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    This simple fm radio receiver circuit consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2.

    Radio Receiver Circuit Diagram

    fm radio receiver circuit diagram

    The critical part of the fm radio receiver is the first stage, TR1/VC1, where the wirings must be kept as short as possible. Coil L1 is formed by winding 8 turns of 1mm (20 swg) enamelled copper wire on a 6 mm diameter former, which is then removed. After that L1 should be stretched carefully and evenly to a length of about 13mm.

    Transistors List
    TR1 = BF199
    TR2 = TR3 = TR4 = BC547

    Video presentation and photos of the working radio receiver

    by Aleksandar

    The tunning capacitor VC1 is one of the two fm sections of a miniature fm transistor radio with built-in trimmers (VC2). The “earthy” end (moving vanes and spindle) is connected to the 22pF capacitor C1. The value of the rf choke L2 is not critical, anything from 1µH to 10µH being suitable.

    The output is suitable for ordinary earphones connected in series to provide an impedance of 64Ω.

    Tuning-in the fm radio receiver

    To operate the radio receiver, potentiometer VR1 must first be advanced slowly (towards the end of the track connected to battery positive) until, at about the half-way point, a sudden slight increase in background noise will be heard, indicating the onset of oscillation. It then should be backed off, very slowly, until oscillation just stops; it then should be possible to tune in some stations.

    The correct frequency range of 87 MHz to 108 MHz can be obtained by adjusting VC2 at the high frequency (108 MHz) and slightly stretching or squeezing together the turns of coil L1 at the end (87 MHz).

    ask a question

    309 Responses to "FM Radio Receiver"

    1. very intersting and simple FM receiver for beginners.

      • shohagmbs says: on November 28, 2015 at 1:07 pm

        How r u? i need help pls .i have made this circuit .but its not working.i don’t know what happen.also i can’t understand how it will get signal from FM transmitter without any antenna.and one more thing on the video that u have posted on the circuit ,did u connect any input in this circuit?i an see on ur video u have two clip for headphone,and on the left side ,what did u connect..pls explain me in my email..tq

    2. Where is the antenna?

      • alexpmgr8 says: on February 23, 2012 at 3:12 am

        Have you bult this circuit ? or are you just guessing that you need one ? The antenna , if you need one at all would go somewhere near the first coil on the left near the trimmers.

    3. I think connect at Collector of TR1.

    4. Oh!very nice project simple and easy………

    5. saba 4rm pakistan says: on December 29, 2010 at 3:40 am

      it doesnt work.very bad,i get f grade due to this circuit

      • alexpmgr8 says: on February 23, 2012 at 3:04 am

        Did you make this circuit with a large ground plane ? or small tracks ? or veroboard ? And what choke combination did you use ? Would be interested how much RF knowledge you have .. Thanks Saba..

      • Abu Umair says: on July 21, 2012 at 3:25 am

        Saba! I am Interested in electronics and have many circuts. Plz reply me if you also interested.

      • I am interested in Electronics.

    6. is it working?

    7. where is the antenna?

    8. OLADIPO, MUMIN O. says: on December 8, 2011 at 4:55 pm

      thanks for the circuit.send me a PLL circuit please

      • alexpmgr8 says: on February 23, 2012 at 3:09 am

        This doesn’t really look all that complicated . You should be able to get hold of one resistor type green chokes that would do the trick. An alternative would be to make a calculated coil with a regular resistor through the middle, also calculated, approx 100ohms res..

    9. OLADIPO, MUMIN O. says: on December 8, 2011 at 4:58 pm

      can someone please send me a PLL circuit

    10. this circuit only works with earphones it ll not work with the speakers. and no antenna is included in the circuit because earphones have built-in antenna in it so this circuit does not require any antenna.

    11. nagesh i required small fm circuit says: on February 16, 2012 at 5:38 pm

      please send me a small fm circuit digram and detlies

      tanku sir
      by nagesh

    12. Hello I am Mahmoud and I am new in the field of electronics and I want to be your friend on Facebook

    13. How stable is the receiver? and can it be silent when no station is tuned?

      • stompid.. the radio is super regenerative. This really won’t be the silent i aim for when building a radio receiver.. There will, by sesign of this schematic be some degree of hiss in the back ground, hence “regenerative”.. Good luck building this though … It will teach you something and be a nice thingto have around.. you buy a radio from a shop and unless it is way over a few hundred pounds sterling just for the reciever , you’ll still get some degree of hiss in the backgrund.. A synthetic silence requires many amplifaction stages and filters to go handin hand, proving you build a pll circuit. This will teach you a valuable lesson in radio my friend.

