Just about any power transistor can be used in this megaphone.Its suitable for boats,playing fields etc.the transistors Q1 & Q2 are the HEP-230 type which are easily available in the market.The transistors are parallely connected to handle the required power and speaker matching.The microphone is a carbon type like that used in telephone hand sets.If a regular carbon mike is used the push-to-talk (PTT) switch can be connected in place of S1 to provide PTT operation.There will be no warm up or “capacitor charge time.
Circuit diagram with Parts list.
- The circuit can be powered from a 12V battery or 12V DC power supply.
- The POT R1 can be adjusted to obtain maximum volume with minimum distortion.
- It will be always better to mount the transistors on heat sink.