Throughout history, long-distance communication had depended entirely upon conventional means of transportation. A message could be moved aboard a ship, on horseback, by pigeon, or in the memory of a human courier.
The story of radio begins in the development of an earlier medium, the telegraph, the first instantaneous system of information movement. The usefulness of telegraphy was such that over the second half of the 19th century wires were strung across much of the world, including a transatlantic undersea cable (about 1866) connecting Europe and North America.
Despite its accomplishments, telegraphic communication was limited. It depended on the building and maintenance of a complex system of receiving stations wired to each other along a fixed route. The telephone, patented by American inventor Alexander Graham Bell in 1876, required an even more complex system.
It may be surprising to consider that just over a hundred years ago the existence of radio waves was only a theory, and a fairly controversial one at that. The existence of electromagnetic radiation, RF, was first predicted by James Clerk Maxwell, in 1865. Maxwell developed a series of mathematical equations, which not only predicted that electromagnetic radiation existed, but that visible light itself was merely a form of high frequency radio waves.
Maxwell’s prediction of radio waves was confirmed by a series of experiments conducted by Heinrich Hertz in 1887, in his physics lab in Germany. For a transmitter, Hertz used simple devices to create spark discharges in the VHF region. His receiver was nothing more complicated than a wire rectangle, which had a small gap in it; tiny sparks would appear in the gap whenever the main spark was discharged.
Sometimes overlooked is the fact that Hertz’s great discovery was not that the tiny sparks could be triggered from across the room. At the time of his tests this was a well-known phenomenon, but it was thought to be due to induction. What Hertz proved through an ingenious series of experiments, was that radiation sent out by the spark discharges had a wave-like structure, which was not characteristic of induction fields, but did match electromagnetic radiation as predicted by Maxwell’s equations.
In 1895 Italian inventor Guglielmo Marconi transmitted a message in Morse code that was picked up about 3 km away by a receiving device that had no wired connection to Marconi’s transmitting device. Marconi had demonstrated that an electronic signal could be cast broadly through space so that receivers at random points could capture it.
Marconi moved to London in 1896 and founded the British Marconi Company to develop and market his invention for military and industrial uses. Within five years a wireless signal had been transmitted across the Atlantic Ocean from England to Newfoundland, Canada. Marconi was awarded the Nobel Prize for Physics in 1909.
Despite Marconi’s groundbreaking efforts, no one had yet “broadcast” messages other than telegraphic dots and dashes. That changed when, in 1906, Reginald Fessenden connected a carbon telephone transmitter into the field winding of an Alexanderson alternator he had installed in a shore telegraph station at Brant Rock, Massachusetts. Astonished ship radio operators heard Bible and poetry readings as well as Fessenden’s own artistry on the violin. He was demonstrating a new sort of “transmitter”, one that generated “continuous waves”, as opposed to Marconi’s spark gaps and their “discontinuous waves”.
Radio’s success spurred technology companies to make huge investments in the research and development of a new form of broadcasting called television, or TV. The invention of television was a lengthy, collaborative process; an early milestone was the successful transmission of an image in 1884 by German inventor Paul Nipkow. His mechanical system, known as the rotating disk, was further developed by Scottish scientist John Logie Baird, who broadcast a televised image in 1926 to an audience at the Royal Academy of Science in London.
The earliest US patent for an all-electronic television system was granted in 1927 to Philo T. Farnsworth, who transmitted a picture of a US dollar sign with his so-called image dissector tube in the laboratories of the Philadelphia Storage Battery Company (Philco).
The Radio Corporation of America (RCA) unveiled television to the American public in grand style at the 1939 New York World’s Fair, with live coverage of the Fair’s opening ceremonies featuring a speech by President Roosevelt. Daily telecasts were made from the RCA pavilion at the Fair; visitors were invited to experience television viewing and were even given the opportunity to walk in front of the television cameras and see themselves on monitors.
Broadcasting dramatically changed life wherever it was introduced. Radio, and later television, brought news and information from around the world into homes. The experiences of professionally crafted drama and music, historically a privilege of the elite, became services expected by the general public. The networks brought the performances of talented artists to large numbers of people who were otherwise isolated from venues such as the concert hall and the theater.
References
autocww.colorado.edu
oldradio.com
smithsonianmag.com
The article was first published in print in SCIplanet, Autumn 2014 Issue "How Things Work".
Cover image by xb100 on Freepik.