      • please note that this reciver is not super regenerative.this is a synchronous reciver.the techology is far apart from regeneration.its better than regeneration.chk out the link http://www.vk2zay.net/article/89

    14. can it work because i see all of them say they do or don’t work, HELP!

    15. Hi everyone, I built this little radio yesterday out of some parts I found in my junkbox and it’s working like a charm. FYI, antenna can be connected to the junction between C1, L1 and C2 (I used 1 meter long telephone wire for the antenna). For TR1 I used BF240 (because that’s the only one I could find in my junkbox that’s suitable for the oscillator/regen. part of the radio). TR1 needs to be suitable for VHF frequency ranges (the FM radio frequency range in particular) otherwise it won’t oscillate/regenerate. As for the quality of reception, this radio can pickup everything the commercial radio can, and quality of the audio received is very good and can be adjusted further with a regeneration control. I also suggest installing the variable capacitor with a plastic knob for changing stations. Because if you use a metal screwdriver on a trimmer capacitor as soon as you tune to some station and when you remove the screwdriver the station is gone, because the screwdriver acts as part of the oscillating circuit and when you remove the screwdriver the frequency changes. So, either use a plastic screwdriver for the trimmer capacitor or use variable capacitor with a plastic knob. As for the headphones, the regular mp3 player headphones/earphones will work just fine. I made couple of photos of it. So, if anyone wants to see what it looks like, ask for the photo and I’ll post it on-line.
      This is a perfect project for beginners in RF engineering or amateur radio constructions and such. Have fun everyone =P

    16. Well done on the video !!!!!!!!. It saves a load of stupid comments and silly questions. Thankyou . I made one of these things yonks ago . It is ideal for a begginer radio enthusiast.

      Radio communications are governed by law, and can interfere with other radio communication devices.

    17. I want to know if this circuit can work without any problem .

    18. can any one send me the inductor pic or whole circuit pics????? plzzzzzzzzz

    19. Aleksandar send me pics plzzzz its urgent plzzzzz

      • swaroopjsh says: on March 10, 2013 at 1:53 pm

        sir , tuning and recieving sections are not working.
        i have used 2 2-22pf trimmer capacitors.
        can u send me photos of L2?
        and what is that long metal plate like thing at the top of the circuit?
        is that band switch o pot?
        is it nessesary to connect that telephone wire or i can use normal antena instead?
        plz reply asap…

      • Aleksandar says: on March 10, 2013 at 2:18 pm

        sir , tuning and recieving sections are not working.
        i have used 2 2-22pf trimmer capacitors.

        Check the connections and solder joints and also check if you read the schematic diagram properly while you were building the circuit. Use the multimeter to check for voltages. Maybe some parts of your circuit are not connected properly? Or perhaps are faulty? Make sure that all components are functional and in value range as described in description and schematic diagram.

        can u send me photos of L2?

        Follow the layout of the schematic.
        The L2 is the “orange resistor looking thingy” on the photo. Components are placed to mimic the component placement in the schematic. L2 is an RF choke. It’s not critical in terms of value.

        and what is that long metal plate like thing at the top of the circuit?

        “long metal plate like thing at the top of the circuit” is a potentiometer VR1. It’s a regeneration control.

        is that band switch o pot?

        It’s not a band switch. It’s a pot VR1.

        is it nessesary to connect that telephone wire or i can use normal antena instead?

        No, it’s not necessary to connect that telephone wire.
        Yes, you can use normal antenna instead.
        You can use whatever you want for the antenna.
        You can mess around with it trough trial&error and find the best solution that works for you.

      • swaroopjsh says: on March 14, 2013 at 4:56 pm

        sir im still having problem with it. i dont have much knowledge about rf . i have used 2-22pf capacitors can it cause problem. i have mounted it on gpp. it is nt recieving.
        can u gv me ur email id ill send u pics of my gpp
        reply asap

      • Aleksandar says: on March 14, 2013 at 7:37 pm

        I’m a member. Feel free to send me a message here.

      • sir i’m from the Philippines and i would like to use this as my project,but it scares me if it didn’t work because i don’t have enough money to buy another materials for another schematic diagram if it fails.

        i’m studying ECE

      • Sir I a 2nd year EE student from India. Can I implement this circuit on a veroboard? Is the circuit comprising of VC1 VC2 and L1 a tuning circuit? Can you please explain me why we are using two variable capacitances VC1 and VC2 instead of just a single one?

