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FM broadcasting
FM broadcasting
is a method of radio broadcasting using frequency modulation (FM) technology. Invented in 1933 by American engineer Edwin Armstrong, it is used worldwide to provide high-fidelity sound over broadcast radio. FM broadcasting
FM broadcasting
is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. FM radio stations use the VHF
VHF
frequencies. The term "FM band" describes the frequency band in a given country which is dedicated to FM broadcasting.

Contents

1 Broadcast bands 2 Modulation
Modulation
characteristics

2.1 Modulation 2.2 Pre-emphasis and de-emphasis 2.3 Stereo
Stereo
FM 2.4 Quadraphonic
Quadraphonic
FM 2.5 Noise
Noise
reduction 2.6 Other subcarrier services

3 Reception distance 4 Adoption of FM broadcasting

4.1 United States 4.2 Europe

4.2.1 United Kingdom 4.2.2 Italy 4.2.3 Greece

4.3 Australia 4.4 New Zealand 4.5 Trinidad and Tobago 4.6 Turkey 4.7 Other countries 4.8 ITU
ITU
Conferences about FM

5 FM broadcasting
FM broadcasting
switch-off 6 Small-scale use of the FM broadcast band

6.1 Consumer use of FM transmitters 6.2 Microbroadcasting 6.3 Clandestine use of FM transmitters

7 See also

7.1 FM broadcasting
FM broadcasting
by country 7.2 FM broadcasting
FM broadcasting
(technical) 7.3 Lists 7.4 History

8 References 9 External links

Broadcast bands[edit] Main article: FM broadcast band Throughout the world, the FM broadcast band
FM broadcast band
falls within the VHF
VHF
part of the radio spectrum. Usually 87.5 to 108.0 MHz is used,[1] or some portion thereof, with few exceptions:

In the former Soviet republics, and some former Eastern Bloc countries, the older 65.8–74 MHz band is also used. Assigned frequencies are at intervals of 30 kHz. This band, sometimes referred to as the OIRT
OIRT
band, is slowly being phased out in many countries. In those countries the 87.5–108.0 MHz band is referred to as the CCIR band. In Japan, the band 76–95 MHz is used.

The frequency of an FM broadcast station (more strictly its assigned nominal center frequency) is usually an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, only odd multiples are used. In some parts of Europe, Greenland
Greenland
and Africa, only even multiples are used. In the UK odd or even are used. In Italy, multiples of 50 kHz are used. There are other unusual and obsolete FM broadcasting
FM broadcasting
standards in some countries, including 1, 10, 30, 74, 500, and 300 kHz. However, to minimise inter-channel interference, stations operating from the same or geographically close transmitter sites tend to keep to at least a 500 kHz frequency separation even when closer frequency spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters, as potentially interfering signals are already more attenuated and so have less effect on neighboring frequencies. Modulation
Modulation
characteristics[edit]

FM has better rejection of static (RFI) than AM. This was shown in a dramatic demonstration by General Electric
General Electric
at its New York lab in 1940. The radio had both AM and FM receivers. With a million-volt arc as a source of interference behind it, the AM receiver produced only a roar of static, while the FM receiver clearly reproduced a music program from Armstrong's experimental FM transmitter in New Jersey.

Crossed dipole antenna of station KENZ's 94.9 MHz, 48 kW transmitter on Lake Mountain, Utah. It radiates circularly polarized radio waves.

Modulation[edit] Frequency
Frequency
modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave; the older amplitude modulation or AM varies the amplitude of the carrier, with its frequency remaining constant. With FM, frequency deviation from the assigned carrier frequency at any instant is directly proportional to the amplitude of the input signal, determining the instantaneous frequency of the transmitted signal. Because transmitted FM signals use more bandwidth than AM signals, this form of modulation is commonly used with the higher ( VHF
VHF
or UHF) frequencies used by TV, the FM broadcast band, and land mobile radio systems.

Armstrong's first prototype FM broadcast transmitter, located in the Empire State Building, New York City, which he used for secret tests of his system between 1934 and 1935. Licensed as experimental station W2XDG, it transmitted on 41 MHz at a power of 2 kW

