by the Educational Media Foundation (EMF), a non-profit Christian ministry, it primarily broadcasts contemporary Christian music. As of June 2019, the network's progr ...
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 and
K-Love K-Love (stylized as K-LOVE) is an American Christian radio network. Owned by the Educational Media Foundation (EMF), a non-profit Christian ministry, it primarily broadcasts contemporary Christian music. As of June 2019, the network's progr ...
owner
Educational Media Foundation Educational Media Foundation (formerly EMF Broadcasting, abbreviated EMF) is an American nonprofit Christian media ministry based in Franklin, a suburb of Nashville. EMF is the parent company of K-LOVE and Air1—the world's largest contempor ...
(EMF), allowing EMF to program WMXD-FM's HD‑2 channel. On a similar note,
Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...
' KRRL 92.3  FM‑HD3 signal rebroadcasts EMF's
Air1 Air1 is an American Christian radio network owned by the Educational Media Foundation (EMF), a non-profit Christian ministry. It primarily broadcasts contemporary worship music, and is a sister to the EMF's K-Love network. History On July 15, ...
, and in Santa Barbara KLSB 97.5  FM airs
K-Love K-Love (stylized as K-LOVE) is an American Christian radio network. Owned by the Educational Media Foundation (EMF), a non-profit Christian ministry, it primarily broadcasts contemporary Christian music. As of June 2019, the network's progr ...
on its primary frequency, and rebroadcasts
Air1 Air1 is an American Christian radio network owned by the Educational Media Foundation (EMF), a non-profit Christian ministry. It primarily broadcasts contemporary worship music, and is a sister to the EMF's K-Love network. History On July 15, ...
on HD‑2 (though neither supports "Artist Experience"). In St. Louis, Missouri, WFUN 96.3-HD2 rebroadcasts K297BI for the classical music station Classic 107.3. In July 2018, as part of a projected one year experiment, WWFD‑AM in
Frederick, Maryland Frederick is a city in, and the county seat of, Frederick County, Maryland, United States. Frederick's population was 78,171 people as of the 2020 United States census, 2020 census, making it the List of municipalities in Maryland, second-largest ...
, became the first
AM station AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transm ...
to eliminate its analog transmissions and broadcast exclusively in digital.


Translators

Although broadcast translators are prohibited from originating their own programming, the FCC has controversially allowed translator stations to rebroadcast in standard analog FM the audio of an HD Radio channel of the primary station the translator is assigned to. This also allows station owners, who already usually own multiple stations locally and nationally, to avoid the
rulemaking In administrative law, rulemaking is the process that executive and independent agencies use to create, or ''promulgate'', regulations. In general, legislatures first set broad policy mandates by passing statutes, then agencies create more de ...
process of changing the table of allotments as would be needed to get a new separately-licensed station, and to avoid exceeding controlling-interest caps intended to prevent the excessive
concentration of media ownership In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...
. Such new translator stations can block new LPFM stations from going on the air in the same footprint. Translator stations are allowed greater
broadcast range A broadcast range (also listening range or listening area for radio, or viewing range or viewing area for television) is the service area that a broadcast station or other transmission covers via radio waves (or possibly infrared light, which i ...
(via less restrictive height and power limitations) than locally originated LPFM stations, so they may occupy a footprint in which several LPFMs might have been licensed otherwise. In addition to the controversial practice of converting the HD-only secondary radio channels of a primary station into analog  FM in areas where the primary station's signal can already readily be received, 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, as is done via the remote transmitter K202BD in
Manti, Utah Manti ( ) is a city in and the county seat of Sanpete County, Utah, Sanpete County, Utah, United States. The population was 3,429 at the 2020 United States Census. Description Manti was the first community in Utah to be settled outside the Wasa ...
, which rebroadcasts both the analog and digital signals of KUER-FM from
Salt Lake City Salt Lake City, often shortened to Salt Lake or SLC, is the capital and most populous city of the U.S. state of Utah. It is the county seat of Salt Lake County, the most populous county in the state. The city is the core of the Salt Lake Ci ...
. In order to do this, HD Radio may be passed along from the main station via a " bent pipe" setup, where the translator simply makes a frequency shift of the entire channel, often by simple heterodyning. This may require an increase in
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
in both the
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...
and
radio antenna In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating electric current into radio waves (transmitting), or radio waves into an electric current (receivi ...
if either is too
narrowband Narrowband signals are signals that occupy a narrow range of frequencies or that have a small fractional bandwidth. In the audio spectrum, ''narrowband sounds'' are sounds that occupy a narrow range of frequencies. In telephony, narrowband is ...
to pass the wider HD Radio signal, meaning one or both might have to be replaced.
Baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into ...
translators which use a separate receiver and transmitter require an HD Radio transmitter, just as does the main station. Translators are not ''required'' to transmit an HD Radio digital signal, and the vast majority of existing translators which repeat FM stations running hybrid HD signals do not repeat the HD part of the radio broadcast, due to technical limitations in equipment designed before the advent of HD Radio technology.


