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You are here: Home / Audio Projects / Simple FM Radio Circuit Using a Single Transistor

Simple FM Radio Circuit Using a Single Transistor

Last Updated on February 23, 2020 by Swagatam 177 Comments

When it comes to making an FM receiver it's always thought to be a complex design, however the one transistor simple FM receiver circuit explained here simply shows that it isn't the case after all. Here a single transistor acts as a receiver, demodulator, amplifier to constitute a wonderful tiny FM radio.

FM radio circuit

Image Courtesy: Elektor Electronics

It's basically based on a superregenerative audion receiver circuit where the use of minimal components becomes the main feature of the unit.

However fewer components also means a few compromises involved, here the receiver requires a large metal base for grounding the unwanted signals, and for keeping the noise factor to the lowest, and also this system would work only in places where the reception is rather strong and thus may not be suitable in areas where the signal strength is thinner.

How the One Transistor FM Radio Receiver Works

As mentioned above, the circuit is basically a single transistor superregenerative RF oscillator with a constant amplitude.
Here we have tried to enhance the design such that the amplitude becomes considerably magnified in order to turn OFF the transistor completely during the oscillations.

This called for an increase in the feedback capacitor and also to use a transistor specifically designed for handling extreme high frequency ranges such as a BF494.

Further modifications include an inductor with the emitter of the transistor, and a capacitor across the emitter resistor of the transistor.

Due to this the transistor is switched ON as soon as the base emitter voltage of the transistor falls significantly, resulting in an abrupt cut off in the oscillations.

However this prompts the emitter capacitor to discharge, allowing the collector current to yet again resume its flow, initiating a fresh cycle of oscillation.

The above happening forces the circuit to flip flop between two situations, oscillator OFF and oscillator ON, resulting a sawtooth frequency of about 50kHz at the output.

Each time the circuit flips across the above ON/OFF states, results in a significant stepping up of the amplitude which in turn constitutes greater amplification of the received signals. The procedure also gives rise to noise but only as long as a station is not being detected.

9V FM radio circuit with output for amplifier

The above design has one drawback, though. The output received from the above circuit would have greater content of sawtooth noise compared to the actual FM reception.

A smart technique can be seen employed in the following single transistor FM radio circuit to attribute better efficiency to this simple design.

Here we pull out the emitter capacitor C5 ground link and connect it with the output.

This results in a fall in the collector voltage as the collector current rises, which in turn forces the emitter voltage to rise, prompting the emitter capacitor to negate the situation at the output.

This enforcement results in making the sawtooth effect on the received signal practically to zero, thus presenting an FM audio with much reduced background noise.

FM radio circuit with reduced noise

Single Transistor Radio with Audio Amplifier

To make the above circuit self-contained, an additional transistor stage may be introduced for enabling the radio to play the music loudly over a small loudspeaker.

The circuit is self explanatory, just the inclusion of a general purpose BC559 transistor along with a few inexpensive passive components can be witnessed in the design.

FM radio circuit with loudspeaker

How to Make the Inductors

The involved coils or the inductors are very simply to wind.

L1 which is the oscillator coil is an air cored inductor, meaning no core is required, wire is super enamelled type, 0.8mm in thickness, diameter of 8mm, with five turns.

L2 is wound over R6 itself using 0.2mm super enameled copper wire with 20 turns.

How to Set Up the Circuit

  1. Initially when the circuit is switched ON, the output will be accompanied with substantial  background noise which will gradually tend to disappear on detection of am FM station.
  2. This may be done by carefully tuning C2 with the help of an insulated screwdriver.
  3. Try to keep the tuning at the edge of the band of the particular FM station, with some practice and patience this would get easier with time.
  4. Once tuned, the circuit would respond to that reception every time its switched without the need for further alignment.
  5. As indicated at the beginning of the article, the circuit should be installed over a wide circular meta plate, preferably a solderable material, and all the ground of the circuit soldered on this plate.
  6. This is important to keep the circuit stable and avoid drifting away of the received stations and also for cancelling unwanted noise.
  7. The antenna in the proposed single transistor FM radio receiver circuit is not crucial and in fact should be kept as small as possible, a 10cm wire would be just enough.