    20. thanks but i’ve a question what is the value of 1st inductor ????

      • Aleksandar says: on April 20, 2012 at 7:51 pm

        Read the text…

        “Coil L1 is formed by winding 8 turns of 1mm (20 swg)

        enamelled copper wire on a 6 mm diameter former, which

        is then removed. After that L1 should be stretched

        carefully and evenly to a length of about 13mm.”

        You can convert that data into imperial measures and put them into the coil calculator that you can find online.

        for eg. http://www.crystalradio.net/cal/indcal2.shtml

        …or, you can do little bit of math for L1 value.
        You have an LC tank circuit formed from VC1, VC2, C1 and L1.
        Vc1 and VC2 can be observed as one capacitor and therefore you can calculate their value as parallel capacitor connection with the formula:

        VC1 + VC2 = 20pF + 5pF = 25pF
        and then since we have one “virtual capacitor (VC1 + VC2)” and C1 … that is serial capacitor connection and we calculate that one
        as (25pF * 22pF) / (25pF + 22pF) = 550 / 47 = 11.702 pF

        Now we have a general purpose C = 11.702 pF

        Since the radio works on the frequency range
        from 88-108 MHz.

        Let’s say that we have frequencies F1 and F2.
        F1 = 88 MHz
        F2 = 108 MHz

        You put those into equation 2*pi*F= 1/sqrt(L*C)


        If C = 11.702 pF and F = 88 MHz then L for L1 should be 280nH.
        If C = 11.702 pF and F = 108 MHz then L for L1 should be 186nH.

        So for L1 you’d have a value between 186nF and 280nH for frequencies between 88 and 108 MHz assuming that you have a fixed value capacitor of 11.702 pF.

        or you can again use another online calculator for LC tank circuits if you don’t like the math, for eg.:


        If you plan on buying an inductor for L1 i’d advise against it, cause it’s much cheaper to take some random piece of wire and wind it on a screwdriver like I did on the video and photos. Check out the photos. There is a photo of me holding a piece of wire wounded on a screwdriver. That wire wasn’t even enamelled … it was just a random striped telephone wire that I found laying arround and then I wound it for L1 =)

        Just try and experiment a little. Have some fun ! =P

      • Aleksandar says: on April 21, 2012 at 11:51 am

        To correct myself:
        “So for L1 you’d have a value between 186nH and 280nH”

        …values for inductors are in Henries (H) =)

      • Hugo Salva says: on February 16, 2014 at 8:13 am

        Hi Aleksandar, I saw the circuit, and it is fantastic. I like the electronic circuits. I would like to build a circuit, but here in my city is difficult to get exactly the same components. I have some transistors, and not sure which one I can use to replace the TR1=BF199.
        Can you help if I give you the list of transistors that I have?
        thanks, and I reiterate, your circuit is very good :) amazing

    21. thank u s000 muCh Aleksandar…..

    22. aleksandar did you use antenna on your receiver ???
      b/c i did’nt find it on your circuit

      • Aleksandar says: on May 2, 2012 at 6:17 pm

        Yes, I used a regular wire as a test antenna. You can see it on the video as a black alligator clip connected on the left, near the tunning capacitors. The antenna is coupled with a gimmick (twisted wire) capacitor.

    23. thank u aleksander my circuit is working perfectly thank u again from me n my friends

    24. the circuit is simple and easy to construct.if an amplifier ciruit is also connected at part of headphones the output will be get as in amplified form and we can hear the output in a loud speaker as in the normal fm radio.

    25. great i’m going to try this circuit and i will show the result

    26. how the antenna is to be connected? what thing can be use as antenna ? where it should be connected?

      • Aleksandar says: on October 7, 2012 at 4:47 am

        Antenna can be connected to the junction between C1, C2, L2 and R2. Or you can experiment a little by attaching it to other points in the tuned circuit and see if that works better. You can try attaching antenna to the junction between VC1, VC2 and C1. For antenna I used an alligator jumper wire. You can just use a random telephone wire as an antenna, about 20 cm long. I just attached it to random point and left it attached if the reception was better, and in my case it was pretty good. You can experiment a little and see what works best. When I first started this radio it worked well without an antenna xD … It could catch about 2-3 stations. But when I attached an antenna it could receive about 12-13 stations.

