This 4-waveband converter circuit was found in Radio Craft September 1948. The power supply is not given, but the supply voltages are indicated.
This oscillator from a 1970 documentation uses an operational amplifier that is no longer common on...
This circuit, with a 12 V input, was found in a Popular Electronics from the 1990s. Information is given...
This circuit is from an old publication of the 70's. It can be implemented with modern transistors like the...