Remember, the circuit also acts a like an effective transmitter circuit, therefore keeping the antenna size bigger would mean transmitting noise across the ether and disturbing your neighbors radio reception.

The upside being that the design can also used as a walkie talkie within a small radial distance....more on this next time.




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About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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  1. Search Related Posts for Commenting

  2. Thom says

    Hi Swagatam,

    Very interesting circuit. I have a question though. Instead of immediately soldering everything together, I’ve first tried to build the circuit on a breadboard. Understanding that this is not optimal, I expected that this would just give me a bunch of static. Instead, I get no sound whatsoever, except for a slight crackle when I connect/disconnect the battery. I double-checked all the components and used a multimeter to verify all connections are OK. Voltages across components are what I’d expect.

    Can you think of a reason why the circuit would behave this way on a breadboard?

    Reply
    • Swagatam says

      Hi Thom, any high frequency RF circuit should be strictly built by soldering and by assembling the parts close to each other. So a breadboard is big no for such designs.

      Moreover, for stability the board must be attached with a large grounded plate, as shown in the first image.
      If a professionally built PCB is used then the PCB must be ground plain type, meaning all the part connections must be surrounded with copper tracks

      Reply
      • Thom says

        Hi Swagatam, that is very informative. As a relative beginner when it comes to electronics, I never realized that a breadboard would not suffice for testing high frequency electronics. Thank you for taking the time to explain this.

        Reply
        • Swagatam says

          No problem Thom, please keep up the good work!

          Reply
  3. Hako says

    This transistors must work:
    C945p: 450 mhz Ft
    Bc237b: 250 mhz Ft
    Bf199: 500 mhz Ft (works better than bf494)
    2n3904: 300 mhz Ft
    S9018: 1.1 ghz Ft (works better than bf494 and bf199)
    S9014: 270 mhz Ft
    Bc547b: 300 mhz Ft

    Reply
  4. Hako says

    Thanks

    Reply
  5. Hako says

    With coil

    Reply
    • Swagatam says

      OK, then it’s fine

      Reply
  6. Hako says

    And can I use fixed capacitor instead of trimmer capacitor ?

    Reply
    • Swagatam says

      Then how will you adjust and tune the transmission frequency?

      Reply
  7. Hako says

    Hi. Can I use bc556 and 2n3904?

    Reply
    • Swagatam says

      you can use them.

      Reply
  8. Hako says

    Can I use bc 557 for amp

    Reply
    • Swagatam says

      yes you can….

      Reply
  9. Hako says

    I built this circuit. but the output is very noisy. I hear only loud buzz sound

    Reply
    • Swagatam says

      Did you use a base plate for the grounding as indicated in the first image?

      Reply
  10. Israel Marcelin says

    I would like to make tuner amplifier

    Reply
    • Swagatam says

      If possible will update it soon!

      Reply
  11. Youcef says

    Hello Dear Sawgatam…
    Please ..Can you Explain us how to replace the LC syntonisation input by the Varicap syntonisation system.. Thanks for All your posts.

    Reply
    • Swagatam says

      Hello Youcef,
      It can be a long explanation, so i would suggest you to refer to this article which has elaborately explained the theory:

      https://en.wikipedia.org/wiki/Varicap

      Reply
  12. Nestor50 says

    Can we get a Printed circuit board?

    Reply
    • Sir Ron says

      If you look at the schematic properly you will see that it is not missing but numbered differently .

      Reply
  13. Mubarak Mohamed says

    Hi
    R2 is missing in the last circuit. Is it ok

    Reply
    • Swag says

      It was designed by elektor electronics engineers, if they have removed R2 in the last diagram it must be OK.

      Reply
  14. FM Radio says

    I think a single transistor radio would only make AM radio instead of the Multi channel FM radio and it only works if the signal really strong in your area. However if the signal is blocked or whatsoever this circuit may not work at all. I would prefer to use a IC that which make things easier.

    Reply
  15. Hariz says

    Hi there sir 🙂
    I want to know Is this circuit working perfectly?. because I have a project assignment to make a FM receiver without using IC. Your replied would be help me a lot.

    Thank you sir.

