2 km FM transmitter

john July 26, 2018 456 Comments

In this project, we learn how to create a high range FM transmitter, which has the range of 2 kilo meter (2KM) radius. This is basically a simple DIY hobby circuit and you can try it in your home with minimal components. Start building this high range FM transmitter and see how your output comes.

With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier.C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna.

Circuit diagram.

2km Fm transmitter

  • Assemble the circuit on a good quality PCB.
  • The circuit can be powered from anything between 9 to 24V DC.
  • Inductor L3 can be a VK220J type RFC.
  • For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2.
  • Frequency can be adjusted by varying C9.
  • R9 can be used to adjust the gain.
  • For optimum performance, value of C8 must be also adjusted.
  • Using a battery for powering the circuit will reduce noise.

  • David Magona
    October 20, 2018

    Thanks for the good job.
    If i may ask, what are the wattage of resistors and vaultage of capacitors used in this project?

  • January 25, 2018

    I have question on the audio input. Can I input a MP3 line in the Audio Input? And what about an Electret Mic? Do I need to add any component to add an electret mic in the input?

  • sheriff
    January 4, 2018

    Hi, I am really excited reading all the comments and the answers from the instructor of the circuit above. With this I have been able to construct this transmitter for my final year project. I was thus having constraints especially getting the components. Now that I have constructed the circuit, I am having a problem regarding the antenna design. can you please help.

  • lakshman
    August 31, 2017

    sir how much it costs for all the components

  • Alex
    June 7, 2017

    Can I connect to a mp3 player via 3.5 mm audio female jack. If possible, can you give me the position to solder the jack and what do I need more to solder (Ex: capacitor, resistor,e.t.c)

  • October 31, 2016

    L1 and L2 how does look like

  • October 7, 2016

    Dear sir,
    can i make a RF remote controller by using this arrangement.please tell me how ? i have made 4 channel RF remote controller by using ask RF modules and ht12d and ht 12e .but its range is low about 60 meter please tell me how can i increase the range of this controller.
    thank you

  • May 15, 2016

    would like to know if i could use this circuit for model aircraft remote control. if so, i would also like to obtain some info on the receiver. can someone help?

  • bash
    April 12, 2016

    Sir seetharanam can you pls tell me how use a unipolar antenna with l2,I couldn’t get a hold of dipole or bipole antenna.and I use 0-40uf for c8 and c9 I dnt knw if it wll do the work.pls reply quickly

  • sanoj
    March 23, 2016

    I don’t understand the connection of L1 L2 and of angina

    March 18, 2016

    where can I get VK 220J RFC?

  • anoop ps
    February 5, 2016

    can u suggest how long this work,……..
    about the inductor…. how many round rolling by hand made this inductor

  • December 12, 2015

    i have build a very similar transmitter kit with the metalic 2N2219
    Lastly i tried it with about 24 volt and it became really hot.
    You must use heatsink with higher than 15 v
    The last point i could have measured was about 2,5 km with point to point eye view.
    Highly recommened type of circuit, because of the efford to success ratio.
    good luck to all …

    • December 12, 2015


      During my test the circuit with a telescopic antenna was placed on the roof of a nine stage high apartment. About 30m from ground.

      Please note that close FM radio stations can get reduce the range of the broadcast extremely.

  • mihir
    October 27, 2015

    can you tell me how the potentiometer is connected in the pcb??
    Also can you upload the photo of the final pcb circuit??

  • Aditya Rao
    October 27, 2015

    I want to verify the output of this circuit using the fm receiver built in our mobiles ( Since the frequency is between 88 and 108). How to determine the central frequency of the transmitter so that i can tune the radio to that particular frequency and verify??

  • moulika
    September 8, 2015

    please give detailed description of this circuit

  • Gowtham
    June 7, 2015

    Sir if we give the encoded signal from RX600E to the transmitter it will be transmitted or not
    Then by using a FM receiver we can encode it or not
    By using this I decided to construct a long range remote control

    • vabso
      June 13, 2015

      yes, you can

    • jhgfd
      November 27, 2015


    • vikram reddy
      August 2, 2016

      i am wiiling to do this project but my doubt is this circuit works for the frequencies in INDIA

  • Gowtham
    June 7, 2015

    Sir if we give the encoded signal from RX600E to the transmitter it will be transmitted or not
    Then by using a FM receiver we can encode it or not
    By using this I decided to construct a long range remote control

    • vabso
      June 13, 2015

      yes, you can…

      please note that
      frequency of input signal should be less than the half of central frequency of your transmitter

  • tenga
    June 1, 2015

    what is the output power of our 2km transmitter

  • May 27, 2015

    Dear Seetharaman, I built this circuit first on a breadboard for testing and it just worked fine. So I assembled it on a piece of general purpose PCB, and it performed just better. For the RF choke I used a choke inductor of 220 uH, I don’t know how to call it officialy, but it looks like an electrolytic capacitor with radial wiring (leads out of the bottom).
    For antenna I used a car whip antanna of approximately 1 m (app. 3 ft 4 inch).

