[TangerineSDR] Demo of Live VLF System

Jonathan emuman100 at gmail.com
Sun Aug 29 23:07:32 EDT 2021


Hi All, 

This week I was able to test my Raspberry Pi VLF SDR box with my VLF receiver! I’m very happy with the results and I’d like to do a demo of the the preliminary setup and signal verification at the Monday night (8/30/21) meeting. This will also include a live stream of the filtered VLF audio and plots of NAA amplitude and phase. I have attached some preview screenshots. 

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This is the oscope program showing the GPS PPS pulse and VLF audio.

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The adjusted time scale shows 60Hz power and harmonics in the VLF audio.

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This shows the density of mains harmonics.

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This is the spectrogram program showing the VLF receiver audio in the frequency domain. Notice most of the spectral power is contained in the portion of the band with the mains and it’s harmonics, as well as some peaks of interesting signals. In a mains heavy environment, these could be switch-mode power supply emissions. 

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This is a short plot of NAA’s amplitude and phase as extracted from the timestamped VLF stream. You’ll notice the variations of both phase and amplitude that are probably local interference, due to being in a very mains heavy suburban area.

Jonathan
KC3EEY




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