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.
This interesting 80's EDN circuit divides the input pulse frequency by a number given by n...
Adafruit Raspberry Pi Perma Proto PCB Kits Adafruit kits are available from Mouser Electronics...
This circuit is from the Motorola Linear Databook of 1990. The coils must be according to the...