Simple FM transmitter Circuit

 

 Simple FM transmitter Circuit

This is a circuit diagram of FM transmitter which constructed very easily. This FM Transmitter circuit needs very less components. This circuit is based on two npn transistor of 2N2222 which is low power amplifier. At the first transistor stage the input signal is preamplified and then the transistor T2 will Amplified the signal as power amplifier and then amplified signal to be modulated and transmitted through output as antenna.Use 9 or 12 v DC regulated power supply, Regulated power supply needed because oscillation affects the frequency at output as power variation occur in supply.
This circuit construction is so easy and very portable to operate. The use of this transmitter is only for educational purpose.
Circuit diagram of small FM Transmitter
 
FM transmitter circuit diagram
 
 
 
 

components

  • Resistors ¼ watt (220Ω-1;  1kΩ -2; 2.2kΩ; 10kΩ-1;  15kΩ; 6.8kΩ;  4.7kΩ -2)
  • Electrolytic capacitors 16V (2.2µF; 10µF x 2)
  • Capacitors ceramic (0.1µF x 2; 4.7pF)
  • Variable capacitor (50pF)
  • Inductor (0.1µH)
  • Transistors (2N2222 x 2)
  • Condenser mic

 

Working

The signal is amplified by transistor Q1 which is come from the condensor mic. Here signal is preamplified. , Transistor 1 acts as a preamplifier. Sound pass through mic is amplified by the transistor 1.The amplified signal is then sent to the base point of Q2 through capacitor and resistor . And collector is connected by coil and capacitor with antenna.

Two resistor connected as biasing providing with the base of transistor1. Amplified sound signal will be available at the collector of Q1 and it coupled to the base terminal of transistor Q2 via the capacitor C3 and R4.

An oscillator circuit built using Q2, C7 and the inductor that operates in the 80 to 130 MHz range, which is basically a voltage controlled oscillator and that frequency can be modulated by the input audio signal. Inductor L2 and variable capacitor C7 forms a tank circuit required for making oscillations. Capacitor C6 is the feedback capacitor for provide required output power signal .

 Resistor R4 conneted for control the input RF signal to oscillatory section. you can use a variable resistor for this.

value of inductor design for FM transmitters

By using the following formula inductor can designed
where,
L – Inductance of the coil in µH
d – Coil diameter in Inches
S – Coil length in Inches and
 
n – Number of turns
                                                                       
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Hi, My name is Aman bharti, I am interested in making and study of Electronics & circuit diagram. I like to share my knowledge and all ideas with people which i get from My Experiment & from different sources. I try to provide any circuit details deeply with test result as possible as. You can contact me on- Email – [email protected]

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