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Friday, December 12, 2003
Ferrous Firma 
| | Ed Cone says, Doc just knows the hell out of NC radio. Once he told me that we get poor reception here because of low soil conductivity. Damn red clay. |
| | Some people in the comments seemed almost interested, so I thought I'd explain. |
| | The map above shows the soil conductivity across the U.S. At the high end it's 30mhos/m. At the low end it's 0.5. |
| | Most of the Dakotas are 30. So is most of Kansas, and much of Oklahoma and North Texas. Also much of California's Central Valley, plus all of Marin County and half of Sonoma. |
| | At the other end, Atlanta is a 1. So is most of New England. Long Island is 0.5. Nearly all of Virginia is 2. Little of The South is better than a 4. |
| | All these values only affect AM radio. Waves on AM are long (hundreds of feet) and adhere to the ground. The longer the waves, the farther they go. The waves on the bottom end of the AM band are the longest. So WNAX, on 570, in Yankton, South Dakota, covers nearly all of South Dakota, Iowa and Nebraska, plus about half of Minnesota and Kansas, plus a corner of Missouri. You can get it from Kansas City to Canada in the middle of the day. WWNC on the same channel in Asheville, NC, makes it from Charlotte to Knoxville. Nice coverage, considering, but a fraction of WNAX's. Other stations with the same power (5000 watts) on 570 in New York, Los Angeles, Seattle and Syracuse have coverage equally restricted by relatively low ground conductivity. KLIF in Dallas is the only one that comes close, again due to high ground conductivity. WSB, a 50,000 watt station on 750 in Atlanta, basically covers North Georgia. (Oddly, here are no 50,000 watt stations low on the AM dial in the highly conductive plains states. The closest we have may be WBAP/820 in Fort Worth.) |
| | So you find lots more little AM stations in the South than in, say, the Midwest. Simply because they all have less range. You can fit more into a given geography. |
| | Nighttime is a different matter. At night, the ionosphere reflects AM waves, so a station like WSB at night covers the whole Southeast. The term "Clear Channel" was originally reserved for the two-dozen AM stations with 50,000-watt signals on channels where nothing else interfered at night. I used to listen to KFI/640 from Los Angeles in New Jersey at night when I was a kid. Country music was a product of WSM/650 out of Nashville, which covered the whole East at night. |
| | An aside... The company called Clear Channel derived its name from WOAI/1200 in San Antonio. Its daytime coverage was good, but at night there wasn't a single other signal in the whole U.S. on 1200AM until the mid-1970s. That meant you could get it from coast to coast. |
| | FM station coverage is mostly a matter of height. Here's what KPFK/90.7 does with 110,000 watts from Mt. Wilson in Los Angeles. And here's what KPCC/89.3 does with just 600 watts from the same mountaintop. The difference is that KPFK's signal pounds through building walls while KPCC's stops at a shingle. But out in the open, in a car, the two stations come in all over the L.A. area pretty much the same. |
| | WUNC/91.5 in Chapel Hill, where Ed, Zephyr and Ruby were on the air talking about politics & blogs yesterday, is a 100,000 watt station on a 1500-foot tower, and covers Central North Carolina pretty darn well. |
| | I also get 'em just fine in Santa Barbara. That's the future. |
| | At some point we need to face the facts. AM and FM broadcasting suck down huge amounts of electricity. Their towers bristle from swamps and mountaintops. And their technologies were developed before the middle of the last century. They use old brute-force technology to deliver what can be done far more efficiently by more "cellular" means. The low number of channels, and high costs of occupying them, makes the industry available to a few grandfathered incumbents. Why shouldn't there be an unlimited number of stations, just like there are an unlimited number of Web sites, of blogs, or or any breed of source on the Net? No reason at all. Unlimited opportunity will truly let the market decide what it can support. |
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