The history
From Armstrong's static-free experiment in 1935 to 585 Akashvani stations, private FM auctions and the first countries switching FM off.
In the 1920s radio meant AM, full of crackle, and experts believed frequency modulation was useless. Edwin Armstrong proved them wrong by making FM swing wide, and after a move to 88–108 MHz, stereo and RDS, FM became the world's favourite way to hear radio. In India it arrived in Madras in 1977 and exploded after private stations came in 2001.
1933
Wideband FM patents
Edwin Howard Armstrong, USA
1941
Fully licensed commercial FM station
W47NV, Nashville, USA
1961
Pilot-tone FM stereo broadcasts
USA (Zenith–GE system)
1984
RDS specification
European Broadcasting Union
1977
FM in India
All India Radio, Madras
2001
Private FM station in India
Radio City, Bengaluru
2004
Community radio in India
Anna FM, Chennai
2017
Country to switch off national FM
Norway
1922 – 1940
Mathematicians doubt it; Armstrong makes the swing wide and proves FM kills static.
1922
February 1922
Engineers hoped that swinging a wave's frequency only a little would squeeze a radio channel into less room. Carson showed with maths that it can't: FM always spreads out at least as wide as AM.
Why it mattered. His analysis of FM's sidebands is where today's bandwidth rule of thumb, Carson's rule, gets its name.
1933
26 December 1933
Armstrong did the opposite of what everyone expected: he made the frequency swing very wide. He was granted a set of US patents covering his wideband FM system on one day, including patent 1,941,066.
Why it mattered. Wide swings make FM far less sensitive to crackle and static than AM, which is the whole point of FM radio.
1935
6 November 1935
At a meeting of the Institute of Radio Engineers, Armstrong played an FM broadcast sent from a friend's station in Yonkers. The audience heard music, water being poured and paper being torn, with no static at all.
Why it mattered. It proved in public that FM could sound far cleaner than any AM station of the day.
1939
Armstrong paid for his own experimental FM station, W2XMN, with a tall tower on the cliffs above the Hudson River. It went on the air in 1939 (the date is given differently in different sources).
Why it mattered. It showed the pattern every FM station still follows: a high antenna, because FM travels in near-straight lines.
1941 – 1976
Commercial stations, the move to 88–108 MHz, Europe's VHF networks and stereo.
1941
1 March 1941
W47NV in Nashville began a regular schedule and was described at the time as the first fully licensed commercial FM station in the USA. It used the old FM band around 42–50 MHz.
Why it mattered. FM stopped being an experiment and became a business.
1945
27 June 1945
The FCC moved FM from 42–50 MHz up to a new band starting at 88 MHz (88–106 MHz at first, later 108). Every pre-war FM radio became useless overnight.
Why it mattered. The 88–108 MHz band became the world standard. India's FM band is the same.
1954
1 February 1954
Worn down by years of patent fights with RCA and others over FM, Armstrong died in 1954. His widow Marion went on to win or settle the patent cases.
Why it mattered. FM's inventor never saw it become the most popular way to hear radio.
1955
2 May 1955
The BBC opened its first VHF FM transmitter at Wrotham, carrying three national programmes to London and south-east England, free of night-time interference from foreign AM stations.
Why it mattered. European FM followed rules that India uses too, such as 50 µs pre-emphasis.
1961
20 April 1961
The FCC picked a combined Zenith–GE system for FM stereo: L+R as normal sound, L−R on a 38 kHz subcarrier, and a 19 kHz pilot tone. Regular stereo broadcasts began on 1 June 1961.
Why it mattered. The same pilot-tone stereo is still used on every FM station, including India's.
1977 – 2010
Akashvani in Madras, FM Rainbow and Gold, private FM phases I and II, and community radio.
1977
23 July 1977
All India Radio began India's first FM broadcasts in Madras, on an experimental basis, fifty years to the day after the Indian Broadcasting Company's first station opened in Bombay.
Why it mattered. FM gave Indian listeners clean, static-free sound for music.