    I didn’t dare to power this circuit up because of the relatively big transmitting distance (I don’t want law enforcement on my doorstep because I try to learn how radio works:P). But thankfully it performs below the stated 2 km in my assembly. I measured the amount of needed curent and it turned out to be 115 mA, with a lab powersupply of 13.8 V, therefore I rate the power P=13.8*0.115=1.6 W. Note that this isn’t the transmitting power but the power that is needed to operate, transmitting power depends on the type of antenna (please refer to the literature on RF electronics for the complete details)
    Because Q3 (a good old metal case 2N2219 tor) gets bloody hot, I just bought myself a 4 cm fan which is to be installed after my schoolday.

    I’d like to thank Seetharaman for his nice circuit, it works fine and it’s easy for people who built multiple circuits before this (like myself). If you are an absolute beginner, skip this project, get familiar with transistors in simpler applications, then return an build this amazing circuit.

    Kind regards,

    • Aditya Rao
      October 27, 2015

      I want to verify the output of this circuit using the fm receiver built in our mobiles ( Since the frequency is between 88 and 108). How to determine the central frequency of the transmitter so that i can tune the radio to that particular frequency and verify??

  • Eng Mahmoud
    May 17, 2015

    Dear All
    I have made this circuit before and it work well to 70 m
    but in analysing the circuit how Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier?
    the third stage is only bandPass amplifier first order
    i ,d like to discuss this point

  • March 21, 2015

    Hello everybody!
    I am Social Science graduate of Business Management. but i have special interest to build simple FM transmitter at home. but as i told you i do not have the basic knowledge. but i tried to read so many websites about how to build simple FM radio transmitter and i got some hints but not the basic one.

    I got difficulties to get answers related to the following questions.

    1, How can i know the voltage of parts used in any homemade FM transmitter? How can i get the exact voltage of parts used in any homemade FM transmitter? I mean how can i determine the voltage of parts used in any homemade FM transmitter? Is there any calculation used/applied to get the voltage of parts used.

    (For example, what are the voltage of each parts used in the above FM transmitter?)

    PLEASE, PLEASE, PLEASE give me some hint??? Waiting your response soon, very soon!!!

    • Neftali Loya
      May 21, 2015

      Hello Tesfae:
      This 2KM FM Transmitter works on low voltage; thus, all of its associated components will do too. However, I am providing you with some hints in this scenario: All the resistors within the schematic will be required to dissipate less than 1/2 Watt, so you should buy at least 1/2 Watt power dissipation resistors; If you plan to plug your transmitter to a +24 VDC source, then you should use 36 VDC rated electrolytic capacitors (C1 and C4), otherwise, 24 VDC rated will do; C3 and C5, being Mylar or Polystyrene capacitors, they should be rated at 50 VDC which is a standard voltage value for these types of components; C6 and C7 “MUST BE CERAMIC CAPACITORS”… I insist… Ceramic Capacitors, and as such, they are normally rated between 500 VDC to 1 KV; last, but not least, we have C8 and C9… variable capacitors come in all shapes and forms, so their final voltage rating will be a function of your preferences. If you buy air- capacitors like the ones furnished in old radios, they can withstand several hundred volts between their plates, if you buy printed-circuit-board-mountable capacitors, they are often times rated at 50 VDC, so as you can see, the standard voltage rating for these components will have you covered. This is a fun project to build and it works just great; nevertheless, you should take into account that temperature changes will make the transmitter´s central frequency to drift back and forth. These variations in your transmitter´s central frequency will create annoying hissing noises in your FM receiver and chances are that you will lose fragments of information every now and then. If you plan to power this unit on batteries alone, you will experience frequency drifting as the batteries begin to become depleted. If you plan to power this transmitter on a fixed power supply, chances are that you will end up changing the transmitter´s output capacitance and your final transmission frequency will need some fine tuning. If this is your case (powering the transmitter from a fixed power supply), and before even striving to use C8 and C9 as your tuning devices, consider widening or stretching L1, L2 and/or L3 coils first, of course, affecting one piece at a time. Although this is a trial-and-error approach, without an RF meter or spectrum analyzer, your ears, an FM receiver, and your fingertips are all you got to succeed in making this extraordinary FM transmitter work. May I wish you the best of lucks and the best of funs while working on this amazing project… enjoy yourself to the bones!

