HD Radio
Overview
 
HD Radio, which originally stood for "Hybrid Digital", is the trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

 for iBiquity's
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...

 in-band on-channel
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....

 (IBOC) digital radio
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...

 technology used by AM
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...

 and FM
FM broadcasting
FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...

 radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...

s to transmit audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

 and data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

 via a digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 signal in conjunction with their analog signal
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

s. It was selected by the United States Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

 (FCC) in 2002 as a digital audio broadcasting method for the United States, and is the only digital system approved by the FCC for digital AM/FM broadcasts in the United States.
Encyclopedia
HD Radio, which originally stood for "Hybrid Digital", is the trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

 for iBiquity's
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...

 in-band on-channel
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....

 (IBOC) digital radio
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...

 technology used by AM
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...

 and FM
FM broadcasting
FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...

 radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...

s to transmit audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

 and data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

 via a digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 signal in conjunction with their analog signal
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

s. It was selected by the United States Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

 (FCC) in 2002 as a digital audio broadcasting method for the United States, and is the only digital system approved by the FCC for digital AM/FM broadcasts in the United States. It is officially known as NRSC-5, with the latest version being NRSC-5B. Other digital radio systems include FMeXtra
FMeXtra
FMeXtra, now marketed as VuCast and oriented at the broadcast data market like MSN Direct, is an in-band on-channel digital radio broadcasting technology created by Digital Radio Express, now VuCast Media. Unlike iBiquity's HD Radio system, it uses any FM radio station's existing equipment and...

, Digital Audio Broadcasting (DAB)
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....

 (Eureka 147), Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...

 (DRM30 and DRM+ configurations), and Compatible AM-Digital
CAM-D
Compatible Amplitude Modulation - Digital or CAM-D is a proposed hybrid digital radio format for AM broadcasting, put forth by well-known broadcast engineer Leonard R. Kahn....

 (CAM-D).

As a standard practice, the kilohertz signal rate is written next to its corresponding data transfer rate kilobits/s or kbits/s in HD Radio documentation. While HD Radio does allow for an all-digital mode, this system currently is used by some AM and FM radio stations to simulcast
Simulcast
Simulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...

 both digital and analog audio within the same channel (a hybridized digital-analog signal) as well as to add new FM channels and text information. Although HD Radio broadcasting's content is currently subscription-free, listeners must purchase new receivers in order to receive the digital portion of the signal. As of May 2009, there were more stations in the world on the air with HD Radio technology than any other digital radio technology. More than 1,900 stations covering approximately 84% of the United States are broadcasting with this technology, and more than 1,000 HD2 and HD3 multicast channels are on the air. According to iBiquity's website, the "HD" is simply a brand name and has no meaning. There is no connection with high-definition television
High-definition television
High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...

 (HDTV), although like HDTV the HD Radio specification provides enhanced capabilities over the old analog format, such as 5.1 surround sound.

The FCC has not indicated any intent to force off analog radio broadcasts as it has with analog television
Analog television
Analog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...

 broadcasts, as it would not result in the recovery of any radio spectrum
Radio spectrum
Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz ....

 rights which could be sold. Thus, there is no deadline by which consumers must buy an HD Radio receiver. In addition, there are many more analog AM/FM radio receivers than there were analog televisions, and many of these are car stereos or portable units that cannot be upgraded.

Overview

Digital information is transmitted
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

 using COFDM with an audio compression algorithm called PAC (Perceptual audio coder
Perceptual audio coder
Perceptual Audio Coder is an algorithm, like MPEG's MP3 standard, used to compress digital audio by removing extraneous information not perceived by most people. It is used by Sirius Satellite Radio for their DARS service....

). However, audio compressed with this method led to complaints about poor sound quality, so in 2003 iBiquity
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...

 combined it with an enhancer called SBR (spectral band replication
Spectral band replication
Spectral band replication is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain....

) that improves audio quality at very low bit rates and branded the codec to HDC (High-Definition Coding
High-Definition Coding
HDC with SBR is a proprietary lossy audio compression codec developed by iBiquity for use with HD Radio. It replaced the earlier PAC codec in 2003. It is thought to be a modified form of MPEG-4 HE-AAC....

). (HDC is a proprietary codec based upon, but incompatible with, the MPEG-4 standard HE-AAC
HE-AAC
High-Efficiency Advanced Audio Coding is a lossy data compression scheme for digital audio defined as a MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio...

). HD Radio equipped stations pay a one-time licensing fee for converting their primary audio channel to iBiquity'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 pay a royalty.

If the primary digital signal is lost the HD Radio 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 are not simulcast on analog, causing the sound to drop-out or "skip" when digital reception degrades (similar to HDTV drop-outs). Alternatively the HD Radio signal can revert to a more-robust 20 kilobit per second stream, though the sound is reduced to AM-like quality. Datacasting
Datacasting
Datacasting 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 television, but may also be applied to digital signals on analog TV or radio...

 is also possible, with metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

 providing song titles or artist information.

iBiquity Digital claims that the system approaches CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

 quality sound and offers reduction of both interference and static; however, some listeners have complained of increased interference on the analog AM band (see AM, below).

AM

Sending pure digital data through the approximately 20 kilohertz AM channel is roughly equivalent to sending data through two 33 kbit/s analog telephone lines, thus limiting the maximum throughput possible. By using spectral band replication
Spectral band replication
Spectral band replication is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain....

 the HDC+SBR codec is able to simulate the recreation of sounds up to 15,000 Hz, thus achieving FM quality on the bandwidth-tight AM band. The HD Radio AM hybrid mode offers two options which can carry approximately 40 or 60 kbit/s of data, but most AM digital stations default to the more-robust 40 kbit/s mode which features redundancy (same signal broadcast twice). HD Radio also provides a pure digital mode, which lacks an analog signal for fallback and instead reverts to a 20 kbit/s signal during times of poor reception. The pure digital mode transmissions will stay within the AM station's channel instead of spilling into the channels next to the station transmitting "HD radio" as the hybrid digital stations do.

