This elementary receiver with a crystal earphone was found in Japanese documentation from the 1960s. The coil has 60 + 40 turns of wire 28 to 32 in a ferrite rod.
This configuration makes use of currently uncommon components. In fact, we found it in...
This 1 kHz oscillator was found in the February 1970 issue of Radio Electronics magazine. It uses...
This circuit was found in Motorola documentation from 1968. Transistors can be modern equivalents, just...