      • Pippen12
        September 26, 2017

        How to make the vk220j type rfc?

  • Achala Athukorala
    February 14, 2015

    Does this circuit do actual FM transmission (Frequency Modulated Transmission) or else does it just amplify the amplitude of the input signal? I don’t see how it can do frequency modulation as it doesn’t have a carrier signal. Forgive me if I’m wrong.

    • Neftali Loya
      May 21, 2015

      It is an actual FM Transmitter! Q3, along with its associated components, comprise the transmitter´s oscillation stage. Then, the sound frequencies coming from Q1 (voltage amplification) and Q2 (current source and impedance isolation) through R9 and C5, are algebraically added to the transmitter´s central frequency. The circuit works outstandingly well for a transmitter this size and caliber!

  • utshab
    February 9, 2015

    Which is correct process for designing L3?
    April 3, 2014 at 2:27 am
    L1 and L2 will be with 18SWG super enameled copper wire and for L3 use 28 SWG 250 turns on 6mm former 5mm width honeycomb winding.
    August 23, 2013 at 4:12 am

    Hi Naren you can use any RH Choke in this place. you can wind around 24 turns of 22swg enemelled copper close wound on 6mm dia self supporting, without any core material(air core)you can wind on a pencil slideout and use.

    • Talha
      December 20, 2015

      are you sure L3 will be 250 turn or it is 25 turns?

  • minu
    February 4, 2015

    please suggest the size of the antenna

    • Neftali Loya
      May 21, 2015

      You can calculate its size according to the transmitter´s wavelength. Let us say that for instance your transmitter’s central frequency if 91.5 MHz (you can find this on the FM receiver you plan to use to receive whatever information you are transmitting with this device), Calculate its wavelength in meters.

      a) Convert MHz to s¯1: 91.5 MHz = 91.5 x 106 s¯1 = 9.15 x 107 s¯1
      b) Use the formula λν = c: (x) (9.15 x 107 s¯1) = 3.00 x 108 m/s, then x = 3.28 m

      3.28 meters would be the perfect antenna size for this frequency; however, any multiple and submultiple of 3.28 will also work perfectly (6.56m, 1.64m, 82cm, 41cm, 20.5cm, and even a 10.25cm-long antenna would work just fine). For practical reasons a too-large or too-short antenna should be discarded, and maybe a 20.5cm long antenna will work just fine for you (believe it or not, it will work), but remember that only 20.5cm equals to 20.5cm. If you use a 20cm long antenna instead, it will not work as well as the original measured at 20.5cm because of a radio frequency transmission phenomena known as “Band Reject”. Remember that you are transmitting through this antenna, and if your antenna is shorter or larger than the transmitter´s frequency wavelength, it will not only transmit but receive radio frequency signals coming from itself. These “received” signals coming from within, will interfere with the signal you are striving to transmit and you will not transmit 100% of the energy generated by the output transistor (in this case Q3).

  • amir hassan
    January 16, 2015

    is C3, .022 MiroFarad electrolytic Correct?
    there is no such a small amount and electrolytic.

    • Neftali Loya
      May 21, 2015

      It is a mylar, paper, or polystirene capacitor.

  • sathish
    January 5, 2015

    Sir pls . I want this circut . where can I purchis this

  • kamya emmanuel
    December 10, 2014

    what are some of the objective of constructing this transmitter?

  • November 27, 2014

    can anyone tell me the purpose of C1 ,i just don’t understand how does it work.ths.

    • gajendra
      March 2, 2015

      c1, can ground directly through a resistane they can absorb the ultrtas noise or ripples which are produs=ced by the feedback or other electro,agnetic wave present in the sarroundins….

  • November 23, 2014

    Can one use a uni-directional antenna?

    • Alberto Hernandez
      April 4, 2016

      Yes, name it directional antenna. You can increase the range by directional antennas at each extreme: transmitter and receiver. This is the best aproach, however on one extreme only ( transmitter or receiver) is a good improvement. Albert, from Uruguay, South America.

  • Arumugam
    October 14, 2014

    Sir i completed the circuit..and I have problem when i am going to touch inductor (L1) with my hands at the time i get the output with clear sound…when i released my hands i get only noisy output…..pls pls help me to get clear sound..

