Unit 9: Technology in America

Early Twentieth Century

James Maxwell

In 1873 the British scientist James Clerk Maxwell published his famous theory linking the phenomena of electricity and magnetism. One implication of this theory is that an electric spark would generate an electromagnetic disturbance that would travel in all directions with the speed of light. In 1887 the German physicist Heinrich Rudolf Hertz experimentally produced electromagnetic pulses and detected them and determined that their properties accorded with Maxwell's theoretical predictions. These purely scientific results led inventors to think that such pulses could be used to transmit messages coded according to procedures used in the telegraph. The Italian engineer and inventor Guglielmo Marchese Marconi was operating a wireless telegraph system for short distances in 1895. By 1899 his system was transmitting signals across the English Channel between England and France, and by 1901 he was successfully transmitting across the Atlantic Ocean.

Reginald Fessenden

The general outline of this story is well known. What is less appreciated is that radio as we know it was not yet developed; only the wireless telegraph was in place. The key invention was due to the little known Canadian-born American physicist Reginald Fessenden who, in 1901, developed a device for transmitting a continuous wave, which could carry a signal in the audio frequency range. This enabled voices and music to be transmitted directly, and on Christmas Eve 1905 many wireless telegraphers were startled to hear music over their crackling earphones.

The whole system of detection was vastly improved by amplification circuits made possible by the invention of the vacuum tube by the American physicist Lee De Forest. At this time radio was used only for the transmission of messages from one point to another, much like cell telephones today. The idea of broadcasting widely to many potential listeners appeared to be a profitless activity, so it was left to amateurs to experiment with such

David Sarnoff

systems.The advent of World War I led the U.S. Government to restrict radio broadcasting by civilians. But David Sarnoff, an emigrant employee of Marconi's company, had plans for profitable radio broadcasting in 1916, although the company showed little interest then in pursuing his ideas. So, in 1920 the first commercial broadcasting station, KDKA, began broadcasting from Pittsburgh, PA to a small band of devoted amateurs.

A Radio Made in 1930

After World War I, America began to change from a predominantly rural and agricultural country to an urban industrial giant. As the population grew and as agriculture became more mechanized, more opportunities for employment were located in cities, mostly in the North and Central states, where industries had located factories. The growing broadcast radio business served many functions. For the isolated farmers who remained in the countryside, radio provided entertainment and information, and served to unify these separate families into one country. For the urban newcomers, who felt socially isolated and alone in unfriendly cities, the radio also served to connect them with "neighbors." And radio was an important locus of advertisements for the products to feed a growing consumerism in America.

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