Using a common crystal diode and a 741, this circuit can be used to detect microwaves. The circuit is from old documentation and the switch selects the gains.
This oscillator with FET was found in Popular Electronics from the 90s. This traditional...
This low-power circuit was found in the March 1990 issue of Radio Electronics magazine. It...
This circuit found in a 1964 US publication reverses the signal level by providing 9 to 0 V...