    • Neftali Loya
      May 21, 2015

      Just open or close the winding loops! One loop at a time! Pull loops togheter (make the spring shorter in length) or pull them apart (make the spring larger).

  • Msala
    September 29, 2014

    Hi Seetharaman
    Could you please email me the detailed design, as in how you arrived at each of the component values. Thanks

    • seetharaman
      September 30, 2014

      Kindly go through text books to understand the design.

      • Pippen12
        September 28, 2017

        Mr.Seetharaman can i use other values of electrolytic cap in c4? because there is no available 15uf

  • naresh.ece
    August 9, 2014

    I have finished every thing in the circuit except inductor L3,any one please tell me how to create L3.THEN I can finish my project.

    • Neftali Loya
      May 21, 2015

      Any choke will do. L3 is used only as a filter so radio frequency waves coming from Q3 do not reach the preamplifying transistors. Use the coil of a 24 Volt relay and it will work just fine! Best of luck with your project!

  • razzel
    July 12, 2014

    iwant to build this for my project ., did someone try to make one? iwant to know if its working.,

  • Victor
    July 10, 2014

    Hi Seetharaman,
    Unfortunately, my project is unsuccessful as I can not get to work, no matter what I do. I’ve done my best, so I’ve decided to finish it up now.

  • victor
    July 4, 2014

    Hi Seetharaman
    is it possible for me to use a smaller diameter wire for l1 and l2?

    • Victor
      July 4, 2014

      im planning to use 0.8 mm

      • seetharaman
        July 4, 2014

        1 mm is preferred, but you can try 0.8 mm wire also.

  • Victor
    June 20, 2014

    Hi Seetharaman,
    I did some research and came across this:

    Carbon film
    A carbon film is deposited on an insulating substrate, and a helix cut in it to create a long,
    narrow resistive path. Varying shapes, coupled with the resistivity of amorphous carbon can
    provide a variety of resistances. Carbon film resistors are available in a power rating range of
    0.125 W to 3 W at 70 °C. Resistances available range from 1 Ohm to 10 MegOhm. The
    carbon film resistor has an operating temperature range of -55 °C to 155 °C. Maximum
    working voltages from 200 to 600 Volt DC. Due to the spiral cut nature of the resistance
    element Carbon Film Resistors are not suitable for use in radio frequency circuits as they
    exhibit high internal inductance.


    Just thought you would like to know.

  • Sabin
    June 16, 2014

    i have searched L3(VK220J type RFC) for more than 2 months in many shop but i didnt found.. i think its very rear, can you suggest me that where i can find it.. or can we make it by simply turning piece of wire like L1 and L2.. plz give me best advice anyone.

    • Victor
      June 16, 2014

      April 3, 2014 at 2:27 am
      L1 and L2 will be with 18SWG super enameled copper wire and for L3 use 28 SWG 250 turns on 6mm former 5mm width honeycomb winding.

  • Victor
    June 14, 2014
  • victor
    June 13, 2014

    Hi Seetharaman,
    Ive put in the proper transistor, but now R12 is smoking and burning. Ive tried 0.5 and 1 watt resistors but they still burn. How many watts is R12 supposed to dissipate?

    • Seetharaman
      June 14, 2014

      Hi Victor it should be 5 watt carbon / 100 ohms 2 watt carbon 2nos in parallel or non inductive wire wound 5 watts resistance, for 24volts operation of the circuit. for 9 volt operation it should be 1/2 watt.

  • Victor
    May 26, 2014

    I think I’ve gotten hold of some 2N2219A trasistors in the TO-5 case from ebay.
    Just one question about them- will they need to be attached to any heat sink, or are they fine on their own?
    Also I’m starting to get worried about my other transistors as they are all replacements. However, they both stay completely cool. Could you please tell me if they are fine?
    BC549 replaced the BC109
    BC557 replaced the BC177
    Sorry for being so much trouble, and thank you in advance.

  • May 23, 2014

    any npn transistor can be used but one should maintain the frequency and battery power

  • Victor
    May 19, 2014

    Hi, I’ve have made the circuit but it is not working and I have a suspicion that its either the transistor or the variable capacitors.

    For Q3, I couldn’t find the exact transistor, so I switched the 2N2219 for the BC337 NPN Transistor. Problem is, it gets so hot that I can’t touch it, though it doesn’t smoke or burn or anything. Do you think there is a problem here?

