The 310B-3 pictured above was a popular exciter for home-brew amplifiers. This unit was put into manufacture circa 1946. It was one of the first applications of the highly stable PTO (permeability tuned oscillator) for radio amateur service operation. This unit has not been restored. Note the Bakelite insulated hole in the rear view providing entry for the antenna transmission line. Coax was rare in those days. This unit came with 5 band coils and one output coil.
