Radio broadcasting
Transmission of audio signals via radio waves to receivers.
Radio broadcasting sends signals—mostly audio—over a wide area using radio waves, which must be picked up by a broadcast radio receiver. Terrestrial broadcasts come from land-based stations and include AM and FM (both analog) as well as DAB (digital). Audio can also be sent via satellite, in either digital or analog form, from a satellite orbiting Earth. Stations can create their own content or join a radio network, which supplies programming through syndication or simulcasting. The main transmission technologies are analog and digital: analog radio uses amplitude modulation (AM) or frequency modulation (FM), while digital radio relies on standards like DAB, HD Radio, or DRM.
**History**
**Pre-radio** Electronic distribution began on a small scale with the telegraph. Tickers, for instance, were mainly used to share stock prices, and time signals were offered as a subscription service. After the telephone was invented, the idea of audio broadcasting emerged. In a few places—mostly in Europe—telephone newspapers gave subscribers news and entertainment. These systems could charge individual customers, but without signal amplification, their range was usually limited to one city. Some early inventors saw the potential for wireless transmission. In 1902, Nathan Stubblefield, who had experimented with ground-conduction wireless, predicted that anyone with a simple receiver—just a telephone, some wire, and a signaling gong—could be alerted by a transmitting station in Washington (or closer) to receive weather news, and eventually all kinds of news.
**Radio** Though it was clear that radio could reach a scattered audience without wires, there was doubt about making money from it. In an 1898 review of early "Hertzian telegraphy," one critic noted that while it might be useful for shouting political speeches to the press, no one would pay for a system that couldn't prevent non-subscribers from listening for free. Another hurdle was that many countries required a license to operate a radio receiver. The earliest radio stations sent radiotelegraphy in dots and dashes—time signals, weather reports, or news summaries for shipboard newspapers. These had limited audiences because listeners needed to know Morse code. Starting in 1904, the U.S. Navy broadcast daily time signals and weather reports; a Canadian Marconi station in Camperdown, Nova Scotia, began time signals in 1907. In Europe, a station at the Eiffel Tower in Paris sent time signals audible across the continent, and even families in London could hear the "beep" to set their clocks. Weather reports also served as entertainment for these early audiences.
Most stations in the first two decades of the 1900s used radiotelegraphy, but there was experimental work on audio transmissions, mostly using amplitude modulation (AM). Early AM technologies included high-frequency spark, alternator, and arc transmitters. Widespread audio broadcasting only became practical with vacuum-tube (or "valve") transmitters. Most early experimenters focused on private radiotelephone systems, not on broadcasting to the general public. Early audio broadcasts included: in 1902, Julio Cervera Baviera transmitted audio from Xàbia to Ibiza; on December 21, 1906, Reginald Fessenden demonstrated audio using an alternator transmitter at Brant Rock, Massachusetts. According to a 1932 letter from Fessenden, he made the first of two broadcasts of music and entertainment on Christmas Eve 1906, and a second on New Year's Eve. He claimed these were widely publicized and heard as far as Norfolk, Virginia, and even the West Indies, but no contemporary evidence has been found to confirm them. Better documented are Lee de Forest’s early broadcasts using an arc transmitter; in February 1907, he transmitted electronic telharmonium music from his lab.
- field
- Telecommunications
- known_for
- Transmission of audio signals via radio waves to a wide audience
- key_technologies
- AM, FM, DAB, HD Radio, DRM, satellite
Lore & Background
Radio Argentina is sometimes cited as beginning regularly scheduled transmissions on August 27, 1920, from Buenos Aires, but this claim is disputed and not universally accepted as established canon.
Reader's Guide
Radio broadcasting transformed communication by enabling audio signals to reach a scattered audience without connecting wires, overcoming early skepticism about financing and licensing. Its development from radiotelegraphy to analog AM and FM, and later digital standards like DAB, HD Radio, and DRM, allowed for widespread distribution of news, entertainment, and time signals. Early pioneers such as Fessenden, de Forest, Herrold, and Idzerda demonstrated the potential of audio broadcasting, though some claims remain unverified. The technology's evolution, including satellite broadcasting, has made it a global medium, despite initial limitations in range and the need for listeners to understand Morse code. Radio's legacy includes its role in providing real-time information and entertainment, shaping public discourse and culture.
Did You Know?
- The earliest radio broadcasting stations transmitted radiotelegraphy dots-and-dashes for time signals and weather reports, requiring Morse code knowledge.
From Sowing Seeds to Sowing Signals
The word broadcasting carries an unexpectedly pastoral origin. It was borrowed from the agricultural practice of scattering seeds broadly across a field, and by the late nineteenth century it had already been applied to the wide distribution of printed materials and telegraph messages. These early efforts marked the decisive shift from the one-to-one model of telegraph and telephone toward true mass communication.
Wars as Catalysts for Mass Airwaves
Before the 1920s, most electronic communication followed a strictly one-to-one pattern: a telephone call, a telegraph message, or a radio signal all intended for a single recipient. World War I shattered that limitation by pushing radio technology into military communications on a scale civilian life had never demanded. In the postwar years, commercial AM broadcasting took off, powered by the spread of vacuum tube transmitters and receivers, and quickly became a dominant medium for both entertainment and news. World War II then accelerated development again, driving advances in aircraft and land communication, radio navigation, and radar. Stereo FM broadcasting began its development in the United States during the 1930s and later in the United Kingdom in the 1970s, gradually displacing AM as the dominant commercial standard. The U.S. Code of Federal Regulations, title 47, part 97, formally distinguishes broadcasting as transmissions intended for reception by the general public, whether direct or relayed, explicitly excluding private two-way telecommunications such as amateur ham radio or citizens band operators.
From Mechanical Disks to Digital Streams
Television's journey from laboratory curiosity to household staple spanned decades of competing technologies. Meanwhile, Philo Farnsworth produced the first cathode-ray-tube television to show real promise, demonstrating it to his family on 7 September 1927. After World War II interrupted further experimentation, television resumed its ascent and became a major home entertainment medium using VHF and UHF spectrum. Satellite broadcasting launched in the 1960s, moved into general industry use in the 1970s, and saw Direct Broadcast Satellites emerge in the 1980s. By the 2000s, the entire field was transitioning from analog signals, where voltage varied continuously with sound pressure, to digital signals representing information as sampled, quantized values, and streaming technology began to be classified as broadcasting as well.
The Expanding Reach of One-to-Many
The sheer volume of information flowing through one-way broadcast networks has grown at a staggering pace. The delivery mechanisms have diversified enormously alongside this growth. Over-the-air terrestrial broadcasting, which in most countries requires a license, remains the classic model: a high-powered tower emits a modulated high-frequency electromagnetic wave, and any receiver tuned to that frequency can demodulate the audio or visual signal. Cable television, which retransmits over-the-air stations with their consent, is also classified as broadcasting but does not always require a license. The field encompasses government-managed services like public radio and community radio alongside private commercial stations, and the U.S. regulatory framework explicitly excludes two-way private transmissions from the definition of broadcasting.
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