Fun with distance

I’m listening to WGBH on 93.7 from Boston on my kitchen radio, on the low floor of an apartment building in Manhattan, thanks to an atmospheric condition called tropospheric bending, or “tropo” for short. Here’s my section of the current map of tropo at work right now:


Screen Shot 2014-08-12 at 9.28.58 AMThe same map shows bigger “ducts” running from Florida to Iowa and Missouri to California. The map is by John Harder, aka @ng0e. Other maps by meteorolgist William Harper abound here.

I would have loved the same thing back when I was (like John) a “DXer” who logged about a thousand different FM stations from my house in the woods north of Chapel Hill, North Carolina, in the late ’70s. “Tropo” showed up in the mornings, and another more dramatic form of long-distance propagation called “sporadic E” would appear in the afternoon and evenings, mostly in the late spring and early summer. Here’s a map source for that one.

One entertaining thing about sporadic E was how it affected channels 2-6 television. I picked up every Channel 3 in a circle that ran from Louisiana, across the prairie states, southeastern Canada, the Maritimes, and then around to Cuba. That whole band is now abandoned in the U.S. TV stations with those channel numbers actually radiate on other ones, while still occupying their old channels virtually. Also, we have the Internet, so watching and listening to faraway stations lacks the old thrill.

Still, it’s fun to hear that faraway stuff showing up every once in awhile.

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2 Responses to Fun with distance

  1. Gideon Klionsky says:

    My fifth grade science fair project consisted of buying a low-end high-end radio, attaching an antenna that draped across my city of Chicago roof, and tuning AM stations one by one a few nights a week, noting down any identifying information I could find about the source of the transmission (call signs, time zone, area codes, names of announcers, etc). Then I’d go to the library the following day to try to find weather information for the city of origin and, ideally, the space between there and Chicago. Way too many variables to make a solid conclusion about much of anything. But I got (again, AM stations) radio from Denver, Schenectady, New Orleans, and one night, New York City. It made summertime family road trips much better for years to come: I knew where to find the Cubs, Sox, Brewers, Cardinals, Tigers, Reds, Indians, Pirates…

    • Doc Searls says:

      Thanks, Gideon. Weather in fact has little or no influence on how AM radio skips off the E layer of the ionosphere at night. (It does affect reception, in the case of thunderstorm.) The station you got from Denver would have been KOA/850. Schenectady would have been WGY/810. New Orleans would have been WWL/870. New York would have been WABC/770, WNBC/660 or WCBS/880. All were 50,000-watt non-directional landmark stations, most of which were on “clear” channels, meaning they were the only stations in North America on those channels at night, so they could be heard up to hundreds of miles away. (Country music spread mostly through WSM/650 from Nashville, another “clear” station.) The hard part of getting the last three — the ones from New York — was channel adjacency to Chicago stations WBBM/780, WMAQ/670, and WLS/890. I had the same problem getting those Chicago stations (plus WGN/720 and WCFL/1000) from my house in New Jersey, which was less than a mile from WABC and only a few miles from WNBC/WCBS (which used the same tower in The Bronx), WINS/1010 and WOR/710, all of which were also 50,000 watts, but some of which were directional, so their signals in my direction were weaker. I also remember listening to the Cubs on WGN/720, the Pirates on KDKA/1020 from Pittsburgh, the Tigers on WJR/760 Detroit, and so on. Now they’re all on SiriusXM or on their home stations over the Net. And the thrill of distance is mostly gone.

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