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HD Radio (HDR) is a
trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from othe ...
for an
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 broadcast technology. It generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily by AM and FM
radio station Radio broadcasting is transmission 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 radi ...
s in the United States, Canada, and Mexico, with a few implementations outside North America. The term "on channel" is a misnomer because the system actually broadcasts on the ordinarily unused channels adjacent to an existing
radio station Radio broadcasting is transmission 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 radi ...
'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 kbps of capacity is available. High-fidelity audio requires only 48 kbps 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 The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
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

iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
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 federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
(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‑D.
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
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 s ...
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 is intended to allow a second all-digital signal to be broadcast in simulcast fashion with an existing analog FM radio station, of ...
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 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. Types In digital broadcasting sy ...
(DAB), a.k.a. Eureka 147, is the most common standard in Europe. * Digital Radio Mondiale ( DRM‑30 and DRM+ configurations) was intended mostly for shortwave 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
apart as opposed to 100 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
elsewhere. Furthermore, long-standing
FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
. 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 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, 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 0  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 and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital commu ...
with an audio compression format called HDC ( High-Definition Coding). HDC is a proprietary
codec A codec is a device or computer program 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 on a signal or ...
based upon, but incompatible with, the MPEG-4 standard HE-AAC. It uses a modified discrete cosine transform (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 compressi ...
algorithm. HD equipped stations pay a one-time licensing fee for converting their primary audio channel to
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
'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 primary digital signal (HD‑1) is lost the HD receiver will revert 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 multi ...
stream, although the sound quality is then reduced to conventional AM-level.
Datacasting Datacasting (data broadcasting) is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital terrestrial television (DTT), but may also be applied ...
is also possible, with metadata 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 the part of the medium frequency (MF) radio band The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0  Hz to 3,000  GHz (3  THz). Electromagnetic waves in this frequency ...
stations. (see §  AM, below).


AM

The AM hybrid mode ("MA1") uses 30 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of bandwidth (±15 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
), and overlaps
adjacent channel In broadcasting an adjacent channel is an AM, FM, or TV channel that is next to another channel. First-adjacent is immediately next to another channel, second-adjacent is two channels away, and so forth. Information on adjacent channels is ...
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-AM owner Bob Savage against WBZ‑AM in Boston. The capacity of a 30 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
channel on the AM band is limited. By using
spectral band replication Spectral band replication (SBR) is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain. It can be combined with any audio compression codec: the codec itself tra ...
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 the part of the medium frequency (MF) radio band The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0  Hz to 3,000  GHz (3  THz). Electromagnetic waves in this frequency ...
. 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 multi ...
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 multi ...
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 ...
– 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, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns an ...
, 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 multi ...
while using 20 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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, the KDE Plasma 4 interface for tablet devices * Contour line, a curve along which the function ha ...
. 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, the KDE Plasma 4 interface for tablet devices * Contour line, a curve along which the function ha ...
, 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 multi ...
while only requiring 10 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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. Four stations operate as all-digital / digital-only broadcasters: *
WWFD WWFD (820 AM HD Radio) is a commercial AM radio station licensed to serve Frederick, Maryland. The station is owned by Hubbard Broadcasting through licensee Washington DC FCC License Sub, LLC and simulcasts the freeform programming branded as ...
has had special temporary authority from the
FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
since July 2018 to broadcast all-digital. * WMGG (since January 2021), WFAS (since May 2021) and
WSRO WSRO (650 AM broadcasting, AM HD Radio) is a radio station now broadcasting classical music. Licensed to Ashland, Massachusetts, it serves the MetroWest, Massachusetts, MetroWest area. The station is owned by Alex Langer. WSRO also operates Broad ...
(since December 2021) broadcast all-digital 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 WWFD (820 AM HD Radio) is a commercial AM radio station licensed to serve Frederick, Maryland. The station is owned by Hubbard Broadcasting through licensee Washington DC FCC License Sub, LLC and simulcasts the freeform programming branded as ...
experimented with using a digital subchannel, 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 The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
concluded from
WWFD WWFD (820 AM HD Radio) is a commercial AM radio station licensed to serve Frederick, Maryland. The station is owned by Hubbard Broadcasting through licensee Washington DC FCC License Sub, LLC and simulcasts the freeform programming branded as ...
