HD Radio
HD Radio (HDR)
The term "on channel" is a misnomer because the system actually broadcasts on the ordinarily unused channels adjacent to an existing
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
History
HD Radio is one of several digital radio standards which are generally incompatible with each other:
- FMeXtra was a competing U.S. standard, but has been stagnant since the 2010s.
- Compatible AM Digital (CAM‑D) for AM stations.
- a.k.a.Eureka 147, is the most common standard in Europe.
- shortwaveradio.
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.[6] This compares with more than 2,200 services operating with the DAB system.
A 400
The FCC has not indicated any intent to end analog radio broadcasting as it did with analog television,[2] since it would not result in the recovery of any radio spectrum rights which could be sold. Thus, there is no deadline by which consumers must buy an HD receiver.
Technique
Digital information is
HD 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.[10] The cost of converting a radio station can run between $100,000 and $200,000.[11] Receiver manufacturers who include HD Radio pay a royalty, which is the main reason it failed to be fully-adopted as a standard feature.[12]
If the HD receiver loses the primary digital signal (HD‑1), it reverts to the analog signal, thereby providing seamless operation between the newer and older transmission methods. The extra HD‑2 and HD‑3 streams do not have an analog simulcast; consequently, their sound will drop-out or "skip" when digital reception degrades (similar to digital television drop-outs). Alternatively the HD signal can revert to a more robust 20
iBiquity Digital claims that the system approaches CD quality audio and offers reduction of both interference and static.[13] 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 stations. (see § AM, below).
AM
The AM hybrid mode ("MA1") uses 30
The capacity of a 30
The digital radio signal received on a conventional
All-digital AM
All-digital AM ("MA3") allows for two modes: "Enhanced" and "core-only".[17]
- In enhanced mode, the primary, secondary and tertiary carriers are transmitted, allowing for a maximum throughput of 40.2 . 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 kHzof 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.[18] 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 have operated as all-digital / digital-only broadcasters:
- FCC since July 2018 to broadcast all-digital.[19]
- WMGG (since January 2021), WFAS (since May 2021) and WSRO (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.[20] However, WMGG subsequently dropped MA3 and WSRO left the air.[21]
- "The [experimental] record does not establish that an audio stream on an [AM] HD-2 subchannel is currently technically feasible".[23]
The FCC requires stations that wish to multiplex their digital AM signals to request and receive permission to do so;[23] in early 2020 it rejected a multiplex request from WTLC.[24]
FM
The
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
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
Although the signals may be synchronized at the transmitter and reach the receiving equipment simultaneously, what the listener hears through an HD unit and an analog radio played together can be distinctly unsynchronized. This is because all analog receivers process analog signals faster than digital radios can process digital signals. The digital processing of analog signals in an HD Radio also delays them. The resulting unmistakable "reverb" or echo effect from playing digital and analog radios in the same room or house, tuned to the same station, can be annoying. It is more noticeable with simple voice transmission than with complex musical program content.[b]
Stations can transmit HD through their existing antennas using a
Artist Experience
HD Radio supports a service called "Artist Experience"[26] 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 certification, which includes displaying the artwork properly.
EAS alerts
Since 2016, newer HD Radios support
Bandwidth and power
In (regular) hybrid mode a station has ±130
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
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.
On 29 January 2010, the U.S. FCC approved a
Comparison to other digital radio standards
HD versus DAB
Some countries have implemented
The first generation
Before DAB+ was introduced, DAB's inefficient compression led in some cases to "downgrading" stations from
Digital radio, such as DAB, DAB+, and HD FM 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, other than HD Radio, digital broadcast technologies, such as DAB+, have not been approved for use on either the VHF band II (FM) or medium wave band.
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
Similar to HD AM, DRM allows either hybrid digital-analog broadcasts or pure digital broadcasts, DRM allows broadcasters to use multiple options:
- Hybrid mode (digital/analog) - 10 kHz analog plus 5 kHz digital bandwidth allows 5–16 kbit/sdata rate;
- 10 kHz digital-only bandwidth confined to ±5 kHz of the channel center allows 12–35 kbit/s;
- 20 kHz digital-only bandwidth using ±10 kHz (including half of the adjacent channels) allows 24–72 kbit/s.
On the medium wave, actual DRM bit rates vary depending on day versus night transmission (
Although DRM 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 channel mask.
Digital Radio Mondiale is an
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".[43]
Some
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.[46]
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.[47] 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.[48]
Different format and compatibility standards
Even though DAB and DRM standards are open standards and predate HD Radio, HD receivers cannot be used to receive these stations when sold or moved overseas (with certain exceptions; there are HD stations in Sri Lanka,[49][needs update] Thailand, Taiwan, Japan, Romania, and a few other countries).