    27. wants to see head phone photo

    28. Hey everyone, here is a little update of what I did, if you’re interested. I made a tiny modification in the tuning part of the circuit I made. I was playing with it a lot and eventually the capacitor that I used with a screwdriver broke ! :/ … So I found another one from another radio, a bigger one with a nice tuning handle and I soldered it in place of the old one. And I made a nice holder for it out of a sheet metal because it was hanging on the side, so I improvised :) . And now it works even better. I photographed everything and made a video of it with a PC audio amplifier hooked to it instead of headphones and I demonstrated how tuning of the radio works. For this particular radio the tuning is done with TWO hands at the same time. On the capacitor knob and on the potentiometer regeneration control. So, you’ll notice that I always touch both controls often when I change the stations. Just so you know, the headphones used for the radio can be anything from 32 Ohms up to 1 MOhm (and probably even more) impedance/resistance. I tried 64 Ohm earphones and also my old Walkman headphones (the orange ones from the photos and the video) that are about 570 Ohms.

      Here’s the link to the gallery with all the new photos I took:


      And the YouTube videos of me playing with the radio xD :


    29. What is the gain,imput impedance and input frequency of this circuit

      • Aleksandar says: on November 13, 2012 at 6:18 pm

        Input frequency for the RF stage of this radio is the FM broadcast band between 88 and 108 MHz. As for the RF input impedance and the amplification gain I couldn’t say what those values are cause I didn’t bother calculating or measuring them since this radio is basically a toy and I never considered using it for something more serious other than playing with it and listening to some retro tunes in the evening hours =)

    30. How many turns did you use for the 2.2 uH inductor and what was its Swg? Thanks :)

      • Aleksandar says: on November 19, 2012 at 8:00 pm

        I used a random choke (that I got from some board that looked like it would work x) ) for L2 between 1 and 10 uH, cause the description text says it’s not critical. If you want to make a choke with an exact value, you can calculate the inductance and number of turns with an on-line calculator here: http://www.crystalradio.net/cal/indcal2.shtml

    31. I have a question.
      First BF199 is RF amplifier.
      The last stage looks like audio amplifier..
      What are second and third ones? I was looking at block diagrams of FM receivers and there are several(mixer, oscillator, fm detector, IF amplifier..)

      • Aleksandar says: on December 6, 2012 at 12:55 am

        This is not a super-heterodyne receiver and therefore it doesn’t have strict block components (stages) like mixer, oscillator, fm detector, IF amplifier etc.

        The first transistor BF199 works as an amplifier and also as very weak oscillator at the same time and it oscillates at the same or similar frequency as the frequency of the station that we want to receive.

        This is a super-regenerative (regen or superregen) type of radio receiver.

        So we could say that it has three building blocks which are:

        1. input RF amp/osc (regenerative circuit with TR1, BF199)

        2. RF choke L2 (used as some sort of VERY simple demodulator for FM. It “chokes” RF component from the RF signal and leaves only audio component that is further amplified. it can also detect AM, CW and SSB when you tune and use the regeneration control. The method used for FM demodulation is called slope detection … Google it, it’s very cool.)

        3. Audio preamplifiers/amplifier with TR2, TR3 and TR4

        Audio part of the circuit is basically three small audio amplifiers hooked in series so that output from one little amp is fed into input of another little amp. And those three little amps work as one big amp. It picks up super tiny signals from RF choke and amplifies it enough through all those little amps so that it can drive headphones or some other bigger amplifier. (I tried both, headphones and PC speakers .. you can see it on my youtube videos that I posted earlier).

      • Thank you sir

    32. Hello,

      I am impressed by your circuit and intend to make one on a PCB. May I ask you the following three questions:

      1. What is the voltage of the 4600 mAH AA size battery you have used in your circuit?

      2. What is the current consumption of the circuit with a moderate level of volume when the circuit is used with a headphone?

      3. May I substitute C9018 or BF494 for TR1: BF199?

      Waiting for your speedy response.

      Thank you and regards.

    33. Hi there,

      Well, I have yet another query/request for you. Since, you have successfully designed this super-heterodyne receiver, therefore may I request you to design and publish a wireless doorbell circuit here. The receiver will be using a super-regenerative oscillator, it will run from 3 volts battery with a range of about 50 meters and the antenna will be built-in type.


      • Aleksandar says: on January 30, 2013 at 1:56 pm

        3 inch x 2 inch would be fine. Just keep in mind that leads in the RF section need to be as short as possible.

