We found this circuit in an Elettronica Pratica magazine [1977]. The edition is number 9 and the circuit can be easily assembled because the components are common. The transistors can be BC548 and the coil has two windings. L1 consists of 100 turns of wire 28 and L2 in 20 turns, both on a ferrite rod about 15 to 20 cm long. The diode can be 1N34.
