FM Transmitter Circuit

FM transmitter circuit with 3km Range

How to make FM transmitter circuit

What is FM transmitter circuit

The FM transmitter (Frequency modulation) circuit is made up of a single transistor or a BJT. In wireless communication, the (frequency modulation) FM carries the data or information by changing the frequency of the carrier wave as per the information or a message signal.

The FM transmitter achieves the application of (very high frequency) VHF radio frequencies of 87.5 HZ to 108 MHZ in both transmission as well as in reception of the Signal. The FM transmitter completes the most excellent volume within less power.

The performance and working of the FM transmitter circuit is dependent upon the variable capacitor and inductor. In this article, you are going to learn that how you can prepare a FM transmitter circuit and how does it work with its various applications.

Things you must know about FM Transmitter

The FM transmitter is a circuit that uses a very low power to operate and does uses (Frequency Modulation) FM Waves to transmit the sound. With the help of such FM transmitters we can easily transmit the audio signals through the carrier waves with different frequencies.

The frequency of the carrier wave would be the same as for the audio signal with an amplitude. The FM Transmitter produces a range of VHF from 88 HZ to 108 MHZ.

Block Diagram for FM transmitter circuit

Components required for FM transmitter circuit are modulator, oscillator, RF-Amplifier, Audio pre-amplifier, microphone and antenna. The Diagram shows the Block diagram for FM transmitter circuit. There are two types of frequency in the signal :

  • Carrier signal (with carrier frequency)
  • Audio signal (With audio frequency)
FM transmitter circuit Block diagram

FM transmitter circuit Block diagram

The carrier frequency is obtained by modulating the audio signals. The (Frequency Modulation) FM signal is obtained by differentiating the carrier frequency and by allowing the Audio frequency. The transistor is used for oscillator purpose in order to obtain Radio Frequency signal.

Working of simple FM Transmitter Circuit explanation

The circuit diagram shown for FM transmitter circuit and the electronic components are the resistor, capacitor, trimmer or variable capacitor, inductor (coil), transmitter, mic, 9v of power supply or 7809 Voltage regulator (in case if you are using input voltage more than 9v) and an antenna. The mic or a microphone is assumed to grab the sound signals and there is a presence of sensor with capacitance value inside the mic. The change in pressure of air or AC signal causes in production of such capacitance.

FM Transmitter Circuit diagram

Simple FM Transmitter Circuit Diagram

The Oscillation circuit could be made with the help of Transistor 2N3904, Inductor and the variable capacitor. The Transistor 2N3904 used in FM Transmitter Circuit. It is a NPN transistor which is basically used for signal and voltage amplification purposes. If the current is passed through L1 Inductor and the variable capacitor, the FM Transmitter Circuit will start oscillating with the resonant to that of the carrier frequency (I.e frequency of the carrier signal).

The negative current or the negative feedback will result C2 Capacitor to the Transmitter Circuit. The oscillator is required in FM Transmitter Circuit in order to generate the radio frequency carrier waves. The transmitter circuit is capable of storing the energy for the oscillation as it is a derived from the (inductor and capacitor) LC circuits. The audio I.e input signal obtained from the mic is passed through the base of the transistor in order to modulate the output signal of the LC circuit in FM (I.e frequency modulation wave) Form.

Here, the main purpose of the variable capacitor becomes that to vary the resonant frequency in order to obtain the best FM Signal Frequency band. The modulated signal is then transmit or radiated as a radio wave with the frequency of FM frequency range. The antenna is nothing but a piece of good conductor, in our application we’d used a copper wire of 30cm long and 26 gauges thick. You can use copper wire up to 25-27 inches long as an antenna in the circuit, the length of the antenna however must be significant.

Application of FM Transmitter Circuit

  • FM Transmitter Circuits are used in a sound system as a signal transmitter.
  • These are used in wireless components for vehicles and offices.
  • The circuits are used to make FM transmitters used to reduce the noise in certain places.

Advantages of FM Transmitter Circuit

  • The FM Transmitter Circuit could be made very easily as the very common components are used which are very cheap and easily available.
  • Above circuit gives the very high efficiency in transmitting signal in a shorter range.
  • The circuit is best suited for demonstration and fm transmitter circuit project.
  • The circuit does have a large and complicated components.
  • The transmitter circuit is capable to neglect the noise signal through the amplitude variation.

Disadvantages of FM Transmitter Circuit

  • In 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 there an interference occurs in the medium.
  • The above circuit is not good enough for high power fm transmitter circuit purpose.

After making the FM Transmitter Circuit you will be able to understand the basic working and application of the transmitter. Hope the article helped you. Feel free to share about how do you like or your queries in a comment below.

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  • 15

Join the discussion

  1. Jiro Kato

    Please, can you help me use this transmitter as a remote control device rather than an audio transmitter ?

  2. Sunshine

    but ENGR. how can I extend the distance like 30km range..please help

  3. Sunshine

    I like your blog

  4. Nimra

    The article says that transistor 2N3904 is used for amplification purposes in ascillator circuit. But there is no such transistor in circuit diagram.
    Please explain how to insert this transistor in circuit.

  5. steven

    what about inductor gage

  6. arun karkare

    Does this “FM transmitter ckt” give a fairly good audio quality at FM receiver ?

