This crystal or galena radio is one of the many versions available on this website. This is from a documentation from the 70s. The coil is formed by 50 + 50 turns of wire 28 in a ferrite rod.
Found in an EDN from the 90s, this circuit uses an electret microphone. The output can be used to...
This circuit is characterized by the configuration that accelerates the switching, being ideal for the...
This circuit makes use of a PLL 567 to invert the phase of a signal, ie to change it from 0 to 180...