A good overview from the Modesto Radio Museum
For most Americans, news of the Japanese attack on Pearl Harbor came as an interruption to their favorite radio programs on an otherwise tranquil Sunday afternoon on December 7th, 1941. An Associated Press bulletin at 2:22 PM Eastern Standard Time first reported the attack to mainland news organizations and radio networks. After confirming the initial bulletin with the government, the major radio networks interrupted regular programming beginning at 2:30 PM, bringing news of the attack which was still in progress.In New York City, station WOR broke into the local broadcast of the Giants and Dodgers game while CBS informed listeners of the attack at 2:25 PM EST. NBC broadcast their first bulletin nearly 4 minutes later at 2:29:50 PM . Within minutes the CBS radio network broke into normal programming with more information read by announcer John Daly.Honolulu NBC radio affiliate KGU, provided the first and most comprehensive radio coverage of the event. What was not known at the time was that Japanese planes, still swarming overhead in Honolulu, had used the station's signal to guide their planes to Hawaii.While the attack was still in progress a reporter for KGU radio climbed to the roof of the Advertiser Building in downtown Honolulu with microphone in hand and called the NBC Blue Network on the phone with the first eyewitness account of the attack, "This battle has been going on for nearly three hours... It's no joke, it's a real war" said the reporter. Ironically, a Honolulu telephone operator interrupted the broadcast after 2 ½ minutes declaring a need for the line for an emergency call.