This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
This circuit was found in a 80s American documentation. The zener diodes determine the points of...
This circuit uses an old National Semiconductor operational amplifier, but it can be implemented with...
The oscillator shown in the figure can generate signals between approximately 3 and 15 MHz,...