We find this circuit in a 1980s Linear Technology documentation. The circuit can be implemented on the basis of more modern equivalent components.
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This interesting circuit was obtained from a 90's EDN. What it does is generate negative voltages...
This circuit is from an 80's electronic component manual. It has the way to simulate an inductor...