2000
India opened FM to private companies. Licences for 108 frequencies were auctioned for high fixed fees. Many winners could not make money, and only about 21 or 22 stations went on air (sources differ).
Why it mattered. It proved that the price and rules of licences decide whether a station can survive.
2001
3 July 2001
Radio City started broadcasting in Bengaluru, widely listed as India's first private FM station. Radio Mirchi followed in Indore that October.
Why it mattered. RJs, jingles and non-stop film music made private FM a big part of city life.
2001
15 August 2001
AIR started FM Gold, with news, current affairs and classic music, in Delhi and then other big cities.
Why it mattered. AIR kept a strong presence on FM beside the new private stations.
2004
1 February 2004
A campus radio station at Anna University in Chennai became India's first community radio, run by students and staff for the people nearby.
Why it mattered. It led to a 2006 policy letting NGOs, colleges and farm bodies run their own small local stations.
2010
25 August 2010
Radio stations and music owners had long fought over how much stations should pay to play songs. The Copyright Board set the royalty at 2% of each station's net advertising revenue, a rate music companies strongly opposed.
Why it mattered. Music is a station's main cost after staff and licence fees; the fight over it continued in courts.
1984 – 2017
RDS puts text inside FM, and digital radio starts to replace it in some countries.
1984
March 1984
The EBU published the first Radio Data System specification: a quiet stream of data on a 57 kHz subcarrier (three times the stereo pilot), carrying the station's name and other information.
Why it mattered. It is why car radios can show station names, song titles and traffic news.
2017
11 January 2017
Norway became the first country to begin turning off national FM, starting in Nordland and finishing on 13 December 2017. Listeners moved to DAB+ digital radio; many local stations kept FM.
Why it mattered. It showed FM can be replaced, and how much it costs listeners to buy new radios.
2011 – today
Phase III auctions, the news rule, FM in phones and plans for digital radio.
2011
July 2011
The Phase III policy aimed private FM at smaller cities, allowed several channels per company in a city, and set technical rules, including 800 kHz spacing between stations in the same city.
Why it mattered. It shaped the numbers on your dial: 91.1, 91.9, 92.7, 93.5…
2015
27 July – 9 September 2015
An online auction offered 135 channels in 69 cities. Bidders won 97 channels in 56 cities, for a total of about ₹1,157 crore, well above the reserve price.
Why it mattered. Auctions put a market price on each city's slice of the FM band.
2019
8 January 2019
Private FM stations still cannot make their own news. From 2019 they were allowed to air All India Radio news bulletins free of charge, but only unchanged and in full. Few stations took it up.
Why it mattered. News on private FM remains one of the biggest differences between Indian and foreign FM.
2023
MeitY advised phone makers to keep built-in FM receivers switched on, and to add them where missing, because FM works free, without data, and during disasters when networks fail.
Why it mattered. A free broadcast that reaches everyone at once is a safety tool.
2025
3 October 2025
TRAI recommended letting private broadcasters start digital radio in 13 big cities in simulcast mode: one analogue FM channel plus several digital channels on the same frequency.
Why it mattered. FM may stay for years, sharing its frequencies with digital channels.
Did you know?
At full volume a 98.3 MHz station swings between 98.225 and 98.375 MHz, 75 kHz either way.
An FM wave at 100 MHz is 3 m long; your phone uses its earphone cord as the antenna.
The RDS data stream runs at exactly 1,187.5 bits a second: 57,000 divided by 48.
Private FM stations in one Indian city must be at least 800 kHz apart, which is why so many cities have 91.1, 91.9, 92.7, 93.5 and 94.3.
In 2025 India had 585 Akashvani FM stations and 388 private ones, according to the Ministry of Information and Broadcasting.
The people
1890 – 1954 · Engineer and inventor · USA
Invented wideband FM, as well as the regenerative and superheterodyne receivers.
1886 – 1940 · Mathematician, AT&T · USA
Analysed FM's sidebands in 1922; the bandwidth rule of thumb carries his name.
1898 – 1979 · Armstrong's widow · USA
Carried on his FM patent lawsuits after his death and won or settled them all.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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