Thanks for this footnote! We're going to look into those suggestions because I dearly miss the weirdness of public access channels and shortwave radio.

My brother and I used to stay up late scanning shortwave to "listen for alien transmissions." In retrospect, I think we actually heard one or two of the number stations that were still broadcasting into the late '80s. (The Tweeter and the Hellmouth, if memory serves. The Tweeter was very reliable).

The Conet Project (circa 2004-ish) was an audio compilation of numbers broadcasts. Highly recommended.