The AM version of HD Radio technology uses the 20 kHz channel (+/- 10 kHz), and overlaps 5 kHz into the opposite sideband of the adjacent channel
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 used in keeping stations from interfering with one...

 on both sides. When operating in pure digital mode, the AM HD Radio signal fits inside a standard 20 kHz channel (20-40 kbit/s) or an extended 30 kHz channel (40-60 kbit/s), at the discretion of the station manager. As AM radio stations are spaced at 9 kHz (Europe) or 10 kHz (Americas) intervals, much of the digital information overlaps adjacent channels when in hybrid mode. Some nighttime listeners have expressed concern this design harms reception of adjacent channels with one formal complaint filed regarding the matter: WYSL owner Bob Savage against WBZ
WBZ (AM)
WBZ is the call sign for an AM radio station in Boston, Massachusetts owned by CBS Radio, itself owned by the CBS Corporation. Originally based in and broadcast from Springfield, Massachusetts, WBZ was the first commercial radio station in the United States...

 in Boston. The digital radio signal received on a conventional AM receiver tuned to an adjacent channel sounds like a large waterfall or similar white noise-like hiss, as can be heard in the audio soundclip referenced in the previous sentence. Listeners (and some professional broadcasters) call it IBUZ because of the "buzz saw" like noise.

FM

The FM hybrid digital/analog mode offers four options which can carry approximately 100, 112, 125, or 150 kbit/s of lossy data depending upon the station manager's power budget and/or desired range of signal. The HD Radio also provides several pure digital modes with up to 300 kbit/s bitrate, and enabling extra features like surround sound. Like AM, pure digital FM provides a "fallback" condition where it reverts to a more-robust 25 kbit/s signal.

FM stations have the option to subdivide their datastream into sub-channels (e.g., 88.1 HD1, HD2, HD3) of varying audio quality. The multiple services are similar to the digital subchannel
Digital subchannel
In broadcasting, digital subchannels are a means to transmit more than one independent program at the same time from the same digital radio or digital television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual...

s found in ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....

-compliant digital television
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...

 using multiplexed broadcasting. For example, some top 40 stations have added hot AC and classic rock
Classic rock
Classic rock is a radio format which developed from the album-oriented rock format in the early 1980s. In the United States, the classic rock format features music ranging generally from the late 1960s to the late 1980s, primarily focusing on the hard rock genre that peaked in popularity in the...

 to their digital subchannel
Digital subchannel
In broadcasting, digital subchannels are a means to transmit more than one independent program at the same time from the same digital radio or digital television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual...

s to provide more variety to listeners. Stations may eventually go all-digital, thus allowing as many as three full-power channels and four low-power channels (seven total). As defined by iBiquity these channels could be sub-divided into CD-quality (100 kbit/s), FM-quality (25-50 kbit/s), AM-quality (12 kbit/s), or Talk-quality (5 kbit/s) channels. Alternatively, they could broadcast one single channel at 300 kbit/s.

Where the digital signal fails, the analog signal is used as a fallback for the main digital channel (normally HD1), requiring synchronization
Synchronization
Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....

 of the two. Current FCC rules require that one channel be a simulcast of the analog signal. In some cases, particularly during tropospheric ducting events, an HD Radio receiver will lock on to the digital sidebands of a distant station, even though there is a much stronger local analog-only station on the same frequency. Because there is no standard identification or other indication sent 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 enjoy listening to the distant stations and trying to get a station ID.

Although the signals may be synchronized at the transmitter and reach your equipment simultaneously, what you hear through an HD unit and an analog radio played together will be distinctly unsynchronized. This is because all analog receivers process analog signals faster than HD radios can process digital signals. The resulting unmistakable "reverb" or echo effect from playing HD and analog in the same room or house can be annoying. It's more noticeable with simple voice transmission than with complex musical signals. (Multiple HD receivers or multiple analog receivers in the same room or house will not cause noticeable echo.) The only way to truly "synchronize" HD with analog radio would be to delay the analog transmission by a few hundred milliseconds, but this is normally not done.

Stations can transmit HD Radio through their existing antennas using a diplexer
Diplexer
A diplexer is a passive device that implements frequency domain multiplexing. Two ports are multiplexed onto a third port . The signals on ports L and H occupy disjoint frequency bands...

 as on AM, or are permitted by the FCC to use a separate antenna at the same location, or at a site licensed as an analog auxiliary
Auxiliary
Auxiliary may refer to:* A backup site or system* Auxiliary input jack, generally for audio* Auxiliary verb* International auxiliary language* Auxiliary police* Auxiliaries, troops supporting the main force of an army** Auxiliaries...

, provided it is within a certain distance and height referenced to the analog main signal. This limitation assures that the two have about the same broadcast range, and that they maintain the proper ratio of signal strength
Signal strength
In telecommunications, particularly in radio, signal strength refers to the magnitude of the electric field at a reference point that is a significant distance from the transmitting antenna. It may also be referred to as received signal level or field strength. Typically, it is expressed in...

 to each other so as not to cause destructive interference with each other at any given location where they may be received.

Bandwidth and power

Currently, FM stations in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 are licensed to carry 100 kilohertz of bandwidth, requiring approximately 200 kilohertz of spectrum
Radio spectrum
Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz ....

. Only 15 kHz of the modulation
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...

 bandwidth is used by analog monaural
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...

 audio (baseband), with the remainder used for stereo, RBDS, paging
Pager
A pager is a simple personal telecommunications device for short messages. A one-way numeric pager can only receive a message consisting of a few digits, typically a phone number that the user is then requested to call...

, radio reading service
Radio reading service
A radio reading service or reading service for the blind is a 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-impaired. It is most often carried on a subcarrier, with...

, rental to other customers, or as a transmitter/studio link
Transmitter/studio link
The transmitter/studio link of a radio station or television station is a return link which sends telemetry data from the remotely-located radio transmitter or television transmitter back to the studio for monitoring purposes...

 for in-house telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...

.

In regular hybrid mode a station has its full ±100 kHz of analog bandwidth and adds an extra ±30 kHz guard band
Guard band
-Radio and electronic signalling:In radio, a guard band is an unused part of the radio spectrum between radio bands, for the purpose of preventing interference....

 and ±70 kHz for its digital signals, thus taking a full 400 kHz of width. FM stations also have the option to discontinue existing subcarrier
Subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...

 services (usually at 92 kHz and 67 kHz) in order to carry extended HD Radio, though such services can be restored through use of the digital subchannel
Digital subchannel
In broadcasting, digital subchannels are a means to transmit more than one independent program at the same time from the same digital radio or digital television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual...

s that are then made available. However, this requires the replacement of all related equipment both for the broadcasters and all of the receivers that use the discontinued services.

The ratio of power of the analog signal to the digital signal is standardized at 100:1 (−20 dBc), making the digital signal 1% of the analog carrier power. Unlike with subcarriers, where the total baseband
Baseband
In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...

 modulation
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...

 is reduced, there is no reduction to the analog carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

 power
Effective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...

