Why Edwin Armstrong developed FM radio

How radio works

Antennae tune a radio to a particular frequency (determined by the listener on their radio's dial) while tuning out all the other stations being broadcast. AM, short for amplitude modulation, and FM, short for frequency modulation, decode audio signals differently, leading to differences in sound quality and the distance a station can travel.

How underground radio revitalized rock 'n' roll

Early FM was a wasteland and quickly became the domain of amateurs and risk-takers, including many stations and DJs who played music that flew in the face of mainstream trends. This history of the band's scrappy beginnings unpacks how it realigned the rock charts.

See a timeline of commercial radio history

Radio, as we know it, began in the 1910s. This FCC timeline traces the evolution of the medium over the century that followed, highlighting groundbreaking broadcasts, speeches, and technological breakthroughs.

Before the invention of transistors, vacuum tubes made radio possible

Discovered by Thomas Edison, vacuum tubes allow electrical currents to travel through empty space. Later modified into a diode—keeping current flowing in only one direction—vacuum tubes allowed electronics to turn alternating current into direct current.

Franklin D. Roosevelt used radio to connect directly with Americans through his 'Fireside Chats'

Beginning in 1933, FDR harnessed the new medium of radio to explain policies and reassure the public during the Great Depression and World War II. His conversational fireside chats revolutionized presidential communication.

The accidental birth of radio astronomy and the benefits of a moon-based telescope

Detecting radio waves from distant celestial objects is complicated by noise from solar wind, which the nighttime side of the moon is shielded from. If lunar temperature extremes can be overcome, the environment may serve as an optimal future home for radio astronomy, a field that began in 1928 when a 30-meter-long directional antenna, mostly out of brass and wood, picked up signals from the Sagittarius constellation.

The electric microphone led to a country music boom

The electric microphone provided enhanced audio and greater portability, saving the fledgling record industry and making recording outside of New York and Camden, New Jersey, possible. This proved critical for capturing early country and rock ‘n’ roll.

The disputed inventor of the radio

Guglielmo Marconi was awarded the 1909 Nobel Prize in physics for inventing the wireless telegraph, which used radio waves to transmit Morse code. Nikola Tesla, however, was experimenting with radio waves in the 1890s, though much of his work was destroyed in a 1895 fire.

The start of commercial radio depends on how someone defines the word 'commercial.'

Microphone technology made crooning possible

Before the electric microphone, vocalists needed to project to have their voices captured. The new technology, however, made softer, more intimate singing possible, leading to a new style of singing that took off in the late 1920s, with "crooners" becoming some of the first American pop stars.

Thomas Edison publicly executed animals with AC to convince the public of its dangers

J.P. Morgan first backed Thomas Edison's direct current system, seeing electricity's potential to usurp John D. Rockefeller's kerosene empire. Despite the investments and smear campaign against alternating current, alternating current ultimately won public support after lighting the 1893 World's Fair, after which Morgan would fund Tesla's wireless transmission tower.

When a radio company was the biggest tech stock around

The Radio Corporation of America was the biggest stock during the 1920s. Originally called Marconi Wireless, the company transformed radio technology. The company pioneered broadcasting, created NBC, and became a tech giant. After remarkable growth and challenges, RCA was acquired by General Electric in 1986, marking the end of its 67-year independent existence.

Guglielmo Marconi overshadowed Nikola Tesla through commercialization

Despite Tesla envisioning wireless power and communication earlier, Marconi developed practical implementations of wireless communication, including transmitting the first transatlantic radio signal. The technology, which facilitated telegraphy critical for warships and navies, earned Marconi the 1909 Nobel Prize in physics.

A professor explains how podcasts built on radio's strengths

When podcasts were first produced in the early 2000s, they were often recordings of radio shows aimed at listeners who wanted to listen outside of the broadcast windows. Siobhan McHugh, an associate professor of journalism at Australia's University of Wollongong, argues that the form is built on radio's intimacy, amplifying the connection listeners feel with their favorite hosts.

