Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
This is the power supply indicated for the previous circuit (CB18905E) providing a voltage of 24 V...
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
In this Radio Electronics from May 1958 we have the now common use of the varicap in a frequency...