    Reply
    • Swag says

      Hi Hariz, this circuit was designed and tested by the Elektor electronic engineers, so this is a tested and a verified design, however this being a very small and a low tech FM receiver/transmitter circuit, the reception quality will be bad, and only the nearby strong stations will be received by this unit.

      Reply
  16. Ajekiigbe Damilare says

    Sir I want to know if I can place an axial lead inductor of the same value in place of the coil L2

    Reply
    • Swagatam says

      Ajekiigbe, you can try it, I don't think that would cause any issues….

      Reply
      • HUSSAIN says

        A0A,SIR WHICH AMPLIFIER IS SUPPOSED TO USE ACROSS C6.

        Reply
        • Swag says

          Any small amplifier like the following one, or if you have any readymade one will also do:

          https://homemade-circuits.com/ic-lm-386-datasheet-explained-in-simple/

          Reply
  17. Wesley Teh says

    Sir, which capacitors and inductor make up the Colpitt's oscillator?

    Reply
    • Swagatam says

      the basic idea is of a colpits oscillator, but different Colpit circuits might have slightly different method of operation….here the L, and the parallel C become responsible for the Colpits oscillator, according to me.

      Reply
    • Wesley Teh says

      Ok. Thank you

      Reply
  18. Wesley Teh says

    Hello sir, in relation to the third circuit above, will the signal go A) up into the emitter and out the collector or B) will it go down and around and through the collector and out the emitter of T1?

    Reply
    • Swagatam says

      Hello Wesley, The process could be much complex and it could be difficult for us to simulate the entire process in our mind.

      Reply
  19. Wesley Teh says

    Ok. Thank you sir.

    Reply
  20. Wesley Teh says

    Sir, what is the function of R1 and c1? And the function of the polarised capacitor and the 1k ohm resistor in the top right corner? And the function of c4 connected to the base of t2?

    Reply
    • Swagatam says

      They all together along with the inductor for a regenerative kind of oscillator circuit

      Reply
  21. Wesley Teh says

    Ok. Thank you sir.

    Reply
  22. Wesley Teh says

    Hello sir, I have one question. What is the distance for the winding for L1 and L2? Like the total length of the winding?

    Reply
    • Swagatam says

      Wesley, please do it as explained below

      L1 which is the oscillator coil is an air cored inductor, meaning no core is required, wire is super enamelled type, 0.8mm in thickness, diameter of 8mm, with five turns.

      L2 is wound over R6 itself using 0.2mm super enameled copper wire with 20 turns.

      Reply
  23. Karmchand Singh says

    hello sir, i want to make FM transmitter and FM radio receiver 2 channel remote control car may you give me idea.

    Reply
    • Swagatam says

      hello Karmchand, FM radio is not recommended, rather you can try the following concept

      https://homemade-circuits.com/2013/07/simple-100-meter-rf-module-remote.html

      Reply
  24. Jaswant says

    Can someone tell me what R6? Sorry did not know

    Reply
  25. Swagatam says

    Thanks Rohit, you can try the following concept

    https://homemade-circuits.com/2015/10/make-this-electric-scooterrickshaw.html

    Reply
  26. rohit pandey says

    Dear sir,
    I'm the big fan of yours
    Kindly tell me about how can I make bldc esc at home.

    Sir Please reply

    My email rohitpandey2199@gmail.com

    Reply
  27. Kashif Mehmood says

    Dear sir
    Kindly tell me about how can I make a home base radio station for what I need. For make a complete
    My email kashifmehmood45@gmail.com

    Reply
    • Swagatam says

      Dear Kashif, you can select any online 10km FM transmitter circuit and build it to make your home based radio station

      Reply
  28. Sunil Vishwakarma says

    Sorry,but I am talking about the 2 circuit for the l2 coil…and can you please post a photo of your succesful project from the top…..

    Reply
    • Swagatam says

      L2 has no core for other circuits, it's air cored

      Reply
  29. Sunil Vishwakarma says

    Hello,can you tell me the value of c2 and it is a pot or not

    Reply
    • Swagatam says

      C2 is a 22pf or 33pf trimmer (variable capacitor), how can a capacitor be a pot?

      Reply
    • Sunil Vishwakarma says

      Hello can I make this circuit in pcb board or bread board and my secound question is that l2 is wounded on what please give reply..

