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This waterfall shows the frequency range from 8 - 33 kHz with a number of the usual stations clearly visible. While the 'official' VLF frequency range spans 3 - 30 kHz, there isn't much to see below 11.9 kHz - the lowest of the Russian Alpha signals. Other than spherics and harmonics of the power line it's pretty much devoid of signals.
A list of stations routinely seen include:
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| 11.9 kHz - Alpha - Russia | 20.9 kHz - HWU - France |
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| 12.7 kHz - Alpha - Russia | 21.4 kHz - NPM - Hawaii, USA |
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| 14.9 kHz - Alpha - Russia | 22.1 kHz - GQD - England |
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| 17.2 kHz - SAQ - Sweden | 23.4 kHz - DHO - Germany |
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| 18.3 kHz - HWU - France | 24.0 kHz - NAA - Maine USA |
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| 19.6 kHz - GBZ - England | 24.8 kHz - NLF - Washington USA |
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| 19.8 kHz - NWC - Australia | 25.1 kHz - NML - North Dakota USA |
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| 20.3 kHz - ICV - Italy | 26.7 kHz - TBB - Turkey
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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 best setup so far is a modified Amrad e probe antenna and Perseus SDR receiver, however more important than the choice of antenna and receiver is the ability to reduce man made noise. 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, can supply adequate signal to overide the receiver noise. The real improvement in signal to noise comes from reducing the noise.
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