  7. Vivek narain

    Such low power transmitter gives a range of about 20
    metres maxing out at 50 metres

  8. Mariely Angeles

    where can i get variable capacitor ? I tried searching them on my local shops but didn’t found any..

  9. Mayonnaise Yen

    Hi i want to make an fm transmitter so that i can transmit the song from my laptop and guitar in all around my home. Also would that be legal ?

    • Farhan Sheikh Ahmad

      You can give the signal output (which goes to the speaker/headphones) as an input to the circuit. It will transmit the songs within the range .

  10. Shameem Hamzap

    Can i use the same circuit for more than 10 KM of range ?

  11. Sameer

    Which ic should i use for the fm circuit ?

  12. Alishba

    Nice article

  13. Richard

    I live in Bolivia, its silly but i donot know if transmitting radio signal is allowed in my country or is it prohibited.

  14. Meguel Alperez

    Hi, i just made the circuit in the video but it seems to bounce the signal. i need a Help simulating FM transmitter circuit

  15. Tom Crosley

    What is the difference between an amplifier and a transmitter in the fm transmitting system?

  16. Ian Quayle

    How does the length and the thickness of antenna effects the noise in the above FM transmitter circuit ?

  17. Mohammad Fahad

    i am looking for a simple fm transmitter circuit diagram and its pcb design

  18. Sam Oay

    what are some important application on fm transmitter circuit other than transmitting signal for radio communication ? i’ve heard that they’re used in our appliances like home-theater etc.

    • Farhan Sheikh Ahmad

      Similar circuits are used in home wireless speakers and many more. However, those transmitter circuits are far advanced and complicated then the one we’ve shown you.

  19. Luna Maya

    i was looking for a simple fm transmitter circuit diagram. it helped with some variations in capacitor, thanks

  20. Sandi Matic

    Can Anyone suggest me a fm transmitter design which would be be very stable and can hold a good amount of Watts output power ?
    Also the transmitter must be very stable and touching it or placing high amount or metals near by would not effect its signal while transmitting.

    Please suggest me a better circuit design.

    • Farhan Sheikh Ahmad

      What you suggest requires a complicated design. The transmitter circuit we’ve shown in the post is just for generic purpose. You can find plenty other high efficiency fm transmitter circuit on the internet.

  21. Allan

    Look what did i found!
    You can increase the antenna’s height and the range of the capacitor and make the fm transmitter circuit for upto 10 km!

  22. Bruce

    I want to make an fm transmitter circuit using ic, is it possible ?

  23. lakshan

    i need more details about it.

  24. JOSEPH

    good job.
    i need more details about it.

  25. Serious Sam

    Is there any way we can use arduino to make fm transmitter?

  26. Max Has

    hey i just powered your fm circuit with my 5000 mah powerbank !

  27. Ganesh

    I want to purchase the project. Plz let me know the price.

  28. Rahul

    What modifications i need to make in the above fm transmitter circuit for the range of 10km ?

  29. FM

    Nice Work! Well done

  30. Arnulfo Hernandez

    I wonder if i can make and sell fm transmitter circuit board. is i legal ? 🙂

  31. Martin

    I was looking forward to make fm transmitter circuit using ic 555. Is it possible the way you did it with the help of a transistor ?

  32. Charlotte Bouabid

    any method to make fm transmitter circuit using ic ??

  33. Andrew

    Nice work !

  34. Sahid

    is there any way i can use variable resistor in the transmitter circuit?

  35. Manvendra

    is there any way to know what frequency is tuned in my FM transmitter circuit ?

  36. Amrendra Kushvaha

    I wanted to see a video similar to your rest of projects for simple fm transmitter project above.

  37. Kulvant Negi

    i want fm transmitter mini project, any suggestion ?

  38. Manoj Prajapati

    hi, i want to make high power fm transmitter circuit please help me

  39. R. K Pavan

    can i use the fm transmitter circuit to transmit signal from my phone ?

  40. Vijay Patil

    how can i use more than one mike in the circuit of fm transmitter you had shown ?

  41. Susan

    Isn’t it illegal to make and use such signal transmitting circuit ?
    in my place it is forbidden

    • Farhan Sheikh Ahmad

      The post is just for educational purpose and to let you know the concept that how does fm transmitter circuit works. You can use it in another projects and applications which would be legal.

  42. Ayush Agrawal

    is there any way i can know what frequency i’m using right now ?

    • Farhan Sheikh Ahmad

      well in this circuit we can’t define the frequency its transmitting. You can calibrate the variable capacitor in order to point at its corresponding frequency, However i do not see any way to just see the frequency which we transmit through it.

  43. Kshitiz verma

    Please do make same for fm receiver which i can use in my car

  44. Rohit Saigal

    i had made the fm transmitter as per your circuit, but i had to add a potentiate in the base of the transistor.

  45. Milind Yadav

    would you mind if i tell you that practicing such kind of fm transmitter circuit is prohibited in certain countries

    • Farhan Sheikh Ahmad

      Actually transmitting radio wave without a government approval is prohibited in most of the places. However, you do can use the transmitter circuit in your projects and indoor applications. You will need to have a shorter range or fm transmitter.

  46. Evelyne

    That’s the best FM transmitter, Everyone can see and make it. 🙂

  47. Nick

    Hi, I read your blog on a regular basis. Your writing style is awesome, keep up the good work!

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