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This horizontal waterfall shows the frequency range from about 16 - 30 kHz captured mid day on 02/04/26 using the setup described below. While the 'official' VLF frequency range spans 3 - 30 kHz, there isn't much to see below 16 kHz - except for the Russian Alpha navigation signals. A number of the usual US and overseas submarine communications stations are clearly visible.
There are some interesting features to note on this rather busy display. An X4.3 solar flare occured at about 1213z which enhanced signal levels of those stations in europe and beyond including GBZ (England) 19.6 kHz, ICV (Italy) 20.3 kHz, HWU (France) 21.75 kHz, GQD (England) 22.1 kHz, DHO38 (Germany) 23.4 kHz and TBB (Turkey) 26.7 kHz. Another flare, an M1.8, occured at about 1534z. Signal levels, for this flare, were enhancement on european stations as well as US mainland and NPM 21.4 kHz (Hawaii). A display like this makes a very effective SID (Sudden Ionospheric Disturbance) detector.
NAA 24 kHz was uncharacteristically off the air for a couple hours on that Wednesday morning. Also, a number of TACAMO 17.8 kHz transmissions from aircraft along the east coast of the US were also captured on this display. The squiggly lines between 18.5 and 19 kHz are interference signals of unknown origin,
A list of stations receive here over the last 15 years include:
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| 11.9 kHz - Alpha - Russia - mp3 of Alpha 'beeps'recorded 02/12/11 |
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| 12.7 kHz - Alpha - Russia |
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| 14.9 kHz - Alpha - Russia |
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| 16.4 kHz - JXN - Norway |
| 17.0 kHz - VTX2 - India |
| 17.2 kHz - SAQ - Sweden - mp3 of SAQ recorded 07/03/11 |
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| 17.8 kHz - Tacamo - Airborne |
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| 18.1 kHz - RDL - Russia |
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| 18.3 kHz - HWU - France |
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| 19.2 kHz - VTX4 - India |
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| 19.6 kHz - GBZ - England |
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| 19.8 kHz - NWC - Australia |
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| 20.2 kHz - RJH69 - Belarus |
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| 20.3 kHz - ICV - Italy |
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| 20.5 kHz - RJH - Russia |
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| 20.9 kHz - HWU - France |
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| 21.1 kHz - RDL - Russia |
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| 21.4 kHz - NPM - Hawaii |
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| 21.75 kHz - HWU - France |
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| 22.1 kHz - GQD - England |
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| 22.2 kHz - JJI - Japan |
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| 22.6 kHz - Tacamo - Airborne |
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| 23.0 kHz - RJH - Russia |
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| 23.4 kHz - DHO - Germany |
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| 24.0 kHz - NAA - Maine |
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| 24.8 kHz - NLF - Washington |
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| 25.2 kHz - NML - North Dakota |
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| 25.5 kHz - RJH - Russia |
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| 26.0 kHz - DG2 - Israel |
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| 26.7 kHz - TBB - Turkey |
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| 37.5 kHz - TFK - Iceland |
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| 40.0 kHz - JJY - Japan - mp3 of JJY ID recorded 02/02/11 |
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| 40.75 kHz - NAU - Puerto Rico |
| 44.2 kHz - SWE - Sweden |
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| 45.9 kHz - NSY - Italy |
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| 51.95 kHz - GYW - Scotland |
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| 53.4 kHz - TBG - Turkey |
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| 55.5 kHz - NPG - California |
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| 57.4 kHz - NRK - Iceland |
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| 60.0 kHz - WWVB - Colorado |
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| 60.0 kHz - MSF - England |
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| 62.6 kHz - FUG - France |
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| 65.8 kHz - FUE - France |
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| 66.7 kHz - RBU - Russia |
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| 68.5 kHz - BPC - China |
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| 73.6 kHz - CFH - Nova Scotia |
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| 75.0 kHz - HBG - Switzerland |
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| 76.2 kHz - CKN - Vancouver |
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| 77.5 kHz - DCF77 - Germany |
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81.0 kHz - MKL - Scotland
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The receiving setup here has evolved over the years and a number of receivers, antennas and noise mitigation techniques have been evaluated. The setup used for this capture is a modified Amrad e probe antenna > LNA > Behringer UMC202HD > Dell Laptop > SpectrumLab software.
When considering the signal to noise equation at VLF and LF, the problem is seldom gathering enough signal. Most properly designed antennas, even though physically small, supply more than adequate levels such that the background 'band noise' significatly overides the preamplifier/receiver noise. The real improvement in signal to noise comes from reducing man made noise to get down to the 'natural' noise floor. This usually requires a combination of noise mitigation techniques and optimum siting of the antenna.
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