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Shortwave radio is radio transmission using shortwave radio frequencies, generally 1.6–30 MHz (187.4–10.0 m), just above the medium wave AM broadcast band.

Radio waves in this band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere.

It is also used for military over-the-horizon radar, diplomatic communication, and two-way international communication by amateur radio enthusiasts for hobby, educational and emergency purposes.

The widest popular definition of the shortwave frequency interval is the ITU Region 1 (EU Africa Russia...) definition, and is the span 1.6–30 MHz, just above the medium wave band, which ends approximately at 1.6 MHz.

There are also other definitions of the shortwave frequency interval: The term short wave is an historic one, dating from the early 20th century, when the radio spectrum was divided on the basis of wavelength into longwave (LW), medium wave (MW), and short wave (SW) radio bands.

Shortwave radio received its name because the wavelengths in this band are shorter than 200 m (1,500 k Hz) which marked the original upper limit of the medium frequency band first used for radio communications.

Extreme interference at the longer 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 (2 MHz).

The name "shortwave" originated during the early days of radio in the early 20th century, when the radio spectrum was considered divided into long wave (LW), medium wave (MW) and short wave bands based on the wavelength of the radio waves.Longer distances and higher frequencies using this method meant more signal loss.This, and the difficulties of generating and detecting higher frequencies, made discovery of shortwave propagation difficult for commercial services.The cable companies began to lose large sums of money in 1927, and a serious financial crisis threatened the viability of cable companies that were vital to strategic British interests.The British government convened the Imperial Wireless and Cable Conference in 1928 "to examine the situation that had arisen as a result of the competition of Beam Wireless with the Cable Services".

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