I'm gonna show you How to make a Simple FM Transmitter that works with only an AA battery.
47 pF Ceramic Capacitor x1
33 pF Ceramic Capacitor x1
10 pF Ceramic Capacitor x1
22 uF Electrolytic Capacitor x1
2SC655 (or BC548) Transistor x1
Single Battery Holder (AA Size)
10cm Magnet wire x2
Audio Signal Source (e.g. a MP3 Player)
Step 1: The Circuit and Parts
Here is the Circuit we're going to make.
Step 2: Start Soldering Parts on PCB
It takes about 10-12 mins to do this.
Step 3: Make the Coils
Wrap the first Magnet Wire around a thick pen or a size AAA battery.
Do the same for the second Magnet Wire, too.
...Then Solder them on PCB
Step 4: Final Steps
Solder the battery holder wires, Antenna Wire, and the Audio Source.
Step 5: Turn on Your Radio
Turn on a radio and set it at 89MHz FM
Connect the "Audio In" of the Transmitter to your MP3 Player (or any other non-amplified things playing music).
Place the Battery in the holder.