    Also, where did you buy capacitors for C8 and C9? If you bought it online could you please give me the link? The ones I bought are so dodgy.

    PS: I’m doing my major project for the HSC and this is very important for me.
    Thank you in advance.

  • May 17, 2014

    I rebuild this circuit. Very high power output, medium sound quality, super sensitive amplifier and less parts: I like it! Tip: Use cooling for Q3 (someting like a small metall strip,… Dipol antenna works best for this!

    • Victor
      May 20, 2014

      yes Q3 definitely gets very hot haha

      • Phones
        May 21, 2014

        shit thing about other transistor cases than TO220 is, that you can nowhere find cooling parts for them.

        • Seetharaman
          May 22, 2014

          TO5 casing gets a nice finned solid heat sinks. Try in the market you will get it.

          • Phones
            May 25, 2014

            I created a cooling by myself. I made a pipe with liquid tin and soldered some “wings” to it. So my transistor wont melt away hahaha

    May 16, 2014

    hello sir what type of antena should be used for this circuit please send a mail, images of this antena with detail

    • Physics guy
      May 20, 2014

      Hi there! Im not the admin here, but I guess U can use a dipole antenna for frequency around 100MHz. Take a long pipe of wood/ plasic. Cut two copper wires with a lenght around 75cm. Then attach them to the pipe, so all in all the lenght should be 150cm. Solder the inner ends to a coaxial cable, one to the coat, and one to the core. Then solder a antenna plug,… to the other ends. It should look like this: ~| (~=cable; |= stick with copper wire) If you need more info, google “dipole antenna”

    • Jimmy
      August 6, 2014

      the biggest whip antenna possible, maybe twenty feet and dont forget the loading coil. (sheesh)

  • Narayan
    April 26, 2014

    Hi- Are there any altranative transitor can be used for 2N2219. Can I use BF494 as the susbstitue – thanks

    • Seetharaman
      April 27, 2014

      You can use the current S8050. BF494 will get damaged being a low power low current transistor.

      • Seetharaman
        April 27, 2014

        2N3553 is the best replacement easily available or use BF494 3nos in parallel

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  • Dean
    April 3, 2014

    Thanks for the cct. Can you please upload a picture of the final pcb with tracks on it

  • March 24, 2014

    Sir this ckt alrady redimade in which city and which on shope plz tell me. i want to this type ckt making in my home

  • suman
    March 11, 2014

    sir, i am doing electrical and electronics engineering last year.
    plz give the swg number of l1, l2 ,l3???
    i have made the rest of the circuit except inductance. plz help me.

    • Seetharaman
      April 3, 2014

      L1 and L2 will be with 18SWG super enameled copper wire and for L3 use 28 SWG 250 turns on 6mm former 5mm width honeycomb winding.

  • Suprovo
    February 23, 2014

    Hello Sir, is this circuit has really more than 1 km range with good quality sound and very low noise?i tried many different 2km FM transmitter circuit on internet but all of those can not go even 150 meter and also full of noise.so i am afraid.PLEASE HELP ME TO INFORM ME ABOUT THIS CIRCUIT…

  • panneerselvam
    February 19, 2014

    L3 how many turns the coil which frency deital the mail please

  • Gaju jayebhaye
    February 8, 2014

    Hell sir, how making the 2km fm transmiter and this circut in whiche components are used , they components availebal in which city on shope plz list of components and designe the circuit send the data in pdf format

  • February 3, 2014

    Yes.you can recievve .

  • January 25, 2014

    pls explain the detail operation of the circuit

  • lubinga fred
    January 15, 2014

    would you also post the receiver circuit for the 2km transmitter

    • Victor
      May 20, 2014

      just buy an fm radio. or just start your car and turn ur radio on.

  • Sam
    November 14, 2013

    Would u pls post the receiver circuit for this fm transmitter 2km…

  • Shane
    November 8, 2013

    Hello Sir, I have gone through the Long Range FM Transmitter project also.
    I want to know whether this one or the long range one works better.

  • sohail
    September 30, 2013

    can we receive fm signal transmitted by fm transmitter from our mobile…..?

  • Rex
    September 15, 2013

    Seetharaman, i want to build this transmitter but i want to know if it is working, is it working?

    • Ashiq bhat
      May 21, 2014

      yes it really 100% works it depends upon the circuit designer if he/she design it well it will work well

  • R. Naren
    August 21, 2013

    what should be done in L3

    • seetharaman
      August 23, 2013

      Hi Naren you can use any RH Choke in this place. you can wind around 24 turns of 22swg enemelled copper close wound on 6mm dia self supporting, without any core material(air core)you can wind on a pencil slideout and use.

