In this instructable I’m going to show you how to build your own portable audio transmitter. This transmits FM waves so you could easily get the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip.
This transmitter is like the ones in the movies which are used to spy on people or try to record conversations, well don’t use this this to spy on anyone, its just for educational purpose only.
What does this do?
- Well all this is a FM transmitter so you could start your own mini FM station.
I’m going to build a mini FM receiver soon, to go with the mini FM transmitter
How does this work?
Well all of us have heard of “frequency modulation”, most commonly known as “FM”, this circuit works on the very same principal to transmit audio signals captured by the microphone. This circuit uses BC547 transistor to amplify the signal and then frequency modulate it. Since it is tiny and powered with just 9v the signal range is limited to only 15m.
If you like my project you can vote for me in the battery powered contest.
OK now enough of the talking and let’s start building.
Step 1: Tools and Components
Like always lets start with getting all the parts, the list is quite simple all you need is
- BC547 Transistor
- An microphone
- A variable capacitor 47pf
- An Inductor (see steps for description)
- 4.7k Resistor
- 330ohm resistor
- 1n capacitor (102)
- 10p capacitor
- 9V battery
For more detail: Mini Audio Transmitter