Brutkasten (Schaltungsidee) (Squelch für FM-Stereo-Empfänger)

Why is long distance shortwave reception possible? Why is MW only good over short distances during the day? There are so many `whys` associated with shortwave reception that many of us are completely in the dark about what frequency to choose, what time to listen, and what is likely to be heard. This article about the ionosphere is intended to take some of the guesswork out of shortwave listening.