N° of component 

Wireless AM Microphone (CB1390E)

 This simple AM transmitter for very small ranges uses in the original version of the 1970s, a carbon microphone. We can use instead a low impedance microphone or even a small speaker. The coil has 50 + 50 turns of wire 28 in a ferrite rod and the variable was obtained from an old receiver. As 22.5 V batteries no longer exist, the power can be made with one or two 9 V batteries and the transistor can be a BC558. A small antenna can be attached to the transistor collector for greater range.

Circuit Bench