. 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 have also been tested, including a 6dB or fourfold increase to 4% (−14dBc or 25:1). National Public Radio is opposed to any increase because it is likely to increase interference to their member stations, particularly to their broadcast translators which are secondary and therefore left unprotected from such interference. Other broadcasters are also opposed (or indifferent), as 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 Radio on FM will increase interference between different stations even though HD Radio at the 10% power level fits within the FCC spectral mask. North American FM channels are spaced 200 kHz apart. An HD Radio station will not generally cause interference to any analog station within its 1 mV/m service contour
Service contour
In US broadcasting, service contour refers to the area in which the Federal Communications Commission predicts and allows coverage....

, the limit above which the FCC protects most stations. However, the IBOC signal resides within the analog signal of the first-adjacent station. With the proposed power increase of 10dB, the potential exists to cause the degradation of the second-adjacent analog signals within its 1 mV/m service contour
Service contour
In US broadcasting, service contour refers to the area in which the Federal Communications Commission predicts and allows coverage....

. Ironically, the National Association of Broadcasters
National Association of Broadcasters
The National Association of Broadcasters is a trade association, workers union, and lobby group representing the interests of for-profit, over-the-air radio and television broadcasters in the United States...

 claims this is not a problem, at the same time using it as justification to keep LPFM stations off the air on second-adjacent channels, excluding NAB members' own translators that are allowed higher power than local community radio
Community radio
Community radio is a type of radio service, that offers a third model of radio broadcasting beyond commercial broadcasting and public broadcasting. Community stations can serve geographic communities and communities of interest...

 LPFMs.

On January 29, 2010, the U.S. FCC approved a report and order to voluntarily increase the maximum digital effective radiated power
Effective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...

 (ERP) to 4% of analog ERP (−14dBc
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

), up from the previous maximum of 1% (−20dBc). Individual stations may apply for up to 10% (−10dBc) if they can prove it will not cause destructive interference to any other station. If at least six verified complaints of ongoing RF interference to another station come from locations within the other station's service contour
Service contour
In US broadcasting, service contour refers to the area in which the Federal Communications Commission predicts and allows coverage....

, the interfering station will be required to reduce to the next level down of 4%, 2% (−17dB), or 1%, until the FCC makes a final determination. The station to which the interference is caused bears the burden of proof and its associated expenses, rather than the station that causes the problem. For grandfathered FM stations which are allowed to remain over the limit for their class, these numbers are relative to that lower limit rather than their actual power.

FM HD Radio versus DAB

Some countries have implemented Eureka-147 Digital Audio Broadcasting
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....

 (DAB). DAB broadcasts a single station that is approximately 1500 kilohertz wide (~1000 kilobits per second). That station is then subdivided into multiple digital streams of between 9 and 12 programs. In contrast FM HD Radio is assigned to the traditional 200 kilohertz-wide channels, with capability of 300 kbit/s in pure digital mode. Thus HD Radio is approximately twice as data-efficient as DAB.

The first generation DAB uses the MPEG-1 Audio Layer II
MPEG-1 Audio Layer II
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...

 (MP2) audio codec which has less efficient compression than newer codecs. The typical bitrate for DAB programs is only 128 kbit/s and as a result most radio stations on DAB have a lower sound quality than FM, prompting a number of complaints. The newer FM HD Radio uses a codec based upon the MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...

 HE-AAC
HE-AAC
High-Efficiency Advanced Audio Coding is a lossy data compression scheme for digital audio defined as a MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio...

 standard. Several psychoacoustic studies/tests have shown HE-AAC codecs achieve the same perceived quality as MP2, but at one-quarter the bit rate (CD quality at 64 kbit/s rather than 256 kbit/s).

A directly related issue with DAB's original inefficient compression is "downgrading" stations from stereophonic to monaural
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...

, in order to include more channels into the limited 1000 kbit/s bandwidth, smaller coverage of markets as compared to analog FM, radios that are overly expensive, poor reception inside vehicles or buildings, and a general lack of interest in DAB in many countries. HD Radio shares most of these same flaws (see criticisms below).

AM HD Radio versus DRM

Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...

 (DRM) is a system designed primarily for world band radio and AM Radio. DRM is very similar to AM HD Radio in that each station is broadcast via a channel 20 kilohertz wide (+/-10 kHz), and the radio is hand-tuned to each individual station's location on the dial. The two standards also share the same modulation scheme (COFDM) and codecs based upon MPEG-4 AAC.

Just like HD Radio which allows either hybrid digital-analog broadcasts or pure digital broadcasts, DRM allows broadcasters to use multiple options:
  • Hybrid mode (digital/analog) — 10 kHz analog plus 5 kHz digital bandwidth allows 5-16 kbit/s data rate;
  • 10 kHz digital-only bandwidth (equal to one-half of one channel) allows 12-35 kbit/s;
  • 20 kHz digital-only bandwidth (equal to one channel with both sidebands) allows 24-72 kbit/s.


Unfortunately DRM shares many of the same flaws as DAB and HD Radio technology: shorter broadcast distance as compared to analog AM signal when in hybrid mode; poor reception inside vehicles and buildings; and interference with adjacent channels (though in all-digital mode the signal fits inside the designated channel mask).

Awareness, coverage

There is low awareness among consumers, and even lower uptake. According to a survey dated August 8, 2007 by Bridge Ratings, when asked the question, "Would you buy an HD radio in the next two months?" only 1.0% responded "yes". Some broadcast engineers have also expressed distrust or dislike of the new system. Also, a survey conducted in September 2008 saw a small percentage still confused HD radio with satellite radio
Satellite radio
Satellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...

.

Most of the first-generation HD Radio tuners have been noted as being very insensitive, making reception problematic. The HD Radio signal is 10 to 20 dB below a station's analog signal. In addition it has been noted that the analog section of some tuners displays poor reception capabilities compared to older non-digital models.

Proprietary and incompatible

Even though DAB and DRM standards are open-standards and pre-date HD Radio, HD Radio receivers cannot be used to receive these stations when sold or moved overseas (with certain exceptions; there are HD Radio stations in Sri Lanka, Brazil, Thailand, Taiwan, Japan, Romania and a few other countries). DAB and DRM receivers cannot receive HD Radio signals in the US. The HD Radio 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 Radios cannot receive DAB format broadcasts of other countries and vice-versa, and that manufacturers must develop separate products for different countries, which typically are not dual-format. Whereas the AAC (Advanced Audio Coding
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....

) family of codecs are publicly documented standards, the HDC codec exists only within the HD Radio system, and is an iBiquity trade secret
Trade secret
A trade secret is a formula, practice, process, design, instrument, pattern, or compilation of information which is not generally known or reasonably ascertainable, by which a business can obtain an economic advantage over competitors or customers...

. Similarly DRM and DAB are open specifications, while iBiquity's HD Radio specification is partly open but mostly private.

