No. 3975 (Model 4)
The Atwater Kent No. 3975 (Model 4) Receiving Set was one of the earliest and rarest in the legendary "breadboard" line, introduced in early 1923. This set was a three-tube Tuned Radio Frequency (TRF) circuit, comprised of a detector and two stages of audio amplification, and it featured four main components on the board: a variocoupler, a variometer, detector and the amplifier island. Unlike the Model 1, 2, and 3, the Model 4 was engineered to be sold as a complete system that was regenerative from the factory. Board dimensions are 24-1/2" x 8-1/2".
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie
Reinhard Brothers Style Model 4 (See Homebrews & NonFactory Sets) / Part of Phil's Collection
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie
Image Courtesy of Grant Kornberg, Technogallerie