Found in a publication for radio amateurs from the 1980s, this circuit amplifies signals in the 60 kHz band (VLF), Winding data from the ferrite antenna are provided along with the diagram.
This different configuration for a crystal galena radio or modernized since a diode is used, has a...
This circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
This version of the test lights a lamp when the ring touches the tortuous wire. The SCR can be the...