The Sounds of the Airwaves: The Evolution of Radio


In the age of instant information and music streaming, the radio remains one of the most popular means of communication to the American public. While we generally think of the radio as a source of music and the morning commute traffic, the history of radio broadcasting includes far more than just the American Top 40. Built on a century’s worth of electronics research, the radio as we know it today is a technological marvel few would have been able to predict at its inception in the late-19th-century.

But how did a technology primarily developed for use by military sailors become the most popular form of entertainment in the 20th century, and a tool for mass entertainment in the 21st? Here, we examine the radio from its beginnings as “Hertzian waves” to its inevitable place as a 20th-century center of American homes and culture.

Electromagnetic Beginnings

Decades before Detroit would be able to air the first radio news program, James Clerk Maxwell was lecturing about his theories of electromagnetism. Maxwell, who began work on the connections between electricity and magnetism as early as 1855, published a landmark essay in 1865 entitled “A Dynamical Theory of the Electromagnetic Field.” Maxwell claimed his findings demonstrated that both electric and magnetic waves travelled within space at the speed of light, and that light itself was a type of wave that could circulate through a vacuum. His research also introduced various mathematical proofs to support his deductions, which would later fuel the research of physicists like Albert Einstein.

Reprinted from Bay Area Radio by John F. Schneider in association with the California Historical Radio Society and its bay Area Radio Museum courtesy of History San Jose (pg. 11, Arcadia Publishing, 2012).
Reprinted from Bay Area Radio by John F. Schneider in association with the California Historical Radio Society and its bay Area Radio Museum courtesy of History San Jose (pg. 11, Arcadia Publishing, 2012).

However, Maxwell’s research focused mainly on the theory behind electromagnetism, rather than its more practical applications. It was not until 1886 that Maxwell’s theories could be practically proven, when physicist Heinrich Hertz discovered that released static electricity could move between two Riess spiral coils. This discovery allowed Hertz to create the earliest version of a radio transmitter, as the spark of electricity between the coils would emit radio waves along the radio frequency spectrum. These waves, which Hertz later proved could be received by simple antennas, quickly became known at the time as “Hertzian waves” – they would not become “radio waves” for another two decades after Hertz’s breakthrough discovery.

The Fathers of Radio: Guglielmo Marconi and Lee de Forest

Reprinted from Capital Region Radio: 1920-2011 by Rick Kelly and John Gabriel (pg. 16, Arcadia Publishing, 2014).
Reprinted from Capital Region Radio: 1920-2011 by Rick Kelly and John Gabriel (pg. 16, Arcadia Publishing, 2014).

Hertz and Maxwell’s various findings quickly excited the scientific community, leading researchers and inventors alike to scramble to build devices similar to Hertz’s transmitter. At the time of Hertz’s experiments, the only way to communicate messages quickly over distances required complex systems of wires, for which the United States had developed an intricate telegraphy system. But with the discovery of the Hertzian wave came a method by which messages could be sent and delivered wirelessly; these various transmitters all operated on Hertz basis of “spark” transmitting, producing intermittent pulses of radio waves.

The most successful of these transmitters came from an Italian inventor name Guglielmo Marconi, who created the first complete and commercially viable transmitter in 1894. His transmitter did not closely resemble the radio transmitters of today – not only was voice transmission impractical due to the broken, intermittent nature of spark radio, but it also required that users send their messages by way of Morse code. As a result of these limitations, Marconi marketed his invention not for entertainment broadcast, but for use in military and maritime endeavors. These industries were slow to accept his invention however, amid fears that it would not efficiently transmit crucial messages. Only after Marconi demonstrated that his transmitter was capable of sending a signal that could be received across the Atlantic Ocean in 1901 did his invention (and radio) begin to take off – soon after his demonstration, which required audio reception spanning 2,200 miles, his transmitters were used for both ship-to-ship and ship-to-shore communications.

Reprinted from New York City Radio by Alec Cumming and Peter Kanze (pg. 9, Arcadia Publishing, 2013).
Reprinted from New York City Radio by Alec Cumming and Peter Kanze (pg. 9, Arcadia Publishing, 2013).

