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.
The circuit shown, with the printed circuit board, was found in an article in the June 1990 issue...
According to the consulted American publication of the 1980s, a zener diode can be used for DC...
This circuit originally appeared in a publication of 1997. With the changes, the circuit can be...