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VLF Radio Stations
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A variety of high-power VLF stations exist around the world. Most of these stations transmit low baud rate encrypted information, over long distances, for military maritime purposes.
Signals from these stations are used opportunistically for scientific research. Sudden changes in received signal strength can indicate ionospheric disturbances caused, for example, by solar activity.
VLF signals are able to propagate over very long distances due to the wave-guide effect created by reflections off the Earth's land and oceans (at the bottom) and the Earth's ionosphere (at the top).
Stanford University maintains a list of VLF stations (including coordinates) usable for science research, from which these frequencies were obtained.
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Frequencies |
Frequency | Bandwidth | Use | Service | Table |
10.6 kHz | 0.25 kHz | 3SB/3SA, Datonge (China) | Maritime Mobile | - |
14.6 kHz | 0.25 kHz | UVA, Batumi (Russia), 100 kW input | Maritime Mobile | - |
15 kHz | 0.25 kHz | UIK, Vladivostok (Russia), 100 kW input | Maritime Mobile | - |
16.4 kHz | 0.25 kHz | JXN, Kolsas (Norway), 45 kW | Maritime Mobile | - |
16.8 kHz | 0.25 kHz | FTA, St. Assie (France), 23 kW | Maritime Mobile | - |
18.1 kHz | 0.25 kHz | UFQE, Matotchkinchar (Russia), 100 kW input | Maritime Mobile | - |
18.2 kHz | 0.25 kHz | VTX3, Katabomman (India) | Maritime Mobile | - |
19.6 kHz | 0.25 kHz | GBZ, Anthorn (UK), 500 kW | Maritime Mobile | - |
19.7 kHz | 0.25 kHz | UGE, Arkhanghelsk (Russia), 150 kW input | Maritime Mobile | - |
19.8 kHz | 0.25 kHz | NWC, Harold E. Holt, Nort West Cape (Australia), 1000 kW | Maritime Mobile | - |
20 kHz | 0.25 kHz | VLF, South Pole | Maritime Mobile | - |
20.27 kHz | 0.25 kHz | ICV, Tavolara (Italy), 43 kW | Maritime Mobile | - |
20.6 kHz | 0.25 kHz | 3SA/3SB, Changde (China) | Maritime Mobile | - |
20.9 kHz | 0.25 kHz | HWU, Rosnay (France), 400 kW | Maritime Mobile | - |
21.1 kHz | 0.25 kHz | Possible new transmitter in western China | Maritime Mobile | - |
21.37 kHz | 0.25 kHz | GYA, London (UK), 120 kW | Maritime Mobile | - |
21.4 kHz | 0.25 kHz | NPM, Lualualei, HI (USA), 566 kW | Maritime Mobile | F |
21.75 kHz | 0.25 kHz | HWV, NATO, LeBlanc (France) | Maritime Mobile | - |
22.1 kHz | 0.25 kHz | GQD, NATO, Anthorn (UK), 500 kW | Maritime Mobile | - |
22.2 kHz | 0.25 kHz | JJI, Ebino (Japan) | Maritime Mobile | - |
23.4 kHz | 0.25 kHz | DHO, Rhauderfehn (Germany), 500 kW | Maritime Mobile | - |
24 kHz | 0.25 kHz | NAA, Cutler, ME (USA), 1000 kW | Maritime Mobile | F |
24.1 kHz | 0.25 kHz | Possible new transmitter in eastern China | Maritime Mobile | - |
24.8 kHz | 0.25 kHz | NLK, Jim Creek, WA (USA), 250 kW | Maritime Mobile | F |
25.2 kHz | 0.25 kHz | NML/NLM?, LaMoure, ND (USA), 500 kW | Maritime Mobile | F |
26.7 kHz | 0.25 kHz | TBB, Bafa (Turkey) | Maritime Mobile | - |
30.3 kHz | 0.25 kHz | UGKZ, Kaliningrad (Russia), 100 kW input | Maritime Mobile | - |
37.5 kHz | 0.25 kHz | TFK, Keflavic (Iceland) | Maritime Mobile | - |
37.5 kHz | 0.25 kHz | NRK, U.S. Navy, Keflavik (Iceland), 100 kW | Maritime Mobile | - |
40.75 kHz | 0.25 kHz | NAU, Aquada, PR (USA), 100 kW | Maritime Mobile | F |
45.9 kHz | 0.25 kHz | NSC, Sicily (Italy) | Maritime Mobile | - |
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Russian Radionavigation System Alpha (RSDN-20)
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The Russian Alpha navaid system, formally called RSDN-20, is a VLF hyperbolic positioning system, similar to the old Omega system. Alpha was first put into service beginning in 1962, and is still in operation today. Its signals can often be heard worldwide due to the nature of radio propagation at VLF frequencies.
The system consists of five transmitters operating with power levels of 500 kW, on eight or nine different VLF frequencies. The frequencies are chosen to be mathematically optimal for hyperbolic positioning, and the geometric layout of the transmitters is optimized for coverage of the polar and North American regions.
Besides its intended use as a navigation system, the high power and low frequency of the transmitters has made them useful for ancillary scientific studies of the ionosphere and magnetosphere.
