Electronic Circuits and Diagrams-Electronic Projects and Design
In Radio Transmitters

Medium power FM transmitter circuit

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Description.
This is the circuit diagram of a moderate power FM transmitter circuit employing two transistors.The voice signals picked by the microphone will be amplified by the transistor Q1.The second transistor is wired as an oscillator operating in the FM band.The output of T1 is given to the base of T2.T2 performs the modulation also.The tank circuit comprising of components L1 and C6 determines the frequency of the signal, and can be varied by adjusting C6.The capacitor C7 couples the FM signal to the antenna.

Circuit diagram with Parts list.

fm-transmitter-circuit


Notes.

  • You can assemble the circuit on a general purpose PCB.
  • The circuit can be powered from a9V PP3 battery.
  • The Antenna A1 can be a 1M long wire.
  • The inductor L1 can be made by making 6 turns of 0.8mm enameled copper wire on a 5.5mm diameter/4.5mm length plastic former.
  • With a matching antenna and proper tuning this transmitter can have range upto 100meters.
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88 Comments

  1. ECE

    What is the operating frequency of this project?

  2. vasudha divedi

    sir..how can i found which frequency is transmit by this transmitter….plzzzz help me…this is my minor project

  3. vasudha divedi

    hello sir….this project is not work and i cant find any fault so plzzzzzzzz help me….

  4. danish

    i made this circuit on breadboard but it is not tuned plz anyone can help me?

  5. amit

    Can i use 0.5uF electrolitic capcitor in place of C3 (0.5uF Ceramic)

    • Seetharaman

      Hi Amit It has to be ceramic or it can be solid tantalum bead type. not wound tubular capacitors, which has inductive component also buit in.

  6. Tabat

    What type of crystal oscillator can I use to replace the tank circuit with? Pls I need a reply with the frequency.

    • Victor

      hmmmmm i dont know much but fm frequency range is 88-108 MHz

  7. naser

    hi. if I use mp3 player out put for this circuit (change Mic with audio in) what I do? can I connect player out to c1 directly?
    with tanks Naser Khiavi

    • Seetharaman

      Remove R1 and C1 and feed direct to C2 and common. Adjust MP3 volume for clear sound from the FM monitoring receiver.

  9. Rex

    Seetharaman, I want to add crystal to the circuit to make it stable.. Where will i connect the crystal.

  10. aiya

    is c1 elctrolitic? cn I have c6 fixed? well that would mean the frequency to be fixed too right?

    please reply asap

  11. Azeem

    Is 0.022j the same as 0.022pf.
    Can 0.022j replace c7

    • Seetharaman

      Hi Azeem 0.022J is 22nF (0.022uF) 250 volts capacitor. C7 should be 2.2pF.

          • Azeem

            i’ve implemented the circuit. But i’m having problems with the frequency of transmission. It is probably the inductor that i didn’t get well. Please can you explain the oscillator stage of the circuit for me. Also is c7 and that 5pf part of the tank circuit?

          • Azeem

            i got the frequency. However it does not transmit voice signals. If i tap the mic, i can hear it. Also At different frequencies by varying c6. But if i speak, i don’t hear it. If i play mp3, i don’t here it also. I used a condenser electret mic. Please help me. I’ve already submited the proposal for this project in school. I can’t drop it.

          • Seetharaman

            Hi Azeem check polarity of capcitor C2 and try by reducing C4 to .002uF.(2k2 pf or 2200pF) it should solve the problem.

          • Azeem

            i’ve done so, it is still not working. How can i measure inductance. May be its the inductor

          • Seetharaman

            In the notes the winding details of L1 is given you try it it should solve your problem.

  12. shameed baig

    dear sir/madam.
    I am shameed baig. I want a FM transmitter ready made kit.
    cell 9886218503

  13. ketan

    and sir, how to choose alternate values for variable capacator n inductor?? please reply asap…..

  14. ketan

    i dont understand how will signal be amplified if R2=R3. Also, aint 0.022pF too low??

  15. DavidCheng

    Will the circuit work if I change C7 to some other value (i.e. 2.2pF or 22pF)? I probably won’t be able to get 0.022pF capacitor

  16. Amit Sharma

    Sir
    Medium power FM transmitter circuit

    in which shop available in mumbai
    because i want to the buy. this circuits

  17. Chintan

    i am unable to see any oscillations on the collector of Q2.
    What can be the reason?
    I have not connected microphone yet.

  18. supath mohile

    please can u describe that on which frequency this medium power FM transmitter circuit will be work.???

    • Abrham

      Please can you describe that on which frequency this medium power FM transmitter circuit will be work.??????????