Pre-emphasis and de-emphasis[edit] Random noise has a triangular spectral distribution in an FM system, with the effect that noise occurs predominantly at the highest audio frequencies within the baseband. This can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver. Reducing the high audio frequencies in the receiver also reduces the high-frequency noise. These processes of boosting and then reducing certain frequencies are known as pre-emphasis and de-emphasis, respectively. The amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used. In the Americas and South Korea, 75 µs is used. This applies to both mono and stereo transmissions. For stereo, pre-emphasis is applied to the left and right channels before multiplexing. The amount of pre-emphasis that can be applied is limited by the fact that many forms of contemporary music contain more high-frequency energy than the musical styles which prevailed at the birth of FM broadcasting. They cannot be pre-emphasized as much because it would cause excessive deviation of the FM carrier. Systems more modern than FM broadcasting
FM broadcasting
tend to use either programme-dependent variable pre-emphasis; e.g., dbx in the BTSC TV sound system, or none at all. Stereo
Stereo
FM[edit] Long before FM stereo
FM stereo
transmission was considered, FM multiplexing of other types of audio level information was experimented with.[2] Edwin Armstrong who invented FM was the first to experiment with multiplexing, at his experimental 41 MHz station W2XDG located on the 85th floor of the Empire State Building
Empire State Building
in New York City. These FM multiplex transmissions started in November 1934 and consisted of the main channel audio program and three subcarriers: a fax program, a synchronizing signal for the fax program and a telegraph “order” channel. These original FM multiplex subcarriers were amplitude modulated. Two musical programs, consisting of both the Red and Blue Network program feeds of the NBC Radio
Radio
Network, were simultaneously transmitted using the same system of subcarrier modulation as part of a studio-to-transmitter link system. In April 1935, the AM subcarriers were replaced by FM subcarriers, with much improved results. The first FM subcarrier transmissions emanating from Major Armstrong’s experimental station KE2XCC at Alpine, New Jersey occurred in 1948. These transmissions consisted of two-channel audio programs, binaural audio programs and a fax program. The original subcarrier frequency used at KE2XCC was 27.5 kHz. The IF bandwidth was ±5 kHz, as the only goal at the time was to relay AM radio-quality audio. This transmission system notably used a 75 µs audio pre-emphasis, a technical innovation that became part of the original FM Stereo
Stereo
Multiplex Standard. In the late 1950s, several systems to add stereo to FM radio were considered by the FCC. Included were systems from 14 proponents including Crosby, Halstead, Electrical and Musical Industries, Ltd (EMI), Zenith, and General Electric. The individual systems were evaluated for their strengths and weaknesses during field tests in Uniontown, Pennsylvania
Uniontown, Pennsylvania
using KDKA-FM in Pittsburgh as the originating station. The Crosby system was rejected by the FCC because it was incompatible with existing subsidiary communications authorization (SCA) services which used various subcarrier frequencies including 41 and 67 kHz. Many revenue-starved FM stations used SCAs for “storecasting” and other non-broadcast purposes. The Halstead system was rejected due to lack of high frequency stereo separation and reduction in the main channel signal-to-noise ratio. The GE and Zenith systems, so similar that they were considered theoretically identical, were formally approved by the FCC in April 1961 as the standard stereo FM broadcasting
FM broadcasting
method in the United States
United States
and later adopted by most other countries.[3][4] It is important that stereo broadcasts be compatible with mono receivers. For this reason, the left (L) and right (R) channels are algebraically encoded into sum (L+R) and difference (L−R) signals. A mono receiver will use just the L+R signal so the listener will hear both channels through the single loudspeaker. A stereo receiver will add the difference signal to the sum signal to recover the left channel, and subtract the difference signal from the sum to recover the right channel. The (L+R) Main channel signal is transmitted as baseband audio limited to the range of 30 Hz to 15 kHz. The (L−R) signal is amplitude modulated onto a 38 kHz double-sideband suppressed-carrier (DSB-SC) signal occupying the baseband range of 23 to 53 kHz. A 19 kHz pilot tone, at exactly half the 38 kHz sub-carrier frequency and with a precise phase relationship to it, as defined by the formula below, is also generated. This is transmitted at 8–10% of overall modulation level and used by the receiver to regenerate the 38 kHz sub-carrier with the correct phase. The final multiplex signal from the stereo generator contains the Main Channel (L+R), the pilot tone, and the sub-channel (L−R). This composite signal, along with any other sub-carriers, modulates the FM transmitter. The instantaneous deviation of the transmitter carrier frequency due to the stereo audio and pilot tone (at 10% modulation) is

[

0.9

[

A + B

2

+

A − B

2

sin ⁡ 4 π

f

p

t

]

+ 0.1 sin ⁡ 2 π

f

p

t

]

× 75  

k H z

displaystyle left[0.9left[ frac A+B 2 + frac A-B 2 sin 4pi f_ p tright]+0.1sin 2pi f_ p tright]times 75~mathrm kHz

