Search results
Results from the WOW.Com Content Network
Before the discovery of electromagnetic waves and the development of radio communication, there were many wireless telegraph systems proposed and tested. [4] In April 1872 William Henry Ward received U.S. patent 126,356 for a wireless telegraphy system where he theorized that convection currents in the atmosphere could carry signals like a telegraph wire. [5]
The early history of radio is the history of technology that produces and uses radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting.
The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history .
Radio waves were first predicted by the theory of electromagnetism that was proposed in 1867 by Scottish mathematical physicist James Clerk Maxwell. [5] His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
Although they often faced obstacles and policy limitations, beginning in the early 1900s a few women were able to participate in the pioneering development of radio communication. Anna Nevins began working for United Wireless in 1906 , and is shown here at the station atop the Waldorf-Astoria Hotel in New York City in 1909.
Invented in 1952 by Virginia Apgar. Disposable diapers The first disposable diaper was invented in 1946 by Marion Donovan, a professional-turned-housewife who wanted to ensure her children's cloth diapers remained dry while they slept. [12] Donovan patented her design (called 'Boaters') in 1951.
The first practical radio transmitters and receivers invented in 1894–1895 by Guglielmo Marconi used radiotelegraphy. [5] It continued to be the only type of radio transmission during the first few decades of radio, called the "wireless telegraphy era" up until World War I , when the development of amplitude modulation (AM) radiotelephony ...
Radio broadcasting has been used in the United States since the early 1920s to distribute news and entertainment to a national audience. In 1923, 1 percent of U.S. households owned at least one radio receiver, while a majority did by 1931 and 75 percent did by 1937.