This primitive solar radio was found in a Gernsback publication from 1960. The transistor is made of germanium of the time and the earphone is magnetic with high impedance.
This small telephone transmitter uses a telephone capsule as a microphone. The L1 coil has 4 to 5...
This circuit was found in an American documentation from the 1980s. The sensitivity ranges from...
This circuit produces a sinusoidal signal whose frequency can be calculated using the formula next...