[5][6]

where A and B are the pre-emphasized left and right audio signals and

f

p

displaystyle f_ p

=19 kHz is the frequency of the pilot tone. Slight variations in the peak deviation may occur in the presence of other subcarriers or because of local regulations. Another way to look at the resulting signal is that it alternates between left and right at 38 kHz, with the phase determined by the 19 kHz pilot signal.[7] Converting the multiplex signal back into left and right audio signals is performed by a decoder, built into stereo receivers. In order to preserve stereo separation and signal-to-noise parameters, it is normal practice to apply pre-emphasis to the left and right channels before encoding, and to apply de-emphasis at the receiver after decoding. Stereo
Stereo
FM signals are more susceptible to noise and multipath distortion than are mono FM signals.[8] In addition, for a given RF level at the receiver, the signal-to-noise ratio for the stereo signal will be worse than for the mono receiver. For this reason many stereo FM receivers include a stereo/mono switch to allow listening in mono when reception conditions are less than ideal, and most car radios are arranged to reduce the separation as the signal-to-noise ratio worsens, eventually going to mono while still indicating a stereo signal is being received. Quadraphonic
Quadraphonic
FM[edit] In 1969, Louis Dorren invented the Quadraplex system of single station, discrete, compatible four-channel FM broadcasting. There are two additional subcarriers in the Quadraplex system, supplementing the single one used in standard stereo FM. The baseband layout is as follows:

50 Hz to 15 kHz Main Channel (sum of all 4 channels) (LF+LR+RF+RR) signal, for mono FM listening compatibility. 23 to 53 kHz (sine quadrature subcarrier) (LF+LR) - (RF+RR) Left minus Right difference signal. This signal's modulation in algebraic sum and difference with the Main channel is used for 2 channel stereo listener compatibility. 23 to 53 kHz (cosine quadrature 38 kHz subcarrier) (LF+RR) - (LR+RF) Diagonal difference. This signal's modulation in algebraic sum and difference with the Main channel and all the other subcarriers is used for the Quadraphonic
Quadraphonic
listener. 61 to 91 kHz (sine quadrature 76 kHz subcarrier) (LF+RF) - (LR+RR) Front-back difference. This signal's modulation in algebraic sum and difference with the main channel and all the other subcarriers is also used for the Quadraphonic
Quadraphonic
listener. 105 kHz SCA subcarrier, phase-locked to 19 kHz pilot, for reading services for the blind, background music, etc.

The normal stereo signal can be considered as switching between left and right channels at 38 kHz, appropriately band limited. The quadraphonic signal can be considered as cycling through LF, LR, RF, RR, at 76 kHz.[9] Early efforts to transmit discrete four-channel quadraphonic music required the use of two FM stations; one transmitting the front audio channels, the other the rear channels. A breakthrough came in 1970 when KIOI
KIOI
(K-101) in San Francisco successfully transmitted true quadraphonic sound from a single FM station using the Quadraplex system under Special
Special
Temporary Authority from the FCC. Following this experiment, a long term test period was proposed that would permit one FM station in each of the top 25 U.S. radio markets to transmit in Quadraplex. The test results hopefully would prove to the FCC that the system was compatible with existing two-channel stereo transmission and reception and that it did not interfere with adjacent stations. There were several variations on this system submitted by GE, Zenith, RCA, and Denon for testing and consideration during the National Quadraphonic
Quadraphonic
Radio
Radio
Committee field trials for the FCC. The original Dorren Quadraplex System outperformed all the others and was chosen as the national standard for Quadraphonic
Quadraphonic
FM broadcasting
FM broadcasting
in the United States. The first commercial FM station to broadcast quadraphonic program content was WIQB (now called WWWW-FM) in Ann Arbor/Saline, Michigan under the guidance of Chief Engineer Brian Jeffrey Brown.[10] Noise
Noise
reduction[edit] Various attempts to add analog noise reduction to FM broadcasting
FM broadcasting
were carried out in the 1970s and 1980s: A commercially unsuccessful noise reduction system used with FM radio in some countries during the late 1970s, Dolby FM
Dolby FM
was similar to Dolby B[11] but used a modified 25 µs pre-emphasis time constant and a frequency selective companding arrangement to reduce noise. The pre-emphasis change compensates for the excess treble response that otherwise would make listening difficult for those without Dolby decoders. A similar system named High Com FM was tested in Germany
Germany
between July 1979 and December 1981 by IRT. It was based on the Telefunken High Com broadband compander system, but was never introduced commercially in FM broadcasting.[12] Yet another system was the CX-based noise reduction system FMX implemented in some radio broadcasting stations in the United States in the 1980s. Other subcarrier services[edit]

