Informational sites about crystals.
Related categories 2
Bliley Electric Company History: The Early Years, 1930-1955
History of the company that invented and patented the overtone crystal, etch-to-frequency and variable crystals. Source for ads, engineering bulletins, patents and manuals.
FT243 information compiled by Paul Carreiro, N6EV.
From N6EV. Tube oscillator schematics, and discussion.