No. 3945 (Model 2)

Introduced in November 1922 for $35.50, the Atwater Kent No. 3945 (Model 2) is a landmark of early radio engineering. This three-tube "breadboard" receiver features a detector-two stage amplifier circuit powered by batteries, utilizing one UV-200 detector tube and two UV-201a amplifier tubes. To legally bypass RCA’s expensive regenerative circuit patents, Atwater Kent strategically sold the unit without the central variometer installed, a clever design choice shared with the No. 3925 Model 1. Board dimensions are 18.5" x 8.5".

Image Courtesy of Grant Kornberg, Technogallerie

Image Courtesy of Grant Kornberg, Technogallerie

Image Courtesy of Grant Kornberg, Technogallerie

Image Courtesy of Grant Kornberg, Technogallerie

Image Courtesy of Dave Slusarczyk // Check out his YouTube Channel!

Image Courtesy of John Jenkins | Visit the SparkMuseum!