In this 1970s receiver, the coil has a primary with 100 turns and a secondary with 20 turns, both with wire 28 in the same ferrite core. The diodes can be the 1N34 and the transistor of any type of general use. The variable is from a common AM radio as well as the transformer that powers a headset or small low impedance speaker. The antenna must be long, and the circuit also works with 6 V.
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