In 1963, FM broadcasters using stereo encoders were still quite few. This would quickly change as large, cabinet home sound systems with AM/FM stereo receivers began to be sold. A few FM broadcasters new to stereo transmission, would air select programs in stereo while reverting to mono for others. A few holdouts, such as 93.3 KBLE-FM & non-commercial 107.7 KRAB would remain mono until the 1980’s.
retired broadcaster: on-air, MD, PD, asst PD, Prod Mgr, IT, station technician/engineer, pioneer Internet webcaster, station installation/maintenance; 12 years in commercial radio, 17 years volunteer in campus/community radio in B.C., Alberta & Wash. Amateur radio operator & “DXer” specializing in AM night-time DX, short-wave DX/listening & remote SDR DXing/listening
I think KRAB went stereo in the mid 70,s. I understand that KBLE-FM was the last commercial FM in mono. Now we have KIRO-FM.