The 97.3 MHz frequency signed on the air as KWBR-FM, dedicated September 14, 1947. The station was owned by the Warner Brothers of Oakland (of no relation to the film studio), with studios and transmitter on the side of Twin Peaks. It was a sister station of KWBR AM (earlier known as KLS and the current day KMKY 1310 AM. After changing its call letters to KGSF in 1949, the station was sold in 1952 to the Electronic Service Corporation and managed by Stephen Cisler, who also owned KEAR (1550 AM) in San Mateo, and renamed KXKX. The two stations broadcast the same classical music format. In 1956, struggling financially, Cisler sold KEAR but retained KXKX and the KEAR call letters, moving the KEAR call letters to the FM frequency.