's experiments: : "The record does not establish that an audio stream on an HD-2 subchannel is currently technically feasible". The FCC requires stations that wish to multiplex their digital AM signals to request and receive permission to do so; in early 2020 it 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 multi ...
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 multi ...
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 multi ...
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 subchannels found in ATSC-compliant
digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative adva ...
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 - a ...
broadcasting. For example, some
top 40 In the music industry, the Top 40 is the current, 40 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. "Top 40" or "cont ...
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 present day, with varying degrees of easy listening, pop, soul, R&B, quiet sto ...
and
classic rock Classic rock is a US radio format which developed from the album-oriented rock (AOR) format in the early 1980s. In the United States, the classic rock format comprises rock music ranging generally from the mid-1960s through the mid 1990s, prima ...
to their digital subchannels, 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 multi ...
. Current 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 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 str ...
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 A diplexer is a passive device that implements frequency-domain multiplexing. Two ports (e.g., L and H) are multiplexed onto a third port (e.g., S). The signals on ports L and H occupy disjoint frequency bands. Consequently, the signals on L and ...
, 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: * A backup site or system In language * Auxiliary language (disambiguation) * Auxiliary verb In military and law enforcement * Auxiliary police * Auxiliaries, civilians or quasi-military personnel who provide support of ...
, 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 is ...
, 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 to each other so as not to cause
destructive interference In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...
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 is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
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 limi ...
and
Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and bot ...
(EAS) alerts in which the transmission of traffic, weather alerts,
AMBER Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In ...
, 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 using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is capa ...
stations typically require up to 280 kilohertz of
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...
. The bandwidth of an FM signal is found by doubling the sum of the peak deviation (usually 75 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
) and the highest baseband modulating frequency (around 60 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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 identificati ...
is used). Only 15 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of the baseband bandwidth is used by analog
monaural Monaural or monophonic sound reproduction (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 reproduc ...
audio (baseband), with the remainder used for stereo,
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 identificati ...
,
paging In computer operating systems, memory paging is a memory management scheme by which a computer stores and retrieves data from secondary storage for use in main memory. In this scheme, the operating system retrieves data from secondary storage ...
,
radio reading service A radio reading service or reading service for the blind is a public service of many universities, community groups and public radio stations, where a narrator reads books, newspapers and magazines aloud for the benefit of the blind and vision-imp ...
, 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'', "remote", an ...
. In (regular) hybrid mode a station has ±130 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of analog bandwidth. The primary main digital sidebands extend ±70 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
on either side of the analog signal, thus taking a full 400 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of spectrum. In extended hybrid mode, the analog signal is restricted to ±100 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
. Extended primary sidebands are added to the main primary sidebands using the extra ±30 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of spectrum created by restricting the analog signal. Extended hybrid provides up to approximately 50 kbps additional capacity. Any existing subcarrier services (usually at 92 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
and 67 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
) that must be shut down to use extended hybrid can be restored through use of digital subchannels. 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 int ...
modulation is reduced, there is no reduction to the analog carrier
power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...
. The National Association of Broadcasters (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, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other ...
was opposed to any increase because it is likely to increase interference to their member stations, particularly to their
broadcast translator A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater (two-way radio) or complementary station (Mexico), is a broadcast transmitter which repeats (or tran ...
s, 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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, the KDE Plasma 4 interface for tablet devices * Contour line, a curve along which the function ha ...
. On 29 January 2010, the U.S. FCC approved a
report and order 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 det ...
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 h ...
(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 Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrost ...
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 A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...
FM stations, which are allowed to remain over the limit for their broadcast class, 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+ version. DAB broadcasts a single multiplex that is approximately 1.5  megahertz wide (≈1 
megabit per second 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 ...