HD Radio is also incompatible with ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....

, the standard for digital television in the United States
Digital television in the United States
In the United States, digital television broadcasts, or DTV, can be received via cable, via internet, via satellite, or via free over-the-air digital terrestrial television - much like analog television broadcasts have been. Full-power analog television broadcasts, however, were required by U.S....

. In the days of analog television, the low end of the FM broadcast band (87.7 to 87.9 MHz) overlapped with the audio subcarrier of analog television's channel 6, which allowed the audio of television stations that broadcast on that channel to be heard on most FM radios. 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 analog broadcasting in June 2009. Because the digital television and digital radio standards are incompatible with each other, HD radios are not able to receive digital TV signals on the 87.7 frequency, eliminating the dual-medium compatibility of channel 6 television stations.

Reduced-quality concerns

Promotion for HD Radio does not always make clear that some of its capabilities are mutually incompatible with other of its capabilities. For example, the FM system has been described as "CD quality;" however, the FM system also allows multiplexing
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...

 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
Free-to-air
Free-to-air describes television and radio services broadcast in clear form, allowing any person with the appropriate receiving equipment to receive the signal and view or listen to the content without requiring a subscription or one-off fee...

 over-the-air
Over-the-air programming
Over-the-air programming refers to various methods of distributing new software updates or configuration settings to devices like cellphones and set-top boxes...

 digital stream [must be] of equal or greater quality than the station’s existing analog signal". (If the FCC discontinues analog simulcasting, each station will have over 300 kbit/s bandwidth available, allowing for CD-quality or even surround sound
Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...

 audio together with multiple sub-channels.)

The broadcasting industry is seeking FCC approval for conditional access
Conditional access
Conditional Access is the protection of content by requiring certain criteria to be met before granting access to this content...

, that is, enabling the extra programs to be available only by paid subscription (on future models of HD Radio). Conditional access will also enable special services for the blind (such as radio reading service
Radio reading service
A radio reading service or reading service for the blind is a 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-impaired. It is most often carried on a subcarrier, with...

s) and hearing impaired. NDS
NDS Group
NDS Group Plc. is a developer of pay TV technology. NDS was established in 1988 as an Israeli start up company. It was acquired by News Corporation in 1992. The company is currently headquartered in Staines, United Kingdom...

, a maker of digital media encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...

 technology, has a deal with iBiquity to provide HD Radio with an encrypted content-delivery system called RadioGuard. NDS claims that RadioGuard will "provide additional revenue-generating possibilities".

A few existing FM tuners tuned to a channel broadcasting an HD Radio signal are prone to increased noise on the analog signal, called "HD Radio self-noise" (http://www.ham-radio.com/k6sti/hdrsn.htm), due to analog demodulation of the digital signal(s). Some rare high fidelity FM tuners in quality playback systems, cause this noise to be audible and irritating. A few, existing FM tuners, might require major internal modifications to the internal filter
Electronic filter
Electronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both...

s (http://www.ham-radio.com/k6sti/iboccer.htm) or the addition of a post-detection filter (http://www.ham-radio.com/k6sti/ibocfltr.htm) may be required to prevent degradation of the analog signal quality on stations broadcasting with HD Radio.

Reduced analog signal

Radio stations are licensed in the United States to broadcast at a specific effective radiated power
Effective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...

 level. NPR
NPR
NPR, formerly National Public Radio, is a privately and publicly funded non-profit membership media organization that serves as a national syndicator to a network of 900 public radio stations in the United States. NPR was created in 1970, following congressional passage of the Public Broadcasting...

 Labs recently did a study of predicted HD radio operation if power levels were increased to 10% of maximum power as is now allowed by the FCC under certain circumstances, and found the digital signal would increase RF interference on FM. However the boosted digital HD signal coverage would then exceed analog coverage, with 17% more population covered in vehicles but 17% less indoors.

High costs

The costs of installing the system, including fees, vary from station to station, according to the station's size and existing infrastructure. Typical costs are at least several tens of thousands of dollars at the outset (including transmitter, diplexer or antenna/feedline, and labor), plus per-channel annual fees to be paid to iBiquity. Large companies in larger media market
Media market
A media market, broadcast market, media region, designated market area , Television Market Area , or simply market is a region where the population can receive the same television and radio station offerings, and may also include other types of media including newspapers and Internet content...

s (such as Clear Channel
Clear channel
A clear-channel station is an AM band Radio station in North America that has the highest protection from interference from other stations, particularly concerning night-time skywave propagation. Usually known as class A stations since 1982, they are occasionally still referred to by their former...

 or Citadel Broadcasting
Citadel Broadcasting
Citadel Broadcasting Corporation was a Las Vegas, Nevada-based broadcast holding company. Citadel owned 243 radio stations across the United States and was the third-largest radio station owner in the country...

) can afford to implement the technology for their stations. However, community radio
Community radio
Community radio is a type of radio service, that offers a third model of radio broadcasting beyond commercial broadcasting and public broadcasting. Community stations can serve geographic communities and communities of interest...

 stations, both commercial and noncommercial, cannot. During mid 2010 a new generation of HD Radio broadcasting equipment was introduced greatly lowering the technical costs of implementing the system.

Current HD Radio receivers cost anywhere from around $50 to several hundred dollars (US), compared to regular FM radios which can even be found at dollar store
Dollar store
A variety store or price-point retailer is a retail store that sells inexpensive items, often with a single price for all items in the store...

s. By contrast, all of the R&D work for DAB
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....

 (and much of DAB+) had already been done using an existing codec, and requires no licensing fees. FMeXtra
FMeXtra
FMeXtra, now marketed as VuCast and oriented at the broadcast data market like MSN Direct, is an in-band on-channel digital radio broadcasting technology created by Digital Radio Express, now VuCast Media. Unlike iBiquity's HD Radio system, it uses any FM radio station's existing equipment and...

 is even less expensive, and requires no installation labor or cost for the broadcaster, other than plugging it into the transmitter. It also requires no FCC approval, coming under a station's subsidiary communications authority
Subsidiary Communications Authority
Subsidiary Communications Authorization in the United States, and Subsidiary Communications Multiplex Operation in Canada, is a subcarrier on a radio station, allowing the station to broadcast additional services as part of its signal.-Background:"Subsidiary Communications Authorization" is the...

. FMeXtra requires no license fees, and does not interfere with adjacent channels. Other digital broadcast technologies have not been approved for use in the United States. The number and cost of HD Radio receivers greatly dropped during 2009 and 2010.

