Claim: KRDU, which was owned by the Radio Dinuba Company with studios on L Street, signed on the air at 1130 kilocycles (cycle per second, a once-common English name for the unit of frequency now known as the hertz ) as a daytimer (required to go off air at night) on December 26, 1948.
Evidence: A clear-channel station is an AM radio station in North America that has the highest protection from interference from other stations, particularly concerning night-time skywave propagation. Since 1941, these stations have been required to maintain an effective radiated power at least 10,000 watts to retain their status.