WOI (AM)

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "WOI" AM – news · newspapers · books · scholar · JSTOR (November 2024) (Learn how and when to remove this message)

WOI (640 kHz) – branded Iowa Public Radio – is a non-commercial AM radio station licensed to Ames, Iowa, and serving the Des Moines metropolitan area. Owned by Iowa Public Radio, it is a listener-supported public radio station airing a news and talk format. WOI 640 is the flagship station for Iowa Public Radio's News Network, affiliated with NPR, Public Radio International and the BBC World Service. Its transmitter is located at a two-tower array off Zumwalt Station Road near Y Avenue, southwest of Ames.^[2]

By day, WOI is powered at 5,000 watts using a single non-directional antenna. Due to its low transmitting frequency and Iowa's flat land (with near-perfect ground conductivity), its daytime footprint is equivalent to that of a full-power FM station, providing at least secondary coverage to almost all of Iowa-as far east as Cedar Rapids and as far west as Sioux City. Its secondary signal also covers portions of Minnesota, Nebraska, Missouri and South Dakota. Its daytime coverage area is similar to that of central Iowa's most powerful AM station, 50,000-watt WHO. But 640 AM is a clear channel frequency reserved for Class A KFI in Los Angeles. To avoid interference, WOI reduces power at night to 1,000 watts, with power fed to both towers in a directional pattern that pushes the signal to the east, concentrating it in the Des Moines and Ames areas.^[2] Programming is also heard on 250-watt FM translator K284CN at 104.7 MHz.^[3]

Historically, WOI is one of the oldest radio stations in the United States, having begun experimental transmissions in 1911.