WOI (AM)

Its transmitter is located at a two-tower array off Zumwalt Station Road near Y Avenue, southwest of Ames.

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.

As 640 AM is a clear channel frequency reserved for Class A KFI in Los Angeles, 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.

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

"Dad" Hoffman, a physics professor at what was then Iowa State College, installed a transmission line between the Campus Water Tower and the Engineering Building and set up a wireless telegraph station.

The first regular programming on WOI was farm market reports gathered by ticker tape and Morse code, broadcast throughout the state.

WOI-AM-FM became a charter member of National Public Radio (NPR) when it began its regular schedule of afternoon news program All Things Considered in 1971.