). That multiplex is then subdivided into multiple digital streams of between 9~12 programs (or stations). In contrast, HD FM requires 400 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
bandwidth – compatible with the 200 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
channel spacing traditionally used in 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 multi ...
in digital-only mode. The first generation DAB uses the
MPEG-1 Audio Layer II MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM) is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III (MP3). While MP3 is m ...
(MP2) audio codec which has less efficient compression than newer codecs. The typical bitrate for DAB stereo programs is 128 
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 multi ...
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+ High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/IEC 14496–3. It is an extension of Low Complexity AAC (AAC-LC) optimized for l ...
codec and HD FM uses a codec based upon the MPEG-4 HE-AAC standard. Before DAB+ was introduced, DAB's inefficient compression led in some cases to "downgrading" stations from
stereophonic Stereophonic sound, or more commonly 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 configuration ...
to
monaural Monaural or monophonic sound reproduction (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 reproduc ...
, 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 mu ...
bandwidth. Digital radio, such as DAB, DAB+, and HD FM currently often have smaller coverage of markets as compared to analog FM, radios are more expensive, and reception inside vehicles and buildings may be poor, depending on the frequencies used. HD Radio shares most of these same flaws ( see criticisms below). On the other hand, digital radio allows for more stations and less susceptibility for disturbances in the signal. In the United States, however, digital broadcast technologies other than HD Radio (such as DAB+) have not been approved for use on either the FM or AM bands. DAB is well suited to 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 (DRM 30) is a system designed primarily for shortwave radio 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
(or 9 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
. The two standards also share the same basic modulation scheme (COFDM), and HD AM uses a proprietary codec. DRM 30 operates with any of a number of codecs, including AAC, Opus, and
HVXC Harmonic Vector Excitation Coding, abbreviated as HVXC is a speech coding algorithm specified in MPEG-4 Part 3 (MPEG-4 Audio) standard for very low bit rate speech coding. HVXC supports bit rates of 2 and 4 kbit/s in the fixed and variable bit rate ...
. 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 DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
allows either hybrid digital-analog broadcasts or pure digital broadcasts,
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
allows broadcasters to use multiple options: * Hybrid mode (digital/analog) - 10 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
analog plus 5 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
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 multi ...
data rate; * 10 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
digital-only bandwidth confined to ±5 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
of the channel center allows 12–35 
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 multi ...
; * 20 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
digital-only bandwidth using ±10 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
(including half of the adjacent channels) allows 24–72 
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 multi ...
. DRM+, a different system based upon the same principles, operates in the VHF band with 100 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
digital-only bandwidth which allows 700 
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 multi ...
data rate. Actual
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
bit rates vary depending on day versus night transmission (
groundwave In physics, a surface wave is a mechanical wave that propagates along the interface between differing media. A common example is gravity waves along the surface of liquids, such as ocean waves. Gravity waves can also occur within liquids, at t ...
versus skywave) and the amount of bits dedicated for error correction (signal robustness). Although
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
offers a growth path for AM broadcasters, unfortunately it shares many of the same flaws as DAB and HD AM: * Shorter broadcast distance in hybrid mode compared to an analog AM signal * Poor reception inside vehicles and buildings * Interference with adjacent channels when using the 20 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
mode though in all-digital mode the signal fits inside the designated channel mask. Digital Radio Mondiale is an open standards 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 enabling disclosure of the invention."A ...
s and
licensing A license (or licence) 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 party (licensee) as an element of an agreeme ...
. HD Radio is based upon the intellectual property of iBiquity Digital Co. / Xperi Holding Co. The United States uses
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
for HF / shortwave 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 engineer Broadcast engineering is the field of electrical engineering, and now to some extent computer engineering and information technology, which deals with radio and television broadcasting. Audio engineering and RF engineering are also essential pa ...
s 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. 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 DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
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, Thailand, Taiwan, Japan, Romania, and a few other countries). DAB and
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
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 DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
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. Designed to be the successor of the MP3 format, AAC generally achieves higher sound quality than MP3 encoders at the same bit rate. AAC has been stan ...
