Radio and television were major agents of social change in the 20th century, opening windows to other peoples and places and bringing distant events directly into millions of homes. Although Guglielmo Marconi was the first to put the theory of radio waves into practice, the groundwork for his feat was laid in the 19th century by James Clerk Maxwell, Heinrich Hertz, and Nikola Tesla. Maxwell theorized and Hertz confirmed the feasibility of transmitting electromagnetic signals. Tesla invented a device—the Tesla coil-that converts relatively low-voltage current to high—voltage low current at high frequencies. Some form of the coil is still used in radio and television sets today.
| 1900 |
Tesla granted a U.S. patent Nikola Tesla is granted a U.S. patent for a "system of transmitting electrical energy" and another patent for "an electrical transmitter"—both the products of his years of development in transmitting and receiving radio signals. These patents would be challenged and upheld (1903), reversed (1904), and finally restored (1943). |
| 1901 |
Marconi picks up the first transatlantic radio signal Guglielmo Marconi, waiting at a wireless receiver in St. John’s, Newfoundland, picks up the first transatlantic radio signal, transmitted some 2,000 miles from a Marconi station in Cornwall, England. To send the signal—the three dots of the Morse letter "s"—Marconi’s engineers send a copper wire aerial skyward by hoisting it with a kite. Marconi builds a booming business using radio as a new way to send Morse code. |
| 1904 |
Fleming invents the vacuum diode British engineer Sir John Ambrose Fleming invents the two-electrode radio rectifier; or vacuum diode, which he calls an oscillation valve. Based on Edison's lightbulbs, the valve reliably detects radio waves. Transcontinental telephone service becomes possible with Lee De Forest's 1907 patent of the triode, or three-element vacuum tube, which electronically amplifies signals. |
| 1906 |
Audion Expanding on Fleming’s invention, American entrepreneur Lee De Forest puts a third wire, or grid, into a vacuum tube, creating a sensitive receiver. He calls his invention the "Audion." In later experiments he feeds the Audion output back into its grid and finds that this regenerative circuit can transmit signals. |
| 1906 |
Christmas Eve 1906 program On Christmas Eve 1906 engineering professor Reginald Fessenden transmits a voice and music program in Massachusetts that is picked up as far away as Virginia. |
| 1912 |
Radio signal amplifier devised Columbia University electrical engineering student Edwin Howard Armstrong devises a regenerative circuit for the triode that amplifies radio signals. By pushing the current to the highest level of amplification, he also discovers the key to continuous-wave transmission, which becomes the basis for amplitude modulation (AM) radio. In a long patent suit with Lee De Forest, whose three-element Audion was the basis for Armstrong’s work, the courts eventually decide in favor of De Forest, but the scientific community credits Armstrong as the inventor of the regenerative circuit. |
| 1917 |
Superheterodyne circuit While serving in the U.S. Army Signal Corps during World War I, Edwin Howard Armstrong invents the superheterodyne circuit, an eight-tube receiver that dramatically improves the reception of radio signals by reducing static and increasing selectivity and amplification. He files for a patent the following year. |
| 1920 |
First scheduled commercial radio programmer Station KDKA in Pittsburgh becomes radio’s first scheduled commercial programmer with its broadcast of the Harding-Cox presidential election returns, transmitted at 100 watts from a wooden shack atop the Westinghouse Company’s East Pittsburgh plant. Throughout the broadcast KDKA intersperses the election returns and occasional music with a message: "Will anyone hearing this broadcast please communicate with us, as we are anxious to know how far the broadcast is reaching and how it is being received?" |
| 1925 |
Televisor Scottish inventor John Logie Baird successfully transmits the first recognizable image—the head of a ventriloquist’s dummy—at a London department store, using a device he calls a Televisor. A mechanical system based on the spinning disk scanner developed in the 1880s by German scientist Paul Nipkow, it requires synchronization of the transmitter and receiver disks. The Televisor images, composed of 30 lines flashing 10 times per second, are so hard to watch they give viewers a headache. |
| 1927 |
All-electronic television system Using his all-electronic television system, 21-year-old Utah farm boy and electronic prodigy Philo T. Farnsworth transmits images of a piece of glass painted black, with a center line scratched into the paint. The glass is positioned between a blindingly bright carbon arc lamp and Farnsworth’s "image dissector" cathode-ray camera tube. As viewers in the next room watch a cathode-ray tube receiver, someone turns the glass slide 90 degrees—and the line moves. The use of cathode-ray tubes to transmit and receive pictures—a concept first promoted by British lighting engineer A. Campbell Swinton—is the death knell for the mechanical rotating-disk scanner system. |
