The Very low frequency reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Very low frequency

Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals are used, such as for radionavigation. Because VLF can penetrate water to a depth of 20 metres (66 feet), they are used to communicate with submarines near the surface. (ELF is used for fully submerged vessels.)

Many natural radio emissions, such as whistlerss, can be also heard in this band.

Radio spectrum ELF | SLF | ULF | VLF | LF/LW | MF/MW | HF/SW | VHF | UHF | SHF | EHF 3Hz | 30Hz | 300Hz | 3kHz | 30kHz | 300kHz | 3MHz | 30MHz | 300MHz | 3GHz | 30GHz | 300GHz

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