We found this circuit in an old American publication from the 1980s. Transistors can be general-purpose types like the BC548, and the tuning frequency is given by the L and C components.
In the figure we have a simple signal tracer circuit to be coupled to the volume control of an AM...
This circuit was found in documentation from the 90s, using components from that time. The...
This circuit, obtained from old documentation, allows the recovery of sulfated batteries. The...