This special episode comes from “On the Media” ’s Peabody-winning series “The Divided Dial,” reported by Katie Thornton. You know A.M. and F.M. radio. But did you know that there is a whole other world of radio surrounding us at all times? It’s called shortwave—and, thanks to a quirk of science that lets broadcasters bounce radio waves off the ionosphere, it can reach thousands of miles, penetrating rough terrain and geopolitical boundaries. How did this instantaneous, global, mass communication tool—a sort of internet-before-the-internet—go from a utopian experiment in international connection to a hardened tool of information warfare and propaganda? This first episode of Season 2 of  “The Divided Dial” is called “Fishing in the Night.”