  19. fatunmbi olalekan

    How to generate voltage through water

  20. NO name

    i think all ground are connected.,correct??
    but i confuse what is the voltage of ceramic cap. it is 50V??
    and electrolytic cap is 16V??

  22. seetharaman

    Hi Ashnuka place order through net and get it or please drop the project, without ceramic capacitors it will not work.

  23. ashnuka

    What are the replacements of the ceramic capacitors?I cannot find any of them.

  25. munna

    I understand everything of this diagram except capacitors. I don’t understand which volt of capacitor i’ll use….?

  26. seetharaman

    Hi Alex it electret condenser microphone.(M1 is Microphone1)

  27. Alex

    Hello, I understand everything on the schematic except for “M1”. Can anyone tell me what component this represents?

    Thanks.

  28. ramesh majhi

    hi i am tired in adjusting inductor sometimes it work and sometimes it is out of work what to do?

  29. tang

    hi i tried to simulate the ckt in multisim 11 in the op i got voltage of nanovolt it s correct??????
    and also i want a formula for calculating the frequency

  30. ResR

    I want to ask is the 0,022pF correct value? I can’t find any capacitor with that value available in Estonia.

  31. seetharaman

    Hi Prudhvi you can use anything between 18 to 22SWG super enameled copper wire. Q1 is the mic amplifier and modulator. Q2 is the oscillator and power amplifier.

  32. prudhvi

    complete discription about this circuit………..plz send me…..its urgent plzzzzzzzzzz……….

  33. prudhvi

    can u give me the gaze value for 0.156uhenry inductor?????
    it is very urgent plzzzzzzzzzz………..

  34. complet description

    plz send me the complet theory of this project as soon as you

  35. ADN

    hey guys I construct the circuit but i want to now the frequency at the output to receive the signal!!
    please reply as soon as possible

  36. ahmad

    iwant jammung circuit with range frequency (800Mhz_2000Mhz)

  37. Seetharaman

    Hi Techno girl it is a standard electret-condenser mic with 2pins and of 10mm dia.

  38. Techno-girl

    Please giv me the specifications of the the device M1 used in this ckt… I wnt it as early as possible.

  40. Rickson

    That bit above that said:

    1uF = 1000000F
    1nF = 1000000000F

    is wrong.

    1 uF is 0.000 001 Farads
    1 nF is 0.000 000 001 Farads.

    A Farad is a very large unit of Capacitance

  42. ammir

    i want a diagram with full theory detail and making process and working process

  43. seetharaman

    Hi Pecanins any standard FM radio will receive the signal. Tune to a frequency where there is no broadcast signal, adjust capacitor C6 till you get the acoustic feed back through mic. now your transmitter is ready.

  44. Pecanins

    will an ordinary FM radio recieve the signal from this circuit?

  45. seetharaman

    Hi Saad the best receiver with 1watt audio output to speaker operation from 2 to 12 volt DC is sony CXA1619

  46. seetharaman

    yes telescopic antenna can be used dimension = wavelength / 4 (wavelength in metres = 300000 / frequency)

  48. linta

    what are the dimensions of antenna and can telescopic antenna be used

  49. saad

    hello sir i want the the circuit for the receiver of the above circuit and want to know the operating range.and also how could i increase it.thanks

  51. nicks

    how to calculate the value of of the component match by antenna ?

  52. MOHAMMAD

    Thanks a lot JOHN it’s worked very well with me.

  53. seetharaman

    Hi writting in 3 digit is similar to color code. Brown black brown is 101 That is 10 X 10¹ 100PF, Brown-green-brown that is 15 X 10¹ 150PF, brown black orange 103, 10 X 10³ 10000PF or 10nF or 0.01µF. First two digits are indicated in then the third digit is the mutiplier. You can represent only preferred E12 values in decade series 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. 159PF is not possible in 3 digit system.

  54. Akinyele Augustine Sola

    Please Engr.help me to convert 10pf,20pf,3pf &159pf to the form of 3-digits number.EG 100,101 etc

  55. Akinyele Augustine Sola

    Please I found it difficult to find capacitors in picofarad instead am asked to convert.But the converted ones are written in 102,104c etc enlighten me on the conversion

    • admin

      Reply to Akinyele Augustine Sola

      104 is 0.1uF
      103 is 0.01uF
      102 is 0.001uF

  56. badr-ess

    can you tell me please about the capacitors? is it o.047MIC 47NF ? and what’s value of 0.5MIC ;0.2MIC and (on nano farad nF) and the value of 0.022PF. thanks a lot

  57. Ajimakin Tunji

    Nice one, really worked for my science project. Thanks a lot.

  58. Akinjolire Gbenga

    please, where should the negative terminal of the 9v dc be attached.

  59. Ajimakin Tunji

    Nice one, really worked for my project. Thanks a lot.