Found in a 1924 book by Gernsback, this circuit uses a double variable capacitor, a component not very common at the time. Listening was done on a loudspeaker at the time.
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...