Receivers


Automotive and home/professional

By 2012, there were several HD receivers available on the market. A basic model costs around
US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
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:


Portable

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 the
Consumer Electronics Show CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typi ...
(CES) in
Las Vegas Las Vegas, colloquially referred to as Vegas, is the most populous city in the U.S. state of Nevada and the county seat of Clark County. The Las Vegas Valley metropolitan area is the largest within the greater Mojave Desert, and second-l ...
,
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
unveiled a prototype of a new portable receiver, roughly the size of a cigarette pack. Two companies made low-power chipsets for HD receivers: * Samsung * SiPort At least five companies made portable HD receivers: * Coby Electronics Corporation produced the first HD portable – the Coby HDR‑700 portable HD receiver for both AM and FM. * Griffin Technology produced an HD receiver designed to plug into the dock connector of an
Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...
iPod The iPod is a series of portable media players and multi-purpose mobile devices that were designed and marketed by Apple Inc. from 2001 to 2022. The iPod Classic#1st generation, first version was released on November 10, 2001, about mon ...
, or
iPhone The iPhone is a line of smartphones developed and marketed by Apple that run iOS, the company's own mobile operating system. The first-generation iPhone was announced by then–Apple CEO and co-founder Steve Jobs on January 9, 2007, at ...
, with tuning functionality provided via
software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...
through the device's
multi-touch In computing, multi-touch is technology that enables a surface (a touchpad or touchscreen) to recognize the presence of more than one somatosensory system, point of contact with the surface at the same time. The origins of multitouch began at CE ...
display. This product was discontinued. *
Best Buy Best Buy Co., Inc. is an American multinational consumer electronics retailer headquartered in Richfield, Minnesota. Originally founded by Richard M. Schulze and James Wheeler in 1966 as an audio specialty store called Sound of Music, it was r ...
started selling the Insignia NS‑HD01, a
house brand A private label, also called a private brand or private-label brand, is a brand owned by a company, offered by that company alongside and competing with brands from other businesses. A private-label brand is almost always offered exclusively by th ...
portable unit on 12 July 2009. It was the second portable HD receiver to come to the general market and featured FM‑only playback and a non-removable rechargeable battery which charges via mini USB. The Insignia unit sold in 2009 for around
US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
50 – the least expensive receiver available.
Best Buy Best Buy Co., Inc. is an American multinational consumer electronics retailer headquartered in Richfield, Minnesota. Originally founded by Richard M. Schulze and James Wheeler in 1966 as an audio specialty store called Sound of Music, it was r ...
discontinued the NS‑HD01 model by September 2019 in favor of the NS-HD02. *
Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
released the on 15 September 2009. It included an HD receiver embedded in the media device. The Zune HD was discontinued in November 2011 in favor of
Windows Phone Windows Phone (WP) is a discontinued mobile operating system developed by Microsoft Mobile for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone featured a new user interface derived from the Metro design languag ...
s. * Sangean Electronics produces multiple portable HD radios with AM and FM reception, like the Sangean HDR-14 portable receiver. By 2012,
iBiquity iBiquity Digital Corporation was a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, Los Angeles, California, and Auburn Hills, Michigan, ...
was trying to get HDR chipsets into
mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...
s.


Footnotes


References


External links

* * — IBOC general information page * — Site with standards documents for the NRSC formats of HD Radio * * — information on an early IBOC installation * — editorial discusses marketing challenges for HD Radio * — audio samples of actual HD broadcasts {{Audio broadcasting Xperi Digital radio Broadcast engineering Articles containing video clips American inventions 2002 introductions 2002 establishments in the United States