This receiver of two transistors for the 3.5 MHz band was found in a circuit manual from the 80's. The coil data are found next to the diagram and the transistors can be general purpose PNP.
The simple transistor test shown in the figure can be powered by a 9V battery. The test is for...
This circuit is from an American publication from 1970. It uses a coal microphone, which is...
The maximum current of this circuit is 250 mA, its purpose being to replace 9 V batteries. Diode D1...