Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 kHz to 30 kHz and wavelengths from 10 to 100 kilometres. Since there is not much bandwidth in this band of the radio spectrum, audio (voice) cannot be transmitted, and only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations which broadcast time signals to set radio clocks, and for secure military communication. Since VLF waves penetrate about 40 meters into saltwater, they are used for military communication with submarines. Also known as the myriametre band or myriametre wave as the wavelengths range from one to ten myriametres (an obsolete metric unit equal to 10 kilometres).
Read more about Very Low Frequency: Propagation Characteristics, Antennas, Applications, VLF Submarine Communication Methods, PC-based VLF Reception, List of VLF Transmissions
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