Marconi was not the only inventor looking to capitalize on the commercial applications of radio however – American Lee de Forest competed alongside Marconi to produce a transmitter that could be utilized for maritime purposes, though to far less success. While these efforts largely failed, de Forest experiments led him to create a variation on the arc transmitter in 1906, which was originally created in Denmark in 1903. The arc transmitter, which produced a continuous radio wave transmission by converting direct electrical current into an alternative radio wave current, created a sparkles current that allowed de Forest to transmit voice across “amplitude modulated” audio transmissions, otherwise known as AM radio.

Despite this major development, de Forest’s early voice transmissions across the AM band struggled with low volume and a poor quality, leading the inventor to devise a solution that would improve his transmissions. This solution presented itself in de Forest’s later design of the Audion, a vacuum tube which proved successful at amplifying signals enough that voice could be heard fairly well across the airwaves.

Although the potential for this technology was wide, de Forest chose to market the invention as useful in maritime and military technology like his competitor Marconi. Ultimately, de Forest was the first to make a ship-to-shore radiotelephone (or voice) communication. The US Navy quickly adopted de Forest’s technology aboard their ships for voice communications, but the Audion was not widely used in other applications at the time. Although its original scope was limited, the Audion provided the basis for later developments of the triode, an improved vacuum tube that would lead to the first commercial radio broadcasts.

Amateur Radio Breaks the Barriers

Reprinted from Pittsburgh’s Golden Age of Radio by Ed Salamon courtesy of KDKA (pg. 12, Arcadia Publishing, 2010).
Reprinted from Pittsburgh’s Golden Age of Radio by Ed Salamon courtesy of KDKA (pg. 12, Arcadia Publishing, 2010).

The novelty of radio broadcasting quickly drew hundreds to the medium. Once Marconi and de Forest’s improved audio technology was introduced in 1906, Amateur Radio operators (who had previously experimented with Hertz’s early radio discoveries and Marconi’s spark transmitters) quickly took to transmitting on the air. The success of early radio was immediately apparent – by 1909 there were 89 registered Amateur Radio stations across the United States and Canada, and the first Amateur Radio club (known then as the Junior Wireless Club) had been formed.

These early broadcasters were completely unregulated by the government, however – due to how new radio was, many did not see the necessity in restricting which groups could speak on various channels. Amateur Radio operators frequently mingled then with government and maritime transmissions alike, often obscuring important messages as a result. Many of these interferences were unintentional, but several younger operators would maliciously interfere with frequencies, making it difficult for official messages to reach their destination.

Reprinted from Richmond, Virginia, and the Titanic by Walter S. Griggs Jr. courtesy of Wikimedia Commons (pg. 30, The History Press, 2015).
Reprinted from Richmond, Virginia, and the Titanic by Walter S. Griggs Jr. courtesy of Wikimedia Commons (pg. 30, The History Press, 2015).

These unregulated practices were allowed to continue for several years until the 1912 sinking of the RMS Titanic. After investigating how the sinking of the ship occurred, it was discovered that in addition to faulty communications from the ship to nearby vessels, amateur transmissions had interfered with the information passed from ship-to-shore about the disaster. As a result, initial reports suggested all passengers had survived, when in reality only 745 of the estimated 2,222 on board were rescued. This was quickly proven to be false, and only served to further the anger surrounding the disaster.

The US government was quick to respond in an attempt to avoid similar disasters by passing the Radio Act of 1912, which not only required all radio operators (amateur or not) to hold a license, but also limited amateur transmissions to frequencies of 200 meters or shorter. These shorter frequencies were widely regarded as less desirable as they restricted how far messages could reach, and amateur transmissions nearly ceased altogether in the wake of the law. 

