This variable frequency (VFO) oscillator was found in a Japanese publication of 1962. Coil details (in Japanese, but can be deduced) are next to the diagram covering the 3.5 MHz band.
This circuit was obtained in a documentation of the 80s, using operational of the time. The...
This circuit was found in an English publication from 1967. The circuit is for listening on a...
This circuit matches a high impedance input signal with a low impedance output. This circuit is...