      Reply
    • Swagatam says

      Not on breadboard, PCB or veroboard will do!
      in last design L2 is wound over the resistor

      Reply
  30. Reschol Jusmin says

    hello sir.. where can i get these component shown above??

    Reply
  31. fatima says

    I am a student of class 12 and i don't have any idea for how to make a radio but i followed ur instructions and have nearly completed the circuit i just want to ask where should I connect the positive and negative terminals of the speaker

    Reply
    • Swagatam says

      positive to +9V

      negative to 0V line which is shown connected with the speaker

      Reply
  32. Swagatam says

    I am sorry, it would be quite difficult for me to understand the fault without actually checking your design…all these circuits were tested by the original authors…the above design was built and tested by the elektor electronic engineers so definitely it has to work.

    please do not measure the inductance, it's not required, the number of turns and the diameter are what we have to consider and must be done exactly as mentioned in the article.

    these circuits are very basic and therefore the FM station must be quite close by for reception by these circuits, weak stations or far away station will not be detected by them.

    Reply
  33. Abu Bakar says

    i can't find 400 ohms resistor..!!! Can i do it using available speaker..!! such as 6 or 8 ohms

    Reply
    • Swagatam says

      will do…use a 1/2 watt speaker or even smaller

      Reply
  34. Anton diana.varbenova says

    I choosed to make cirquit number 2 (the one with reduced background noise) .I pluged in a breadboard and works great.But there is one big problem-the tuning does not work at all.I clearly hear that an FM statio is playing.The local electronics shop did not have the transistor BF494,so I put 2N3904.Is the problem from the transistor or something else.Do you have any ideas to solve the problem?

    Cheers

    Toni

    Reply
    • Swagatam says

      2N3904 can handle upto 270MHZ so that cannot be a problem…check C2 connections, if it's not correctly connected or the part is faulty then tuning can become impossible, additionally if the one of the stations is too close by then tuning other stations could become a lot difficult

      Reply
  35. Unknown says

    sir can you tell me the values of inductors and their turns
    have a good day

    Reply
  36. EE35US says

    OH AND COULD YOU ALSO TELL ME THAT IN THE PIC OF THE CIRCUIT ABOVE WHAT IS THAT BLACK BOX TYPE THING ON THE PLATE AND THAT GREENISH CYLINDER SOLDERED ONTO THE PLATE TOO

    Reply
    • Swagatam says

      The black box is the earphone socket, and the yellowish color cylinder is the variable capacitor or the trimmer C2

      Reply
  37. EE35US says

    HI. i am ATTEMPTING THIS CIRCUIT.HOWEVER I CANT FIND THE WIRE FOR INDUCTORS WHICH SATISFIES THE GIVEN DIMENSIONS. IS THERE ANY ALTERNATIVE TO WIRE WINDING THE INDUCTORS?

    Reply
    • Swagatam says

      I'm sorry there's no alternative to the wire specification for the coil.

      Reply
    • Ante says

      I couldn’t find 0.8mm wire so I used 1.2mm wire with one additional turn. It worked.

      I used online inductance calculator to calculate inductance of specified inductor. Then I put my 1.2mm wire in the calculator and modified number of turns until I got the same inductance.

      Reply
      • Swagatam says

        Thanks for sharing this info! appreciate it!

        Reply
  38. Ciit Cluster says

    sir i want a general receiver with antenna, if the length of antenna increase the range should also increased. please upload this. Thanks in advance.

    Reply
    • Swagatam says

      Ciit, that's never possible…the antenna will work only to a minor extent after that no matter how much you increase it the reception quality will not respond

      Reply
  39. zakarya alsalahi says

    Hi sir , thanks for all the effort. I have a few questions too. 1st: Can i use a BF495 transistor instead of BF494? because I was not able to find it. 2nd which circuit will i use the first or second circuit the one with two transistors? lastly: will an 8 ohm speaker do the job ?. Thanks again sir.

    Reply
    • Swagatam says

      thanks Zakarya, yes BF495 will work instead of BF494, and 8 ohm speaker will do.

      Reply
    • zakarya alsalahi says

      Thank you sir .

      Reply
  40. Shrutheesh Raman says

    Hello sir!
    I have 2 doubts.
    1) Can you use a copper clad board, instead of a PCB?
    2) What does Amp in the circuit mean? What should we ask for in shops?
    Thank you sir 🙂

    Reply
    • Swagatam says

      Hello Shrutheesh, A PCB is made from a copper clad, so there's nothing wrong using a copper clad.

      amp refers to amplifier for boosting the sound level…..the last circuit can be build without the need of an external amp.

      Reply
    • Shrutheesh Raman says

      Thank you sir 🙂
      I'm sorry, I'm a bit confused with the last circuit.
      What does the 'O' stand for?

      Reply
    • Swagatam says

      that's 0 (zero) , the point where the negative of the battery needs to be connected.

      Reply
    • Shrutheesh Raman says

      Oh, thank you!
      One last question, where does the outlet, I'm using headphones
      Where do I connect them?

      Reply
    • Swagatam says

      you can use the second last circuit and connect the headphone across the points "to amp" and 0V

      Reply
  41. Alejandro Hidalgo says

    Hi, can I use NTE229 as replacement for the BF494? I can't find that one in my country…If not, is there any other NPN I can use? Also, do you know the numeration of the wire in AWG? Is it 20 AWG and 32 AWG? Does it matter if I use wire a little bigger in diameter or tinier?

    Reply
    • Swagatam says

      Hi, please check the datasheet of the transistor and check its "f" value, if it's rated to handle around 200Mhz then it can be used

      Reply
    • Swagatam says

      wire thickness is not critical, the winding diameter is critical…

      Reply
  42. Alexander McPhail says

    How do I modify his circuit for 3V operation? PP3s are rather expensive… Also, I can't find that specific rf BJT on digit key for one unit. ( minimum order qty. is like 10k) How do I choose a replacement?

    Reply
    • Swagatam says

      modification of any kind can affect the circuit performance, so it's not advisable…since 9V was suggested in the original article, this voltage should be only tried…or perhaps you can add many 1.5V cells in series to achieve the same.

      you can try BC547 in place of the shown device

      Reply
  43. Easyrock Iloilo says

    Hi, just want to ask if i need to sand the wires for L1 & L2..and what is the distance between turns on L2?

    Reply
    • Swagatam says

      I did not understand what you meant by "sand the wires" please clarify…if it means scraping the ends then yes you must do it in order to solder it…..L2 is not critical, wind it tightly wound and adjust it the to the indicated value

      Reply
  44. Buddhi Saini says

    how can i made a fm transmitter for this circuit send m link

    Reply
  45. daniel inoo says

    thank you so much sir, please can you help me with any good fm receiver circuit that can pick fm radio from a long distance

    Reply
    • Swagatam says

      Daniel, you can make a good quality FM radio using IC TDA7000

      Reply
  46. daniel inoo says

    sir, in this circuit , i always receiver a weak station and the noise is too much , how can i make it to receiver strong station and reduce noise

    Reply
    • Swagatam says

      daniel, you will be able to receive strong receptions only if the radio station is relatively closer to your place, otherwise it will be noisy and unclear….

      Reply
  47. daniel inoo says

    sir, you are good and kind , may god bless you so much ,i will like to be your friend more ,

    Reply
    • Swagatam says

      thank you Daniel, God bless you too…

      Reply
  48. bashir salami says

    Swagtam pls can u pls post a very simple rc reciever circuit for a rc plane

    Reply
    • Swagatam says

      Bashir, if i find one will surely post it for you…

      Reply
  49. daniel inoo says

    thank you so much sir, i use S 9018 transistor and it works fine but can you tell me the different between regenerative fm receiver and this circuit that you post,

    Reply
    • Swagatam says

      the above circuit is also a regenerative kind of circuit which does not rely on external oscillators.

      Reply
  50. daniel inoo says

    sir , how many turns of coils L1 and L2 that will a frequency range of 88 MHz TO 120 MHz

    Reply
    • Swagatam says

      it's mentioned in the article.

      Reply
  51. iyiola semiu says

    Sir,can this reciever work as on and off when my transmitter is turn on and off switch when connecting it to some deviceses.tnx

    Reply
    • Swagatam says

      you mean like a remote control?…yes it can be modified for such application also….

      Reply
  52. PSK™ says

    Good day sir. I would like to ask the following:

    1. BF494 to 2SD756 ; BC559C to BC558B is these replacement ok?
    2. Is there anyway to boost the FM Signal (88-108 MHz) coming in to the circuit?
    3. How would I wire the Varicap and tune it using the trimmer screws? In my case I shorted the Oscillator and Amplifier pins then solder them on the PCB.
    4. I used 0.8mm for the L2, is that ok sir?

    Your site and works is a very big help to me as a student. Every time I have projects, this site is my first option and I even recommended this site to my classmates. Many thanks to you, for your ideas and help. More power and God Bless !

    Reply
    • Swagatam says

      Thanks PSK,

      For selecting the transistor you'll have to refer to their datasheets and confirm if their transition frequency is above 200MHz, only those will work here.

      Boosting is not possible with this circuit.

      Varicap is not recommended for the above design so can't comment on it.

      The inductors must be wound exactly as per the data given in the article, others will not work correctly.

      Reply
    • PSK™ says

      Thanks for the speedy reply sir.

      For the Transistors, I've checked them and fortunately they're good.

      Sorry for the misconception, I used Variable Cap. not a varicap. I shorted the A and the O.

      Oh I see. then I must replace them.

      Thanks a lot sir…

      Reply
    • Swagatam says

      You are welcome PSK

      Reply
  53. ivan dela cruz says

    good day sir, i have something to clarify regarding with your comment above about this, "However the above circuit will be able to receive the signals only if the FM station is fairly close by, for weaker receptions the circuit will not respond."

    i have a transmitter and i want to use the circuit above as a receiver so that i can make a simple walkie talkie. i have set my transmitter at 89.8Mhz and i assure that there is no station that occupies this range, if i set the circuit above also at 89.8Mhz is it possible that i can transmit?if yes can it transmit within 20meters?

    Reply
    • Swagatam says

      good day Ivan, yes you can give it a try, it might work but I am not sure about the range, will depend on the strength of the Tx…

      Reply
    • ivan dela cruz says

      thank you sir, i have another question, the BF494 transistor is not available in our country (Philippines) do you have another alternative transistor that have the same characteristics with BF494?

      Reply
    • Swagatam says

      you can try BC547

      Reply
    • ivan dela cruz says

      thank you sir. i'll try this one.

      Reply
  54. Aniket Bose says

    Thanx for the reply, jst 1 more question, where should i connect the antenna?

    Reply
    • Swagatam says

      at the emitter of the transistor T1

      Reply
  55. Carl Winter says

    those 3 circuits are a nightmare –they DO NOT WORK !—3 months sweat —just a hum !
    —-how do u get 9 volts at the base of bf 494 TRANSISTOR when u adjust the 22pf trim cap –
    then u get zero —turn more –u get 6-9 volts at the base again —madness !

    Reply
    • Swagatam says

      if it's not working for you, doesn't mean the circuit is incorrect, it has been tested by elecktor electronics engineers.

      Reply
  56. Aniket Bose says

    Hello sir i need to know the voltages of the capacitors. Plz reply.

    Reply
    • Swagatam says

      Hello Aniket, C6 could be 16V or higher, rest all are ceramic type which are by default always 50V rated.

      Reply
  57. Jeremiah Ballos says

    thank you for the reply sir, is L2 and r6 are parallel each other sir.? sorry im a beginner sir ^_^

    Reply
    • Swagatam says

      yes they are connected in parallel

      Reply
  58. Jeremiah Ballos says

    sir about the inductor , what material did you used , is it magnetic wire ? what number corresponds to awg ? plz help

    Reply
    • Swagatam says

      yes a magnet wire is used, you can use an online mm to AWG software for the conversions.

      Reply
  59. faisal says

    hare is only given the structure of L1 and L2…………but i need value……….please help me………….its designed by you………so u know it batter……….

    Reply
    • Swagatam says

      No, it's not designed by me,

      to know the values you can quickly make the coils practically, and measure the values using an Inductance meter, it's very simple.

      Reply
  60. faisal says

    what are the actual value of L1 and L2………….i need it emergency ………because its my project…………and i have to submit it very soon…………

    Reply
    • Swagatam says

      the values are not known, the construction details are given which is more important than exact values.

      Reply
  61. WillS says

    Well, what can I say? All I get is a "humming" noise from the speaker. I built it ugly fashion, on a bit of copper-clad, everything in the air apart from grounds, where indicated, and everything as short as possible. I made the circuit third picture down from the top. I am not at all sure what that winding around the resistor is for, but I suspect it.

    I have never been able to get an FM receiver or even an oscillator to work. Ever. This one is no exception, and now I really do give up. In any case, thanks for the effort and your time posting this, it was fun to make, at least :D.

    Reply
    • Swagatam says

      optimizing tuned circuits is never easy unless you are an expert in the field.

      As for the above circuit it's a tested design from elektor electronic engineers so definitely the design is OK.

      you'll need to attach a ground plate under the circuit with all the negative connections soldered to this plate…as shown in the top image.

      However the above circuit will be able to receive the signals only if the FM station is fairly close by, for weaker receptions the circuit will not respond.

      by the way be positive, keep trying I am sure you'll succeed some day:)

      Reply
  62. Duong Nguyen says

    Hi bro, i'm a beginner and have some troubles with this circuit, so please tell me how this circuit can:
    – acts as a tuned RF circuit.
    – detects audio signal from modulated -RF signal.
    my e-mail: dnv1836@gmail.com
    Thanks a lot.

    Reply
    • Swagatam says

      Hi bro, I have roughly explained the working in the article, please refer to it.

      Reply
  63. Rui Oliveira says

    How can I change the circuit to tune with a varicap and a pot?

    Reply
    • Swagatam says

      I'll have to do some research and figure it out, presently I do not know about it.

      Reply
  64. ABDUL AZEEZ says

    hi sir.,
    i m your big fan
    i want a walkie talkie circuit within the range of 100m or variable distance above 100m
    plz sir help me to do this by your circuit…

    Reply
    • Swagatam says

      Hi Abdul,

      Thanks! I would surely try to post one such circuit very soon in this blog. Please keep in touch.

      Reply
  65. Jambunathan Venkatraman says

    can i use a bread board instead of a metal base ?
    can you give me the entire list of components with its specifications ?

    Reply
    • Swagatam says

      metal base is strictly required, therefore a general purpose board would suit better with a metal base.

      Components are all standard: resistors are 1/4 watt rated and the capacitors 25V rated.

      Reply
    • Jambunathan Venkatraman says

      can you suggest me ways for making the antenna ?

      Reply
    • Swagatam says

      antenna is a piece of 3 inch wire.

      Reply
    • Kashyap Ravichandran says

      any specific wire for making this antenna

      Reply
    • Swagatam says

      any ordinary flexible wire will do

      Reply
    • Jambunathan Venkatraman says

      hi !
      can i use a voltage regulator instead of the variable capacitor ?
      if not how do you turn the capacitors screw ?

      Reply
    • Swagatam says

      turn it with a screw driver

      Reply
  66. prasenjit saha says

    sir,

    Is it possible to sweep radio station by 555 timer wave genarator instead of trimer.,actually I am making a "ghost box". where i need to change fm station very fast without lock any station.this circuit is eligible for this method.

    Reply
    • Swagatam says

      555 with a 4017 IC can be used but will be a complex circuit.
      The above circuit is a crude FM receiver, will work only if the FM radio station is very near.

      Reply
  67. Rui Oliveira says

    Other question: There is no R2 in the cirtuit? And I don't really understand your notation, wich side of C6 is the +? black or white strip? thanks

    Reply
    • Swagatam says

      R2 is there in the first two circuits. the white block is the positive.

      Reply
  68. Rui Oliveira says

    What must be the range of C2 for 87-108MHz range? Should we use 1/4W or 1/2W resistors?

    Reply
    • Swagatam says

      C2 is a trimmer you will need to tweak it manually for the required range.

      all are 1/4 watts

      Reply
    • Stefanos Kantzilaris says

      Is 22pf the max of C2 ?

      Reply
    • Stefanos Kantzilaris says

      C2 must be 1-22pf ? or 22pf is the value at the middle of our variable component?