Programming

Currently the HD Digital Radio Alliance, a consortium
Consortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....

 of major owners such as ABC, CBS, and ClearChannel, is acting as a liaison for stations to choose unduplicated formats for the extra channels (HD2, HD3, etc.). This is designed to provide additional choices for listeners instead of several stations all independently deciding to create the same format. HD1 stations broadcast the same format as the regular FM (and some AM) stations, and most of these stations offer an HD2 subchannel to complement their current programming.

Clear Channel
Clear channel
A clear-channel station is an AM band Radio station in North America that has the highest protection from interference from other stations, particularly concerning night-time skywave propagation. Usually known as class A stations since 1982, they are occasionally still referred to by their former...

 is selling programming of several different music genre
Music genre
A music genre is a categorical and typological construct that identifies musical sounds as belonging to a particular category and type of music that can be distinguished from other types of music...

s to other competing stations, in addition to airing them on its own stations. Some stations are simulcast
Simulcast
Simulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...

ing their local AM or lower-power FM broadcasts on sister stations' HD2 or HD3 channels, such as KMBZ-FM in Kansas City
Kansas City, Missouri
Kansas City, Missouri is the largest city in the U.S. state of Missouri and is the anchor city of the Kansas City Metropolitan Area, the second largest metropolitan area in Missouri. It encompasses in parts of Jackson, Clay, Cass, and Platte counties...

 simulcasting 610 KCSP
KCSP (AM)
KCSP is a sports/talk radio station located in Kansas City, Missouri. The Entercom-owned station broadcasts on 610 kHz. Beginning March 31, 2011, its programming is simulcast on KMBZ-FM's 98.1-HD2 subchannel....

's programming on 98.1-HD2. It is common practice to broadcast an older, discontinued format on HD2 channels; for example, with the recent disappearance of the smooth jazz
Smooth jazz
Smooth jazz is a genre of music that grew out of jazz fusion and is influenced by R&B, funk, rock, and pop music styles ....

 format from the analog radio dial in many markets, stations such as WDZH in Detroit, Michigan
Detroit, Michigan
Detroit is the major city among the primary cultural, financial, and transportation centers in the Metro Detroit area, a region of 5.2 million people. As the seat of Wayne County, the city of Detroit is the largest city in the U.S. state of Michigan and serves as a major port on the Detroit River...

 (formerly WVMV), WQCD
WQCD
WEMP , known on-air as FM News 101.9, is an all-news radio station located in New York City. WEMP is owned by Merlin Media LLC, and has studios located in New York's West Village neighborhood. WEMP's transmitter is located at the Empire State Building...

 in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

, WPGB
WPGB
WPGB is a conservative talk radio station based in Pittsburgh, Pennsylvania. Owned by Clear Channel Communications, the station broadcasts at 104.7 MHz with an ERP of 13 kW...

 in Pittsburgh, Pennsylvania
Pittsburgh, Pennsylvania
Pittsburgh is the second-largest city in the US Commonwealth of Pennsylvania and the county seat of Allegheny County. Regionally, it anchors the largest urban area of Appalachia and the Ohio River Valley, and nationally, it is the 22nd-largest urban area in the United States...

 and WNWV
WNWV
WNWV — branded V107.3 Cleveland — is a commercial radio station licensed to Elyria, Ohio broadcasting an adult album alternative format. The station serves the Cleveland radio market and much of surrounding Northeast Ohio, and is one of the few remaining locally-owned stations in the entire...

 in Cleveland, Ohio
Cleveland, Ohio
Cleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...

 program smooth jazz on their HD2 or HD3 bands. Other recent additions include introduction of air staff on HD2 stations, like KDWB
KDWB
KDWB-FM is an American commercial radio station broadcasting in the Twin Cities region of Minnesota, the radio format was known for over fifty years as a major contemporary hit radio Top 40 pop music outlet. Its transmitter is located in Shoreview, Minnesota. It broadcasts in 5.1 cinema-quality...

's Party Zone
Club Phusion
Club Phusion is a HD2 Dance Top 40 station, one of three Dance-formatted HD2 stations programmed by Clear Channel Communications through their Format Lab, a new division set up to expand music formats over their HD2 subcarriers...

 channel in Minneapolis-Saint Paul. Some HD2 or HD3 stations are even simulcasting sister
Sister station
In broadcasting, sister stations or sister channels are radio and/or television stations operated by the same ownership....

 AM stations. In St. Louis, Missouri for example, clear-channel KMOX AM (1120 kHz analog and HD) is simulcast on KEZK FM 102.5 HD3. KBCO
KBCO
KBCO is a AAA radio station licensed to Boulder, Colorado, United States, that serves the Denver-Boulder area. The station's format, dubbed "World Class Rock," is an eclectic variety of pop, rock, blues, reggae and folk, from the late-1960s to the present.The Clear Channel Communications outlet...

 in Boulder, Colorado
Boulder, Colorado
Boulder is the county seat and most populous city of Boulder County and the 11th most populous city in the U.S. state of Colorado. Boulder is located at the base of the foothills of the Rocky Mountains at an elevation of...

 uses its HD2 channel to broadcast exclusive live recordings from their private recording studio. CBS Radio
CBS Radio
CBS Radio, Inc., formerly known as Infinity Broadcasting Corporation, is one of the largest owners and operators of radio stations in the United States, third behind main rival Clear Channel Communications and Cumulus Media. CBS Radio owns around 130 radio stations across the country...

 recently announced plans to introduce its more popular superstation
Superstation
Superstation in United States television can have several meanings. In its most precise meaning, a superstation is defined by the Federal Communications Commission as "A television broadcast station, other than a network station, licensed by the FCC that is secondarily transmitted by a satellite...

s into distant markets (KROQ-FM
KROQ-FM
KROQ-FM — branded 106.7 KROQ — is a commercial modern rock radio station licensed to Pasadena, California serving the Greater Los Angeles. The call sign is pronounced "kay rock." It is the flagship station of Loveline hosted by Dr...

 into New York City, WFAN
WFAN
WFAN , also known as "Sports Radio 66" or "The FAN", is a radio station in New York City. The station broadcasts on a clear channel and is owned by CBS Radio...

 into Florida, and KFRG and KSCF
KSCF
KSCF, also known as Sophie @ 103.7, is a San Diego Hot AC radio station, owned and operated by CBS Radio. "Now. New. Next" is the tagline of this San Diego radio station. The station broadcasts in HD Radio. The HD2 broadcast a simulcast of sister station KROQ-FM/Los Angeles...

 into Los Angeles) via HD2 and HD3 channels.