Typical spectrum of composite baseband signal

FM broadcasting
FM broadcasting
has included SCA capability since its inception, as it was seen as another service which licensees could use to create additional income.[13] Initially the users of SCA services were private analog audio channels which could be used internally or rented out, for example Muzak type services. Radio
Radio
reading services for the blind became a common use, and remain so, and there were experiments with quadraphonic sound. If a station does not broadcast in stereo, everything from 23 kHz on up can be used for other services. The guard band around 19 kHz (±4 kHz) must still be maintained, so as not to trigger stereo decoders on receivers. If there is stereo, there will typically be a guard band between the upper limit of the DSBSC stereo signal (53 kHz) and the lower limit of any other subcarrier. Digital services are now also available. A 57 kHz subcarrier (phase locked to the third harmonic of the stereo pilot tone) is used to carry a low-bandwidth digital Radio
Radio
Data System signal, providing extra features such as Alternative Frequency
Frequency
(AF) and Network (NN). This narrowband signal runs at only 1,187.5 bits per second, thus is only suitable for text. A few proprietary systems are used for private communications. A variant of RDS is the North American RBDS or "smart radio" system. In Germany
Germany
the analog ARI system was used prior to RDS for broadcasting traffic announcements to motorists (without disturbing other listeners). Plans to use ARI for other European countries led to the development of RDS as a more powerful system. RDS is designed to be capable of being used alongside ARI despite using identical subcarrier frequencies. In the United States, digital radio services are being deployed within the FM band rather than using Eureka 147 or the Japanese standard ISDB. This in-band on-channel approach, as do all digital radio techniques, makes use of advanced compressed audio. The proprietary iBiquity system, branded as "HD Radio", currently is authorized for "hybrid" mode operation, wherein both the conventional analog FM carrier and digital sideband subcarriers are transmitted. Eventually, presuming widespread deployment of HD Radio
Radio
receivers, the analog services could theoretically be discontinued and the FM band become all digital. In the United States, services (other than stereo, quad and RDS) using subcarriers are sometimes referred to as subsidiary communications authorization (SCA) services. Uses for such subcarriers include book/newspaper reading services for blind listeners, private data transmission services (for example sending stock market information to stockbrokers or stolen credit card number blacklists to stores[citation needed]) subscription commercial-free background music services for shops, paging ("beeper") services, traffic data for commercial GPS receivers[14][15], and providing a program feed for AM transmitters of AM/FM stations. SCA subcarriers are typically 67 kHz and 92 kHz. Reception distance[edit] FM radio waves do not travel far beyond the visual horizon, so reception distances for FM stations are usually limited to 30—40 miles (48.3—64.4 km) They can also be blocked by hills. This is less than the range of AM radio waves, which because of their lower frequency can travel as ground waves or reflect off the ionosphere, so AM radio stations can be received at hundreds (sometimes thousands) of miles. This is a property of the carrier wave's typical frequency (and power), not its mode of modulation. The range of mono FM transmission is related to the transmitter's RF power, the antenna gain, and antenna height. The U.S. FCC publishes curves that aid in calculation of this maximum distance as a function of signal strength at the receiving location. Many FM stations, especially those located in severe multipath areas, use extra audio compression to keep essential sound above the background noise for listeners, occasionally at the expense of overall perceived sound quality. In such instances, however, this technique is often surprisingly effective in increasing the station's useful range.[citation needed] Adoption of FM broadcasting[edit]

One of the first FM radio stations, Edwin Armstrong's experimental station W2XMN in Alpine, New Jersey, USA. The insets show a part of the transmitter, and a map of FM stations in 1940

United States[edit] Despite FM having been patented in 1933, commercial FM broadcasting did not begin until the late 1930s, when it was initiated by a handful of early pioneer stations including W8HK, Buffalo, New York (now WTSS); W1XOJ/ WGTR and W1XTG/WSRS, both transmitting from Paxton, Massachusetts (now listed as Worcester, Massachusetts); W1XSL/W1XPW/WDRC-FM, Meriden, Connecticut (now WHCN); W2XMN/KE2XCC/WFMN, Alpine, New Jersey
Alpine, New Jersey
(owned by Edwin Armstrong himself, closed down upon Armstrong's death in 1954); W2XQR/WQXQ/WQXR-FM, New York; W47NV Nashville, Tennessee (signed off in 1951); W1XER/W39B/WMNE, whose studios were in Boston but whose transmitter was atop the highest mountain in the northeast United States, Mount Washington, New Hampshire
Mount Washington, New Hampshire
(shut down in 1948); W9XAO Milwaukee, Wisconsin (later WTMJ-FM, off air in 1950, returning in 1959 on another frequency). Also of note are General Electric
General Electric
stations W2XDA Schenectady and W2XOY New Scotland, New York—two experimental frequency modulation transmitters on 48.5 MHz—which signed on in 1939. The two were merged into one station using the W2XOY call letters on November 20, 1940, with the station taking the WGFM call letters a few years later, and moving to 99.5 MHz when the FM band was relocated to the 88–108 MHz portion of the radio spectrum. General Electric
General Electric
sold the station in the 1980s, and today the station is called WRVE. WEFM (in the Chicago area) and WGFM (in Schenectady, New York) were reported as the first stereo stations.[16] The first commercial FM broadcasting
FM broadcasting
stations were in the United States, but initially they were primarily used to simulcast their AM sister stations, to broadcast lush orchestral music for stores and offices, to broadcast classical music to an upmarket listenership in urban areas, or for educational programming. By the late 1960s, FM had been adopted for broadcast of stereo "A.O.R.—'Album Oriented Rock' Format", but it was not until 1978 that listenership to FM stations exceeded that of AM stations in North America. During the 1980s and 1990s, Top 40 music stations and later even country music stations largely abandoned AM for FM. Today AM is mainly the preserve of talk radio, news, sports, religious programming, ethnic (minority language) broadcasting and some types of minority interest music. This shift has transformed AM into the "alternative band" that FM once was. (Some AM stations have begun to simulcast on, or switch to, FM signals to attract younger listeners and aid reception problems in buildings, during thunderstorms, and near high-voltage wires. Some of these stations now emphasize their presence on the FM dial.) Europe[edit] The medium wave band (known as the AM band because most stations using it employ amplitude modulation in North America) is overcrowded[citation needed] in Western Europe, leading to interference problems and, as a result, many MW frequencies are suitable only for speech broadcasting. Belgium, the Netherlands, Denmark
Denmark
and particularly Germany
Germany
were among the first countries to adopt FM on a widespread scale. Among the reasons for this were:

