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This frequency range is used nowadays for the transmission of instructions to submerged submarines (for example with the transmitter DHO38), since radio waves can penetrate some dozen of meters in sea water in this frequency band. They are also used for radio navigation (alpha) and for the transmission of time signals (beta). Early in the history of radio engineering within the band starting from 20 kHz attempts were made to use radiotelephone using amplitude and single-sideband modulation, but the result was unsatisfactory, because of the small avalable bandwidth. The frequency range under 30 kHz also is used for time signals and radio navigation beacons. The very long wave transmitters, SAQ in Grimeton and Varberg in Sweden can be visited by public at certain times, such as on Alexanderson Day. As a rule very long wave transmitters work in the frequency range between 10kHz and 30kHz. There are also stations, which work in the frequency range under 10 kHz. This frequency range is subject to no control on the part of the international communications organization ( International Telecommunication Union) and may be used in some states by license-free.
In the USA, the time signal station WWVL began transmitting a 500 W signal on 20 kHz in August 1963. It used Frequency Shift Keying ( FSKFrequency-shift keying (FSK is frequency modulation in which the modulating signal shifts the output frequency between predetermined values. Note 1: Usually, the instantaneous frequency is shifted between two discrete values termed the " mark frequency" a) to send data, shifting between 20 kHz and 26 kHz. The WWVL service was discontinued in July 1972.
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Many natural radioFor other uses see: radio (disambiguation Radio is a technology that allows the transmission of signals by modulation of electromagnetic waves with frequencies below those of light. Radio waves Radio waves are a form of electromagnetic radiation, and are emissionThe word emission generally means sending something out. It can be used in the following contexts: In chemistry emissions are the products of a reaction, either chemical or nuclear. In physics and physical chemistry emissions are outputs of electromagnetis, such as whistlerA Whistler is a very low frequency radio wave generated by lightning. In addition to Earth they have been received from Jupiter showing the presence of lightning there. See Also Dawn chorus (electromagnetic) Further Reading Whistlers and Related Ionosphers, can be also heard in this band.
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| Callsign | Frequency | Location of transmitter | Remarks | |
| - | 11.905 kHz | Russia (various locations)) | AlphaAlpha by itself may refer to: The first letter of the Greek alphabet, Α α, which also has some cultural meanings; see alpha (letter). The letter A in the NATO phonetic alphabet, which is spelled Alfa for the benefit of native Spanish speakers.-Navigation | |
| - | 12.649 kHz | Russia (various locations) | AlphaAlpha by itself may refer to: The first letter of the Greek alphabet, Α α, which also has some cultural meanings; see alpha (letter). The letter A in the NATO phonetic alphabet, which is spelled Alfa for the benefit of native Spanish speakers.-Navigation | |
| - | 14.881 kHz | Russia (various locations) | ||
| - | 15.625 kHz | - | Frequency for horizontal deflection of electronic beam of TV sets | |
| ? | 15.8 kHz | ? | ||
| JXN | 16.4 kHz | Helgeland ( Norway) | ||
| SAQ | 17.2 kHz | Grimeton ( Sweden) | Only active at special occasions ( Alexanderson Day ) | |
| - | ca. 17.5 kHz | ? | Twenty second puls es | |
| ? | 17.8 kHz | ? | Transmit occasionally Superpuls es | |
| RDL/UPD/UFQE/UPP/UPD8 | 18.1 kHz | Russia (various locations) | ||
| HWU | 18.3 kHz | Le Blanc (France) | Frequently inactive for longer periodes | |
| RKS | 18.9 kHz | Russia (various locations) | Rarely active | |
| GBZ | 19.6 kHz | Criggion (Great Britain) | Many operation modes, even Superpuls es | |
| ICV | 20.27 kHz | Tavolara (Italia) | ||
| RJH63, RJH66, RJH69, RJH77, RJH99 | 20.5 kHz | Russia (various locations) | Time signal transmitter BetaBeta can stand for: Β or β the 2nd letter of the Greek alphabet. See Beta (letter). Beta should not be confused with a similar-looking but unrelated letter in German language orthography, ss, which denotes a long "s" sound. The plant genus Beta | |
| ICV | 20.76 kHz | Tavolara (Italia) | ||
| HWU | 20.9 kHz | Le Blanc (France) | ||
| RDL | 21.1 kHz | Russia (various locations) | rarely active | |
| HWU | 21.75 kHz | Le Blanc (France) | ||
| ? | 22.1 kHz | Anthorn (Great Britain) | ||
| ? | 22.3 kHz | Rußland? | Nur Only active on 2nd of each month for a short periode between 11o'clock and 13o'clock (respectively 10o'clock and 12o'clock in winter), if 2nd of each month is not a Sunday | |
| RJH63, RJH66, RJH69, RJH77, RJH99 | 23 kHz | Russia (various locations) | Time signal transmitter BetaBeta can stand for: Β or β the 2nd letter of the Greek alphabet. See Beta (letter). Beta should not be confused with a similar-looking but unrelated letter in German language orthography, ss, which denotes a long "s" sound. The plant genus Beta | |
| DHO38 | 23.4 kHz | Saterland (Germany) | ||
| NAA | 24 kHz | Cutler (USA) |
The well known VLF transmitter GBR Rugby on 16 kHz was shutdown on April 1st, 2003.
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ELF | SLF | ULF | VLF | LF/ LW | MF/ MW | HF/ SW | VHF | UHF | SHF | EHF 3 Hz | 30 Hz | 300 Hz | 3 kHz | 30 kHz | 300 kHz | 3 MHz | 30 MHz | 300 MHz | 3 GHz | 30 GHz | 300 GHz |