On March 8, 2009, CBS Radio inaugurated the first station with an HD4 subchannel, WJFK-FM
WJFK-FM
WJFK-FM, known on-air as 106.7 The Fan, is a sports radio-formatted broadcast radio station licensed to Manassas, Virginia, serving the metro Washington DC area...

 in Washington, DC, a sports radio
Sports radio
Sports radio is a radio format devoted entirely to discussion and broadcasting of sporting events. A popular format with an almost exclusively male demographic in most areas, sports radio is characterized by an often-boisterous on-air style and extensive debate and analysis by both hosts and...

 station which also carries sister sports operations WJZ-FM
WJZ-FM
WJZ-FM is a radio station licensed to Catonsville, Maryland, and broadcasting from studios in suburban Towson, Maryland. The station is owned by CBS Radio.-History of the WJZ-FM callsign:...

 from Baltimore
Baltimore
Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...

, Philadelphia's WIP and WFAN from New York.

Public broadcasters
Public broadcasting
Public broadcasting includes radio, television and other electronic media outlets whose primary mission is public service. Public broadcasters receive funding from diverse sources including license fees, individual contributions, public financing and commercial financing.Public broadcasting may be...

 are also embracing HD Radio. Minnesota Public Radio
Minnesota Public Radio
Minnesota Public Radio , is the flagship National Public Radio member network for the state of Minnesota. With its three services, News & Information, Classical Music and The Current, MPR operates a 42-station regional radio network in the upper Midwest serving over 8 million people...

 offers a few services: KNOW, the MPR News station in the Twin Cities
Twin cities
Twin cities are a special case of two cities or urban centres which are founded in close geographic proximity and then grow into each other over time...

, offers music service Radio Heartland
Radio Heartland
Radio Heartland is a Web-and HD Radio- service from Minnesota Public Radio . Its playlist consists primarily of acoustic, singer-songwriter, folk and Americana music. The service launched in December 2008.-Programming:...

 on 91.1 HD2 and additional news programming called BBC News
BBC News
BBC News is the department of the British Broadcasting Corporation responsible for the gathering and broadcasting of news and current affairs. The department is the world's largest broadcast news organisation and generates about 120 hours of radio and television output each day, as well as online...

 and More on 91.1 HD3; KSJN
KSJN
KSJN is the flagship station of Minnesota Public Radio's classical music network, serving the Twin Cities region. Prior to 1991, 99.5 was known as WLOL, best known as a top-rated CHR station during the 1980s.-KSJN intellectual unit:...

, the Classical MPR station in the Twin Cities, provides Classical 24
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 service is operated 24 hours a day and is used by some...

 service on 99.5 HD2; and The Current
KCMP
-WCAL:The station began with physics experiments in 1918 when five students and a professor built a small radio transmitter at St. Olaf College. Using a wire antenna strung between the campus chapel and the college's "Old Main" , signals from these experiments were picked up as far away as New...

, on 89.3 in the Twin Cities, offers Wonderground Radio, music for kids and their parents, on 89.3 HD2.

Southern California Public Radio, heard on 89.3 FM in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

, offers Ahora, the Spanish-language service of Radio Netherlands
Radio Netherlands
Radio Netherlands Worldwide is a public radio and television network based in Hilversum, producing and transmitting programmes for international audiences outside the Netherlands...

 on 89.3 HD2 and MPR's music service The Current
KCMP
-WCAL:The station began with physics experiments in 1918 when five students and a professor built a small radio transmitter at St. Olaf College. Using a wire antenna strung between the campus chapel and the college's "Old Main" , signals from these experiments were picked up as far away as New...

 on 89.3 HD3 in Los Angeles.

WNYC
WNYC
WNYC is a set of call letters shared by a pair of co-owned, non-profit, public radio stations located in New York City.WNYC broadcasts on the AM band at 820 kHz, and WNYC-FM is at 93.9 MHz. Both stations are members of National Public Radio and carry distinct, but similar news/talk programs...

 in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 broadcasts a locally programmed, all-classical music
Classical music
Classical music is the art music produced in, or rooted in, the traditions of Western liturgical and secular music, encompassing a broad period from roughly the 11th century to present times...

 service called Q2
WQXR-FM
WQXR-FM is an American classical radio station licensed to Newark, New Jersey, and serving the New York City metropolitan area. It is the most-listened-to classical-music station in the United States, with an average quarter-hour audience of 63,000...

, on 93.9 HD2. The service launched in March 2006. On October 8, 2009, the format was moved to WQXR-HD2 on 105.9 when WQXR was acquired by WNYC as part of a frequency swap with Univision Radio
Univision Radio
Univision Radio is the radio division of media giant Univision Communications, Inc., which also ownsthe Univision television network. The company was formerly known as Hispanic Broadcasting Corporation. It is the eighth largest radio company in the United States, and the largest Hispanic radio...

 for their former frequency. The programming on the WNYC HD2 channel now is a rebroadcast of WQXR in order to give full coverage of WQXR programming in some form, as the 105.9 signal is weaker and does not cover the whole area.

WMIL-FM
WMIL-FM
WMIL-FM is a country music-formatted radio station in Milwaukee, Wisconsin, licensed to Waukesha, Wisconsin. They are known on-air simply as "FM 106.1". WMIL is owned by Clear Channel Communications....

 in Milwaukee has offered an audio simulcast of Fox
Fox Broadcasting Company
Fox Broadcasting Company, commonly referred to as Fox Network or simply Fox , is an American commercial broadcasting television network owned by Fox Entertainment Group, part of Rupert Murdoch's News Corporation. Launched on October 9, 1986, Fox was the highest-rated broadcast network in the...

 affiliate WITI on their HD3 subchannel since August 2009 as part of a news and weather content agreement between Clear Channel and WITI. This restored WITI's audio to the Milwaukee radio dial after a two month break after the digital transition; as a Channel 6 analog television station
Television station
A television station is a business, organisation or other such as an amateur television operator that transmits content over terrestrial television. A television transmission can be by analog television signals or, more recently, by digital television. Broadcast television systems standards are...

 WITI exploited the 87.7 FM audio quirk as an advantage in order to allow viewers to hear the station's newscasts and Fox programming on their car radios.

College radio has also been impacted by HD radio, stations such as WBJB which is a public station on a college campus offer a student run station as one of the multicast channels.

Some commercial broadcasters also use their HD2's to broadcast the programming of noncommercial broadcasters. Bonneville International
Bonneville International
Bonneville International Corporation is a broadcasting company wholly owned by The Church of Jesus Christ of Latter-day Saints through its for-profit arm, Deseret Management Corporation...

 uses its HD2 and HD3 channels to broadcast Mormon Channel
Mormon Channel
Mormon Channel is an over the air and Internet radio station owned and operated by The Church of Jesus Christ of Latter-day Saints . It is based in Salt Lake City, Utah....

