This circuit has a sensitivity of 2uW. We found it in documentation from the 1980s. The integrated circuit is from that time. Equivalents can be tried.
We found this circuit in the October 1980 issue of Radio Electronics magazine. The circuit uses...
Found in an English publication from the 1980s, this circuit uses components that are still common...
With two cascading tunnel diodes, this circuit found in a 196 General Electric documentation...