The Army Signal Corps operated a radio station from the grounds of the Presidio, San Francisco, between 1920 and 1923. The station was first known as 6XW, and later by the call letters AG-1, and was operated by Sgt. Richard C. Travers. The Army's purpose in operating the station was to educate amateur radio operators in the benefits of using C.W. (continuous wave) transmitters instead of spark transmitters, thus lessening the interference to the Army's radio operations. The station also offered daily concerts and educational talks to the listening public.