Earth's Natural Radio: Strange sounds at VLF frequencies and below. NVARC Presentation May 2022
Channel: Nashoba Valley Amateur Radio Club (NVARC) / N1NC
Date: 2022-05-24

This month's guest speaker will be our own Phil, W1PJE, whose topic is "Earth's Natural Radio: Strange sounds at VLF frequencies and below". In his own words:  

"I will provide an overview of natural emissions at very low electromagnetic frequencies in the VLF  (3 - 30 kHz) and ULF (300 Hz - 3 kHz) ranges.  These radio emissions are generated by physical phenomena, such as lightning discharges or interactions with plasma in the ionosphere, and in some cases are global in nature.  They are also very interesting because their RF frequencies are primarily within human hearing range (although they are not acoustic waves!), and so heterodyne receiver architectures are not needed - making both receiver and transmitter design quite simple.

I will cover natural emissions, including audio samples, and describe what they tell us about the ionosphere and magnetosphere, including whistlers, chorus hiss, sferics, and more.  Also covered will be human signals in this frequency range, such as power line harmonics and VLF communications signals used by almost every government for information transfer to submerged vessels.  Some information will be provided as well on the challenges of receiving and transmitting signals in this range within your backyard, including the "Dreamer's Band" amateur frequencies below 9 kHz and the new "EbNaut" digital mode for this frequency range."

Embedded video links:
Chorus Waves Recorded by NASA’s Van Allen Probes: https://youtu.be/SGjIJaMqnUI
2016-07-03 Radio Station SAQ in Grimeton Sweden spins up the massive Alexanderson alternator: https://www.youtube.com/watch?v=yYZjz745yGA