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 operational amplifier is old. The circuit is from an 80's documentation but can be designed...
The connection of high-value input resistors causes the circuit to behave like a conventional...
We find this encoding circuit in an American 1980s amateur radio documentation. The circuit can be...