| 1928 |
Televisor system produces images in crude color John Logie Baird demonstrates, with the aid of two ventriloquist’s dummies, that his Televisor system can produce images in crude color by covering three sets of holes in his mechanical scanning disks with gels of the three primary colors. The results, as reported in 1929 following an experimental BBC broadcast, appear "as a soft-tone photograph illuminated by a reddish-orange light." |
| 1929 |
Television camera and a cathode-ray tube receiver Vladimir Zworykin, who came to the United States from Russia in 1919, demonstrates the newest version of his iconoscope, a cathode-ray-based television camera that scans images electronically, and a cathode-ray tube receiver called the kinescope. The iconoscope, first developed in 1923, is similar to Philo Farnsworth’s "image dissector" camera tube invention, fueling the growing rivalry between the two inventors for the eventual title of "father of modern television." |
| 1933 |
FM radio Edwin Howard Armstrong develops frequency modulation, or FM, radio as a solution to the static interference problem that plagues AM radio transmission, especially in summer when electrical storms are prevalent. Rather than increasing the strength or amplitude of his radio waves, Armstrong changes only the frequency on which they are transmitted. However, it will be several years before FM receivers come on the market. |
| 1947 |
Transistor is invented The future of radio and television is forever changed when John Bardeen, Walter Brattain, and William Shockley of Bell Laboratories co-invent the transistor. |
| 1950s |
Cathode-ray tube (CRT) for television monitors improved Engineers improve the rectangular cathode-ray tube (CRT) for television monitors, eliminating the need for rectangular "masks" over the round picture tubes of earlier monitors. The average price of a television set drops from $500 to $200. |
| 1953 |
RCA’s new system for commercial color adopted RCA beats out rival CBS when the National Television System Committee adopts RCA’s new system for commercial color TV broadcasting. CBS has pioneered color telecasting, but its system is incompatible with existing black-and-white TV monitors throughout the country. |
| 1954 |
First coast-to-coast color television transmission The New Year’s Day Tournament of Roses in Pasadena, California, becomes the first coast-to-coast color television transmission, or "colorcast." The parade is broadcast by RCA’s NBC network to 21 specially equipped stations and is viewed on newly designed 12-inch RCA Victor receivers set up in selected public venues. Six weeks later NBC’s Camel News Caravan transmits in color, and the following summer the network launches its first color sitcom, The Marriage, starring Hume Cronyn and Jessica Tandy. |
| 1954 |
First all-transistor radio Regency Electronics introduces the TR-1, the first all-transistor radio. It operates on a 22-volt battery and works as soon as it is switched on, unlike tube radios, which take several minutes to warm up. The TR-1 sells for $49.95; is available in six colors, including mandarin red, cloud gray and olive green; and is no larger than a package of cigarettes. |
| 1958 |
Integrated circuit Jack S. Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor, working independently, create the integrated circuit, a composite semiconductor block in which transistor, resistor, condenser, and other electrical components are manufactured together as one unit. Initially, the revolutionary invention is seen primarily as an advancement for radio and television, which together were then the nation’s largest electronics industry. |
| 1962 |
Telstar 1 Communications satellite Telstar 1 is launched by a NASA Delta rocket on July 10, transmitting the first live transatlantic telecast as well as telephone and data signals. At a cost of $6 million provided by AT&T, Bell Telephone Laboratories designs and builds Telstar, a faceted sphere 34 inches in diameter and weighing 171 pounds. The first international television broadcasts shows images of the American flag flying over Andover, Maine to the sound of "The Star-Spangled Banner." Later that day AT&T chairman Fred Kappel makes the first long-distance telephone call via satellite to Vice President Lyndon Johnson. Telstar I remains in orbit for seven months, relaying live baseball games, images from the Seattle World's Fair, and a presidential news conference. |
| 1968 |
200 million television sets There are 200 million television sets in operation worldwide, up from 100 million in 1960. By 1979 the number reaches 300 million and by 1996 over a billion. In the United States the number grows from 1 million in 1948 to 78 million in 1968. In 1950 only 9 percent of American homes have a TV set; in 1962, 90 percent; and in 1978, 98 percent, with 78 percent owning a color TV. |