DAB and DRM receivers cannot receive HD signals in the U.S. The HD system, which enables AM and FM stations to upgrade to digital without changing frequencies, is a different digital broadcasting standard. The lack of a common standard means that HD receivers cannot receive DAB or DRM broadcasts from other countries, and vice versa, and that manufacturers must develop separate products for different countries, which typically are not dual-format.
Whereas the Advanced Audio Coding (AAC) family of codecs are publicly documented standards, the HDC codec exists only within the HD system, and is an iBiquity trade secret.
Similarly DAB or DRM are open specifications, while iBiquity's HD specification is partly open, but mostly private.[clarification needed][50]
HD Radio does not use
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 over-the-air digital stream [must be] of equal or greater quality than the station's existing analog signal".[51]
If the FCC disallows analog simulcasting, each station will have over 300
The broadcasting industry is seeking FCC approval on future HD receiver models, for
Mostly all existing FM receivers tuned to a channel broadcasting a HD signal are prone to increased noise on the analog signal, called "HD Radio self-noise", due to analog demodulation of the digital signal(s). In some high fidelity FM receivers in quality playback systems, this noise can be audible and irritating. Most all existing FM receivers will require modifications to the internal filters or the addition of a post-detection filter to prevent degradation of the analog signal quality on stations broadcasting HD Radio.
Reduced analog signal
Radio stations are licensed in the United States to broadcast at a specific
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
HD Radio receivers cost anywhere from around
Power consumption
This section appears to contradict itself.(March 2023) |
Conventional analog-only FM transmitters 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%.[g] Digital transmitters operate in one of the other amplifier classes – one that is close to linear, and linearity lowers the efficiency. A modern hybrid HD FM transmitter typically achieves 50~60% efficiency, whereas an HD digital-only FM transmitter should manage just 40~45%. The reduced efficiency causes significantly increased costs for electricity and for cooling.
Programming
Until 2013, the HD Digital Radio Alliance,[h] acted as a liaison for stations to choose unduplicated formats for the extra channels (HD‑2, HD‑3, etc.). Now, iBiquity works with the major owners of the stations to provide various additional choices for listeners, instead of having several stations independently deciding to create the same format. HD‑1 stations broadcast the same format as the 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.
On 8 March 2009, CBS Radio inaugurated the first station with an HD4 subchannel, WJFK-FM in Washington, D.C., a sports radio station which also carries sister sports operations WJZ-FM from Baltimore; Philadelphia's WTEL‑AM and WIP-FM; and WFAN‑AM from New York.[i][54] 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.[55]
WMIL-FM in Milwaukee has offered an audio simulcast of Fox affiliate WITI‑TV on their HD‑3 subchannel since August 2009 as part of a news and weather content agreement between iHeartRadio and WITI‑TV. This restored WITI‑TV's audio to the Milwaukee radio dial after a two-month break, following the digital transition; as a channel 6 analog television station WITI‑TV exploited the 87.7 FM audio quirk as an advantage, in order to allow viewers to hear the station's newscasts and Fox programming on their car radios.
College radio has also been impacted by HD Radio, stations such as WBJB-FM which is a public station on a college campus offer a student run station as one of the multicast channels. WKNC-FM in Raleigh, NC, runs college radio programming on HD‑1 and HD‑2, and electronic dance music on WolfBytes Radio on WKNC-FM‑HD3.
Some commercial broadcasters also use their HD‑2 channels to broadcast the programming of noncommercial broadcasters.
In July 2018, as part of a projected one year experiment, WWFD‑AM in Frederick, Maryland, became the first AM station to eliminate its analog transmissions and broadcast exclusively in digital.[59]
Translators
Although
In addition to the controversial practice of converting the HD-only secondary radio channels of a primary station into analog FM in areas where the primary station's signal can already readily be received, translators can also be used in a more traditional manner to extend the range of the full content of the primary station, including the unmodified main signal and any HD Radio sub-channels, in areas where the station has poor coverage or reception, as is done via the remote transmitter K202BD in Manti, Utah, 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 "
Receivers
Automotive and home/professional
By 2012, there were several HD receivers available on the market. A basic model costs around US$50.
