What is high-frequency range?

High frequency (HF) is the ITU-designated range of radio frequency electromagnetic waves (radio waves) between 3 and 30 MHz . It is also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters (ten to one hundred metres).

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What is very low frequency used for?

The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and for secure military communication . Since VLF waves can penetrate at least 40 meters (131 ft) into saltwater, they are used for military communication with submarines.

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