  • R. Naren
    August 21, 2013

    hi sir iam naren how many turns should be used for the inductor L3. pls reply me soon

  • August 14, 2013

    hi sir ,i js wanna knw the final power for he transistor Q3,and the inductance value do i hv to calculate it using resonances ???

  • August 12, 2013

    I need 2 make ths circuit but I want to kno z volts for each capacitors so help me out guys

  • laxman rawat
    August 7, 2013


    • October 11, 2013

      go get a life…if you don’t know about capacitor and coil how u will develop these things…get thorough knowledge on capacitor and inductor then start doing FM-transmitter

    • Manish h
      January 1, 2014

      Actually Laxma,C9 and C8 are the Variable capacitors which you can buy in electric stores….Difficult to find in Local Markets But sure you can buy that online..

  • July 27, 2013

    so pl give me rply as earlier as possible there by i can start my project

  • July 27, 2013

    i want make an FM in my clg so pl give complete details about Fm making and the components required and procedure to do this process

  • Raphael Muhoro
    July 23, 2013

    Hae its me again,is there something i can do to the circuit to increase that radius.And also i would like to knw the approximate cost of making the whole circuit.Thank you

  • sushil
    July 22, 2013

    Seetharaman sir, I have made L1 L2 couple inductor bt my circuit does not give any output. would u plz upload the photo of this couple inductor?

  • Aahwin
    July 22, 2013

    Does this transmitted signal can be recieved by common fm radio?

  • sushil
    July 19, 2013

    would u plz explain abt L3 inductor?
    is it aircore?
    inductance value=???uH
    no. of turn=???
    coil diameter =???

    abt L1 & L2 ?
    is it aircore?
    wht distance should be between L1 & L2?
    no.of turn =???

    • Seetharaman
      July 20, 2013

      Hi Sushil see the notes it is clearly given how to wind L1 & L2. for rf choke L3 you can use any RF choke from market in 100 to 500uH range.

      • sushil
        July 20, 2013

        wht is plastic former? is it hollow tube or solid tube? can I use marker pen which is hollow tube? why L3 is used here? what does it do? what happened if I remove this L3 part?

        • Seetharaman
          July 21, 2013

          Hi Sushil you can use any hollow tube even pvc electric conduit. marker pen etc etc without any metal in them. L3 is an RF choke it is a must.

          • masthan
            July 22, 2013

            hi this is masthan. pls help me what is the triangular symbol enclosed in a circle in receiver circuit. and the symbol of 4.7uf left to it? will you explain pls…..

      • Ramzan
        November 7, 2015

        Sir plZ send snap L1 &L2 of FM transmitter
        Ye wind kis diameter PR kren air side PR ya erdgerd wind krein.

  • July 16, 2013

    I like that circuit diagram but please tell us what type of receiver is required for reception of the waves.

    • Seetharaman
      July 18, 2013

      Hi Any sensitive standard FM receiver will do.

  • July 15, 2013

    hi sir im using part is
    15uf place in 22uf
    0.033uf in 333
    0.022 in 203
    0.47uf in 474
    1000pf in 102
    40pf in 39pf
    and vk 220j in 2 torn 1mm copper wire

    other is on the your droing list bot i can not proved -ve triminnal plz send me solution. this is right or not right please healp me.

    • Seetharaman
      July 18, 2013

      The negative of the supply should be connected to common line shown as connected to ground. All your components are ok except choke. See my earlier comment.
      (Hi venkatesh it is an rf choke to prevent rf entering the audio amp stage through power supply. any choke around 200 to 500uH will do. it is normally aircored with 200 to 300 turns honey comb winding to 5mm width with an ID of 6 to 10mm.)

  • sushil
    July 15, 2013

    can I used fixed capacitor c8 & c9 bcoz I donot found trimmer capacitor. how can I increase range of this transmitter?

    • Seetharaman
      July 15, 2013

      Hi Sushil you can try 5.6PF for C8 and 22PF for C9. To get the right frequency you may compress or expand the tank coil L1. (that is increasing / decreasing the gap between winding)

  • ricco yabes
    July 7, 2013

    Hi can you explain how L1 will couple the signal to L2. It wasnt quite clear, can u send a video or picture on how to make the coils and their connection. Thanks

    July 5, 2013

    i need power invertor with 2000w and opportunity from your there

  • san
    July 3, 2013

    details are not enough….