Automotive HD receiver manufacturers include:
- Alpine Electronics
- Clarion
- Delphi Corporation
- Directed Electronics
- Dual
- Harman
- Hirschmann Car Communication[j]
- Insignia
- Jensen
- JVC
- Kenwood
- Pioneer
- Sony (discontinued)
- Visteon
Most car manufacturers offer HD receivers as audio packages in new cars, including:
Home and office listening equipment is available from a number of companies in both component receiver and tabletop models, including:
- Audio Design Associates
- Boston Acoustics (discontinued)
- DaySequerra
- Denon
- DICE Electronics
- Directed Electronics
- Insignia
- Jensen Electronics
- LG (discontinued)
- Marantz
- McIntosh
- Onkyo
- Polk Audio
- Radiosophy (discontinued)
- Radio Shack(discontinued)
- Rotel
- Sangean
- Sony (discontinued)
- TEAC
- Visteon
- Yamaha
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 unveiled a prototype of a new portable receiver, roughly the size of a cigarette pack. Two companies made low-power chipsets for HD receivers:
At least five companies made portable HD receivers:
- Coby Electronics Corporation produced the first HD portable – the Coby HDR‑700 portable HD receiver for both AM and FM.[64]
- Griffin Technology produced an HD receiver designed to plug into the dock connector of an Apple iPod, or iPhone, with tuning functionality provided via software through the device's multi-touch display. This product was discontinued.
- discontinued the NS‑HD01 model by September 2019 in favor of the NS-HD02.
- Microsoft released the Zune HD on 15 September 2009. It included an HD receiver embedded in the media device.[66] The Zune HD was discontinued in November 2011 in favor of Windows Phones.
- Sangean Electronics produces multiple portable HD radios with AM and FM reception, like the Sangean HDR-14 portable receiver.
By 2012, iBiquity was trying to get HDR chipsets into mobile phones.
Footnotes
- ^ Station identification is sent by voice, or as RBDS data, but not all stations transmit RBDS.
- ^ Note that the "reverb" effect is limited to analog vs. digital receivers, or in rare cases, digital receivers with remarkably different circuitry. Multiple receivers that are all HD (of the same make and model, at least), or multiple receivers that are all analog, in the same room or house, will not produce a noticeable echo.
- ^
Holm (2007)[37] The sound quality in DAB digital radio, SUMMARY (in English):
This analysis of the audio quality of DAB has been made independently of the broadcasting companies and aims at balancing their information. Through measurement of the audio signal and through informal listening, we have found that DAB suffers from several problems:
- The stereo image is smeared due to heavy use of joint stereo coding. Often the stereo image lacks focus and gives incorrect localization of instruments, in certain cases there is also incorrect balance between a vocalist and the background music.
- The treble cut-off frequency is usually as low as 14 kHz and the result is a lack of brightness and a veiled sound stage. In particular young people will notice this degradation.
- Three stations use 160 kbit/s with an audio quality similar to FM: P2, Alltid Klassisk1 and P4
- Twelve stations use 128 kbit/s with lower quality than FM, incl. P1 and P3.
- Two stations transmit in mono at rates of 80 and 96 kbit/s (Radio 2 Digital Moox and NRK Barn2)
The broadcast companies want us to make a choice between FM, with the best audio quality in stationary receivers, and DAB which is best in a car. Today this is an unnecessary choice as there are no technological problems in making a digital radio which is better than FM on all accounts:
- Reception without garbling in cars
- Capacity for all the stations one wants
- Audio with near-CD quality
- — Steve Holm (2007)[37]
- ^
Former U.S. analog TV channel 6 occupied the upper end of the lower MHz.
- ^
NDS Group is a maker of digital media encryptiontechnology.
- ^ a b
HF Radio startup costs include transmitter, diplexer (or a new, separate feedline), and installation labor.
- ^
"electrical power it consumes. Efficiencies differ by amplifier class, ranging over all classes from 25% at the worst-of-the-worst, to 90% at the best-of-the-best.
- ^
The Clear Channel Communications).
- ^
Note however, that at some point, the Dallas, Texas, sister sports station KRLD-FM.
- ^ Hirschmann Car Communication GmbH is now a subsidiary of TE Connectivity.
- ^ SiPort is a Santa Clara, CA, startup acquired by Intel in 2011.[63]
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External links
- "HD Radio". HD Digital Radio (hdradio.com) (official site).
- "IBOC digital radio broadcasting for AM and FM radio broadcast stations". U.S. Federal Communications Commission. Archived from the original on 30 September 2007. — IBOC general information page
- "NRSC standards" (main page). — Site with standards documents for the NRSC formats of HD Radio
- "Canadian HD Radio stations". My HD Radio. Archived from the original on 24 April 2018. Retrieved 22 September 2017.
- "WOR transmitter tour". hawkins.pair.com. — information on an early IBOC installation
- Ramsey, Mark (16 May 2005). "The premature death of HD Radio". Hear 2.0. Mercury Radio Research. Archived from the original on 3 May 2007. — editorial discusses marketing challenges for HD Radio
- Dingus, Doug (11 March 2005). HD Radio, analog FM, MP3 and OGG audio samples. Open Geek (opengeek.blogspot.com) (MP3 and OGG audio clips). — audio samples of actual HD broadcasts