Radio microphones are used extensively by stage performers and professional eavesdroppers (Spies) but they can also be used for other fun projects such as monitoring of sounds. For example you can take an ordinary household portable radio and tune it to your desired FM frequency, then tune the microphone to the same frequency and place the microphone in a location around the home such as in your new born baby’s room and now using the radio you can pick up any sounds coming from the room, you have effectively created your very own baby monitor!

Tools Required:

• standard 9 volt battery
• Soldering Iron and some solder
• Printed Circuit Board (We got creative and used a piece of paper cardboard)
• Some copper wire
• Condenser Microphone (We got one out of our old home telephone)
• 4x Resisters
• Trimmer Cap (Can be salvaged from any old radio)
• 1x Transistor
• 4x Capacitor

Diagrams

Step by Step Build

 Finished Product

Microphone Disguised as a Night Light