  • winston
    July 2, 2013

    frequency equation pliz

  • June 28, 2013

    what is idea of Vk220J to made

  • mj
    June 24, 2013

    hello sir,could u please tell me which electronic componemt is used to generate frequency like remote controlled cars,fm transmitters,nd what we have to do to increase the frequency range

  • June 1, 2013

    I’m so excited to see this today and I’m moving right away to implement it. I will get back to you. Thanks to circuitstoday.

  • sushil
    May 24, 2013

    what is c8 & c9? is it gang capacitor. I have gang capacitor bt it has 4 terminal. how to use it, i don’t know.

    • Seetharaman
      May 25, 2013

      No, they are individual trimming capacitors. C8 for making the circuit to oscillate. C9 is for tuning to the required frequency of transmission.

  • sushil
    May 24, 2013

    can I used dipole antenna for transmission?

  • Mercle
    May 8, 2013

    and can i reduce the transistor number by using LM386 or any thing else ??
    is there any smd LM’s

  • Mercle
    May 8, 2013

    can you please convert it to SMD please what are the value how can i convert it to SMD

  • salut
    May 2, 2013

    you can send me the simulation of this transmitter in isis or workbensh or pspice
    thank you in advance

    April 29, 2013

    Pls tell me how to connect the antenna to the coil?
    As antenna has only one terminal..would the other end of the coil l2 end up in the ground?

    • Bilal
      May 3, 2013

      no other end of the coil l2 will not end up in the ground, connect a bipolar antenna to l2

  • Rafn
    April 22, 2013

    Would also love full details of all components. You have many great schematics but should also have full detail lists with them

  • anshad
    April 20, 2013

    please give me the full details of the components used in this ckt.

  • sam
    April 19, 2013

    sir i want to find out the values of all componant. . Can u give me releted formule for this .and tecnique how to find that. . Plz reply me its imp for me

  • Bilal
    April 14, 2013

    use 350uH inductor instead of VK220J type RFC….

  • Allah
    April 11, 2013

    So how many of my middle eastern children are using this circuit for IEDs I wonder?

  • BetaRajab
    March 29, 2013

    hi i am BetaRajab,
    i appreciate the circuit..i really like the range
    my problem is i cant find some of the components to finish my projects.
    these are..
    capacitors- 1000pF,0.033uF,0.022uF,15uF,40pF(trimmer)
    also the type of antenna to be used.

    can you help with the voltages of each component..and if possible the equivalent components of each mentioned above in case i cant find them in my area..


  • Tarek
    March 14, 2013

    Hello seethamaran, can you please tell me why the antenna has two connections to the circuit and wether the “ground” indications mean directly to the negative line. Thanks.

  • Alex
    March 8, 2013

    I like it. Much Appreciation

  • Md Adnan ilahi
    February 3, 2013

    how to set component in any circuits

  • Md Adnan ilahi
    January 31, 2013

    hi i’m adnan
    i want to know that how to use different-2 componen or device in any circuits ?

  • Md sabrej
    January 31, 2013

    i want sir how i increase the capacity of transmitar.

  • piyush rawat
    January 31, 2013

    which factor decides the range of fm tranmitter.?

    • March 8, 2013

      many factors,but antenna height is most important factor.if you want to transmit signal in 2km range,make min height of antenna above 75cm.

  • sumanth
    January 22, 2013

    hi sir,
    can we use any ferrite RF Choke instead of vk200j

  • Pushpender
    January 20, 2013

    Sir plz u cn explain how to l1 and l2 r connected??????plz rply me sir

  • Anees
    January 14, 2013

    Sir i want to know more about that VK220J type RFC.what is this .is it a coil?

    • Anish
      January 15, 2013

      Yes it is a radio frequency choke/coil

  • Salami AZEEZ Adeyemi (S'Baz - Propose Engineer)
    January 13, 2013

    I have successfully made the transmitter and I want to say a big thank you to you….. I now want another help from you in making a long distance (above 3km in distance)…. Please help me send the detail to my e-mail address…. salami_azeez0619@yahoo.com …… Please

    • anees
      January 14, 2013

      What is VK220J type RFC.Is it a coil or not.Please iam worried about that.pls help me

    • Ahsan
      March 7, 2013

      Plz tell me! spose I have made a very basic FM TRANSMITTER having a 100 meter of rang. Now my question is that is every Fm radio receiver can recieve my voice, witch is transmitted by my FM TRANSMITTER at this rang.

      • venkatesh
        March 14, 2013

        yah ofcourse every fm radio within your range can hear your FM

    • Ahsan
      March 7, 2013

      Plz tell me! spose I have made a very basic FM TRANSMITTER having a 100 meter of rang. Now my question is that is every Fm radio receiver can recieve my voice, witch is transmitted by my FM TRANSMITTER at this rang. Reply me! ahsan_mehmood21@yahoo.com

      • junaid ahmed
        March 15, 2013

        YES within ur range(100m) every FM receiver will receive whatever transmitted

    • vamsi
      April 9, 2013

      Sir, can u tel me the budjet for doing 2km radio transmitr . . N is this wrk lyk the normal fm r not , .means sngs etc

    • August 12, 2013

      what volt did u use for each capacitor? pls help

  • December 28, 2012

    what is the power rating of the 2km transmitter? is there a way i can calculate the power using the componenet ratings?

  • December 28, 2012

    I have worked on 100meters fm transmitter, but i will try this 2000meters.But what kind of antenna should i use? can i use the normal unidirectional antenna?

    • Alberto Hernandez
      April 4, 2016

      Yes, you can use the same antenna, but remember: the better the antenna, the better the range. This is applicable for the transmitter and for the receiver too. Albert from Uruguay, South America.

  • eshwar
    December 9, 2012

    what are the values of c9 &c8 capacitors for 99mhz fm output?

    • Andrew
      March 9, 2015

      The reason they are adjustable is because according to tolerance differences in ALL of the components you will need to fine tune these two to get the frequency you want. The best way to get the frequency you want is to attach an easily identifiable audio source and set your receiver to the desired frequency. Adjust c9 until you start receiving.

  • Crazy Guy
    November 27, 2012

    Hello Sirz, I am crazy guy. I cannot get range to neighboring village of Kazadh-Bhi-Srinivas. What capacitor needs to make 4.9 TeraHertz frequency?

    Please explain all electrical concepts of life and universe. Also, please to post schematic of 50″ LCD TV with 3D effex.

  • Jean Elvis Lagaillarde
    November 10, 2012

    please tell me more about the vk220j and where can i buy it

  • Appah Evans
    October 31, 2012


  • deepak champati
    October 16, 2012

    iwant to make a small radio station, that 1 transmit the song and 50 reciver can recive the song. can any one help me

  • mazhar f.sathliya
    October 12, 2012

    Hi Sir ….
    My rikavayamenta f. M the transmitter and 2 from
    5 km’s and Anne F.M phikvensi. radio
    The phikvensi should be separate from …
    Do you have a circuit that I receive phikvensi of the person
    I’m just so it can be heard …
    About 500 to 700 homes in the
    I speak only of which can be heard in the house …
    mazhar f sathliya-gujarat-dahod-+919227100786

  • imunna
    September 22, 2012

    I need a 25watt fm transmitter. Can anyone give me a ready made fm transmitter. I’ll pay for it, just i want to buy a fm transmitter of 25 watt. I’m from bangladesh. My phone number:+8801719974170, email: imtiaz2580@yahoo.com
    please help me.

    • November 3, 2012

      Help me. i need fm tramsimitor which can transimit up to 15km

      • venkatesh
        March 18, 2013

        It is totally illegal in indian country because some radio signals which is used by our police and military will interfere with your signals.

  • September 14, 2012

    first of all i would like to thanx 4 ua various circuit that help us to learn more electronic knowledges.
    i expect to build about 50m fm transmitter of few components, kindly help please,,,,,,,,,,,
    by faustine from Dar es salaam Institute of Technology (DIT)

  • August 26, 2012

    Sir, where I going to connect the L2 terminals/antenna to the circuit diagram? please reply, I am very much excited to create this project, Thank you… please reply to my email address: roygee30@yahoo.com.

  • shah alam
    August 13, 2012

    i can not found bc177 have it any exchange transistor. if any 1 know it please send me information please pls…….

  • Seetharaman
    August 6, 2012

    Hi ad tune an FM receiver to 89MHz. Adjust C9 trimmer to get the carrier ine the receiver. (use nonmagnetic screw driver for adjustment best is an ebonite rod)

  • ad
    August 5, 2012

    how con i make exact frequency of 89mhz

  • August 2, 2012

    sir can u provide pcb circuit diagram of 2km fm transmitter

  • Yakubu Bano jnr.
    August 1, 2012

    I want to construct the 2km fm transmitter as my project, but i want to change one of the BJT with either of the other transistors, how can i do that?

  • arun
    July 22, 2012

    what is equivalent of 2n2219

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