Day 3 of our drive from Santa Barbara to Boston, pausing at a motel outside St. Louis…
Between our Sirius satellite radio receiver, the MP3 player, breaks for public radio and talking to each other, I didn’t have much time to indulge my interest in exploring the high soil conductivities that make AM radio so anomalously advantaged in the plains states. But I did notice that KOA/850 from Denver carried halfway across Kansas by day, and WNAX/570 was audible across all of Kansas, from one end to the other — from Colby to Kansas City and beyond that well into Missouri — with just 5000 watts (1/10th the licensed max) from Yankton, South Dakota. That’s what I listened to most, and it was fascinating.
Long distance AM is no big deal at night, when stations bounce off the ionosphere, giving some stations coverage across half the country. But when the sun is up AM signals rely on ground conductivity, which ranges on land from a low of 0.5 (millimhos per meter) to a high of 30. In almost the entire Northeast, East and south, there is nothing over 4. From Denver to the middle of Missouri, I drove over nothing lower than 15. WNAX sits on 30.
By contrast, WMCA/570 in New York is also 5000 watts, but focuses its signal across New York City and lengthwise down Long Island, where the ground conductivity is just 0.5. The map here shows what happens. What the map won’t show (because it’s not big enough) is that WMCA’s signal is listenable across the Atlantic to past Bermuda.That’s because the ground conductivity of sea water is 5000 (vs. tops of 30 on land).
WNAX’s programming is all about agriculture. Listeners across five states (big ones) also call in with stuff they have for sale. So I’ve been wondering what this kind of largeness contributes to the unity of America’s vast rural center. My mother grew up in Napoleon, North Dakota, where her family’s fave daytime radio station was WNAX, 280 miles away. At night it was the big Chicago stations—WMAQ/670, WGN/720, WBBM/780, WLS/890 and WCFL/1000 (though the channels weren’t the same back then, in the ’20s and ’30), and from there came a sense of culture as well.
Stations in New York, where I grew up, were meaningful over the much shorter range of even their biggest signals. Some of them did have big night coverage, but I don’t think they meant as much withi those footprints as did the big night signals from Little Rock, Chicago, Des Moines and Minneapolis, which covered all the midwest at night. And no single station served and shaped tastes of a whole region more than WSM/650 and its Grand Ole Opry did for The South.
Not much of what my mother experienced survives today. Except, perhaps, through the persistence of WNAX and other stations like it.