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. Advertising quickly became the main source of profits, and stations were aggregated into national networks—NBC in 1926, CBS in 1928. At the same time, the U.S. government took control of the spectrum to deal with the increasing problem of signal interference. Elsewhere, some governments chose to go into the broadcasting business themselves, but the American approach was inarguably dynamic. Four out of five U.S. households had radio by the late 1930s. Favorite network shows such as The Jack Benny Program drew audiences in the millions and were avidly discussed the next day. During the Depression and the years of war that followed, President Franklin D. Roosevelt regularly spoke to the country by radio, as did other national leaders.
Major advances in radio technology still lay ahead, but many electrical engineers were now focused on the challenge of using electromagnetic waves to transmit moving images. The idea of electrically conveying pictures from one place to another wasn't new. Back in 1884 a German inventor named Paul Nipkow patented a system that did it with two disks, each identically perforated with a spiral pattern of holes and spun at exactly the same rate by motors. The first whirling disk scanned the image, with light passing through the holes and hitting photocells to create an electrical signal. That signal traveled to a receiver (initially by wire) and controlled the output of a neon lamp placed in front of the second disk, whose spinning holes replicated the original scan on a screen. In later, better versions, disk scanning was able to capture and reconstruct images fast enough to be perceived as smooth movement—at least 24 frames per second. The method was used for rudimentary television broadcasts in the United States, Britain, and Germany during the 1920s and 1930s. Major advances in radio technology still lay ahead, but many electrical engineers were now focused on the challenge of using electromagnetic waves to transmit moving images. The idea of electrically conveying pictures from one place to another wasn't new. Back in 1884 a German inventor named Paul Nipkow patented a system that did it with two disks, each identically perforated with a spiral pattern of holes and spun at exactly the same rate by motors. The first whirling disk scanned the image, with light passing through the holes and hitting photocells to create an electrical signal. That signal traveled to a receiver (initially by wire) and controlled the output of a neon lamp placed in front of the second disk, whose spinning holes replicated the original scan on a screen. In later, better versions, disk scanning was able to capture and reconstruct images fast enough to be perceived as smooth movement—at least 24 frames per second. The method was used for rudimentary television broadcasts in the United States, Britain, and Germany during the 1920s and 1930s. But all-electronic television was on the way. A key component was a 19th-century invention, the cathode-ray tube, which generated a beam of electrons and used electrical or magnetic forces to steer the beam across a surface—in a line-by-line scanning pattern if desired. In 1908 a British lighting engineer, Campbell Swinton, proposed using one such tube as a camera, scanning an image that was projected onto a mosaic of photoelectric elements. The resulting electric signal would be sent to a second cathode-ray tube whose scanning beam re-created the image by causing a fluorescent screen to glow. It was a dazzling concept, but constructing such a setup was far beyond the technology of the day. As late as 1920 Swinton gloomily commented: "I think you would have to spend some years in hard work, and then would the result be worth anything financially?" A young man from Utah, Philo Farnsworth, believed it would. Enamored of all things electrical, he began thinking about a similar scanning system as a teenager. In 1927, when he was just 21, he successfully built and patented his dream. But as he tried to commercialize it he ran afoul of the redoubtable David Sarnoff of RCA, who had long been interested in television. Several years earlier Sarnoff had told his board of directors that he expected every American household to someday have an appliance that "will make it possible for those at home to see as well as hear what is going on at the broadcast station." Sarnoff tried to buy the rights to Farnsworth's designs, but when his offer was rebuffed, he set about creating a proprietary system for RCA, an effort that was led by Vladimir Zworykin, a talented electrical engineer from Russia who had been developing his own electronic TV system. After several years and massive expenditures, Zworykin completed the job, adapting some of Farnsworth's ideas. Sarnoff publicized the product by televising the opening of the 1939 World's Fair in New York, but in the end he had to pay for a license to Farnsworth's patents anyway.
Do'stlaringiz bilan baham:
|