Radio waves are used in broadcasting, weather radar, telecommunications, and GPS

Its ability to bend around obstacles and reflect off the ionosphere—an electrified layer of Earth's upper atmosphere—allows this type of light to travel long distances without damaging living things due to its low energy. MRI scanners, WiFi, and Bluetooth technologies are also applications of this form of light.

Radio quiz shows took off in the '40s

The concept took hold during the Great Depression, with 50 shows on the air by 1940, because they allowed families to imagine a financial windfall was just a few questions away. Although the genre had a slight downturn during World War II, it experienced a resurgence by the end of the decade, with 200 shows on the air.

In 1938, 1.7 million people were fooled into believing a Martian invasion was underway because of a radio play

Orson Welles' realistic radio dramatization of a Martian invasion of Earth, called "The War of the Worlds," caused quite a stir with audiences. The broadcast resulted in panic, with some people in the area where the story took place attempting to flee. It also helped Welles secure a contract with a Hollywood studio, leading to the creation of "Citizen Kane."

Thomas Edison, eager to communicate with ghosts, tinkered with an apparatus called the 'spirit phone.'

Pierre Curie's knowledge of electromagnetism helped decipher radioactivity

Alongside his brother, he studied electric fields in crystals and the magnetic properties of substances, which required the construction of delicate electrometers. He would use this apparatus with Marie Curie to measure radioactive emissions and the presence of undiscovered radioactive elements.

Many scholars consider the first commercial radio broadcast to be during the 1920 presidential election

On Nov. 2, Pittsburgh, Pennsylvania, station KDKA broadcast the results of the presidential election. Leo Rosenberg delivered the news that Warren Harding had won in a landslide to an audience of around 100 people.

Before 1932, when particle accelerators were first used for nuclear research, scientists relied on naturally radioactive substances to advance their understanding of the atomic nucleus.

Phil Spector's 'wall of sound' revolutionized girl groups—and pop music

The method captured a room of live musicians and transmitted the sound into a basement outfitted with more speakers and microphones. That sound was then sent into the central control room, producing a massive recording that sounded unlike anything else in pop music.

'Every day sees humanity more victorious in the struggle with space and time.'

- Radio inventor Guglielmo Marconi

Before radio jingles arrived in the 20th century, advertisers used poetry to sell their products.

How Lyndon Johnson created public radio

The Public Broadcasting Act of 1967, part of the president's Great Society plan, established the Corporation for Public Broadcasting, which later led to the incorporation of National Public Radio. Originally, the bill was intended solely to establish public television; before Johnson signed the act, slips of paper reading "and radio" were literally Scotch-taped next to each mention of "television."

Within an anechoic chamber, all surfaces are covered with specialized materials that prevent wave reflection, helping prevent sound from echoing in the space.

Calvin Coolidge brought the State of the Union to the radio age

On Dec. 6, 1923, President Coolidge delivered his Annual Message from the US House chamber as millions listened by radio—crowds gathered outside with amplifiers—making it the first nationally broadcast address and the only in-person State of the Union of his presidency.

Billie Holiday's distinctive vocal technique was aided by new microphone technology, which allowed for quieter singing.

A map of religious radio stations in the US

A Pew analysis of 440,000 hours of broadcasts found more than 4,000 faith-based AM/FM stations reach 98% of American adults (out of a total of 17,000 licensed stations). Ownership is highly concentrated, with the top 30% of stations belonging to large groups; Educational Media Foundation's K-LOVE and Air1 networks alone hold hundreds of licenses nationwide.

The Curies developed a way to measure radioactivity in an old medical dissecting room

Despite lacking proper laboratory conditions, Marie and Pierre built an ionization chamber and a piezoelectric quartz electrometer to measure the amount of charged particles released by radiation, with a sensitivity of ten-trillionth of an ampere. Substances with different emission rates indicated different elements.

Orson Welles' 1938 broadcast of 'War of the Worlds' invoked real panic

The raconteur's teleplay of HG Wells' 1898 science fiction novel presented the plot as a news broadcast, leading some listeners to believe that New Jersey was being invaded by Martians. This retrospective from the National Endowment for the Humanities unpacks how he made it happen, and the media fallout that ensued.