The medium wave band in Western Europe
Europe
became overcrowded after World War II, mainly due to the best available medium wave frequencies being used at high power levels by the Allied Occupation Forces, both for broadcasting entertainment to their troops and for broadcasting Cold War propaganda across the Iron Curtain. After World War II, broadcasting frequencies were reorganized and reallocated by delegates of the victorious countries in the Copenhagen Frequency
Frequency
Plan. German broadcasters were left with only two remaining AM frequencies and were forced to look to FM for expansion.

Public service broadcasters in Ireland and Australia
Australia
were far slower at adopting FM radio than those in either North America
North America
or continental Europe. United Kingdom[edit] In the United Kingdom, the BBC
BBC
began FM broadcasting
FM broadcasting
in 1955, with three national networks: the Light Programme, Third Programme and Home Service. These three networks used the sub-band 88.0–94.6 MHz. The sub-band 94.6–97.6 MHz was later used for BBC
BBC
and local commercial services. However, only when commercial broadcasting was introduced to the UK in 1973 did the use of FM pick up in Britain. With the gradual clearance of other users (notably Public Services such as police, fire and ambulance) and the extension of the FM band to 108.0 MHz between 1980 and 1995, FM expanded rapidly throughout the British Isles and effectively took over from LW and MW as the delivery platform of choice for fixed and portable domestic and vehicle-based receivers. In addition, Ofcom
Ofcom
(previously the Radio
Radio
Authority) in the UK issues on demand Restricted Service Licences on FM and also on AM (MW) for short-term local-coverage broadcasting which is open to anyone who does not carry a prohibition and can put up the appropriate licensing and royalty fees. In 2010 around 450 such licences were issued. When the BBC's radio networks were renamed Radio
Radio
2, Radio
Radio
3 and Radio 4 respectively in 1967 to coincide with the launch of Radio
Radio
1, the new station was the only one of the main four to not have an FM frequency allocated, which was the case for 21 years. Instead, Radio
Radio
1 shared airtime with Radio
Radio
2 FM, on Saturday afternoons, Sunday evenings, weekday evenings (10pm to midnight) and Bank Holidays. Eventually in 1987 a frequency range of 97.6-99.8 MHz was allocated as police relay transmitters were moved from the 100 MHz frequency, starting in London before being broadly completed by 1989.[17] Italy[edit] Italy
Italy
adopted FM broadcast widely in the early 1970s, but first experiments made by RAI dated back to 1950,[18] when the "movement for free radio", developed by so-called "pirates", forced the recognition of free speech rights also through the use of "free radio media such as Broadcast transmitters", and took the case to the Constitutional Court of Italy. The court finally decided in favor of Free Radio. Just weeks after the court's final decision there was an "FM radio boom" involving small private radio stations across the country. By the mid 1970s, every city in Italy
Italy
had a crowded FM radio spectrum. Greece[edit] Greece
Greece
was another European country where the FM radio spectrum was used at first by the so-called "pirates" (both in Athens and Thessaloniki, the two major Greek cities) in the mid 1970s, before any national stations had started broadcasting on it; there were many AM (MW) stations in use for the purpose. No later than the end of 1977, the national public service broadcasting company EIRT (later also known as ERT) placed in service its first FM transmitter in the capital, Athens. By the end of the 1970s, most of Greek territory was covered by three National FM programs, and every city had many FM "pirates" as well. The adaptation of the FM band for privately owned commercial radio stations came far later, in 1987. Australia[edit] FM broadcasting
FM broadcasting
