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Radio Repair Class


No one person invented radio. While Marconi was the first to develop a system of wireless telegraphy that worked reliably and over long distances, many other innovators around the world contributed to radio’s technology.

Numerous 18th and 19th century scientists carried out experiments and developed the basic understanding of electrical phenomena essential for the evolution of radio. Important early contributors included: Michael Faraday (England), Georg Ohm (Germany), Alessandro Volta (Italy), Andre Ampere (France), Hans Christian Oersted (Denmark), and Joseph Henry (U.S.).

Many others worked to develop radio’s theory and technology. Among them:

Wireless Pioneers

Maxwell:  In 1865 James Clerk Maxwell, a Scot working at Cambridge University in England, developed a complex theory and published a set of important mathematical papers that predicted that radio waves could be propagated through the air from a suitable transmission source, such as a spark discharge.

Loomis:  In 1866 Mahlon Loomis, a dentist from Washington, D.C., sent and received wireless signals over a short distance in the Blue Ridge mountains of Virginia. His system was never fully implemented because projected congressional funding fell through after a national financial panic in 1872. Loomis received the first American patent for a wireless system—and is an example of the American penchant for tinkering in new fields.

Hertz:  In 1888 Heinrich Hertz, a German professor of physics, conducted the first experiments that proved the existence of radio waves, thus verifying Maxwell’s predictions. But he was focused on research, not developing a practical system, and he died tragically young not long after his pioneering experiments.

Branley:  About 1890, Edouard Branley in France developed his “coherer” to detect the presence of radio signals. A coherer is a glass tube containing two electrodes separated by loosely packed metal filings. They adhere or cohere when a radio pulse is present. The coherer must be tapped after each dot or dash is received to shake loose the metal particles in order that they may detect the next signal. A doorbell-like “tapper” was used to do so. David Hughes in England improved the coherer, as did Marconi and other inventors.

Lodge:  Sir Oliver Lodge in England carried out laboratory demonstrations of his own wireless transmitter and coherer receiver as early as 1894. Another university professor, Lodge had no personal interest in developing a practical commercial system although he did receive some key patents exploited by the Lodge-Muirhead company that were later purchased by Marconi.

Popov:  During this same era, Alexander Popov in Russia developed a wireless system with an improved coherer and a better antenna and ground system. He experimented with and improved his equipment over several years in the 1890s. For many years the Soviet Union claimed Popov was the real inventor of radio.

Developing Practical Radio

Marconi:  As a young man growing up in Italy, by 1895, Guglielmo Marconi was experimenting with wireless and had developed a spark transmitter and coherer receiver system that worked better than others. He foresaw radio’s potential commercial importance, and in 1896 moved to England (where his mother had social contacts) to seek financial backing.  In December 1901, he sent the first wireless signal (the Morse code of three dots representing the letter “s”) across the Atlantic, creating a public sensation. Within a few short years, his Marconi Wireless Telegraphy Co. Ltd. was a world leader in both shipboard and long distance radio communication.

Fessenden:  Reginald Fessenden came to America from Canada. With help from Ernst Alexanderson, an engineer at General Electric, in the early 1900s he developed his “alternator” technology for sending continuous radio waves rather than spark signals. This paved the way for using radio to transmit music and voice signals. For a time he carried out experiments for the U.S. Weather Bureau at Cobb Island, MD. By late 1906 he was transmitting voice and music signals from his coastal station south of Boston.

Armstrong:  Edwin Howard Armstrong, a Columbia University professor and an army officer in World War I invented the concept of “regeneration,” a feedback effect that permitted a high degree of amplification from a single vacuum tube. He also invented the superheterodyne radio, a superior design still used today. Armstrong and de Forest engaged in lengthy patent litigation over regeneration that reached the U. S. Supreme Court in 1934. Wealthy from his earlier inventions, Armstrong would later develop FM radio, operating the world’s first FM station. He is among the most important inventors in radio history.

Others:  In about 1902, Greenleaf Pickard and General H. C. Dunwoody independently discovered that certain crystals (for example, galena or lead-sulfide) could serve as radio detectors. Crystal detectors were very popular in radio’s early days as they were inexpensive and worked well in tropical conditions. Danish inventor Valdemar Poulsen, and later Cyril Elwell of Palo Alto, CA, developed the continuous wave “arc” transmitter early in the 1900s. It remained popular until replaced with vacuum tube transmitters about 1920. Ambrose Fleming, a consultant to the Marconi company in England, invented the vacuum tube in 1904 and discovered that it could be used as a radio detector. And Georg Slaby, Count von Arco, and Ferdinand Braun developed wireless systems in Germany. Others were active elsewhere.

Early Broadcasters

De Forest:  Lee de Forest made a number of contributions to early radio. In 1906 he invented the three-element vacuum “audion” tube, which could serve as a radio detector, an amplifier, or a generator of radio signals. He started several wireless and radio companies during his career, none of which proved successful. In 1910 he broadcast music from the Metropolitan Opera House in New York. He later worked to develop sound motion pictures.

Herrold:  Charles “Doc” Herrold began regular experimental broadcasts of music and voice from his arc transmitter station in San Jose, CA about 1909. Primarily operating a radio operator school, he provided a growing schedule of programs until the government closed down most stations in 1917. The station eventually became San Jose station KQW, later KCBS in San Francisco.

Conrad:  Frank Conrad, a Westinghouse engineer in Pittsburgh, was a “ham” operator who began broadcasts of music to local radio fans after World War I. His popular broadcasts encouraged Westinghouse to establish station KDKA, the first radio station licensed by the federal government specifically for entertainment purposes (in 1920). Thus began the development of entertainment radio as we know it today.