A DJ helped popularize the term 'rock 'n' roll' to resell rhythm and blues to a broad audience.

If a source of music traveled past someone at twice the speed of sound, assuming sufficiently sensitive hearing and powerful equipment, they would hear the music backward.

Jazz legend Louis Armstrong was once the honorary king of the Zulu krewe

The historically Black krewe invited Armstrong to lead their parade in 1949. The invitation fulfilled a lifelong dream for the musician, who grew up in New Orleans. "After that," he told Time magazine in advance of the parade, "I'll be ready to die."

A government mandate changed the sound of Canadian radio

In 1971, Canadian radio stations were required to ensure their programming included at least 30% Canadian artists. The impact was both cultural and commercial, with Canadian artists gaining more visibility at home and Canadian studios and songwriters earning more pay.

Stream live radio from anywhere on Earth

Spin a 3D globe and tune into thousands of live radio stations by clicking any dot on the map. The project is seamless and acts as a reminder that somewhere, right now, someone is broadcasting music, news, or a call-in show in a language you've never heard.

Hear Roosevelt's first 'Fireside Chat'

The president's casual radio addresses ditched the language of sloganeering and politiciking, intentionally framing the broadcasts as conversational explanations of current events and politics. The inaugural episode was broadcast in 1933, during the Great Depression, and outlined his plans to restore faith in the banking system.

The origin of atmospheric science while testing nuclear weapons during the Cold War

The arms race between the US and the Soviet Union saw both countries stockpiling and detonating hundreds of bombs underground, underwater, and in the atmosphere. To better predict where nuclear fallout would travel after these tests, scientists developed models that would serve as a foundation for those used to explain atmospheric circulation.

J.P. Morgan provided Nikola Tesla with funding for the Wardenclyffe Tower

The structure was part of a project to transmit electricity and communication signals wirelessly across the globe. Shortly after construction began, Guglielmo Marconi beat Tesla to the punch and transmitted a trans-Atlantic signal, preventing Tesla from getting additional funding to finish his project.

By measuring them in hot-air balloons during a partial solar eclipse and at night, Victor Hess discovered cosmic rays and concluded they came from beyond the solar system.

By igniting flammable gas in a tube filled with holes and playing music into it, the fire will take the shape of the sound waves, enabling the visualization of audio.

The Wrights’ patent battles delayed the development of aviation technology in the US

By the time World War I began in 1914, the US was lagging behind European powers in aviation. This stemmed primarily from wars over patents between the Wrights and competitor Glenn Curtiss. The pair argued their 1906 patent covered all mechanisms enabling lateral flight.

Carlin's 'Seven Words' led to a landmark Supreme Court ruling

The original recording of Carlin's bit aired on a New York radio station in 1973, leading to an FCC complaint. The case went up to the Supreme Court, which ruled that the FCC had the right to penalize broadcasters that aired obscene content during the daytime.

The earliest known country recording is a 1891 wax cylinder of Louis Vasnier's 'Thompson's Old Gray Mule' that was discovered by accident over a century later.

130,000 working musicians once went on strike

The early days of the record industry looked much different than they do now. There were few national record labels and there were organized musicians who viewed themselves more as day laborers rather than artists. That allowed for an organized strike by the American Federation of Musicians.

Watch a timeline of the history of electricity, from observations of static electricity in antiquity to the War of the Currents—a rivalry to establish the ideal system for electric grids.

Many of Wright's buildings used radiant heating

Frank Lloyd Wright’s buildings weren’t just radical because of how they looked, but many of them also incorporated stunning technological innovations. Radiant heating is one of Wright’s most popular heating systems, offering the comfort of walking on warm floors on a cold day.

The Grateful Dead pioneered a massive 3-story, 75-ton, 600-speaker sound system that revolutionized live audio in the early 1970s.

Marie Curie pioneered radioactivity research, for which she won two Nobel Prizes

Marie Curie and her husband isolated polonium and radium despite poor lab conditions and financial hardship. President Harding, on behalf of the women of America, presented her with one gram of radium in 1921 in recognition of her service to science.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.