started in Australian capital cities in 1947 on an "experimental" basis, using an ABC national network feed, consisting largely of classical music and Parliament, as a programme source. It had a very small audience and was shut down in 1961 ostensibly to clear the television band: TV channel 5 (102.250 video carrier) if allocated would fall within the VHF
VHF
FM band (98–108 MHz). The official policy on FM at the time was to eventually introduce it on another band, which would have required FM tuners custom-built for Australia. This policy was finally reversed and FM broadcasting
FM broadcasting
was reopened in 1975 using the VHF
VHF
band, after the few encroaching TV stations had been moved. Subsequently, it developed steadily until in the 1980s many AM stations transferred to FM due to its superior sound quality and lower operating costs. Today, as elsewhere in the developed world, most urban Australian broadcasting is on FM, although AM talk stations are still very popular. Regional broadcasters still commonly operate AM stations due to the additional range the broadcasting method offers. Some stations in major regional centres simulcast on AM and FM bands. Digital radio using the DAB+ standard has been rolled out to capital cities. New Zealand[edit] Like Australia, New Zealand adopted the FM format relatively late. As was the case with privately owned AM radio in the late 1960s, it took a spate of 'pirate' broadcasters to persuade a control-oriented, technology averse government to allow FM to be introduced after at least five years of consumer campaigning starting in the mid-1970s, particularly in Auckland. An experimental FM station, FM 90.7, was broadcast in Whakatane
Whakatane
in early 1982. Later that year, Victoria University of Wellington's Radio
Radio
Active began full-time FM transmissions. Commercial FM licences were finally approved in 1983, with Auckland-based 91FM and 89FM being the first to take up the offer.[1]. Broadcasting
Broadcasting
was deregulated in 1989. Trinidad and Tobago[edit] Trinidad and Tobago's first FM Radio
Radio
station was 95.1FM, now rebranded as 951 Remix, was launched in March 1976 by the TBC Radio
Radio
Network. Turkey[edit] In Turkey, FM broadcasting
FM broadcasting
began in the late 1960s, carrying several shows from the One television network which was transferred from the AM frequency (also known as MW in Turkey). In subsequent years, more MW stations were slowly transferred to FM, and by the end of the 1970s, most radio stations that were previously on MW had been moved to FM, though many talk, news and sport, but mostly religious stations, still remain on MW. Other countries[edit] Most other countries implemented FM broadcasting
FM broadcasting
through 1960s and expanded their use of FM through the 1990s. Because it takes a large number of FM transmitting stations to cover a geographically large country, particularly where there are terrain difficulties, FM is more suited to local broadcasting than for national networks. In such countries, particularly where there are economic or infrastructural problems, "rolling out" a national FM broadcast network to reach the majority of the population can be a slow and expensive process. Despite this, mostly in east European counties, national FM broadcast networks were established in the late 1960s and 1970s. In all Soviet-dependent countries but GDR, the OIRT
OIRT
band was used. First restricted to 68–73 MHz with 100 kHz channel spacing, then in the 1970s eventually expanded to 65.84–74.00 MHz with 30 kHz channel spacing.[19] ITU
ITU
Conferences about FM[edit] The frequencies available for FM were decided by some important conferences of ITU. The milestone of those conferences is the Stockholm agreement of 1961 among 38 countries.[20] A 1984 conference in Geneva made some modifications to the original Stockholm agreement particularly in the frequency range above 100 MHz. FM broadcasting
FM broadcasting
switch-off[edit] Further information: FM radio switch-off or Main article: Digital audio
Digital audio
broadcasting Small-scale use of the FM broadcast band[edit]

