of test transmissions, WPTF made its formal debut on November 14, 1927. On December 1, 1927 the station moved to 550 kHz, which was followed by a power increase to 1,000 watts. William Wynne initially stayed on as station engineer, but later left, continuing to work in the radio industry, and in 1933 set up WEED, the first radio station in Greenville. On November 11, 1928, with the implementation of the Federal Radio Commission's General Order 40, WPTF was assigned to 680 kHz. KPO in San Francisco was designated as the primary occupant of this "clear channel" frequency, so WPTF was restricted to "limited time" operation, which prohibited WPTF from operating after San Francisco sunset, unless special permission had been received to operate with reduced power for additional hours. In the early 1930s, WPTF was a pioneer in educational radio. Students in area schools that had radios were able to listen to a daily broadcast, with topics that included "Citizenship", "Science", "Social Studies" and "Art, Music and Literature". Although many attempts were made over the next several years, it was not until 1933 that the station was authorized to increase its power to 5,000 watts. WPTF purchased new equipment and moved its transmitter site to near Cary, North Carolina, on US Highway 1. Two towers were built, that turned out to be defective, and in June of the next year winds from a thunderstorm collapsed one of the towers and damaged the other, requiring their replacement. These towers served as a prominent local landmark, and some nearby companies advertised their locations by noting their proximity. Station upgrade In June 1940, WPTF was authorized to operate unlimited hours, using a directional antenna to limit westward signals after sunset in San Francisco. A month later the station was granted a construction permit to install new transmitter equipment and increase its power to 50,000 watts, the maximum for AM stations in the U.S. A new transmission plant was constructed at the Cary transmitter site, which included replacing the two existing towers with 370-foot (113 meter) Blaw Know towers. The upgrade to 50,000 watts was delayed when a fire destroyed a new transmitter before it could go into regular service. On May 24, 1941, WPTF began operating with a replacement 50,000 watt transmitter. The next day, the station held an "open house" at the transmitter site, to show off "the new equipment, as modern