In a previous post, I made one transistor FM transmitter that is also very nice and easy to make. This is just another one, a two-transistor FM transmitter. It has two stages. In the first stage, amplifying the audio signal and generating a carrier signal using an oscillator, and in the second stage, modulating the carrier signal with the amplified audio signal. The amplification is done by an amplifier, whereas the modulation and carrier signal generation are done by a variable frequency oscillator circuit. Frequency can be set anywhere within the FM frequency range from 88 MHz to 108 MHz. The power of the FM signal from the oscillator is then amplified using a power amplifier to produce a low impedance output, matching that with the antenna.
Two-transistor FM transmitter Circuit diagram
list of components
| 1 | 10k | R1, R4 |
| 2 | 1M | R2 |
| 3 | 100k | R3, R5 |
| 4 | 0.1 uF | C1 |
| 5 | 4.7 pF | C5 |
| 6 | EMP | U1 |
| 7 | 2n2222A | Q1, Q3 |
| 9 | ANTENNA | U2 |
Notes.
- The circuit can be powered from anything between 6 and 12V DC.
- Noise can be eliminated with the use of a battery.
- If you are going with a battery eliminator, then it must be well filtered and regulated.
- The antenna can be a 1 m copper wire.
- L1 can be constructed by making 4 turns of 1 mm enameled copper wire on a 10 mm diameter plastic former.
- Most of the components required for this circuit can be taken from old circuits.
- Range can be increased with a high antenna and a powerful battery.
- A list of all components is also given on the circuit diagram.
Application of FM Transmitter Circuit
- FM transmitter circuits are used in a sound system.
- These are used in wireless components used in vehicles and offices.
- The circuits are used to make FM transmitters used to reduce the noise in important places.
Advantages of FM Transmitter Circuit
- The FM transmitter circuit could be made very easily, as very common components are used.
- The above circuit gives very high efficiency in transmitting signals.
- The circuit is best suited for demonstration and the FM transmitter circuit project.
- The circuit does have large and complicated components.
- The transmitter circuit is capable of neglecting the noise signal through the amplitude variation.
Disadvantages of FM Transmitter Circuit
- In the above FM transmitter circuit, there is a large, wider channel needed.
- With the circuit, the transmitter as well as the receiver tends to become more difficult.
- The received signal gets poor quality as interference occurs in the medium.
- The above circuit is not good enough for high-power FM transmitter circuit purposes.