( AAC) family of codecs are publicly documented standards, the HDC codec exists only within the HD system, and is an
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
trade secret Trade secrets are a type of intellectual property that includes formulas, practices, processes, designs, instruments, patterns, or compilations of information that have inherent economic value because they are not generally known or readily ...
. Similarly DAB or
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement milita ...
are open specifications, while
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
's HD specification is partly open, but mostly private. HD Radio does not use ATSC, the standard for
digital television in the United States Digital television in the United States is available via digital terrestrial television (DTT), digital cable, satellite television, and IPTV providers (including those delivered over private networks, and those delivered as over-the-top streaming t ...
, 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 (87.7–87.9 
MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
) overlapped with the FM audio carrier of U.S. analog television's channel 6; because the
NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
analog television standard used conventional analog FM to modulate the audio carrier, the audio of television stations that broadcast on channel 6 could be heard on most FM receivers. In earlier days of television and radio, several television stations exploited this overlap and operated as radio stations (a process that still continues with some low-powered stations, which are still allowed to broadcast in analog, for the time being). Full-powered television stations were forced to cease their analog broadcasts in June 2009, with low-powered stations scheduled to cease analog broadcast by September 2015. 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), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
frequency, eliminating the former dual-medium compatibility of channel 6 television stations.


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 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 be UST or Ust may refer to: Organizations * UST (company), American digital technology company * Equatorial Guinea Workers' Union * Union of Trade Unions of Chad (Union des Syndicats du Tchad) * United States Television Manufacturing Corp. * UST Gro ...
of 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 multi ...
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 s ...
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 portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s, computers, and other devices to legacy analog  FM receivers. The broadcasting industry is seeking FCC approval on future HD receiver models, for conditional access; that is, enabling the extra subchannels to be available only by paid subscription.
NDS NDS may stand for: * Low German ( nl, Nedersaksisch, links=no, german: Niederdeutsche Sprache, links=no, ISO 639-2 language code: nds), a West Germanic language native to Northern Germany, Denmark and the Netherlands * Lower Saxony (german: Niedersa ...
has made a deal with
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
to provide HD Radio with an encrypted content-delivery system called "RadioGuard".
NDS NDS may stand for: * Low German ( nl, Nedersaksisch, links=no, german: Niederdeutsche Sprache, links=no, ISO 639-2 language code: nds), a West Germanic language native to Northern Germany, Denmark and the Netherlands * Lower Saxony (german: Niedersa ...
claims that RadioGuard will "provide additional revenue-generating possibilities". Most 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
filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
s 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 h ...
level. In 2008,
NPR National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other ...
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 Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrost ...
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 and radio station offerings, and may also incl ...
s – such as iHeartRadio or
Cumulus Broadcasting Cumulus Media, Inc. is an American broadcasting company and is the third largest owner and operator of AM and FM radio stations in the United States behind Audacy and iHeartMedia. As of June 2019, Cumulus lists ownership of 428 stations in 87 ...
– 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 and public broadcasting. Community stations serve geographic communities and communities of interest. They broadcast content that is popula ...
stations, both commercial and noncommercial, in many cases cannot afford the
US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
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. Current HD Radio receivers cost anywhere from around
US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
50 to several hundred dollars, compared to regular FM radios which can sometimes even be found at
dollar store A variety store (also five and dime (historic), pound shop, or dollar store) is a retail store that sells general merchandise, such as apparel, automotive parts, dry goods, toys, hardware, home furnishings, and a selection of groceries. It us ...
s. 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 is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
s normally operate with " class C" amplifiers, 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 is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
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 is selling programming of several different music genres 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 programmes/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, simulta ...
ing their local AM or lower-power FM broadcasts on sister stations' HD‑2 or HD‑3 channels, such as
KMBZ-FM KMBZ-FM (98.1 MHz) is a commercial radio station licensed to Kansas City, Kansas. Owned by Audacy, Inc., KMBZ-FM airs a news/talk radio format. Its studios and offices are located on Squibb Road in Mission, Kansas. KMBZ-FM broadcasts at 98, ...