Belkin
Belkin
TuneCast II FM microtransmitter

Consumer use of FM transmitters[edit] In some countries, small-scale (Part 15 in United States
United States
terms) transmitters are available that can transmit a signal from an audio device (usually an MP3 player
MP3 player
or similar) to a standard FM radio receiver; such devices range from small units built to carry audio to a car radio with no audio-in capability (often formerly provided by special adapters for audio cassette decks, which are becoming less common on car radio designs) up to full-sized, near-professional-grade broadcasting systems that can be used to transmit audio throughout a property. Most such units transmit in full stereo, though some models designed for beginner hobbyists might not. Similar transmitters are often included in satellite radio receivers and some toys. Legality of these devices varies by country. The U.S. Federal Communications Commission and Industry Canada
Industry Canada
allow them. Starting on 1 October 2006, these devices became legal in most countries in the European Union. Devices made to the harmonised European specification became legal in the UK on 8 December 2006.[21] The FM broadcast band
FM broadcast band
is also used by some inexpensive wireless microphones sold as toys for karaoke or similar purposes, allowing the user to use an FM radio as an output rather than a dedicated amplifier and speaker. Professional-grade wireless microphones generally use bands in the UHF
UHF
region so they can run on dedicated equipment without broadcast interference. Some wireless headphones transmit in the FM broadcast band, with the headphones tunable to only a subset of the broadcast band. Higher-quality wireless headphones use infrared transmission or UHF ISM bands such as 315 MHz, 863 MHz, 915 MHz, or 2.4 GHz instead of the FM broadcast band. Microbroadcasting[edit] Low-power transmitters such as those mentioned above are also sometimes used for neighborhood or campus radio stations, though campus radio stations are often run over carrier current. This is generally considered a form of microbroadcasting. As a general rule,[vague] enforcement towards low-power FM stations is stricter than with AM stations, due to problems such as the capture effect,[citation needed] and as a result, FM microbroadcasters generally do not reach as far as their AM competitors. Clandestine use of FM transmitters[edit] FM transmitters have been used to construct miniature wireless microphones for espionage and surveillance purposes (covert listening devices or so-called "bugs"); the advantage to using the FM broadcast band for such operations is that the receiving equipment would not be considered particularly suspect. Common practice is to tune the bug's transmitter off the ends of the broadcast band, into what in the United States
United States
would be TV channel 6 (<87.9 MHz) or aviation navigation frequencies (>107.9 MHz); most FM radios with analog tuners have sufficient overcoverage to pick up these slightly-beyond-outermost frequencies, although many digitally tuned radios have not. Constructing a "bug" is a common early project for electronics hobbyists, and project kits to do so are available from a wide variety of sources. The devices constructed, however, are often too large and poorly shielded for use in clandestine activity. In addition, much pirate radio activity is broadcast in the FM range, because of the band's greater clarity and listenership, the smaller size and lower cost of equipment. See also[edit] FM broadcasting
FM broadcasting
by country[edit]

FM broadcasting
FM broadcasting
in Australia FM broadcasting
FM broadcasting
in Canada FM broadcasting
FM broadcasting
in Egypt FM broadcasting
FM broadcasting
in India FM broadcasting
FM broadcasting
in Japan FM broadcasting
FM broadcasting
in New Zealand FM broadcasting
FM broadcasting
in Pakistan FM broadcasting
FM broadcasting
in the UK FM broadcasting
FM broadcasting
in the United States

FM broadcasting
FM broadcasting
(technical)[edit]

AM broadcasting AM stereo
AM stereo
(related technology) FM broadcast band FM stereo Frequency
Frequency
modulation Long-distance FM reception (FM DX) Ripping music from FM broadcasts RDS ( Radio
Radio
Data System)

Lists[edit]

List of broadcast station classes Lists of radio stations in North America

History[edit]

History of radio Oldest radio station

References[edit]

^ "Transmission standards for FM sound broadcasting at VHF". ITU
ITU
Rec. BS.450. International Telecommunications Union. pp. 4–5.  ^ RWO. "How FM Stereo
Stereo
Came to Life".  ^ Théberge, Paul; Devine, Kyle; Everrett, Tom (2015-01-29). Living Stereo: Histories and Cultures of Multichannel Sound. Bloomsbury Publishing USA. p. 189. ISBN 9781623566876.  ^ van Duyne, John P. (Fall 1961). "The Notebook:A Modulator for the New FM Stereo
Stereo
System". Boontown Radio
Radio
Corp. Retrieved 27 December 2016.  ^ "Stereophonic Broadcasting: Technical Details of Pilot-tone System", Information Sheet 1604(4), BBC
BBC
Engineering Information Service, June 1970  ^ "Subsidiary communications multiplex operation: engineering standards" (PDF). www.fcc.gov. US Federal Communications Commission. Retrieved 12 January 2017.  ^ "FM Stereo
Stereo
demodulation circuit". USPTO. Retrieved 6 December 2015.  ^ "FM Reception Guide: FM Propagation". WGBH. Archived from the original on 8 July 2007. Retrieved 9 May 2010.  Includes tips for multipath & fringe problems. ^ "Compatible four channel FM system". pdfpiw.uspto.gov. USPTO. Retrieved 19 October 2016.  ^ Ann Arbor
Ann Arbor
News, Ann Arbor, Michigan, January 3, 1973 ^ Mielke, E.-Jürgen (1977). "Einfluß des Dolby-B-Verfahrens auf die Übertragungsqualität im UKW-Hörrundfunk". Rundfunktechnische Mitteilungen (in German). Institut für Rundfunktechnik (IRT). 21: 222–228.  ^ "Prüfung eines modifizierten HIGH COM-Kompanders für den Einsatz bei der RF-Übertragung im UKW-Hörfunk" (in German). Institut für Rundfunktechnik (IRT). 1981-12-30. Technical Report 55/81.  ^ "Full text of " Radio
Radio
Electronics (August 1987)"". archive.org.  ^ "Traffic Services".  ^ "Traffic Message Channel".  ^ "Stereophonic FM Broadcast Begun by WEFM", The Chicago Tribune, June 2, 1961, p. B-10. ^ " Radio
Radio
1 History - Transmitters". Radio
Radio
Rewind. Retrieved 11 August 2013.  ^ "[IT] Radio
Radio
FM in Italia". Retrieved 22 September 2015.  ^ " OIRT
OIRT
Tuner".  ^ " ITU
ITU
Publications". ITU.  ^ "Change to the law to allow the use of low power FM transmitters for MP3 players". Ofcom. 23 November 2006. Retrieved 8 August 2015. 