        As for the wireless doorbell, I’ll see what I can do in my spare time.

    34. aleksandar?
      i’m only highschool student, but i’m really interested in this circuit. can you help me to do this. can you send to my email the materials and the pcb design of this circuit.. co’z i cant understand this circuit, how they our connected..

    35. Aleksander.. It doesn’t work on the bread board. the voltage is not reaching the inductor and variable caps and my teacher says that the specified transistors wont turn on at 1.5v. Please help

      • Aleksandar says: on April 22, 2013 at 5:34 pm

        Check if you’ve inserted all components in the breadboard correctly. Sometimes, on an old breadboards contacts are not perfect and you might have a dead contact somewhere. Check the contacts on transistor TR1, and resistors R1 and R2 and also pot VR1. Also, try turning the knob VR1 to make sure you hear whistle or some kind of noise on the output. It might turn out that VR1 wasn’t set to proper bias point on the transistor. Also you might have used a wrong transistor for the project. You have to be 100% sure that all the components you inserted have good electrical connection. Post the transistor type you used in your project. When you build radios like these, you have to start with RF part first and have oscilloscope or some amplifier laying around to check the RF as soon as you’ve built it. And then after you’ve built the RF part and everything’s running OK, you move onto the audio section and build the audio amplifier.

      • Aleksandar says: on April 22, 2013 at 6:20 pm

        Also, it would be nice if you posted some photos too :)

      • I used C829 as TR1 and BC547 as TR2, 3 and 4. I have also checked the connections and even did it 3 times with no result…. And the bread board is new:)

      • Aleksandar says: on April 23, 2013 at 12:41 am

        I believe that transistor you used for TR1 might not be suitable. Try a different one. Try using BF199 or BF240. Those are known to work the best so far for this particular radio. Theoretically, the one you choose for TR1 should have worked but there might be an issue with the minimum transition frequency characteristic. I think that C829 cannot oscillate bellow 150MHz. Don’t take my word for it because I might be wrong on this (I’d like to hear other people’s opinion on this one). Anyway, you should most definitively try different transistors for TR1. Try and see what happens and post back results. That’s the advantage of the breadboard, if something doesn’t work you can just simply switch out everything you don’t like on it =) lol

      • I can’t find BF199 or BF240. They are very hard to come by here… Can u plz suggest an equivalent.

      • Will BF494 do?

      • Aleksandar says: on April 25, 2013 at 12:54 am

        Yes, BF494 should work. Try it out and see what happens. If not, get some RF transistors from some old junk electronics and try those out. I built mine mainly through trial and error. The RF transistor is the trickiest part of the entire circuit. I had to switch out the RF transistor couple of times until I found one that works best, which was BF240 that I found on some board that I had laying around. Ofcourse my method was purely amateurish regarding this particular project (which you can obviously see from the photos and youtube videos). I was bored and wanted to have some fun… I was like, “Hey why not just build a small fm radio on a wooden board”. I came across a schematic on the net, picked some transistors at random from my junk box and soldered it onto the plank, lol. No datasheet, no nothing. When you do electrical engineering, these methods are something you should be doing after you’ve made electrical calculations and designs. When you make your prototype that is. Anyway, I hope you have fun making this one. It’s fairly simple and insanely fun… At least it was for me. I still use that thing to listen to my favorite songs in the evening :)

    36. Can I use bf259 instead of bf199 or am I stupid to think that?

      • Aleksandar says: on May 12, 2013 at 2:16 pm

        The datasheet for BF259 says that Transition Frequency Typ is 75MHz. Which is bellow 88MHz. So, theoretically it shouldn’t work. But, datasheets aren’t always 100% right. If I were you, I’d try that BF259 in place of BF199 and see what happens =) You can always try some other transistor in case that one doesn’t work.

    37. Hi,
      I do have a lot of transistors but just not the ones that are sugessted in these commends. I did try to get it working with the bf495c, but i dont recieve anything.
      This is the list of transistors i have. Could you suggest one?

