Radios, how do they work?
A brief introduction to antennas, superheterodyne receivers, and signal modulation schemes.
lcamtuf put together an excellent primer on how radios work. Their goal was to “provide an introduction to radio that’s free of ham jargon and advanced math” and I think they succeeded. It’s well worth a review, even if you’re an experienced ham.
The video below is one of the excellent demos in the article: