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.



  1. Lijo joseph

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

  2. 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 🙂


  4. Niladri Shekhar Mondal

    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

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


  7. masiriwa henry

    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.

  8. Seetharaman

    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.

    • 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)

  9. Tete Erastus

    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.

  10. 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….

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

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

  13. Amarino Mpotwa

    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,

  14. Salami AZEEZ Adeyemi (S’Baz – Propose Engineer)

    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.

  15. 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

  16. Hi..
    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..!!

  17. 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. yq

  18. Ghost Rider

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

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

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

  21. Sir,
    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.

  23. ankit sharma

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

  24. seetharaman

    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.

  25. ankit sharma

    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 . Plz sir help me i have to submit this as major project…

  26. Hi..
    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

  27. Hi..
    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


    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 🙁

  29. 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!:)

  30. dnyaneshwar fulare

    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

  31. Godwin Auquo

    i have some problem with the matching antenna omee help pls

  32. 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

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

  34. 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.

  35. 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

  36. 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)

  37. hello,

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

  38. Amarino Mpotwa

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

  39. Seetharaman

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

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

  41. Amarino Mpotwa

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

  42. Amarino Mpotwa

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

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

  44. World of Technology

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

  45. Seetharaman

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

  46. how to know the frequency of transmitting signal?

  47. Seetharaman

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

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

  49. 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……………………

  50. Seetharaman

    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)

  51. Srinivasan.E

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

  52. Srinivasan.E

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

  53. seetharaman

    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.

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

  55. seetharaman

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

  56. 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.

  57. 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

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

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

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

  61. Sir please give me the circuit of simple metal detector

  62. mirza parvez

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

    T h a n k s

  63. mirza parvez

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

  64. mirza parvez

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

  65. mirza parvez

    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

  66. mirza parvez

    Your Transmitter V Nice Cower 10km so Nice project

    M i r z a P a r v e z

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

  68. Seetharaman

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

  69. 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.

  70. 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.

  71. seetharaman

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

  72. thiyagarajan

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

  73. seetharaman

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

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

  75. Kamal enjiniya

    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

  76. seetharaman

    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.

  77. 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

  78. 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

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

  80. Peer mohammed

    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

  81. seetharaman

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

  82. aravinthraj

    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.


    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

  84. seetharaman

    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.

  85. Ukeme Etim

    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)

  86. Venkatesh

    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

  87. sohan gosain

    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.

  88. 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.

  89. 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

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

  91. Seetharaman

    Hi Iodpoi R9 is for audio modulation level.

  92. 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

    • Guy from Ethiopia

      Hi how much volt did u use to make the circuit for each capacitors?

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

  94. Seetharaman

    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.

  95. Seetharaman

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

  96. manoharan

    Thank you Seetharaman for your replay.Manoharan

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

  98. manoharan

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

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

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

  101. Thank you your information that I will make this circuit.

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

  103. Ankita Mittal

    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?

  104. Seetharaman

    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.

  105. Devendra Siddharth

    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.

  106. 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

  107. 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?

  108. Seetharaman

    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.

  109. Seetharaman

    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.

  110. 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?

  111. Seetharaman

    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.

  112. vengadasamy

    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.

  113. Seetharaman

    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).

  114. 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.

  115. 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?

  116. Seetharaman

    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.

  117. himanshu gupta

    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.

  118. himanshu gupta

    sir i mailed you last night plz rely me.

  119. Seetharaman

    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.

  120. himanshu gupta

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

  121. himanshu gupta

    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.

  122. himanshu gupta

    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.

  123. Seetharaman

    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.

  124. 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.

  125. 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?

    • 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.

  126. 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?

  127. Seetharaman

    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)

  128. nithin kamal


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

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

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

  131. 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.

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

  133. Sir,
    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.

  134. saheed mustopha

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

  135. Seetharaman

    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.

  136. 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).

  137. hi,sir,
    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

  138. 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.

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

  140. Seetharaman

    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.

  141. 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

  142. Seetharaman

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

  143. 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

  144. babatunde odunnaike

    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)

  145. Hi Ineed to know circuit diagram of simple preamplifier

  146. babatunde odunnaike

    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

  147. Seetharaman

    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

  148. 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.

  149. 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

  150. Seetharaman

    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

  151. 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

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

  153. babatunde odunnaike..

    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..

  154. Seetharaman

    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.

  155. babatunde odunnaike..

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

  156. Seetharaman

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

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

  158. 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.

  159. Seetharaman

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

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

  161. Seetharaman

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

  162. tunde babajide

    thanks for 2km circuit transmitter it works pefectly

  163. hello seetharaman

    what is the price of this IC BA1404

  164. is this omnidirectional

    i want omnidirectional and also stereo FM transmitter is needed

  165. babatunde odunnaike

    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

  166. Seetharaman

    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.

  167. Shreyansh

    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…

  168. seetharaman

    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

  169. shihanook

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

  170. seetharaman

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

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

  172. brycesprung

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


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

  175. seetharaman

    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.

  176. Kamal joshi

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

  177. Kamal joshi

    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.

  178. Kamal joshi

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

  179. Senthil Kumar

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

  180. kamal joshi

    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.

  181. kamal joshi

    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.

  182. christopher

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

  183. kamal joshi

    plese, explain me details about the anteena system

  184. kamal joshi

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

  185. seetharaman

    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.

  186. kamal joshi

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

  187. venkatesh

    pls tell me whether i can make that vk220j rfc by myself is yes how???

  188. seetharaman

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

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

  190. Muhammad Hassan

    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 i shell be highly thankfull to that person.

  191. seetharaman

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

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

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

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

  195. 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

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

  197. seetharaman

    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.

  198. Ashok Shah

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

    • i did complete the circuit,but how could i know dat my transmitter is tuned to 89mhg(receiver frequency)

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

  200. frozenangel

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

  201. how do i make an antenna suitable for the transmitter

  202. Manjinder

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

    • 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

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

    • 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.

  204. seetharaman

    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.

  205. 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.

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

    • 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.

  207. 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

  208. 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.

    • Reply to Adex
      One end of R5 is connected to the base of Q3 and other end is connected to the wiper of POT R9

  209. hello sir i want to get updates from your website often