History of Short Wave
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History of Short Wave
The discovery of long-distance communication on shortwave bands is attributed to amateur radio operators. Early long-distance services used surface wave propagation (a ground wave that propagates close to the surface of the Earth) at low frequencies attenuated along the path. Higher frequencies and longer distances under this method meant more signal attenuation. More signal attenuation, combined with the difficulties of generating and detecting higher frequencies, made shortwave propagation difficult for commercial services.
In 1921, operating in the 200 meter mediumwave band, Radio amateurs conducted the first successful transatlantic tests.
In 1922, at 200 meters, hundreds of North American amateurs were heard in Europe, and at least 20 North American amateurs heard signals from Europe.
In 1922, the first two-way communications began between North American and Hawaiian amateurs at 200 meters.
In 1923, the Second National Radio Conference allowted the wavelengths of 150-200 meters for amateur use, forcing them to shift to shorter and shorter wavelengths, although some had special permission to use lower meterages.
In 1923, the first transatlantic two-way contacts occured on 110 meters. By 1924, additional specially licensed amateurs were routinely making transoceanic contacts at distances of 6000 miles and more: New Zealand to California; New Zealand to England, and so forth.
On October 10 of the same year, the Third National Radio Conference made three shortwave bands available to U.S. amateurs at 80 meters (3.75 MHz), 40 meters (7 MHz) and 20 meters (14 MHz). These were allocated worldwide, while the 10-meter band (28 MHz) was created by the Washington International Radiotelegraph Conference on 25 November 1927.
The 15-meter band (21 MHz) was opened to amateurs in the United States on 1 May 1952.
As observed, the 1920s saw a rapid growth of shortwave communications, a spur similar to the Internet in the late 20th centure. By 1928, more than half of long distance communications had moved from transoceanic cables and longwave wireless to shortwave. This rise in changing technology also signaled the end of the need of new transoceanic telegraph cables and massive longwave wireless stations, although some remained until the 1960s.
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