Summary of Building Simple FM Transmitter
Parts used in the Simple FM Transmitter:
- Thirteen components
- Printed Circuit Board (PCB)
- 9v battery
- Vero board (strip board)
- Capacitor C5
- Coil L1
- Transistors
This article shows you how to build a very simple FM transmitter from thirteen components, a Printed Circuit Board (PCB) and a 9v battery. This project was designed to be mounted on a PCB, however you don’t have to. You could construct the project on Vero board (strip board) or any other 0.1” pitch style of project board. If you just want to experiment with this circuit, you don’t even need a board; you can just solder the component s together and let the completed project just rest on the work top.
No matter which style you choose, try to keep all component leads nice and short. You could also make the PCB much smaller than the one shown here which is approx. 3 cm square. This is a good size to keep the unit small but nicer to work on for beginners. If you wanted to make one really small, you could use all SMT parts.
Selecting the operating frequency range
The value of capacitor C5 controls the transmission frequency range.
In the UK, domestic FM radio receivers cover from around 88 – 108MHz.
The following table shows an approximate frequency range that can be expected for different values of C5.
These are only approximate as frequency is determined by the L1 and the specification of the transistors, but these ranges were observed in the prototype unit. Also note that the closer the coil windings are, the lower the frequency will be. Just slightly compressing the coil dropped the transmission frequency by over 1 MHz.
For more detail: Building Simple FM Transmitter
- What components are required to build this project?
The project requires thirteen components, a Printed Circuit Board (PCB), and a 9v battery. - Can I construct this on a Vero board instead of a PCB?
Yes, you can construct the project on a Vero board or any other 0.1 pitch style of project board. - Do I need a circuit board to experiment with this circuit?
No, you do not need a board; you can solder the components together and let the completed project rest on the work top. - How does the value of capacitor C5 affect the device?
The value of capacitor C5 controls the transmission frequency range. - What is the domestic FM radio receiver frequency range in the UK?
Domestic FM radio receivers in the UK cover from around 88 to 108MHz. - Does compressing the coil windings change the frequency?
Yes, making the coil windings closer lowers the frequency, and slightly compressing the coil can drop the transmission frequency by over 1 MHz. - What is the approximate size of the PCB shown in the article?
The PCB shown is approximately 3 cm square. - Is it possible to make the unit smaller using specific parts?
Yes, you could use all SMT parts to make one really small.