      3002 2sc2361 bf493 br101 bu506 byw29 tip135
      2n12105 2sc959 bf495c bs08 bu508 byw29 tip135
      2n2219a 2sd1064 bf583 bsd215 bu806 j106 tip135
      2n2222 2sd438 bf591 bsr50 bu806 mje13004 tip3055
      2n2222 2sd636 bf593 bss68 bu807 mje13006 tip3055
      2n2905a bat85 bf671 bst97 buk426 mje13008 tip32c
      2n2906 baw62 bf859 bsv15 buk436 mje13009 –
      2n2907 baw62 bf869 bsv64 buk455 mpsa42 –
      2n3572 bb212 bf872 bsv78 bup22a of444 –
      2n3706 bb304 bf926 bsw66 but11a on222 –
      2n4032 bd943 bf980 bsx21 but11f on624 –
      2n4093 bd943 bf981 bsx62 but18a on824 –
      2n4289 bd955 bf981 bsx63 but31a ph3055 –
      2n5415 bd956 bfg96 bsx69 buv26 ph5415 –
      2n5449 bdt21 bfq10 bt134 buv26 ph5415 –
      2n5496 bdt21 bfq12 bt136 buv27 ph655 –
      2n6400 bdt31bf bfq13 bt136 buv27 ph655 –
      2n6661 bdt31 bfq14 bt136 buv48 ph6678 –
      2n929 bdt31cf bfq16 bt137 buw132 prf640 –
      2sa671 bf247b bfq23 bt138 buw84 rt383 –
      2sa699a bf256c bfr29 bt138 buw85 ryp95 –
      2sa794 bf259 bfr54 bt139 bux84 ryp97 –
      2sa815 bf259 bfr84 bt139 bux99 s53 –
      2sa850 bf327 bfr96 bt151f buz31 s53 –
      2sb793 bf422 bfs21 bt157 buz31 t2800 –
      2sb856 bf422a bfs21a bdt62af buz60b tic106 –
      2sc1061 bf423 bfs21a btr59 buz71 tic206 –
      2sc1318 bf459 bft45 bts59 byp22 tic206 –
      2sc1407 bf461 bft45 btx18 byr29 tip131 –
      2sc1518 bf462 bfx34 btx18 byt28 tip131g –
      2sc1568 bf483 bfx34 bu306f byv133 tip131g –
      2sc1737 bf485 bfx88 bu406 byv19 tip131g –
      2sc1885 bf493 blu98 bu505 byv72 tip135 –

      • Aleksandar says: on May 30, 2013 at 11:19 am

        Go to http://www.alldatasheet.com/ website. Find the datasheets for all those transistors you listed and compare the characteristics with the ones needed on the schematic. You should look for hFE, Transition frequencies, base and colector saturation, turn on voltages .. and I-V curves.

        Also take a look at http://www.elexp.com/t_tranmk.htm so you can know what transistors you have right away when you look at transistor markings.

        Here, an example:

        2sc1061, Japanese Standard, 2-tr, SC – NPN HF transistor ..
        For the RF transistor, you’d want an NPN HF transistor that has transition frequency not lower than 120MHz.
        For other transistors you’d want AF NPN transistors.

      • Aleksandar says: on May 30, 2013 at 11:26 am

        Also bare in mind that the transition frequency can reduce with voltage. That means that for eg. if test conditions produced 120MHz @ 10V (Vce) … they might produce 80MHz @ 5V .. or 50MHz @ 3 .. the values that I’ve put here are highly approximated .. just to give you an idea.

        The rf circuit here operates in range of 88-108MHz at 1.5V … And also the regenerative control regulates CURRENT to the BASE of RF transistor.

        Build a circuit on a breadboard and try all BF’s you have for RF tr.

    38. Hello,

      I gave it another try, this time with a BSX20. Its working like a charm. The quality is also very nice.

      • Aleksandar says: on June 1, 2013 at 12:14 am

        There you have it. You just needed to tinker with it a little : )

      • hardbass says: on June 1, 2013 at 3:43 pm

        I know :P, A while ago i made a transmitter. That worked even with a bc546. It needed a little finetuning before it worked.

    39. Post some pictures and videos of your working radio. 😉

    40. Wel, thats a good idea.
      As soon as i get my hands on the camera ill post some pics.

    41. paschal fortunatusy says: on August 22, 2013 at 9:33 pm

      you have to keep the project for fm receiver on internet so that people can check it clearly

    42. hi sir, can you post all possible replacement for tr1, ?

    43. what is that color yellow in the circuit aside from the tunning capacitor?

