This circuit was found in an article in Radio Electronics magazine. The issue is from July 1992 and the circuit uses components that are common today.
This circuit was found in a 1967 US documentation. The FET is general purpose and the 6V zener....
This electronic voltmeter circuit was found in a documentation from the 50's. The sensitivity is...
This modern regenerative receiver was featured in the March 1994 issue of Electronics Now...