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  • High frequency is the ITU designation for the range of radio frequency electromagnetic waves between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency, and the next higher frequencies are known as very high frequency. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere, called "skip" or skywave propagation, these frequencies can be used for long distance communication, at intercontinental distances. The band is used by international shortwave broadcasting stations, aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.