| 1988 |
Sony "Watchman" Sony introduces the first in its "Watchman" series of handheld, battery-operated, transistorized television sets. Model FD-210, with its 1.75-inch screen, is the latest entry in a 30-year competition among manufacturers to produce tiny micro-televisions. The first transistorized TV, Philco’s 1959 Safari, stood 15 inches high and weighed 15 pounds. |
| 1990 |
FCC sets a testing schedule for proposed all-digital HDTV system Following a demonstration by Philips two years earlier of a high-definition TV (HDTV) system for satellite transmission, the Federal Communications Commission sets a testing schedule for a proposed all-digital HDTV system. Tests begin the next year, and in 1996 Zenith introduces the first HDTV-compatible front-projection television. Also in 1996, broadcasters, TV manufacturers, and PC makers set inter-industry standards for digital HDTV. By the end of the century, digital HDTV, which produces better picture and sound than analog television and can transmit more data faster, is on the verge of offering completely interactive TV. |
Many people doubted that such a thing was possible, but a young inventor named Guglielmo Marconi proceeded to make good on the promise, using cumbersome sparking devices on observation boats to transmit Morse code messages to land stations a few miles away.
A hundred years later that trickle of dots and dashes had evolved into mighty rivers of information. When another America's Cup competition was held in New Zealand in early 2000, for instance, every detail of the action—the swift maneuvers, straining sails, sunlight winking in spray—was captured by television cameras and then relayed up to a satellite and back down again for distribution to audiences around the world. The imagery rode on the same invisible energy that Marconi had harnessed: radio waves.
Any radio or television signal of today, of course, amounts to only a minuscule fraction of the electromagnetic flow now binding the planet together. Day and night, tens of thousands of radio stations broadcast voice and music to homes, cars, and portable receivers, some that weigh mere ounces. Television pours huge volumes of entertainment, news, sports events, children's programming, and other fare into most households in the developed world. (The household penetration of TV in the United States is 98 percent and average daily viewing time totals 7 hours.) Unrivaled in reach and immediacy, these electronic media bear the main burden of keeping the public informed in times of crisis and provide everyday coverage of the local, regional, and national scenes. But mass communication is only part of the story. Police and fire departments, taxi and delivery companies, jetliner pilots and soldiers all communicate on assigned frequencies. Pagers, cell phones, and wireless links for computers fill additional slices of the spectrum, a now precious realm administered by national and international agencies. As a force for smooth functioning and cohesion of society, radio energy has no equal.
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.
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.
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.
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.
In the ensuing years RCA flooded the market with millions of black-and-white TV sets and also took aim at the next big opportunity—color television. CBS had an electromechanical color system in development, and it was initially chosen as the U.S. standard. However, RCA won the war in 1953 with an all-electronic alternative that, unlike the CBS approach, was compatible with black-and-white sets.
During these years Sarnoff was also locked in a struggle with one of the geniuses of radio technology, Edwin Howard Armstrong, the man who wrested revolutionary powers from De Forest's vacuum tube. Armstrong had never stopped inventing. In 1918 he devised a method for amplifying extremely weak, high-frequency signals—the superheterodyne circuit. Then in the early 1930s he figured out how to eliminate the lightning-caused static that often plagued radio reception. His solution was a new way of imposing a signal on radio waves. Instead of changing the strength of waves transmitted at a particular frequency (amplitude modulation, or AM), he developed circuitry to keep the amplitude constant and change only the frequency (FM). The result was sound of stunning, static-free clarity.
Once again Sarnoff tried to buy the rights, and once again he failed to reach an agreement. His response this time was to wage a long campaign of corporate and governmental maneuvering that delayed the industry's investment in FM and relegated the technology to low powered stations and suboptimal frequencies. FM's advantages eventually won it major media roles nonetheless—not only in radio but also as the sound channel for television.