    44. Hi aleksandar, can you explain me how this circuit extract the audio signal from the modulated signal?

    45. Audio signal is extracted from the FM signal by the means of “slope detection”. As FM signal is signal modulated by CHANGING FREQUENCY, when you tune in to some station, as frequency changes (very fast, cause it’s frequency modulation), as it goes off tuned frequency .. the amplitude of the signal lowers or dissapears for a moment and then when it comes back the amplitude gets higher/appears again. And that “off the frequency, on the frequency” on/off and higher/lower action of the signal is what this simple circuit uses to retrieve a useable low quality AM audio signal. It’s basically AM demodulator used to demodulate FM, but in order to use it properly you have to tune in into a “sweet spot” part of the signal in order to have “higher quality” sound from it.

      On the schematic, the rf choke L2 does most of the work in “slope detection”. It removes high frequencies and the remainder of signals (AM/AF) is used and further amplified into sound that you can hear on your headphones/speakers.

      • Aleksandar says: on September 29, 2013 at 9:23 pm

        Also, the actual FM radio signal is received and partially demodulated by the means of “very weak oscillator” that excites when it receives weak radio signal .. and it goes wild in the rhythm of the signal thus it kind of oscillates following the oscillation pattern of the received signal at the same frequency and that action is further processed by the L2 rf choke etc.

        The principle used here is superregenerative principle.
        Also superregen or regen for short. There are plenty of schematics on the net. Google it.

        Google “slope detection” and “superregenerative radio” to get more information on it. It’s very interesting and fun if you decide to build it :)

    46. paschal fortunatusy says: on September 30, 2013 at 10:36 pm

      can you explain the function of each transitor from the circuit and please show me the output wave form of this circuit during simulation.

    47. The function of each transistor has already been explained in earlier posts. What simulation program do you want to be used for simulation of this circuit? What parameters in particular are you interested in?

    48. Hi aleksandar, does VR1 adjusts volume?

    49. No, VR1 is the regeneration control. Because this is a superregenerative receiver. You adjust the amount of regeneration in order to get the best possible quality of reception. However, if you wanted to add volume control you could probably add an aditional potentiometer before C3.

    50. You can use a PC Speakers (with amplifier in them) instead of headphones. That way you won’t have to put in a volume control because you would adjust volume on the speakers. Take a look at the youtube videos I posted ealier.

    51. aleksandar, I have a question for you. I bought an FM variable condenser but I do not know how to connect it. I tried to google it but i found nothing. Do you know how to use it?

    52. IS this possible? I just learned that the frequency I am receiving is for AM. Its 846kHz.

    53. Yeah, it’s possible. Theoretically you can make it to receive on any frequency just by changing values of capacitors and inductor in the tuning circuit. My suggestion is this .. try changing pin on that capacitor you got. You would typically need a smaller value of capacitor to get into FM band. Try different pins on a capacitor until you get an FM station or at least an unteligeable HISSing noise.

    54. unintelligible speech like noise usually means that you got an FM station when you try tuning. And than you fine tune it with VR1 and VC1 slowly until you can understand the speech or music or whatever.

    55. by the way, how can I eliminate that hissing noise?

      • Aleksandar says: on October 12, 2013 at 3:31 pm

        The hissing noise is important, it lets you know that the regen is regenerating/oscillating. You have to change the value of VR1 to adjust the hissing (reduce it) until you get understandable signal when you tune in with VC1.

    56. I can’t reduce the hissing noise.

    57. try increasing R1. Put a 100 Ohm resistor in series with R1 and see if that makes any change.

    58. You gotta tinker with it. Change values for some components in order to make it work. Lots of it is based on trial-error :)

    59. still the same. i can’t reduce the hiss.

      I just remembered that I replaced BF199 by BF240. Is that ok?

    60. Yeah, that should be fine. I used the same one on mine.
      Take a multimeter and check if you connected everything properly, somehow I have a feeling that VR1 might not be connected properly or something like that. VR1 should eliminate the hiss when you adjust it. Do you get any change at all when you adjust VR1?

    61. ok i’ll do that. Yes. I get changes when I adjust VR1 but the hiss is not reduced. But when I touch the antenna, I get a more intelligible signal.

      • Aleksandar says: on October 12, 2013 at 4:09 pm

        Hiss is normal, you can’t eliminate it completely. But it kind of lowers when you tune into a station. You could try attaching antenna elsewhere in the circuit. Also try switching out the R1 resistor to a lower or higher value by couple of K’s or 10k’s. It might give you better results. Also try swithing out the VR1, maybe it’s faulty? Like I said you need to play with it so you can figure out what’s wrong. Check and recheck everything. VR1 should be linear 10K.