While the limitations placed on amateur wavelengths hurt radio’s recreational practice, it also opened up the door for more local (and personalized) commercial transmissions. While some radio programs had begun as early as 1906, they did not become common until after the passage of the Radio Act and World War I, during which a ban on all non-military radio transmissions was placed. This ban was lifted following the end of the war in 1918, and by 1920 the first radio news broadcast found its way onto the air under the call sign 8MK. The call sign, operated by a small news station in Detroit, was registered as an amateur call sign – a practice that quickly became common for commercial radio stations around the country, as amateur radio gave way to the new local commercial broadcasts.

The Golden Age of Radio

The practice of commercial radio using amateur call signs continued until the government released the Radio Act of 1927, which, among other things, established the Federal Radio Commission (a predecessor to the FCC), and created commercial call signs under a new federal license. Many stations were quick to obtain such licenses, the first being given to Pittsburgh station 8XK, which became the historic KDKA. KDKA was known as a pioneer of  commercial radio broadcasting, being not only the first station to receive a federal license, but also the first to introduce programming for children, concert band broadcasts, and scheduled church services.

Reprinted from Pittsburgh’s Golden Age of Radio by Ed Salamon courtesy of KDKA (pg. 18, Arcadia Publishing, 2010).
Reprinted from Pittsburgh’s Golden Age of Radio by Ed Salamon courtesy of KDKA (pg. 18, Arcadia Publishing, 2010).

The near-instant success of KDKA encouraged radio stations across the country to begin their own regularly scheduled programming, and by 1927 both the National Broadcasting Company (NBC) and the Columbia Broadcasting System (CBS) had been established for regular broadcast. Early commercial radio through these systems focused on providing news with small bits of entertainment to audiences, but that changed with the formation of the Mutual Broadcasting System (MBS) in 1934. MBS had been created by a variety of independent radio stations coming together to exchange syndicated radio programs, and was responsible for the success of major radio dramas throughout the 1930s and 40s like The Lone Ranger and The Adventures of Superman. As a result, radio became one of the main sources of entertainment prior to the invention of television following World War II.

Radio also served as one of the main channels of official communications from the government to the people. Starting in 1933, President Franklin D. Roosevelt began a series of what are today known as the “fireside chats,” during which he updated the American people on issues of public concern, including the recession, his New Deal proposals, and the status of World War II. These addresses set a precedent for future presidents, as every successor to FDR has provided a periodic update to the American public – first by radio, and later by television. By the early 1950s, radio had become the most popular medium for entertainment and news, and its immense popularity had led to the invention of transportable pocket radios.

Television, the Late-20th-Century, and Radio Today

With the creation of television in the mid-to-late 1950s, radio began to suffer as an entertainment medium, as more and more listeners moved on to television for their amusement. TV, which was initially regarded as “radio with pictures,” used the technology of radio waves to transmit a picture along with its audio. Many traditional radio programs had ceased by 1960 as a result, and radio stations moved to producing programs like the Top 40 countdown, focusing on broadcasting news headlines alongside popular music.

Despite radio’s decreasing popularity in entertainment, it continued to hold a formidable place throughout the late-20th-century. By the late 1960s, radio had evolved beyond basic AM and FM bands to digital radio, which converted sound into a series of digits (hence digital), rather than the traditional electrical signals. Digital radio was used to develop technologies like the US long-distance telephone network, and was later adopted by broadcasting in the late 1990s to create satellite radio services like Sirius and XM. Radio was also instrumental in the development of the Global Positioning System (GPS) via space satellites, and radio navigation systems like the LORAN system of the 1970s.

Reprinted from New York City Radio by Alex Cumming and Peter Kanze courtesy of Library of American Broadcasting (pg. 112, Arcadia Publishing, 2013).
Reprinted from New York City Radio by Alex Cumming and Peter Kanze courtesy of Library of American Broadcasting (pg. 112, Arcadia Publishing, 2013).

Today, AM and FM (also known as terrestrial) radio remains a popular means of entertainment for the American public, with nearly half of all Americans discovering new music through traditional terrestrial radio. Despite the popularity of music-streaming services such as Spotify, radio continues to hold a strong presence within American culture, with a legacy that can be felt throughout all of modern technology.

Do you want to learn more about the Golden Age of radio, or have an interest in broadcasting? Explore our various titles about radio in American cities.