The exact frequencies of the nine Alpha signals are:
F1: 11904.76190 Hz F2: 12648.80952 Hz F3: 14880.95238 Hz F3b: 14881.09127 Hz F4: 12090.77381 Hz F5: 12044.27083 Hz F6: 12500.00000 Hz (rarely used) F7: 13281.25000 Hz (rarely used) F8: 15625.00000 Hz (rarely used)
According to some sources, only F1, F2, and F3 are currently operating, and only three of the five transmitter sites are on air.
Substantial additional information on the Alpha system is available from the references.
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Frequencies |
Frequency | Bandwidth | Use | Service | Table |
11.905 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F1) | Radionavigation | - |
12.044 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F5) | Radionavigation | - |
12.091 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F4) | Radionavigation | - |
12.5 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F6) | Radionavigation | - |
12.649 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F2) | Radionavigation | - |
13.281 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F7) | Radionavigation | - |
14.881 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F3) | Radionavigation | - |
15.625 kHz | 0.2 kHz | Russian Alpha radionavigation system (frequency F8) | Radionavigation | - |
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Lightning Detection
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ITU studies have determined that the optimal frequency for long-distance Arrival Time Difference (ATD) lightning detection systems is 9.76 kHz. However, the currently-operating ATD system uses the frequency 13.733 kHz due to interference near the 9.76 kHz frequency.
According to the ITU:
"Long-range lightning detection using observations near 10 kHz has been performed since 1939, originally with a very manpower-intensive system measuring the direction from which signals were received, but since 1987 detection has been carried out with an automated Arrival time difference system (ATD) using the time differences of signals received to derive strike locations.
"The ATD system utilizes a network of “detector” out-stations to monitor spectral emissions of cloud to ground lightning strikes centred between about 5 and 20 kHz. At these frequencies the sky waves, reflected off the ionosphere, propagate for very large distances with relatively little attenuation and are preceded by a ground wave at shorter ranges. Thus, it is possible to receive the emissions from the cloud to ground strokes at thousands of kilometres from the stroke location. A distributed network of ground based sensors can locate the origin of the lightning stroke, using the time differences between the arrivals of the lightning emission at the individual sensor sites.
"At June 2010, the network comprised 11 sensors distributed across Europe from Iceland to Cyprus, operating in collaboration with Finland, France, Germany, Iceland, Ireland, Portugal and Switzerland."
At the 2012 World Radiocommunication Conference, the use of the band 8.3 - 11.3 kHz for passive meteorological aids service (i.e., ATD lightning detection) was noted, formally extending the table of frequency allocations below 9 kHz.
In FCC 15-50 (2015), the FCC has proposed to adopt the 8.3-11.3 kHz MetAids allocation in the U.S.
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Frequency Bands |
Band | Use | Service | Table |
8.3 - 11.3 kHz | WRC-12 allocation for lightning detection | Meteorological Aids | - |
Frequencies |
Frequency | Bandwidth | Use | Service | Table |
9.76 kHz | - | Optimal frequency for Arrival Time Difference (ATD) lightning detection | Meteorological Aids | - |
13.733 kHz | - | Operational ATD long-range lightning detection system | Meteorological Aids | - |
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Omega Radionavigation System
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Omega was one of the first global radionavigation systems. It operated in the VLF portion of the radio spectrum, and its eight stations spread around the globe allowed hyperbolic fixes to an accuracy of 2-4 nautical miles (about 2.2-4.4 miles). Omega was typically used for navigation by ships and airplanes.
The eight Omega stations were located in Norway, Liberia, Hawaii, North Dakota, La Reunion, Argentina, Australia, and Japan. Each transmitted, in a predetermined sequence, on four common frequencies of 10.2, 11.05, 11.33, and 13.6 kHz, and on one additional frequency that was unique to each transmitter site.
Development and initial deployment of Omega began in the 1960's, and the full deployment of eight stations was operational in 1987. Omega operations were formally terminated on September 30th, 1997, at 0300 UT, its functions having been replaced by modern GPS.
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Frequencies |
Frequency | Bandwidth | Use | Service | Table |
10.2 kHz | 0.05 kHz | Omega (used by all eight sites) | Radionavigation | F |
11.05 kHz | 0.05 kHz | Omega (used by all eight sites) | Radionavigation | F |
11.33 kHz | 0.05 kHz | Omega (used by all eight sites) | Radionavigation | F |
11.8 kHz | 0.05 kHz | Omega (Hawaii site only) | Radionavigation | F |
12 kHz | 0.05 kHz | Omega (Liberia site only) | Radionavigation | F |
12.1 kHz | 0.05 kHz | Omega (Norway site only) | Radionavigation | F |
12.3 kHz | 0.05 kHz | Omega (La Reunion site only) | Radionavigation | F |
12.8 kHz | 0.05 kHz | Omega (Japan site only) | Radionavigation | F |
12.9 kHz | 0.05 kHz | Omega (Argentina site only) | Radionavigation | F |
13 kHz | 0.05 kHz | Omega (Australia site only) | Radionavigation | F |
13.1 kHz | 0.05 kHz | Omega (North Dakota site only) | Radionavigation | F |
13.6 kHz | 0.05 kHz | Omega (used by all eight sites) | Radionavigation | F |
External Links:
Associated Files:
 Omega station locations (from "The Evolution of Synchronization in the World-Wide Omega Navigation System," Vannicola & McManus).
 Omega signal transmission format (from "The Evolution of Synchronization in the World-Wide Omega Navigation System," Vannicola & McManus).
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