in Kansas City simulcasting 610  AM KCSP‑AM'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 a genre of commercially-oriented crossover jazz and easy listening music that became dominant in the mid 1970s to the early 1990s. History Smooth jazz is a commercially oriented, crossover jazz which came to prominence in the 19 ...
format from the analog radio dial in many markets, stations such as WDZH‑FM in
Detroit, Michigan Detroit ( , ; , ) is the largest city in the U.S. state of Michigan. It is also the largest U.S. city on the United States–Canada border, and the seat of government of Wayne County. The City of Detroit had a population of 639,111 at ...
, (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. It ...
in
New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...
, and WNWV-FM in Cleveland, Ohio, 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 one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a family, familial relationship, it is sometimes used endearingly to r ...
AM stations. In St. Louis, for example, clear-channel KMOX‑AM (1120 
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
analog and HD) is simulcast on
KEZK-FM KEZK-FM (102.5 MHz) is a commercial radio station licensed to St. Louis, Missouri. It broadcasts an adult contemporary radio format and is owned by Audacy, Inc. From mid-November through the Christmas holiday, KEZK switches to an all-Christma ...
102.5  FM‑HD3. KBCO‑FM in Boulder, Colorado, uses its HD‑2 channel to broadcast exclusive live recordings from their private recording studio. CBS Radio is implementing plans to introduce its more popular superstations into distant markets ( KROQ-FM 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 MHz "106.7 The Fan") is a commercial radio station licensed to serve Manassas, Virginia, and serving the Washington metropolitan area. WJFK-FM airs a sports radio format and is owned and operated by Audacy, Inc. WJFK-FM's studi ...
in
Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
, a
sports radio Sports radio (or sports talk radio) is a radio format devoted entirely to discussion and broadcasting of sporting events. A widespread programming genre that has a narrow audience appeal, sports radio is characterized by an often- boisterous on ...
station which also carries sister sports operations
WJZ-FM WJZ-FM (105.7 MHz) is a commercial radio station licensed to Catonsville, Maryland, and serving the Baltimore metropolitan area. The station is owned by Audacy, Inc. through licensee Audacy License, LLC, and it broadcasts a sports radio for ...
from
Baltimore Baltimore ( , locally: or ) is the List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...
;
Philadelphia Philadelphia, often called Philly, is the List of municipalities in Pennsylvania#Municipalities, largest city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, the List of United States cities by population, sixth-largest city i ...
'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 within Audacy's corporate hea ...
; 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, News & Information, YourClassical MPR and The Current, MPR operates a 46-station regional radio network in the upper Midwest. MPR ha ...
offers a few services:
KNOW-FM KNOW-FM (91.1 FM) is the flagship radio station of Minnesota Public Radio's news and information network, primarily broadcasting a talk radio format to the Minneapolis-St. Paul market. The frequency was the original home of KSJN, but the purc ...
, the
MPR News Minnesota Public Radio (MPR), is a public radio network for the state of Minnesota. With its three services, News & Information, YourClassical MPR and The Current, MPR operates a 46-station regional radio network in the upper Midwest. MPR ha ...
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 sta ...
, 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 KSJN (99.5 FM broadcasting, FM, "YourClassical MPR") is the flagship station of Minnesota Public Radio's European classical music, classical music network, serving the Minneapolis-Saint Paul, Twin Cities region. KSJN's studios are located at the ...
, 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 sta ...
, provides "
Classical 24 Classical 24 is a syndicated, satellite-delivered public radio service providing classical music to its carrying stations. It generally airs overnights on many non-commercial and a handful of commercial classical music stations. However, the se ...
" service on 99.5  FM‑HD2; and
KCMP-FM KCMP (89.3 FM, 89.3 The Current) is a radio station owned by Minnesota Public Radio (MPR) that broadcasts a AAA music format including a significant rotation of songs by local artists. Licensed to Northfield, Minnesota and covering the Minneapo ...
