The scientific groundwork for radio and television was laid by the Scottish physicist James Clerk Maxwell, who in 1864 theorized that changes in electrical and magnetic forces send waves spreading through space at 186,000 miles per second. Light consists of such waves, Maxwell said, adding that others might exist at different frequencies. In 1888 a German scientist named Heinrich Hertz confirmed Maxwell's surmise with an apparatus that used sparks to produce an oscillating electric current; the current, in turn, generated electromagnetic energy that caused matching sparks to leap across a gap in a receiving loop of wire a few yards away. And in 1900 brilliant inventor Nikola Tesla was granted two patents for basic radio concepts and devices that inspired others after him. The scientific groundwork for radio and television was laid by the Scottish physicist James Clerk Maxwell, who in 1864 theorized that changes in electrical and magnetic forces send waves spreading through space at 186,000 miles per second. Light consists of such waves, Maxwell said, adding that others might exist at different frequencies. In 1888 a German scientist named Heinrich Hertz confirmed Maxwell's surmise with an apparatus that used sparks to produce an oscillating electric current; the current, in turn, generated electromagnetic energy that caused matching sparks to leap across a gap in a receiving loop of wire a few yards away. And in 1900 brilliant inventor Nikola Tesla was granted two patents for basic radio concepts and devices that inspired others after him. Fascinated by such findings, Guglielmo Marconi, son of an Irish heiress and Italian aristocrat, began experimenting with electricity as a teenager and soon was in hot pursuit of what he called "wireless telegraphy." In the system he developed, Hertzian sparks created the electromagnetic waves, but Marconi greatly extended their effective range by electrically grounding the transmitter and aerial. At the heart of his receiver was a device called a coherer—a bulb containing iron filings that lost electrical resistance when hit by high-frequency waves. The bulb had to be tapped to separate the filings and restore sensitivity after each pulse was received. As evidenced by his America's Cup feat in 1899, Marconi was a master of promotion. In 1901 he gained worldwide attention by transmitting the letter "s"—three Morse pips—across the Atlantic. Although his equipment didn't work well over land, he built a successful business by selling wireless telegraphy to shipping companies, maritime insurers, and the world's navies. Telegraphy remained his focus. He didn't see a market beyond point-to-point communication.
Meanwhile, other experimenters were seeking ways to generate radio waves steadily rather than as sparkmade pulses. Such continuous waves might be electrically varied—modulated—to convey speech or music. In 1906 that feat was achieved by a Canadian-American professor of electrical engineering, Reginald Fessenden. To create continuous waves, he used an alternator, designed by General Electric engineer Ernst Alexanderson, that rotated at very high speed. Unfortunately, the equipment was expensive and unwieldy, and Fessenden, in any event, was a poor businessman, hatching such unlikely profit schemes as charging by the mile for transmissions. Meanwhile, other experimenters were seeking ways to generate radio waves steadily rather than as sparkmade pulses. Such continuous waves might be electrically varied—modulated—to convey speech or music. In 1906 that feat was achieved by a Canadian-American professor of electrical engineering, Reginald Fessenden. To create continuous waves, he used an alternator, designed by General Electric engineer Ernst Alexanderson, that rotated at very high speed. Unfortunately, the equipment was expensive and unwieldy, and Fessenden, in any event, was a poor businessman, hatching such unlikely profit schemes as charging by the mile for transmissions. Fortune also eluded Lee De Forest, another American entrepreneur who tried to commercialize continuous-wave transmissions. In his case the waves were generated with an arc lamp, a method pioneered by Valdemar Poulsen, a Danish scientist. De Forest himself came up with one momentous innovation in 1906—a three-element vacuum tube, or triode, that could amplify an electrical signal. He didn't really understand how it worked or what it might mean for radio, but a young electrical engineer at Columbia University did. In 1912, Edwin Howard Armstrong realized that, by using a feedback circuit to repeatedly pass a signal through a triode, the amplification (hence the sensitivity of a receiver) could be increased a thousandfold. Not only that, but at its highest amplification the tube ceased to be a receiving device and became a generator of radio waves. An all-electronic system was at last feasible.
By the early 1920s, after further refinements of transmitters, tuners, amplifiers, and other components, the medium was ready for takeoff. Broadcasting, rather than point-to-point communication, was clearly the future, and the term "wireless" had given way to "radio," suggesting omnidirectional radiation. In the business world, no one saw the possibilities more clearly than David Sarnoff, who started out as a telegrapher in Marconi's company. After the company was folded into the Radio Corporation of America (RCA) in 1919, Sarnoff rose to the pinnacle of the industry. As early as 1915 he wrote a visionary memo proposing the creation of a small, cheap, easily tuned receiver that would make radio a "household utility," with each station transmitting news, lectures, concerts, and baseball games to hundreds of thousands of people simultaneously. World War I delayed matters, but in 1921 Sarnoff demonstrated the market's potential by broadcasting a championship boxing match between heavyweights Jack Dempsey and Georges Carpentier of France. Since radios weren't yet common, receivers in theaters and in New York's Times Square carried the fight—a Dempsey knockout that thrilled the 300,000 gathered listeners. By 1923 RCA and other American companies were producing half a million radios a year.
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