External links[edit]

Library resources about FM broadcasting

Resources in your library Resources in other libraries

Related technical content

U.S. Patent 1,941,066 U.S. Patent 3,708,623 Compatible Four Channel FM System Introduction to FM MPX Frequency Modulation
Frequency Modulation
(FM) Tutorial Stereo
Stereo
Multiplexing
Multiplexing
for Dummies Graphs that show waveforms at different points in the FM Multiplex process Factbook list of stations worldwide Invention History – The Father of FM Audio Engineering Society FM Broadcast and TV Broadcast Aural Subcarriers - Clifton Laboratories

v t e

Analog and digital audio broadcasting

Terrestrial

Radio
Radio
modulation

AM FM COFDM

Frequency
Frequency
allocations

LW (LF) MW (MF) SW (HF) VHF
VHF
(low / mid / high) L band
L band
(UHF)

Digital systems

CAM-D DAB/DAB+ DRM/DRM+ FMeXtra HD Radio CDR DVB-T2
DVB-T2
Lite

Satellite

Frequency
Frequency
allocations

C band Ku band L band S band

Digital systems

ADR DAB-S DVB-SH S-DMB SDR

Commercial radio providers

1worldspace Sirius XM Holdings SiriusXM Canada

Codecs

AAC AMR-WB+ HDC HE-AAC MPEG-1 Audio Layer II

Subcarrier signals

AMSS DirectBand PAD RDS/RBDS SCA/SCMO DARC

Related topics

Technical (audio)

Audio data compression Audio signal processing

Technical ( AM stereo
AM stereo
formats)

Belar C-QUAM Harris Kahn-Hazeltine Magnavox

Technical (emission)

AM broadcasting AM expanded band Cable radio Digital radio Error detection and correction FM broadcast band FM broadcasting Multipath propagation Shortwave relay station

Cultural

History of radio International broadcasting

Comparison of radio systems

v t e

Telecommunications

History

Beacon Broadcasting Cable protection system Cable TV Communications satellite Computer network Drums Electrical telegraph Fax Heliographs Hydraulic telegraph Internet Mass media Mobile phone Optical telecommunication Optical telegraphy Pager Photophone Prepay mobile phone Radio Radiotelephone Satellite communications Semaphore Smartphone Smoke signals Telecommunications history Telautograph Telegraphy Teleprinter
Teleprinter
(teletype) Telephone The Telephone Cases Television Timeline of communication technology Undersea telegraph line Videoconferencing Videophone Videotelephony Whistled language

Pioneers

Edwin Howard Armstrong John Logie Baird Paul Baran Alexander Graham Bell Tim Berners-Lee Jagadish Chandra Bose Vint Cerf Claude Chappe Donald Davies Lee de Forest Philo Farnsworth Reginald Fessenden Elisha Gray Erna Schneider Hoover Charles K. Kao Hedy Lamarr Innocenzo Manzetti Guglielmo Marconi Antonio Meucci Radia Perlman Alexander Stepanovich Popov Johann Philipp Reis Nikola Tesla Camille Tissot Alfred Vail Charles Wheatstone Vladimir K. Zworykin

Transmission media

Coaxial cable Fiber-optic communication

Optical fiber

Free-space optical communication Molecular communication Radio
Radio
waves Transmission line

Network topology and switching

Links Nodes Terminal node Network switching (circuit packet) Telephone exchange

Multiplexing

Space-division Frequency-division Time-division Polarization-division Orbital angular-momentum Code-division

Networks

ARPANET BITNET Cellular network Computer CYCLADES Ethernet FidoNet Internet ISDN LAN Mobile NGN NPL network Public Switched Telephone Radio Telecommunications equipment Television Telex WAN Wireless World Wide Web

.