| Shortwave Radio Article | For more information about the shortwave radio read below this article Shortwave radio operates between the frequencies of 3 MHz (3,000 kHz) and 30 MHz (30,000 kHz) and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than the long wave lengths widely in use at that time. An alternate name is HF or high frequency radio. Short wavelengths are associated with high frequencies because there is an inverse relationship between frequency and wavelength. Amateur radio operators are usually credited with the discovery of long distance communication in the shortwave bands. The first successful transatlantic tests were conducted by radio amateurs in December 1921 operating in the 200 meter mediumwave band, the shortest wavelength then available to amateurs. In 1922 hundreds of North American amateurs were heard in Europe at 200 meters and at least 20 North American amateurs heard amateur signals from Europe. The first two way communications between North American and Hawaiian amateurs began in 1922 at 200 meters. Although operation on wavelengths shorter than 200 meters was technically illegal (but tolerated as the authorities mistakenly believed at first that such frequencies were useless for commercial or military use), amateurs began to experiment with those wavelengths using newly available vacuum tubes shortly after World War I. Extreme interference at the upper edge of the 150-200 meter band--the official wavelengths allocated to amateurs by the Second National Radio Conference in 1923--forced amateurs to shift to shorter and shorter wavelengths; however, amateurs were limited by regulation to wavelengths longer than 150 meters. A few fortunate amateurs who obtained special permission for experimental communications below 150 meters completed hundreds of long distance two way contacts on 100 meters in 1923 including the first transatlantic two way contacts in November 1923, on 110 meters.
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