 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 HD2 and HD3 stations was launched on May 18, 2009 and was fully functional within two weeks. Also, in Detroit, WMXD
WMXD
WMXD is a Clear Channel-owned Urban AC FM radio station in Detroit, Michigan, United States, that broadcasts on the frequency of 92.3 MHz. WMXD, which bills itself as "Today's R&B and the Best Old School Jamz," is consistently a very highly rated station in Detroit's Arbitron ratings reports,...

, an urban adult contemporary
Urban Adult Contemporary
Urban adult contemporary is the name for a format of radio music, similar to an urban contemporary format. Radio stations using this format usually would not have rap music on their playlists. The format was designed by Barry Mayo when he, Lee S. Simonson and Bill Pearson organized Broadcast...

 station, airs the contemporary Christian K-Love
K-LOVE
K-LOVE is a Contemporary Christian music radio programming service in the United States operated by the Educational Media Foundation. As of January 2011, K-LOVE's programming is carried on over 440 FM stations and translators in 45 states. K-LOVE claims an audience of 250,000 people each week via...

 format on its HD2 band (the HD2 also feeds several analog translators around the metropolitan area—see below), due to an agreement between Clear Channel and K-Love owner Educational Media Foundation
Educational Media Foundation
Educational Media Foundation is a not-for-profit organization that operates the K-LOVE and Air 1 radio networks. EMF is based in Rocklin, California....

 allowing EMF to program WMXD's HD2.

Translators

Although broadcast translators are prohibited from originating their own programming, the FCC has controversially allowed translator stations to rebroadcast
Simulcast
Simulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...

 in standard analog FM the audio of a HD Radio channel of the primary station the translator is assigned to (see, for instance, W237CS
W237CS
The HD Radio digital subchannel of radio station WXMT is currently used as an experimental station airing spoken-word programming. The station, based in Smethport, Pennsylvania, is owned by Jeff Androlunis's Colonial Radio Group, making it a sister station to WXMT, WBYB and WVTT...

, which is licensed as a translator to WXMT but originates its own schedule). This also allows station owners, who already usually own multiple stations locally and nationally, to avoid the rulemaking
Rulemaking
In administrative law, rulemaking refers to 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 detailed regulations through rulemaking.By bringing...

 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
Concentration of media ownership
Concentration of media ownership refers to a process whereby progressively fewer individuals or organizations control increasing shares of the mass media...

. 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 (via less restrictive height and power limitations) than locally-originated
Community radio
Community radio is a type of radio service, that offers a third model of radio broadcasting beyond commercial broadcasting and public broadcasting. Community stations can serve geographic communities and communities of interest...

 LPFMs, 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 Radio-only secondary 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 at K202BD in Manti, Utah
Manti, Utah
-Demographics:As of the census of 2000, there were 3,040 people, 930 households, and 742 families residing in the city. The population density was 1,560.2 people per square mile . There were 1,010 housing units at an average density of 518.3 per square mile...

, which rebroadcasts both the analog and digital signals of KUER 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 heterodyning
Heterodyne
Heterodyning is a radio signal processing technique invented in 1901 by Canadian inventor-engineer Reginald Fessenden where high frequency signals are converted to lower frequencies by combining two frequencies. Heterodyning is useful for frequency shifting information of interest into a useful...

 it through the use of an intermediate frequency
Intermediate frequency
In communications and electronic engineering, an intermediate frequency is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called...

. This may require an increase in bandwidth in both the amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...

 and radio antenna if they are too narrowband
Narrowband
In radio, narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. It is a common misconception that narrowband refers to a channel which occupies only a "small" amount of space on the radio spectrum.The opposite of...

 to pass the wider signal, meaning one or both would have to be replaced. Baseband
Baseband
In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...

 translators which use a separate receiver and transmitter require an HD Radio transmitter, just as does the main station. Translators are not required to pass through HD Radio, and the vast majority of existing translators which repeat FM stations running hybrid HD Radio signals do not repeat the HD Radio part of the broadcast due to technical limitations in equipment designed before the prominence of HD Radio.

Automotive and home/professional

There are as many as 100 different HD Radio receivers to choose from, far more than are available to receive any other digital radio signal. Receivers are becoming less expensive, starting at around US$
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....

50. Manufacturers have initially focused on making car stereos. In 2008, Ford Motor Company
Ford Motor Company
Ford Motor Company is an American multinational automaker based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...

 became the first U.S. automaker to feature HD Radio tuners in its vehicles; starting with the 2009 model year, Ford began offering HD Radio tuners as a factory-installed option (Compatible with SYNC
Ford Sync
Ford SYNC is a factory-installed, integrated in-vehicle communications and entertainment system that allows users to make hands-free telephone calls and control music and other functions using voice commands...

), and was upgraded to standard on all of its brands for the 2011 model year. BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

 offers Factory-Installed HD Radio on nearly all 2008+ models. Hyundai
Hyundai
Hyundai ) is a global conglomerate company, part of the Korean chaebol, that was founded in South Korea by one of the most famous businessmen in Korean history: Chung Ju-yung...

 offers factory-installed HD Radio on the Genesis 2008+ model year. Mercedes-Benz
Mercedes-Benz
Mercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG...

 offers factory-installed HD Radio on the R320, ML320 and GL320 models (2009 model year). MINI
Mini
The Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...

 offers factory-installed HD Radio on the Cooper, Cooper S (2008+ model year). Scion offers HD Radio on select audio systems. Volvo
Volvo
AB Volvo is a Swedish builder of commercial vehicles, including trucks, buses and construction equipment. Volvo also supplies marine and industrial drive systems, aerospace components and financial services...

 offers factory-installed HD Radio on the S40 T5, V50 T5, C30, C70, S80, V70, XC60, XC70 and XC90 models (2009 model year).

The growing list of HD Radio automotive receiver manufacturers includes Alpine Electronics
Alpine Electronics
is traditionally known as an aftermarket car audio and navigation systems manufacturer, famed for their high quality, premium in-car audio units commonly known as headunits. It is a subsidiary of Alps Electric Co. and its registered head office is in Tokyo, Japan. However its main offices, or the...

, Clarion
Clarion (car audio)
is a Japanese manufacturer of car audio, automotive navigation systems, AutoPCs, visual equipment, bus equipment, and communication equipment.Up until the end of 2005, products in Japan were marketed under the brand name AddZest, while outside of Japan the same product typically carried the Clarion...

