Introduction:
The frequency modulation transmitter operates on low power and the sound is transmitted using FM signals. The FM transmitters take an audio signal from an established source and convert it into an analog signal while the frequency modulator takes the input signal and converts it to match the frequency of the transmitter with the radio frequency.
Here we will briefly describe the construction of a long-range FM transmitter circuit using two transistors. It uses a general-purpose transistor 2N3904 as its main component, the first transistor is used as an oscillator while the second is used as an RF amplifier and also separated the antenna from the oscillator keeping the frequency constant. Few other passive components are used to make the circuit work properly. The working principle and applications of the circuit are described below in detail.
Hardware Components
The following components are required to make FM Transmitter Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Transistor | 2N3904 | 2 |
| 2. | Condenser Mic | – | 1 |
| 3. | Antenna | – | 1 |
| 4. | Inductor | 10 turns | 2 |
| 5. | Trimmer Capacitor | 5-30pF | 2 |
| 6. | Ceramic Capacitor | 0.001μF, 0.33μF, 5pF, 20pF | 2, 1, 1, 1 |
| 7. | Alkaline Battery | 9V | 1 |
| 8. | Resistor | 1KΩ, 5.6KΩ, 22KΩ, 47KΩ, 220Ω | 1 |
2N3904 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3904
FM Transmitter Circuit
Working Explanation:
The circuit is built using two transistors (2N3904), a mic, a few resistors, capacitors, inductors, and an antenna. The two transistors are used for different purposes. The first transistor is used as an oscillator using a variable capacitor and an inductor to produce a periodic and alternative waveform by converting the current from the DC source to an AC signal. The second transistor is used as a power amplifier
Applications & Uses:
- The low-power transmitters are used to transmit the sound over a long range of distances.
- They can be used commercially like in a car to listen to CDs that do not have CD players.
- It enables the phone to play the music saved in its memory on FM frequencies by tuning it to the accessible receiver.
Advantages
- FM transmitters have a large operating range.
- The FM transmitters are easy to use and cheap.
- It emits less power.
- The signal-to-noise ratio is improved in FM transmitters.