The engineering of radio and television was far from over. The arrival of the transistor in the mid-1950s led to dramatic reductions in the size and cost of circuitry. Videocassette recorders for delayed viewing of TV shows appeared in 1956. Screens grew bigger and more vivid, and some dispensed with cathode-ray technology in favor of new display methods that allowed them to be flat enough to hang on a wall. Cable television—the delivery of signals by coaxial cable rather than through the air—was born in 1949 and gained enormous popularity for its good reception and additional programming. The first commercial telecommunications satellite began service in 1965 and was followed by whole fleets of orbiting transmitters. Satellite television is able to provide far more channels than a conventional TV transmitter because each satellite is allocated a big slice of the electromagnetic spectrum at very high frequencies. With all new wireless technologies, finding room on the radio spectrum—a realm that ranges from waves many miles long to just a millimeter in length—is always a key issue, with conservation growing ever more important.
By century's end the move was toward a future known as high-definition television, or HDTV. The U.S. version, to be phased in over many years, will bring television sets whose digital signals can be electronically processed for superior performance and whose images are formed of more than a thousand scanned lines, yielding much higher resolution than the current 525-line standard. Meanwhile, TV's reach has extended far beyond our world. Television pictures, digitally encoded in radio waves, are streaming to Earth from space probes exploring planets and moons in the far precincts of the solar system. For this most distance dissolving of technologies, no limits are yet in sight.
Robert W. Lucky
Retired Corporate Vice President
Applied Research
Telcordia Technologies, Inc.
When I was young there was no television. This was difficult to explain to my children. "Oh no, Dad," they would say, "There was always TV." They can't understand what people did at night in that incomprehensible time when lives were not illuminated by television.
But I remember. My world at night was filled with the magic sounds of radio. I would lie in bed in the darkness, watching the dancing glows of the filaments in my bedside radio. I imagined sometimes that there were little people encased in those tubes and their voices were those I heard. Now in the modern daylight of television it is hard to explain the reality of radio in that long-lost time. I rode with the Lone Ranger. I sent away for the secret decoder ring from Captain Midnight so I could unscramble the coded messages about the next episode. The pictures I drew in my mind may have been more real than the ever-changing, evanescent images from the ubiquitous cathode-ray tubes of today.
I wanted to create this miracle of radio myself. I built crystal radios with "cat whiskers" that touched delicately on little cubes of quartz and listened acutely through earphones as I moved a steel pointer across a coil wound on a cardboard tube. Sadly, I never heard a peep. So I studied a book entitled Boys' First Book of Radio and dog-eared a precious copy of the Amateur Radio Handbook. From them I learned about superheterodyne receivers. I designed and built one and experienced an unforgettable thrill when I turned the switch and music came from the speaker. That radio made an engineer of me.
The magic of radio lives with me today, but now I see it through the eyes of an experienced engineer. I look out the window at the clear blue sky and think of all the radio waves crossing that seemingly empty space. If those waves had visible color, the sky would be as bright as a laser light show.
It wasn't all that long ago when there were no waves at all. I remember the feeling I had when I visited Marconi's home outside Bologna, Italy, with his daughter, Gioia, who had become a good friend. I looked out the window where he had sent the first radio pulse and wondered what he must have felt like when the iron filings in the glass tube of the coherer detector across the hill jumped at the recognition of his pulse.
Somewhere out there, 100 light-years distant, that first pulse is still traveling among the stars. Its creator, Marconi, must have believed that the heavens had been opened to unlimited communication. As an engineer in the late 20th century, however, I came to realize that the precious spectrum that had seemed free and infinite in Marconi's day had been sold in tiny slivers for billions of dollars.
Today, we again use Marconi's word, "wireless," to describe cellular radio. There has been a renaissance in thinking about the capabilities of that empty sky. New methods of transmission, of processing signals, and of sharing the spectrum have cascaded out of universities and research laboratories. The 20th century saw radio emerge, blossom, and ultimately devour all the capacity that nature had given us. The 21st century may see us reclaim the vastness of Marconi's dream with these new technologies.