Shortwave radio and Very Low Frequency waves

I was recently thinking about radio waves.
(Actually, the whole electromagnetic spectrum)

But I was curious about radio-waves in particular because they aren’t absorbed by our atmosphere.

I found some good explanations of AM / FM radio: Quick Video

And some older, slower, but great detail:
Basic Principles of Frequency Modulation, 1944
Oscillators, 1974

I also found an online shortwave radio receiver. This guy has a receiver set up in his attic and wrote a script to allow anyone online to change the channel. 😀

Here’s a list of countries and stations broadcasting shortwave radio.

I also discovered that, naturally, there is ongoing research in Very Low Frequency phenomena:
http://vlf.stanford.edu/research

And it sounds like this is old news to those involved in Earth science and studying our atmosphere, but an article there mentions that the lower ionosphere changes because of lightning. Specifically, in part of it they model resulting changes in concentration / voltage / heat because of a charge released at a lower altitude. Great references here.

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