, 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 sta ...
, 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 ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
, offers a digital simulcast of its analog channel on 89.3  FM‑HD1 and MPR's music service
KCMP-FM KCMP (89.3 FM, 89.3 The Current) is a radio station owned by Minnesota Public Radio (MPR) that broadcasts a AAA music format including a significant rotation of songs by local artists. Licensed to Northfield, Minnesota and covering the Minneapo ...
on 89.3  FM‑HD2 in Los Angeles.
New York Public Radio New York Public Radio (NYPR) is the owner of WNYC (AM), WNYC-FM, WNYC Studios, WQXR-FM, New Jersey Public Radio, and the Jerome L. Greene Performance Space. Combined, New York Public Radio owns WNYC (AM), WNYC-FM, WQXR-FM, WQXW, WNJT-FM, WNJP ...
in
New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...
,
WNYC-AM WNYC (820 AM) is a nonprofit, non-commercial, public radio station licensed to New York City. The station is owned by New York Public Radio along with sister stations WNYC-FM and Newark, New Jersey-licensed classical music outlet WQXR-FM (105.9& ...
and
WNYC-FM WNYC-FM (93.9 MHz) is a non-profit, non-commercial, public radio station licensed to New York City. It is owned by New York Public Radio along with WNYC (AM), Newark, New Jersey-licensed classical music outlet WQXR-FM (105.9 MHz), Ne ...
, ( d.b.a.
WNYC WNYC is the trademark and a set of call letters shared by WNYC (AM) and WNYC-FM, a pair of nonprofit, noncommercial, public radio stations located in New York City. WNYC is owned by New York Public Radio (NYPR), a nonprofit organization that ...
) re-broadcasts a locally programmed, all- classical service from
WQXR-FM WQXR-FM (105.9 FM) is an American non-commercial classical radio station, licensed to Newark, New Jersey and serving the North Jersey and New York City area. It is owned by the nonprofit organization New York Public Radio, which also operates ...
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 WXNY-FM (96.3 FM ''La X 96.3'') is a commercial radio station that broadcasts an Hispanic rhythmic format. It is licensed to New York City, and serves the New York metropolitan area. WXNY is owned by Uforia Audio Network and its transmitter i ...
) on 105.9  FM when
WQXR-FM WQXR-FM (105.9 FM) is an American non-commercial classical radio station, licensed to Newark, New Jersey and serving the North Jersey and New York City area. It is owned by the nonprofit organization New York Public Radio, which also operates ...
was acquired by
New York Public Radio New York Public Radio (NYPR) is the owner of WNYC (AM), WNYC-FM, WNYC Studios, WQXR-FM, New Jersey Public Radio, and the Jerome L. Greene Performance Space. Combined, New York Public Radio owns WNYC (AM), WNYC-FM, WQXR-FM, WQXW, WNJT-FM, WNJP ...
as part of a frequency swap with Univision Radio for their former frequency. The programming on the
WNYC-FM WNYC-FM (93.9 MHz) is a non-profit, non-commercial, public radio station licensed to New York City. It is owned by New York Public Radio along with WNYC (AM), Newark, New Jersey-licensed classical music outlet WQXR-FM (105.9 MHz), Ne ...
‑HD2 channel now is a rebroadcast of
WQXR-FM WQXR-FM (105.9 FM) is an American non-commercial classical radio station, licensed to Newark, New Jersey and serving the North Jersey and New York City area. It is owned by the nonprofit organization New York Public Radio, which also operates ...
, in order to give full coverage of
WQXR-FM WQXR-FM (105.9 FM) is an American non-commercial classical radio station, licensed to Newark, New Jersey and serving the North Jersey and New York City area. It is owned by the nonprofit organization New York Public Radio, which also operates ...
programming in some form, as the 105.9  FM signal is weaker, and does not cover the whole area.
