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.
Other amplifiers of the series like the MC3301, MC3401 and LM2900 can be used in this circuit. We found...
This type of sensor was used in sensitive infrared systems from the 1960s. This circuit was found...
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...