A reader, Floyd Backes of New Ipswich, called me recently to tell me about something interesting that happened to him: He was driving his truck in hilly Temple, a town in southern New Hampshire, when the New Hampshire public radio signal at 89.1 FM turned into a college station from Florida.

What happened? “Sporadic E propagation,” he told me. (He had to repeat it three times: “Sporadic whee? Sporadic he? What?”)

This is an occasional – sporadic, if you will – change in the ionosphere that allows VHF radio signals to bounce a much greater distance than normal. That confusing name desired from the fact they bounce off a lower portion of the ionosphere called the E band, rather than the usual F bank used to bounce shortwave and other signals.

What’s weird is that sporadic E propagation is pretty seasonal – mid-June is peak time in the Northern Hemisphere. It’s not clear why this phenomenon, which doesn’t have any obvious connection to weather patterns, is seasonal, at least not according to sources I can find.

Pretty cool – and particularly learning about it from a stranger. Backes said he called me because he wanted to talk to somebody about it and I was the geekiest person he could think of at the moment. I took that as an enormous compliment.


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