This crystal or galena radio was found in documentation from the 1990s. The earpiece must be a high impedance crystal or magnetic earpiece and D1 can be any germanium diode.
This circuit was found in a 90s American documentation from the 90s. The components are from that...
In the figure we have the circuit of a clamp-type microammeter described in the Radio Electronics...
The voltage-gain for this amplifier is 10. Other operational amplifiers can be use and the Power...