      Reply
    • Swagatam says

      yes 22pF means variable from it's 0 to 22pF (max), however any other value such as 33pF or 60pF will also do.

      Reply
  69. M Ali Raza Khan says

    will it work on frequency band 88-108 MHz??
    Please Rply

    Reply
    • Swagatam says

      yes it will work.

      Reply
    • M Ali Raza Khan says

      Please c0nfirm 2 things:
      Thickness of L2 is 0.2mm ??
      What is the Diameter 0f L2?

      Reply
    • Swagatam says

      it's to be wound on R6

      Reply
    • M Ali Raza Khan says

      can y0u tell me the values 0f L1 and L2 in 'henry' ?
      It is aesy to found induct0rs in henry..

      Reply
    • Swagatam says

      that's not important, you can make it as per the give instructions

      Reply
    • Swagatam says

      ….readymade coils will not work.

      Reply
    • martial7 says

      what's the thickness and diameter of L2??

      Reply
  70. MANU MOHAN says

    sir
    how much cost is reqired for making this project

    Reply
    • Swagatam says

      Rs.40/-

      Reply
  71. Syed Arham says

    sir, i have a fm transmitter of range just 1 feet. it works on 1.5v.
    how can i increase its range?
    Can i use any amplifier circuit?

    Reply
    • Swagatam says

      Syed, even the most ordinary FM Tx circuit will have a range of 20 meters and above, your circuit could be faulty or not tuned correctly.

      Reply
  72. achilles hector says

    Good day sir!!
    I have some questions and doubts.
    1. Can I change the L1 w/ inductor? And if possible what value?
    2. Where is the antenna?
    3. Can I use a 9V pp3 battery as power source?
    4. Can I connect the output to an earphone instead of amplifier?

    that's all thanks in advance!!!

    Reply
    • Swagatam says

      Good day Achilles,
      Here are the answers:
      1) You can change but it's not recommended, moreover the given data is too straightforward to need a change.
      2)Antenna for the receiver is not crucial ad may not be used.
      3)yes will do.
      4) yes that would be OK.

      Reply
  73. Max Payne says

    its a crank circuit, macq.comuv.com/projects/img/lED.png
    the battery discharges so fast in this design. i need an efficient circuit to charge battery from variable voltage source, like wind charger (0~30v, 1watt), and protect battery from quick discharge.

    Reply
    • Swagatam says

      OK, I'll try to figure out a circuit and let you know! By the way you could also try a buck boost design as shown here:

      https://homemade-circuits.com/2013/06/universal-ic-555-buck-boost-circuit.html

      Reply
  74. Swagatam says

    Good day! All the caps are ordinary disc ceramic types.

    Reply
  75. Max Payne says

    Hi Swagatam,
    super circuit, adding a band-pass_filter to allow only a particular frequency and reject all others will reduce noise and give a smooth tuning. is it?

    -AND, i am making a wind charger setup to charge a 6V 4.2Ah battery. Can you provide some details on winding coils, turns & voltages.

    Reply
    • Swagatam says

      Hi Max,

      Thanks very much!

      I am not very sure how that would be possible in this smallish design, will try to it figure it out.

      For the wind charger what kind of circuit are you using? If you specify some more details then may be i can help.

      Reply
  76. Salman Usman says

    Thank's I will try

    Reply
  77. Salman Usman says

    Hey Mr. Swagatam,
    Is a good circuit and very simple, I have 2 question.
    1. How many turns for L1
    2. The circuit is't work on DTMF Decoder?

    Reply
    • Swagatam says

      Hi Saman,

      It's five turns

      yes it will work with DTMF inputs, apply it at the base of T1 via a 0.1uF cap

      Reply
    • Swagatam says

      yes you can do it.

      Reply
  78. riyaz says

    Send you a mail regarding a project to ' homemadecircuits@gmail.com ' hope this is the mail id that you check regularly

    Riz

    Reply
    • Swagatam says

      read your email, but sorry to say i won't be able to make the prototype for you….you can use the specified circuit for your purpose, there's no restriction from my side.

      Reply
    • Mohammad Shoaib says

      which circuit will i make from above tree circuits?

      Reply


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