WMIL-FM WMIL-FM (106.1 MHz) is a commercial radio station licensed to Waukesha, Wisconsin, and serving the Greater Milwaukee/Southeast Wisconsin radio market. It carries a country music radio format and is owned by iHeartMedia. The studios and offices ...
in
Milwaukee Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County. With a population of 577,222 at the 2020 census, Milwaukee ...
has offered an audio simulcast of
Fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...
affiliate WITI (TV), WITI‑TV on their HD‑3 subchannel since August 2009 as part of a news and weather content agreement between iHeartRadio and WITI (TV), WITI‑TV. This restored WITI (TV), 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 WITI (TV), WITI‑TV exploited the NTSC#NTSC-M, 87.7 FM audio quirk as an advantage, in order to allow viewers to hear the station's newscasts and
Fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...
programming on their car radios. KYXY, KYXY‑FM, operated by Columbia Broadcasting System, CBS in San Diego on 96.5  FM and offers their HD‑2 channel as one of the few "subchannel only" independent Christian music based formats on HD Radio. Branded as "The Crossing", it is operated by Azusa Pacific University. 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, North Carolina, Raleigh, NC, runs college radio programming on HD‑1 and HD‑2, and electronic dance music 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 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. 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 station, airs the contemporary Christian K-Love format on its HD‑2 band (the HD‑2 also feeds several analog translators around the metropolitan area – see below), due to an agreement between iHeartMedia and K-Love owner Educational Media Foundation (EMF), allowing Educational Media Foundation, EMF to program WMXD-FM's HD‑2 channel. On a similar note,
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
' KRRL 92.3  FM‑HD3 signal rebroadcasts Educational Media Foundation, EMF's Air1, and in Santa Barbara KLSB 97.5  FM airs K-Love on its primary frequency, and rebroadcasts Air1 on HD‑2 (though neither supports "Artist Experience"). In July 2018, as part of a projected one year experiment, WWFD, WWFD‑AM in Frederick, Maryland, became the first AM broadcasting, AM station to eliminate its analog transmissions and broadcast exclusively in digital.


Translators

Although
broadcast translator A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater (two-way radio) or complementary station (Mexico), is a broadcast transmitter which repeats (or tran ...
s are prohibited from originating their own programming, the
FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
has controversially allowed translator stations to simulcast, 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 Duopoly (broadcasting), multiple stations locally and nationally, to avoid the rulemaking 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. 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 is ...
(via less restrictive height and power limitations) than community radio, 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 KUER-FM, K202BD in Manti, Utah, which rebroadcasts both the analog and digital signals of KUER-FM from Salt Lake City. 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 heterodyne, heterodyning. This may require an increase in bandwidth (signal processing), bandwidth in both the amplifier and radio antenna if either is too narrowband to pass the wider HD Radio signal, meaning one or both might have to be replaced. Baseband 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 broadcasting, 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 (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
50. The list of automotive HD receiver manufacturers includes: Most car manufacturers offer HD receivers as audio packages in new cars, including: Home and office listening equipment is currently available from roughly a dozen 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) in Las Vegas,
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
unveiled a prototype of a new portable receiver, roughly the size of a cigarette pack. Two companies are currently making low-power chipsets for HD receivers: * Samsung * SiPort At least four companies presently make 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 Inc., Apple iPod, or iPhone, with tuning functionality provided via software through the device's multi-touch display. This product is now discontinued. * Best Buy started selling the Insignia NS‑HD01, a house brand portable unit on 12 July 2009. It was the second portable HD receiver to come to the general market and features 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 (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
50 – the least expensive receiver available. Best Buy discontinued the NS‑HD01 model by September 2019, but it continued to be sold. * Microsoft released the on 15 September 2009. It includes an HD receiver embedded in the media device. The Zune HD is now discontinued. By 2012,
iBiquity iBiquity Digital Corporation is 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, and Auburn Hills, Michigan, iBiquity is a privately ...
was trying to get HDR chipsets into mobile phones.


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 {{DEFAULTSORT:HD Radio HD Radio, Xperi Digital radio Broadcast engineering Articles containing video clips American inventions 2002 introductions 2002 establishments in the United States