This circuit was described in an article in the February 1993 Radio Electronics magazine. The frequency depends on the crystal and L1 is optional.
To use the instrument for AC measurement, the tips are A and B. For CC use tips A or B for...
The interesting circuit shown in the figure, can have its gain digitally controlled and present two...
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...