I found this circuit in a documentation for radio amateurs from 1975. The FET could be the BF245. The circuit works in the range of 40, 80 and 160 meters of radio amateurs.
This circuit activates a buzzer when the voltage applied to the input falls below a preset value in...
This simple window comparator based on the well-known LM339 was found in the June 1998 issue of...
This circuit, which can act as a shield, was found in a 1990 PE Hobbyst Handbook. The circuit...