Online Encyclopedia
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 waves can penetrate water only to a depth of roughly 10 to 40 metres (30 to 130 feet), depending on the frequency and the salinity of the water, they are used to communicate with submarines near the surface. (ELF is used for fully submerged vessels.)
This frequency range is used nowadays because of the small range possible within this range nearly only for the transmission by instructions to submerged submarines (for example with the transmitter DHO38), since radio waves can penetrate some dozen of meter in this frequency band in the sea water. Besides they are used also for the radio navigation (alpha) and for the transmission by zeitzeichen (beta). In the start time of the radio engineering within the range starting from 20 kHz repeats Telefonie with the help of the amplitude or single-sideband modulation tried, but was unsatisfactory, because of the small transmission bandwidth, the result according to today's requirements. In the frequency range under 30 kHz also some zeitzeichen and radionavigation beacons work. The very long wave transmitter SAQ in Grimeton (with Varberg in Sweden) can at certain times, as the Alexanderson Day is visited, by the public. As a rule very long wave transmitters in the frequency range between 10kHz and 30kHz work. There are also stations, which work in the frequency range under10 kHz. This frequency range is subject to International Telecommunication Union of no adjustment on the part of the international communications organization and may be used in some states (however not in Germany) by everyone license-free.
(Source: Längstwelle in German-language Wikipedia )
Many natural radio emissions, such as whistlers, can be also heard in this band.
List of VLF transmitters
.
| Callsign | Frequency | Location of transmitter | Remarks | |
| - | 11.905 kHz | Russia (various locations)) | Alpha-Navigation | |
| - | 12.649 kHz | Russia (various locations) | Alpha-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 occassionally 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 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 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.
|
Radio spectrum |