, Delphi Corporation, Directed Electronics, Dual
Dual (brand)
Dual is a brand name of audio and video electronics.-History:In 1927, Gebrüder Steidinger, a German gramophone power supply manufacturer, adopted the name Dual in reference to the dual-mode power supplies it pioneered. The power supplies allowed gramophones to be powered from mains electricity or...

, Insignia
Insignia
Insignia or insigne pl -nia or -nias : a symbol or token of personal power, status or office, or of an official body of government or jurisdiction...

, Jensen
Jensen Loudspeakers
Jensen Loudspeakers is a company that manufactures speakers in many different models and sizes, originally located in Chicago, IL. They built a reputation during the 50's and 60's providing speakers used mainly in guitar and bass amplifiers. Though the American company is long gone, "reissue"...

, JVC
JVC
, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...

, Kenwood
Kenwood Electronics
is a Japanese manufacturer of amateur radio as well as Hi-Fidelity and portable audio equipment.-History:The company first started in 1946 as the Kasuga Radio Co. Ltd. In Komagane City, Nagano Prefecture, Japan. In 1960 the firm was renamed "Trio Corporation"...

, Pioneer, Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

 and Visteon
Visteon
Visteon is one of the world's largest suppliers of automotive parts. The company formed in 1997 and spun off from the Ford Motor Company in 2000. In 2005, Visteon moved to new headquarters in Van Buren Township, Michigan...

.

Home and office listening equipment is currently available from many companies, in both component tuner and tabletop models, including Audio Design Associates, Boston Acoustics
Boston Acoustics
Founded in 1979 by Advent veterans Andy Kotsatos and Frank Reed, Boston Acoustics is a manufacturer of home and mobile audio equipment operated out of Peabody, Massachusetts. Boston Acoustics entered the mobile audio category in 1983...

, DaySequerra, Denon
Denon
is a Japanese electronics company that was involved in the early stages of development of digital audio technology, while specializing in the manufacture of high-fidelity professional and consumer audio equipment. For many decades, Denon was a brand name of Nippon-Columbia, including the Nippon...

, DICE Electronics, Directed Electronics, Insignia
Insignia
Insignia or insigne pl -nia or -nias : a symbol or token of personal power, status or office, or of an official body of government or jurisdiction...

, Jensen Electronics
Jensen Electronics
Jensen Is a consumer electronics brand with a history that dates back to 1915 with Peter Jensen's invention of the first loudspeaker. Over the years the Jensen family of brands has grown to include Jensen, Advent, Acoustic Research , Phase Linear and NHT Loudspeakers in the United States and...

, LG
LG
LG may refer to:*LG Corp., a South Korean electronics and petrochemicals conglomerate*LG Electronics, an affiliate of the South Korean LG Group which produces electronic products* Lawrence Graham, a London headquartered firm of business lawyers...

, Marantz
Marantz
Marantz is a company that develops and sells upper-mid range to high-end audio products.The first Marantz audio product was designed and built by Saul B. Marantz in his home in Kew Gardens, New York...

, Onkyo
Onkyo
is a Japanese consumer electronics manufacturer, specializing in home cinema and audio equipment including receivers and surround sound speakers. The word Onkyo translates as "sound harmony".The company started under the name of Osaka Denki Onkyo K.K in 1946...

, Polk Audio
Polk Audio
Polk Audio is a manufacturer of audio products best known for their home and automobile speakers. The company also produces a wide range of other audio products such as amplifiers and FM tuners. The company is headquartered in Baltimore, Maryland and in 2006, was acquired by Directed...

, Radiosophy, Radio Shack
Radio shack
Radio shack is a slang term for a room or structure for housing radio equipment.-History:In the early days of radio, equipment was experimental and home-built. The first radio transmitters used a noisy spark to generate radio waves and were often housed in a garage or shed. When radio was first...

, Rotel
Rotel
Rotel is a Japanese manufacturer of high end audio and video equipment: home theater, amplifiers, compact disc players, etc. The company was established in 1966. The company was formed by the "elder" Tachikowa and currently run by the son, Bob Tachikowa...

, Sangean
Sangean
Sangean is a globally active Taiwanese electronics company specialised in radios. The company was founded in 1974 and has built its worldwide reputation especially on shortwave radios and recently also made a name for itself with digital receivers...

, Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

, TEAC, Visteon
Visteon
Visteon is one of the world's largest suppliers of automotive parts. The company formed in 1997 and spun off from the Ford Motor Company in 2000. In 2005, Visteon moved to new headquarters in Van Buren Township, Michigan...

 and Yamaha
Yamaha
Yamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...

.

Portable

Previously, portable HD Radio receivers were unavailable due to the early chipsets either being too large for a portable enclosure 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 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 Radio receivers: Samsung and SiPort.

The portable Coby HDR-700 unit receives AM HD and FM HD stations. Griffin Technology
Griffin Technology
Griffin Technology is a privately held U.S. company founded in Nashville, Tennessee in 1992 by Paul Griffin. The company designs and manufactures computer peripherals, consumer electronics, and accessories, the first products being primarily video adapters, in particular those to enable the...

 produces an HD Radio tuner designed to be plugged into the dock connector of an Apple iPod
IPod
iPod is a line of portable media players created and marketed by Apple Inc. The product line-up currently consists of the hard drive-based iPod Classic, the touchscreen iPod Touch, the compact iPod Nano, and the ultra-compact iPod Shuffle...

 or iPhone
IPhone
The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...

, with tuning functionality provided via software through the device's multi-touch
Multi-touch
In computing, multi-touch refers to a touch sensing surface's ability to recognize the presence of two or more points of contact with the surface...

 display.

On July 12, 2009, Best Buy
Best Buy
Best Buy Co., Inc. is an American specialty retailer of consumer electronics in the United States, accounting for 19% of the market. It also operates in Mexico, Canada & China. The company's subsidiaries include Geek Squad, CinemaNow, Magnolia Audio Video, Pacific Sales, and, in Canada operates...

 started selling a house brand portable unit, the Insignia NS-HD01, which was the second portable HD Radio to come to the general market and features FM-only playback and a non-removable rechargeable battery which charges via mini USB. Coby produced the first portable HD radio (HDR-700). The Insignia unit sells for around $50 and is the least expensive receiver currently available.

On September 15, 2009, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 released the Zune HD
Zune HD
The Zune HD is a portable media player in the Zune product family released on September 15, 2009 by Microsoft. It is a direct competitor with the Apple iPod and iPhone series of mobile devices. It was initially released in 16 and 32 GB capacities. A 64 GB version was released on April 9, 2010...

, which includes an HD Radio receiver within the media device.

The radio industry is trying to get HDR chipsets into mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

s by 2012.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK