2 km FM transmitter

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.


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397 Responses to “2 km FM transmitter”

  • razzel says:

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

  • Victor says:

    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 says:

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

  • Victor says:

    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 says:

    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 says:

      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 says:

    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 says:

      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 says:

    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.

  • gajmer says:

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

  • Victor says:

    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.

  • Physics guy says:

    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!


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

    • Physics guy says:

      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”

  • Narayan says:

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

  • Pare Wires is a manufacturing industry which started as a small unit of manufacturing copper wires and cables like car wiring harness, coiled cords, Instrumentation signal cable, Coaxial cables, Telecommunication cable, Electrical wires, Automotive wires cables, PVC wires and cable manufacture and suppliers in Bangalore India.

  • Dean says:

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

  • 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 says:

    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 says:

      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 says:

    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 says:

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

  • Gaju jayebhaye says:

    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

  • mahes says:

    pls explain the detail operation of the circuit

  • lubinga fred says:

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

  • Sam says:

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

  • Shane says:

    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 says:

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

  • Rex says:

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

    • Ashiq bhat says:

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

  • R. Naren says:

    what should be done in L3

    • seetharaman says:

      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 says:

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

  • 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 ???

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

  • laxman rawat says:


    • shubham says:

      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 says:

      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..

  • krishna says:

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

  • krishna says:

    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 says:

    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 says:

    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 says:

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

  • sushil says:

    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 says:

      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 says:

        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 says:

          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 says:

            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…..

  • Raphael says:

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

  • lukesh says:

    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 says:

      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 says:

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

    • Seetharaman says:

      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 says:

    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

  • ISAAC ANTWI says:

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

  • san says:

    details are not enough….

  • winston says:

    frequency equation pliz

  • lukes says:

    what is idea of Vk220J to made

  • mj says:

    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

  • 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 says:

    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 says:

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

  • sushil says:

    can I used dipole antenna for transmission?

  • Mercle says:

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

  • Mercle says:

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

  • salut says:

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

  • SONIA BHATIA says:

    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?

  • Rafn says:

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

  • anshad says:

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

  • sam says:

    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 says:

    use 350uH inductor instead of VK220J type RFC….

  • Allah says:

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

  • BetaRajab says:

    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 says:

    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 says:

    I like it. Much Appreciation

  • Md Adnan ilahi says:

    how to set component in any circuits

  • Md Adnan ilahi says:

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

  • Md sabrej says:

    i want sir how i increase the capacity of transmitar.

  • piyush rawat says:

    which factor decides the range of fm tranmitter.?

  • sumanth says:

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

  • Pushpender says:

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

  • Anees says:

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

  • Salami AZEEZ Adeyemi (S'Baz - Propose Engineer) says:

    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

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

  • 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?

  • eshwar says:

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

  • Crazy Guy says:

    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 says:

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

  • Appah Evans says:


  • deepak champati says:

    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 says:

    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 says:

    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.

  • fausitine says:

    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)

  • ABDUL WAJID says:

    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 says:

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

  • Seetharaman says:

    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 says:

    how con i make exact frequency of 89mhz

  • sk says:

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

  • Yakubu Bano jnr. says:

    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 says:

    what is equivalent of 2n2219

  • Lijo joseph says:

    What is vk220j ? Can we get it from shops send some photos of that

  • matar says:

    pls can you help me with a 7km fresh transmitter circuit for fm

  • @ Seetharaman u are right i changed it in my ckt at blog. thanx for advice :)

    @ kpkpkalpesh.blogspot.in

  • can you pls send me a photo of vk200j rfc….pls help me I selected it as my project of my college and in progress..som pls help me

  • Ajeesh says:

    Realy good,iam expecting more

  • shashank says:

    you can design above circuit in my website check it out it will be great.

  • GHOST says:


  • GHOST says:


  • masiriwa henry says:

    Am really gratefully, if you were God, i would say He has answered my prayers. you eased my research thank you. I wish you make that one of inverters also.

  • Seetharaman says:

    Hi Kaplesh in your blog for C3 C4 and C7 you have given as 103 it is actually 102 (1000PF). In this circuit 102 to 104 anything will work.

    • shareef says:

      hello sir,nice to interact with you.sir,i made the circuit b4 1week.but,how can i know dat my transmitter is tuned 89mhz(u had given dat,the receiver is to be tuned to 89mhz)

  • Hello friends my you get some help for the making of FM transmitter of long rang. so visit my blog http://kpkpkalpesh.blogspot.in/2011/12/fm-radio-transmitter.html may be it is helpful to u :)

  • Tete Erastus says:

    i have been enjoying your circuits for quite sometimes now
    am grateful. please if you can help me with notes on how to program a microcontroller i will much thankful. i count on your usual respond.

  • Ingocha says:

    Sir from where to get the 3.5 turns variable coil that is need in IC BA 1404 stereo FM transmitter.Everything is there in my place nut only that 3.5turns variable coil is not available yet. Its very very urgently need it pls help me my contact no is 8793388142 if you know about the availability in India. thanks you….

  • Ingocha says:

    Sir how to made the L3 vk220j type RFC coil? Pls help me..

  • Amit says:

    sir u have given the detail of transmitter but what will do for receiver circuit

  • Amarino Mpotwa says:

    Hi!I want to knw the ANTENNA used in cct, i made coil 3 turns in
    10mm diameter, bt other 2 turn where can connect?and i substute BC 177 to BC 556,and 2N2216 to 2N2222A,bt nothing occur!pliz for any one who made it,

  • Salami AZEEZ Adeyemi (S'Baz - Propose Engineer) says:

    Sir, i will want you to help me with a detailed Fm transmitter without omitting any detail from it. If i can even get more than 2Km as my distance. I am using it as my project and my school are planning to have a Radio station for the school to broadcast in the campus area. I will be glad if u make them recognize me, since i recognize you as a mentor. I have once built more than 4-perfect 200m Fm transmitter through you. Thanks sir. U are always impressing.

  • RICK says:

    It is a Beautiful Circuit!!!

  • hellen says:

    Hello, what measures have the coil? Can I make this project in a veroboard or similar? How have i made to do the antena? can i put a wire directly on the L1? thanks

  • raman says:

    What is the use of C8 (15pf trimmer capacitor)…???
    Can I use 22pf trimmer capacitor in place of 15 pf trimmer capacitor..???
    Thanks in advance..!!

  • theren says:

    hi guys.. im doing tis as my assignment.. can any1 plz send me the full detail n picture of assemble circuit tat u all hv build for my references. it may b can help me.. my email id. ganga_5771@yahoo.com. yq

  • Ghost Rider says:

    How to find the frequency of the transmitted signal……..!
    vk220j pictures please.!
    if possible post the pictures of the assembled circuit

  • Chandru says:

    Can you please post the picture of vk220j………!

  • AMAN says:

    Thanks a lot for giving this circuit… :) :)
    It’s working very nicely..!!!!

  • Chandru says:

    What is that l3……..what is vk220j rfc…………


    Hello seetharaman and friends,
    plz help us to make the inductor. 50% of the friends have same problem. if any one have maid it successfully then help us.and if no one is able to make it then stop the comment and remove it from site.

  • ankit sharma says:

    Hi seetharaman sir , can u plz clear me the connections of variable capacitor C9 AND C8 ?? I dont get it clearly how to make.

  • seetharaman says:

    Hi Aman you can use by adding a 10K fixed resistance in parallel with the 10K pot. it is required to maintain the current through Q2.
    Hi Ankit you can use a wave length / 4 whip antenna. this can be directly connected to just at a tap at 1/2 turn from + supply on L1. L2 need not be wound L1 of 3 turns alone will do.
    Hi for L1 and L2 the notes gives the clear data for L3 it can be any RF choke for decoupling purposes.

  • ankit sharma says:

    hi seetharaman sir , can i use a FM radio antenna instead of dipole antenna.?? And how will i make connections of L2 ?? plz send me the circuit of pre amplifier. And sir ,IS the circuit before the variable resistor canl not work as a amplifier ? So why we need extra pre amplifier ?? . My email id is ankitsharma3247@gmail.com . Plz sir help me i have to submit this as major project…

  • Aman says:

    can I use 10k variable resisitor in place of 4.7k variable resistor..!!
    If u don’t mind please mail me the details regarding working of the circuit
    (How frequency modulation is achieved in this circuit..??)

    Thanks in advance..:) :)

    my id is a.parmar33@yahoo.com

  • aman says:

    can i use 10k variable resistor in place of 4.7k variable resistor…??
    and please if u don’t mind can u please mail me the details regaring the working of the circuit (how FM modulation is achieved in the circuit..?)…!!!

    Thanks in advance

    my id is a.parmar33@yahoo.com


    hello Friends plz someone help me to get out of all three INDUCTOR (L1,L2&L3). I Maid the circuit but because of inductor i not able to get the output……….. plz someone help me :(

  • Gimbz says:

    hello guys, i cannot find anywhere the ba1404 ic nor the ba1417 or ba1418,
    pleeease someone tell me what can i use as a substitute that is easlily obtainable! because i dont wanna buy from the internet! thank alot for your help!:)

  • dnyaneshwar fulare says:

    आपण दिलेल्या लेआउट प्रमाणे मि सर्किट बनवले परंतु ओके झाले नाही मला trimar capacitor मिळाले नाही तर त्या जागी मि सादे त्याच value चे पी एफ टाकले परंतु ओके झाले नाही काय अडचण असेल

  • Godwin Auquo says:

    i have some problem with the matching antenna omee help pls

  • mike says:

    can u pls send me the comprehensive write up for this project?
    i will appreciate it if u can
    thanks.send it to my mail box pls

  • vamsi says:

    thanq anish….can you guide me clearly how to make L1,L2,L3….

  • Anish says:

    You can have a ceramic cap for 0.033uF and 0.47uF. The 15pf and 40pf are the variable capacitors commonly called trimmers or Gang capacitor.

  • vamsi says:

    Wat type of capacitors are 0.033 and 0.47…? Wat about 15pf and 40 pf parts….wat parts should be placed there….can someone reply me plsssssss

  • Anish says:

    Hi Amarino,
    Unless specified in circuits, all resistors are 1/4 watts. 16 to 25 volts rated polar capacitors will do (only for the polar ones)

  • obli says:


    can anybody tell me the value of the RF choke (L3)? and specifications of the antennae?

  • Amarino Mpotwa says:

    Hi Seetharaman i sent my comment pliz help me,i need to knw the watt of resistors and volts in capacitors

  • Ashok s says:

    Thank u sir

  • Seetharaman says:

    Hi Ashok you can use Yagi for radiating the RF signal from the transmitter. The end to end measurement should be wavelength / 2.

  • Ashok s says:

    Hi sir, can i use Yagi antenna as a transmitter?

  • Can i use the transfomer of input 220ac to output of 15v (1 Ampere) shall i use it or?

  • Hi Guyz! Can any one help me to knw the voltage in those capacitors and watt of the resistors used in circuit! plz guyz

  • Ashok s says:

    ThankQ u so much sir. Sir i’m doing this as mini project.

  • World of Technology says:

    pls sir Im abt to stat this project but I stil need more lit about how to go about a quality pcb. tnx

  • Seetharaman says:

    Hi ashok the transmitted frequency is as per FM radio dial setting.

  • ashok s says:

    how to know the frequency of transmitting signal?

  • Seetharaman says:

    Use any FM receiver tune it to required frequency. adjust C9 till you get the transmitted signal in your receiver.

  • ashok s says:

    hi sir, how to set(or know) the frequency of transmitting signal?

  • ashok s says:

    dear sir, what type of receivers we can use in this project? can we use mobile as a receiver? if so then how? plz reply soonnn……………………

  • Seetharaman says:

    Hi Srinivasan signal output from any source can be fed. for using mic you require a pre amplifier with a gain of not less than 100.
    Use an FM receiver to check the transmitted signal. (the present digital FM receivers are better-covering FM TV signal etc)

  • Srinivasan.E says:

    How the input audio signal is provided?
    How can see when the signal is trasmitted or not? Please reply me.

  • Srinivasan.E says:

    How can see when the signal is trasmitted or not? Please reply me.

  • rajiv says:

    can i use this transmitter with this radio coder?
    the coder is for a scratch built RC plane

  • seetharaman says:

    Hi Gustav C1 and C4 will be electrolytic others are ceramic. C8 & 9 are film dielectric variable. For L1 and L2 please read the notes in the article. L3 can be wound or purchased ready made. refer to our earlier comments on this.

  • gustav says:

    -Should I use electrolytic or ceramic capacitors?
    -What’s the value of L1, L2 and L3? Can I choose whatever I want?

  • seetharaman says:

    Hi Dennis connect supply negative to common shown as ground bus. Connect a dipole to L1 secondary or a whip through a suitable Balun.

  • Dennis says:

    Plz sir,where can i connect the negetive terminal of my battery,and again how can i couple my antenna to L3.I need guidline.

  • Rajeev says:

    how can i transmit rf vedio signals to a long range of 30-40m
    from a cc cammera to rf input of tv ?
    which are the matching antenas can i use in this purpouse !

    can you please help me to do my project
    please respond me to rajeevprasad402@gmail.com

  • Rajeev says:

    I would like to do this could you please tell me how can i do this

  • ali says:

    Can I replace VK220j by VK200?

  • kishan says:

    could you tell me the requirements for this 2km FM transmission

  • bimacknyas says:

    pls tell me the value of L3

  • SHINOJ says:

    Please give the circuit of Erorr checking circuit use in sound system ( low cost)

  • Shinoj says:

    What is mean by 16 turns and 24SWG.What is SWG

  • Shinoj says:

    Sir please give me the circuit of simple metal detector

  • mirza parvez says:

    Mors code 2w transmitter 7mhz 40m only make 3 Japaney
    transtar send me circuits and diagrams.

    T h a n k s

  • mirza parvez says:

    L1 L2 Problem caper wire 1mm no under stand wire AWG guage,number #14 # 24 # 28# 32
    T h a n k s

  • mirza parvez says:

    Vereabel Capster 750pf Not aw… Eq…
    and 800pf…………….in shop only 820pf
    800pf same work 820?
    T h a n k s

  • mirza parvez says:

    This Transmitter V good Rang 3km Nice Sir.
    Than sir 3.59mhz 80m with BF51y Transter sw rang send me circuit and diagram.
    M i r z a P a r v e z

  • seetharaman says:

    Hi Pankaz you can use the following site for your L1 L2 requirement for L3 see my july reply

  • mirza parvez says:

    Your Transmitter V Nice Cower 10km so Nice project

    M i r z a P a r v e z

  • pankaz says:

    dear sir plz take my respect, actually i wana make 2km range fm transmetter.my mine problem is making l1,l2,and l3.plz10000000

  • Seetharaman says:

    Hi Dhirendra you have to use 4,7K or 5K potentiometer as it is used to set modulation level.

  • DHIRENDRA says:

    hi sir can i use 4.7k is rasistance

  • ajiboye says:

    am ajiboye pls sir help me 2 send d write up 2 my email-adress-prince_phemmy@yahoo.com

  • ajiboye says:

    pls sir,I need the write up or probably reliable source of obtaining relevant information inrelation 2 d 2km fm transmitter 4 my year project.

  • subash says:

    dear sir,
    i am going to use this transmitter in a singnal transmitter in purpose of commands of robot at different frequency.what can i use in replacement of rfc vk200.what is it?can i use inductor instead.

  • B says:

    What is the voltage of C 2-3-4-5?

  • seetharaman says:

    Hi Thiyagarajan the frequency can be tuned between 80 and 110MHz, by adjusting L1 and C9.

  • thiyagarajan says:

    hello sir i need the frequency for this 2km fm transmitter

  • seetharaman says:

    Hi Arun use a mixer (mic and aux) and feed the the mixed signal to audio input of the transmitter

  • arun says:

    hello sir.,
    I want to transmit my voice as well as audio songs..is it possible through this circuit?
    Plz sir mail me the answer….
    Thank u sir…..

  • Kamal enjiniya says:

    Hi,guys am electronics man i am living in bauchi state nigeria,i have 2km fm transmitter circuit,so i want to add long range to 10 km distance so i added 8 transistor in series it give me 10km distance use dis transistors 2N2222 OR 2N2219.for more information call me

  • seetharaman says:

    Hi Oladapo please go through the notes it gives the detail for L1 and L2.
    center one is common and one of the outer ones can be used.
    you have to use dipole for radiation, connect from L2.
    There is no need for 741 here.

  • oladapo says:

    good day, i would like to know if it will be possible for one to use a transformer for the L1 and L2? If yes what would be the nos of windings.
    Secondly, in a variable capacitor with three legs how would we connect the three legs e.g. Like in C9.
    Thirdly, can one use two of the type of antenna used in radio receivers folded in L shape with one end connected to the output and the other connected to the earth of the circuit, but there would be close to each other
    And finally, can one use a uA741 op amp for the amplification stage.
    Thank you so much. Awaiting your response

  • oladapo says:

    good day, i would like to know if it will be possible for one to use a transformer for the L1 and L2? If yes what would be the nos of windings.

    Secondly, in a variable capacitor with three legs how would we connect the three legs e.g. Like in C9.

    Thirdly, can one use two of the type of antenna used in radio receivers folded in L shape with one end connected to the output and the other connected to the earth of the circuit, but there would be close to each other

    and finally, can one use a uA741 op amp for the amplification stage.

    Thank you so much. Awaiting your response

  • Guna says:

    This is a really good place for young people to develop!
    Keep it up

  • offor daniel says:

    i ned corect 2km xmiter cct pls.

  • Peer mohammed says:

    Sir i want made a 2 k.m. Range fm radio teansmitter. Plz give me suitable circuit and detail all component which is used. And give me some instuction about it . Thank you

  • seetharaman says:

    Hi Aravinthraj for what purpose and where you are going to use, the frequency and the range proposed.

  • aravinthraj says:

    Hi sir i’m aravind,i want detail abt the high level RF transmitter,

    bcz i’m doing a project using this type of transmitter. so send me the detail abt this.

  • KAMAL ETM says:

    MY name is technology man .i have 2km fm transmitter circuit.if you want to make 4 km fm transmiter you can add 4 transistor in parallel each transistor has 1kilometer power.for more information call 08057583786

  • seetharaman says:

    Hi Raspol Your ideas are fine. with Ham Licence you can be on 144MHz FM band not on broadcast bands 88 to 108MHz. For walkie talkies use in India, you have to get licence from Department of Wireless communication, New Delhi (now regional offices for wireless monitoring are also there at various locations, you can contact wireless inspector available for guidelines). (the application contains all the required data like location, antenna height, radiated power output, nearest airport etc) You will be allotted one frequency and also the place of operation, based on that you have to place order with walkie talkie companies and buy a suitable handset/base station and inform ministry accordingly. The present cost may be around INR1200 annual licence fee per set.

  • Ukeme Etim says:

    please in my project, am to design and construct a 2km range FM transmitter. but am really confused on which circuit to use since am not that really good in this. please kindly suggest a perfect circuit for this work for me. thanks

    this is my number +2348023746404 (from Nigeria)

  • Venkatesh says:

    hi everyone i have a doubt abt that audio in…
    Can i you a any simple mic(mic that v use in cellphones) and feed the music from an speaker or any audio output…..

    and about L1 and L2 hw can i design it whether it is available in the market….????

    and about the antenna… Can i use a single long copper wire… or any specific antenna is required if any specific is required means plz specify

  • sohan gosain says:

    Dear sir, Plz. let me know what kind of receiver will receive signals out from 2KM FM Transmitter project. Plz. also let me the same receiver circuit with full detail.
    with thanx.

  • Raspal says:

    Hi Seetharaman, admin and everyone else!

    I’m looking to make a FM transmitter that convers a distance of about 1km. I know this one can cover a 2km range.

    I’ve read most of the comments and know that it’s illegal to use a transmitter for long duration or other than experimentation.

    However, my use of the transmitter is for a 45 minutes to 1 hour daily spiritual speech. What do I intend to use it for? I want to help the people who aren’t able to come to listen to the spiritual speech, over their FM radio, using an FM transmitter.

    My question is, if I get a HAM radio license, can I use this kind of transmitter for daily (early morning) use for about an hour? Or are there any other ways that I can use this kind of transmitter for daily use?

    My other question is regarding walkie talkies. Many models from Motorola are available from ebay these days. Can we use such walkie talkies during times when phones won’t work or during emergencies?

    If yes, what are the requirements or is there any special license required, and how to get it? How much does it cost?

    Thanks for the replies and thanks for the great website and great circuits.

  • iodpoi says:

    hi sir! just want to ask again what’s wrong with my transmitter. it only covers 5meters. i used my 8.2V batttery coz i dont have 9volts yet. would it help if i increases the supply? and one thing, what’s the difference of having 100 turns and 60 turns on L3? i just dont know if it could increase the range.THNX

  • HABTOM says:

    i need a help on design of low range(1 km) FM transmitter

  • Seetharaman says:

    Hi Iodpoi R9 is for audio modulation level.

  • iodpoi says:

    ow thanks sir SEETHARAMAN. i just finally made it work on breadboard and looking forward to transfer it on pCB.
    but one thing i want to ask. what is the purpose of placing a potentiometer? thnks

  • marvin says:

    good day, im planning to create this fm transmitter, may i asked if L1,L2, and L3 are an air core inductors?

  • Seetharaman says:

    Hi Sawkat regarding number of turns for L1 & L2 refer to notes above and type of winding refer to May 12th comment and regarding L3 please refer to my comment dated sept 18th and Jan 27th.

  • sawkat says:

    i want to know about L1,L2.i want to know (L3) how to make it ( number of turns , diameter of wire and diameter of the coil itself )

    please i want your kindly answer as fast as you can

    Read more: http://www.circuitstoday.com/2-km-fm-transmitter#ixzz1MEDc2mTR
    Under Creative Commons License: Attribution

  • Seetharaman says:

    Hi Iodpoi L1 3 turns & L2 2 turns it can be side by side or inter leaved type.

  • manoharan says:

    Thank you Seetharaman for your replay.Manoharan

  • iodpoi says:

    sir im confused if L1 and L2 should have the same number of turns?

  • manoharan says:

    How can construct the L1&L2 inductors and how can tune the required frequency.pls replay with picture.will thankfull for
    yoy. vmrmano2004@gmail.com.

  • Khan says:

    Hi could u please send us a PCB CAD file. So that it would be easier to print and use.

  • SATYA says:

    i want to know the details about designing fm tranmitter n receiver for 60 to 100mhz range, could u plz help.

  • m jusuf says:

    Thank you your information that I will make this circuit.

  • Deepa says:

    Hi, i want the details about designing fm tranmitter n receiver for 40 to 80mhz range, could u plz help.

  • Ankita Mittal says:

    Hi!! I am making a burglar alarm system and I wish to transmit the audio output using FM transmitter..The output is about 2 volts.can u plz tell me which transmitter should I use?

  • Seetharaman says:

    Hi Karim any RF choke will do.
    Hi Siddharth you are right, so that we will have better confidence, that it is not a reproduction of an article but it is a working model.

  • Devendra Siddharth says:

    why do not people post photo of parts,current status and a look of his project. Because I think a single picture depicts more than text.

  • Karim says:

    there are some comments about how to make L3, but NO answer?
    does it mean that we can put a random Coil, and it will work ?
    thanks in advance

  • JOHN says:

    thank you sir seetharaman. its like crossing the two dipole without touching each other.

    i observe after operation the frequency changes and as i use it how many times, the how many times also change. from 101.6Mhz, now it’s 99MHz. My instructor told me that using crystal oscillator would be better and maintain the stability of the operating frequency. How can i do or connect it if possible?

    and i also observe that as i increase the gain from 1/3 to 1 cycle of the potentiometer, it creates noise. i already reduce the input audio voltage as little in that case thinking that would be an over modulation only but still has noise. is there something wrong with my variable resistor using 5Kohms instead of 4.7Kohms? or its just because what i have are local componennts?

  • Seetharaman says:

    Hi John with a single dipole in horizontal polarization you will get a transmission pattern of 8. say your dipole is horizontal and in line with east west. then the radiation pattern will be 8 as north south. but what about east west radiation you require another dipole in line with north -south. you can refer to any standard dipole transmission antenna design for horizontal polarization.

  • JOHN says:

    sir seetharanman, what do you mean dipole 2nos?

  • JOHN says:

    thank you again Sir Seetharaman

  • Seetharaman says:

    Hi John By using wiper antenna the propagation will become omni directional the loss will be high. By using 1/2 wave folded dipole 2nos, perpendicular to each other will be best for your polarized radiation, you get a better range.

  • JOHN says:

    my project is working. Thanks to this site. however, since what i have are local components, it does not operating in its maximum performance.

    Seetharaman, thank you…
    how can i improve my antenna for maximum power transmission? i’m currently using wiper antenna at approximately .85 meter. is it much better if i’ll use dipole antenna to match the L2?

  • Seetharaman says:

    Hi Vengadasamy quality romba nannave irukkum. side by side winding level coupling will do. if you want to wind them together for tight coupling take two wires together and wind as bi filler, both the end unwind half a turn in the secondary. VR9 can be adjusted for best perfrmance. assemble panni enjoy pannunga.

  • vengadasamy says:

    seetharaman sir,inductor L1&L2 coils wounded method,one coils upper one coils or one coil side another coils which method is correct pls.inductors mattumthan enaku confuce iruku!.sir confirm audio clarity irukuma.

  • JOHN says:

    thank you Seetharaman.

  • Seetharaman says:

    Hi John L1 & L2 are air cored and close wound. You can use a 10mm dia plastic former, to support the coil primary and secondary (Which are wound side by side-first wind L1 and continue winding L2).

  • JOHN says:

    good day. hello!. May I ask you sir or to those who could help me.

    I have no available rfc transformer. For L3, I used ferrite core tube and swg 22 to produce a 250uH Choke. Is it applicable for the L1 and L2 to use the same material? could you suggest me on how to do it manually? the statement above does not include if what core should be used…

    Thank you.

  • joshnnn says:

    First test of this circuit and it didn’t seem to be in the right frequency band(nothing in the reciever fm band). I used a 2-10pF, instead of 15pF for c8, and a 2-22pF in parralel with a 15pF for c9 (17-37pF).

    I think c9 is the fault. 68pF is the only other trimmer i have. would a 68pF be better?

    i also used this inductor for L3? :Axial Miniature Inductor/RF Choke, Tolerance ±10% 1mH.

    What is the most likely fault?

  • Seetharaman says:

    Hi Gupta you are correct full yagi is not required (if you want directivity for transmission)as ours is omni directional transmission, stack one above other as indicated by you.

  • himanshu gupta says:

    Sir,you told me – The antenna can be 2 nos folded dipole parallel to earth plane perpendicular to each other to achieve a transmission pattern of almost a circle.
    Plz tell me,would i have to use full yagi antenna or only two dipoles(without director and reflector)stacked one above another at the distance of 75 cm perpendicular to each other.

  • Seetharaman says:

    Hi Gupta I have replied you

  • himanshu gupta says:

    sir i mailed you last night plz rely me.

  • Seetharaman says:

    Hi Gupta you can feed audio signal from ear phone socket of any equipment like tape recorder, iPod, computer etc. not from live mobile phone, may be music from mobile phone on flight mode.

  • himanshu gupta says:

    can i transmit the audio songs from computer using this 2 km fm transmitter.

  • himanshu gupta says:

    sir,i want to connect 2km fm transmitter with the audio output of computer(where we connect headphone or ear phone), plz tell me if it is possible.waiting for your reply.

  • himanshu gupta says:

    sir,can i connect the audio input of 2 km fm transmitter with the audio output terminal of computer where we connect headphone.sir plz tell me soon i m waiting.

  • Seetharaman says:

    Hi Joshnnn you can connect one end of the coil to ground and other end to wavelength / 4 whip antenne if you want omni directional transmission.

  • joshnnn says:

    i am confused as to how to connect a whip antenna to this circuit (my first rf).

    Does each end of the whip connect to the terminals of L2?

    Could L2 be the centre point of the whip? (no connections either end)

    I think the magnetic loop antenna is the only antenna i know how to connect to this circuit, and may just stick with that.

  • joshnnn says:

    Thankyou very much for the schematic. I’m about to start making it with the BC547b, BC557b and 2N2222. I think these should be suitable? if so what range could be attained with a 1/4 wave whip antenna?

    • admin says:

      2N2222 is almost identical in performance when compared to 2N2219 but 2N2219 can handle a bit more power. I used a dipole antenna while testing . I think whip antenna is quite ok , but I will say the final word only after trying it.

  • chirag says:

    what about L3,how can make it rpy to chirag_savaliya43@yahoo.com

  • NOypi says:

    sir, just want to know.. is it really 2km? does the local setting contribute to the range.? i mean, i live in an urban area. do i need to have wide open space for this?

  • Seetharaman says:

    Hi Nitin yes you can use FM ganged capacitor or PVC2X MW set tuning capacitor with 47PF in series with the lower value section (Oscillator side – few plates can be seen)

  • nithin kamal says:


    can we use the gang capacitor seen in radios instead of the 40 pf variable ?

  • ziakansi says:

    hw v can increase the range of this transmitter and plz also tell me about the value of L3

  • Ravi says:

    hiii, plyz give me a circuit diagram for radio on/off switch for my aeroplane. thank uuuuuuuu

  • kamal says:

    your fm transmitter is not working.please help

  • NOypi says:

    hi. i will be making this proto for my project in communications. i just want to ask how to increase the range of the transmitter, e.g. varying the transmitting power. how? thanks.

  • manoj says:

    can u say which type of antenna is suitable for 2 km fm transmitter. as soon as possible

  • Subhash says:

    i want to make a FM transmitter of range 5-8 km for my final year college project, please give me it full circuit description.

    Thanks in advance.

  • BOSE says:

    i like this !!!!!!!!!!!!!!!!

  • saheed mustopha says:

    than you so much sir. Please may you help on the reciever circuit?

  • Seetharaman says:

    Hi Nivas the inductor is just to decouple RF and Audio stage. it can be any value from 100uH to 250mH (since RF is at VHF 100 to 250uH will do). for your turns vs inductance calculation refer the following site.

  • mahmoud says:

    هزا المرسل لابرسل 500 متر

  • gben says:

    need a write-up on an fm transmitter

  • NIVAS says:

    hi sir,
    I verified through the ckt., but I`m not getting clear cut idea on VK2000J inductor, although you gave an expalanation on no. of copper coil windings on one of your comments,I`m not getting any idea of them.
    Could you please suggest any suitable value of inductor for this element of VK2000J, or please give me some knowledge about how to find inductor value frm copper turns(any formula).

  • kamal says:

    sir,please reply.i am waiting

  • kamal says:

    transistor 2SC1590 suggested by you to increase the range of fm tansmitter is a 136-174MHz RF power amplifier.Is it suitable for amplification of fm signal(88-109MHz).
    sir, i need the answers of above questions urgently beacause i require this for my final sem. project.
    please please please mind my questions quikly

  • kamal says:

    sorry,i forget to ask you one question;
    whether the half wave dipole is vertically polarised or horizontly polarised.
    please reply as fast you can.

  • kamal says:

    thanks from deep of my heart.you are very helpfull.
    i will tell you when i will make this fm transmitter. i think it takes two or three days.

  • Seetharaman says:

    Hi Kamal Dipole length is 1.5 met end to end but at what height from ground you have to fix the dipole is 20 to 40 feet depends on the local conditions.

  • kamal says:

    hi, sir
    now, today i am making this transmitter but facing one difficulty;
    according to formula;(V=WAVELENTH\TIME PERIOD)and lenth of half wave dipole is(lenth=wavelenth\2).
    it,s lenth comes 1.5M instead of 30feet,as you stated above.
    please replay as fast you can.
    thanks in advance

  • Seetharaman says:

    Hi Ryan stereo transmission is complex, there are ICs available for stereo transmission like BA1404, BH1417 and BH1418. Try BA1404 simplke and best.

  • Ryan says:

    cheers for a great guide, i will be constructing this afternoon. can you tell me what it would take to produce a stereo signal? either by modifying this actual circuit, or by -processing the audio signal, or whatever?

    thanks in advance

  • babatunde odunnaike says:

    plsss i need answers….

  • babatunde odunnaike says:

    I’m very glad to let you know that I’ve finished this project, and its
    working fine. However I’m having some problem defending it in school
    cos, there are some questions I was asked and couldn’t answer…

     How we arrive at the 2Km range (Any calculations to prove?)

     What calculations do we need if we are to improve/increase the
    distance say 4km?

     Is there any relationship between the frequency and the distance (2km?)

     Concerning the formula you gave me, LC = (λmax-λmin)/(1885 sqr)
    after using the highest and the lowest freq which is 108Mhz and 88Mhz
    respectively, I got 2.77 and 3.4 for the wavelengths (λ). Using the
    values above gives me the frequency to be (151). Which does not
    correspond to the frequency I’m operating on which is around 92.00

     Pls, I need more light on this…

     Also I need all write-ups you can help me get on this project… (if
    you have anyone that has done it before)

  • noel says:

    Hi Ineed to know circuit diagram of simple preamplifier

  • babatunde odunnaike says:

    hi man, pls concerning the info on our two calc the freq.. pls i need to know the actual value of the inductors, cos you said it’s 1/2rt LC and i know the value for the capacitor.. and not the inductor.. thanks for your help

  • Seetharaman says:

    Hi Fady it is an RF choke. refer to my comment dated september 18th for details
    Hi Kosovari there is no polarity for ceramic capacitors. it is non polar. The value is similar to resistance color code instead of color numerals are given. 102 means 10 X 10 to the power 2. that is 1000PF. 222 is 22 X 100 = 2200PF.
    331 is 33 X 10 to the power one. 10 X 10= 100PF etc,( the values are shown in PF.
    .001uF is 0.001 X 10 to the power 6 PF that is .001 X 1000000 = 1000PF

  • kosovari says:

    HI can sameone explain to me,about ceramic disc, i dont know which side is [ -negative] or[+positive],,all ceramic disc capacitior, have text one side,for example,102,222,331,,I dont know what size are for this,uF .pF ,n ,,same are 0.001uf, can sameone explain me about all this.

  • Fady says:

    Thanks Seetharaman for your kindly response
    please i have other question about L3
    i want to know how to make it ( number of turns , diameter of wire and diameter of the coil itself )

    please i want your kindly answer as fast as you can
    thanks alot

  • Seetharaman says:

    Hi Fady the amplification of the first two transistors are just 47only. it will suit any aux level from any audio equipment. mic has to go through an additional amplifier with a gain of around 50, depends on the type of MIC. (you can use dynamic or condencer micro phone

  • Fady says:

    please , what kind of microphones should be used?
    or this an AUX input from mp3 or TV or etc….
    please any one know answer me

  • harpal says:

    plz sir give information about inductor L1 and L2. i dont understand about this one..
    please answer me..

  • Seetharaman says:

    Hi Baba you can contact me on my email id seethasub@hotmail.com when ever you want any guidance.

  • babatunde odunnaike.. says:

    thank yu very much man… i’m very happy for your help.. i’m doing this as my final project in school.. i hope i’ll be able to defend it when it works thanks.. i’ll still need your help when i want to do the write-up for the project..

  • arun kumar says:

    i want to transmeter circuit

  • Seetharaman says:

    Hi C9 and L1 decide the frequency. the formula is
    f = 1 / 2 pi rt L X C
    Power input to power amplifier can be measured with voltage and current consumed by transmitting transistor. since we do not know the standing wave ratio, we can not predict the radiated power ( we also donot know about the antenna etc). if you have a field strength meter you can measure.

  • babatunde odunnaike.. says:

    pls @ all i need the calculations for the power rating and the ferquency

  • Seetharaman says:

    Hi Amir kindly refer to my comment on september 18th.

  • amir says:

    sir,i want to know about VK220J type RFC.plz help me. and have any substitute of it??????

  • HB says:

    Hello Seetharaman,
    i regularly visit your site and seriously i haven’t seen you ignoring the requests for help from people and you are actually dedicated to help instead of simply filling up your web space…
    You are a true engineer and keep helping people like this in future too…
    Best wishes.

  • Seetharaman says:

    Hi Vinit yu can use half way dipole. the height can be between 20 to 40 feet

  • vinit says:

    sir, please give me description about type & height of the antena used

  • Seetharaman says:

    Hi Emmi it is around $9 but in india it is around Rs200/-

  • tunde babajide says:

    thanks for 2km circuit transmitter it works pefectly

  • emmi says:

    hello seetharaman

    what is the price of this IC BA1404

  • Seetharaman says:

    Hi Emmi you have to use BA1404 IC for stereo transmission. a simple but very good chip.

  • emmi says:

    is this omnidirectional

    i want omnidirectional and also stereo FM transmitter is needed

  • babatunde odunnaike says:

    hi SEETHARAMAN, thanks for the job well done.. i’m doing this job for my final project at school.. the problem i’m having with it now is to know the actual matching antenna to use
    2. the power 1.e is it 4w, 2.5kw, etc.. thanks

  • Seetharaman says:

    Hi Emmi you can use one more 2N2219 in parallel reducing emitter resistance to 27 ohms you can achieve better range.
    or replace Q3 with 2SC1591 with 22 ohms emitter resistance you will get still better range.

  • emmi says:

    Hello seetharaman

    I want it for 5km

  • Seetharaman says:

    Hi Shreyansh It is just an RF choke. can be 50 to 100 turns close wound 22 to 28 SWG enamelled copper wire
    the magnetic loop antenna is a circular vertical antenna of wavelength / 2 in dia.

  • Shreyansh says:

    sir.. plz help me in building dis ckt…. wat is dat vk220j inductor?? is it easyily available?? and wat is magnetic loop antenna..?? wer can i get its circuit?
    plz help me soon… i m doing dis for my final year project…

  • seetharaman says:

    Hi Shihanook you can use the same 88 to 108 transmitter and receiver, you can tune them away from broadcast band to say 150MHz or so as 144 MHz if ameture band, with the coil or the capacitor in the tuned circuit and use them

  • shihanook says:

    i need fm transmitter and receiver which works not the normal
    fm radio(without 88-108) the transmitter must work nearly 0.75km radios

  • seetharaman says:

    Hi Brycesprung yes without modulated signal it will be a blank carrier hence can be a good jammer.

  • myakar says:

    what should i do if equal value of component is not found.
    substitution of this transistor is available and also of c3,c5,c2

  • brycesprung says:

    what if you disconnected the audio would it make the circuit a fm jammer

  • SHREERAM says:


  • shreya says:

    Hi seetharaman
    subject: 100watt sub-woofer
    i shorted R9 & R10 the temperature of transistors decreased but Q7 is getting hotter than Q5 why ?

  • seetharaman says:

    Yes you can use Yagi but with refector and director it will become directional radiator. only signal will get radiated in one forward direction only. if you use a copper wire of say 14 swg wave length / 4 whip antenna (vertical antenna) it will be omni directional and get radiated in all direction.

  • Kamal joshi says:

    At least tell Me whether you will respond to my comment or not

  • Kamal joshi says:

    Can I make it (anteema suggested by you) at home with copper wire or some other means if yes then what should be the diameter of the wire.
    *does it available in the market.
    *does Yagi-udi antenna having folded dipole length 1.5m, having one reflector and 3-director,used as a T.V. receiver work perfectly.
    expecting for your kind response.

  • Kamal joshi says:

    Do you not think that,anteena suggested by you(1.5m length folded dipole anteena staked one above) is too bulky.

  • how to use the FM 2Km Transmitter. How to Connected……….

  • Senthil Kumar says:

    How to use the FM 2Km transmitter.

  • kamal joshi says:

    sir, please tell me that whether we have to use co-axial (unbalanced)or parallel(balanced)wire transmission lines to connect anteena to transmitter or not.
    may,i connect it directly or not.
    please tell urgently.

  • ALOY says:

    this circuit have a receiver???
    if have the receiver can you give me??
    my email aloy_jkl@yahoo.com

  • madan says:

    details of vk220j coil

  • seetharaman says:

    Hi Joshi you can use a simple 2 stage BC547 RC coupled amplifier.
    my email id is seethasub@hotmail.com

  • kamal joshi says:

    sir,please tell me which transistor we have to use to act as mic pre-amplifier.
    whether we can use 2-stage RC coupled amplifier(using transistor BC547).
    SIR, also i am trying to sending a mail to your EMAIL id but i am not succeed.please mail these details at my email id if space is not sufficient here.

  • christopher says:

    how can construct the L1&L2 inductors and how can tune the required frequency.pls replay must.

  • kamal joshi says:

    plese, explain me details about the anteena system

  • kamal joshi says:

    hi, sir
    please tell me the name of transistor which we can use here

  • seetharaman says:

    Hi Joshi you should have minimum a single transistor amplifier with a gain of around 150 to 200 between the mic and this transmitter input.
    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.

  • kamal joshi says:

    hi sir, please tell me what we have to use as a mic pre amplifier

  • venkatesh says:

    pls tell me whether i can make that vk220j rfc by myself is yes how??? id:venkatesh.hkmvt@gmail.com

  • seetharaman says:

    Hi Kamal it cannot handle mic directly, you require a mic pre amplifier. existing circuit is suitable for line input.

  • kamal says:

    whether, we have to use mic for audio input or not.please tell

  • the inductor l3, if we make it at home or not, any one who have any idea about this question so plz reply me on my id:cancer_cadet@yahoo.com. i shell be highly thankfull to that person.

  • seetharaman says:

    Hi Grab if you want detailed description of the above circuit, mail me your requirement to seethasub@hotmail.com i will reply your mail, here the space may not be sufficient

  • Grab says:

    I’m building this transmitter as a project for my B.sc. Can i get more info.

  • kris says:

    does it work? how long is the range for it to still transmit?

  • superguy says:

    If i want to make L3 by myself
    what is the value of its inductance?

  • rohini says:

    how do i design receiver for this???

  • sampath says:

    i made a head/dim light circuit for vehicles,when vehicle are come face to face both head light are dim and it on when the vehicles pass,head light also dim in traffic,cross jucntion ,when vehicle enter to main road.if u like to interest tihs please comment me.bye

  • Richards says:

    thanks John….! this web page is really helping and worthy

  • seetharaman says:

    Hi Gideon you may Connect the L2 through balanced feeder to a two 1.5 metre length folded dipole antenna staked one above another by a distance of 75 cms and in right angle.

  • Ashok Shah says:

    Please throw some light on “how to make L3 or get it readymade if possible”.

  • hamed says:

    خیلی ممنون از شما

    thank you

  • Abey says:

    Is there any legal problem to make this and transmit audio..??

  • frozenangel says:

    hello sir,
    what do mean by matching antenna?
    can you provide details for that?

  • gideon says:

    how do i make an antenna suitable for the transmitter

  • Manjinder says:

    Which transistors we can use in replacement of these (BC109, BC177, 2N2219) transistors

    • admin says:

      possible substitutes for BC109 are 2N2222, BC546, BC547, BC548 etc.
      possible substitutes for BC177 are 2N2907, 2N2905, BC556,BC558 etc.
      possible substitutes for 2N2219 are 2N2222, 2N2221, 2N2219 etc

  • Ray says:

    Can you please share some information on the construction of the antennae to be used in this circuit

    • admin says:

      Reply to Ray

      A foot dipole antenna will do the job. A whip antenna can be also used, but the performance will be reduced. Do some experiments with the length for getting optimum performance.

  • seetharaman says:

    Hi L1 and L2 are primary and secondary of RF transformer. This is for impedance matching of antenna with the tuned circuit(tank circuit). Admin has given a clear reply for your question on C5 & R9. C5 should be connected to the slider (center point) of the potentiometer, and one end (cold end)of the potentiometer connected to earth (-ve common rail)the other end (hot end)connected to R7 Q2 collector junction. R9 is for proper modulation of audio signal. by varying R9 slider from cold end to hot end it can be achieved.

  • Anamds says:

    Thank you sir,sir again L1 and L2 and they connected together because i don’t see any wire that cross.and c5 and r9 can you leave them like that or they must be grounded.

  • Anamds says:

    Please sir am a little confused is c5 and r9 grounded,and is l2 together with l1.

    • admin says:

      R9 is a potentiometer (POT) and it has three terminals, two end terminals and a wiper terminal.One end terminal of C5 is connected to the wiper of R9 and one end terminal of R9 is connected to ground.Other end of R9 is connected to the collector of Q2.

  • sandeep says:

    dear sir
    if u have a more than to 2 km fm range transmission then give the circuit digram of that transmission please , immediatly or now i do the work on yore circuit of 2 km range
    thank u

  • mohamed says:

    what about L3,how cam i make it?

  • anil says:

    matching mic

  • anil says:

    which is the matching antenna

  • Adex says:

    Please sir, (referring to the 2km fm transmitter), how is the capacitor C5 connected, is it connected to resistor R5 or grounded. because i am confused.

  • sudha says:

    hello sir i want to get updates from your website often