This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100 turns of 26 or 28 wire in a 1 inch PVC pipe. The antenna must be a long wire.
Found in an old publication, this is a transmitter with a spark coil. The high frequency...
This circuit was found in a 90s Hands-On Electronics. When a signal appears at the headphone...
In the figure we give a suggestion of a high-power stage to excite a speaker with the 2N3055. The...