    62. I think I put a wrong a value of L2. I just bought it without knowing the value. I’ll just try to wind my own. Can I use an ordinary wire used in bread boarding for this one?

      Is L2 a critical part of this circuit?

    63. L2 is not critical. It shouldn’t be a problem, but still try using another one. Wind your own and see if that helps (use the calculator I posted links for). I’d also consider changing resistor values R1 and/or R2. I believe you might be getting too much current into the TR1 transistor. It might happen that it’s over-oscillating. Use a multimeter to check the voltages and see how they change when you adjust VR1.

    64. paschal fortunatusy says: on October 16, 2013 at 10:44 am

      from the fm circuit show me demodulator, oscillator, mixer,audio frequency amplifier and tuner

    65. paschal fortunatusy says: on October 16, 2013 at 10:48 am

      from the fm circuit show me\label the demodulator, oscillator, mixer,audio frequency amplifier and tuner

    66. Hi

      How can it be adjusted to radio stations?

    67. I´ve build this circuit and fm transmitter and it worked like a charm thank you :)
      but I would like to understand how the things work.
      I´ve read this article http://vsagar.com/2011/12/modulation-transmit-signals-fundamentals-modulation-demodulation/

      in some part about the problems involved without modulation it says “our voice frequency constantly changes So we will have to change height of antenna constantly” and it tells modulated can solve all transmission problem including this one.
      The problem is I dont understund how modulation can solve that problem above…
      I really understund we now can transmit 3khz signal using a higher carry (300mhz) but on my head the problem presists we would need to change the height of antenna. How really modulation solve this problem?

      I know this question is not related to this topic but as a student I´m very curious about these topics if you can help me as a friend I would be very grateful
      I really need help sir

      • Aleksandar says: on October 20, 2013 at 9:38 am

        LENGTH is more important than the height, and sometimes it’s the other way around.. but read this text and you’ll figure out what I’m talking about. Antenna is a type of a resonant circuit, and it can only resonate on certain frequencies depending on it’s length and type of construction. The simplest antenna is a simple wire, and it’s length determines on which frequencies it will be most sensitive.

        Our voice or for eg. male voice, has frequencies (pitch) between 300 Hz and 3400 Hz. In order to hear this voice we should be able to hear all frequencies from that spectrum as it changes. That means 300Hz, 301Hz, 302Hz … etc ’till 3400Hz .. all of it. Let’s try some examples.

        You’d have some formula like lambda=c/f for eg., lambda being the wavelength, c being speed of light, f being the frequency.

        Here’s a calculator for that:

        Now imagine if we wanted to construct an antenna that would transmit that voice directly.

        In order to transmit the 300Hz you’d need an antenna that’s roughly around 1000 kilometers long.

        And for 3400Hz you’d need an antenna that’s around 88Km long.

        So if there was some guy singing, and you had one of those two antennas receiving him. You’d only hear his highest possible pitch or his lowest possible pitch from his singing. Cause antenna can typically only receive one frequency and a very tiny bandwidth depending on the construction.

        So if we had an antenna that could change it’s length between 88 and 1000Km in the rythm of the singers pitch, theoretically we’d hear him just fine.
        We can’t.

        That’s where MODULATION comes in.

        Here’s another example.
        Let’s say that we had an FM modulated signal with a deviation of 3100Hz (which should theoretically suffice for male singing voice).

        So, if we had a modulated radio signal that’s for example set on ~90MHz … we would have something like a frequency signal that’s rapidly changing between 90000300 and 90003400 Hz (90.0034 MHz). (It’s slightly different in terms of exact frequency in real life but this is just for example purposes)

        So for receiving this modulated signal we would have an FM radio that is tuned to 90MHz with approx. 3KHz audio bandwidth or so. And the antenna we would use should be
        between 3.3333222222592593 and 3.3332074121644295 meters long. Notice the change of ~0.00011481 meters? That’s almost nothing in real life. Basically if you made an antenna that is 3.3 meters long and just hooked it up to your FM radio you’d receive this male voice singing just fine on 90 MHz.

        So tell me … which one’s better and easier?
        Changing antenna length between 88 and 1000 kilometers or
        changing antenna length between 3.3332 and 3.3333 meters? 😀

        So like I said before. It’s mainly the LENGTH of the antenna that makes the difference (or difficulty).

        Of course, you do know that LENGTH easily becomes HEIGHT if you install antenna VERTICALLY :)

        Now, here’s another question. How would you install a 1000Km long vertical antenna? :)

        I hope this helped a little.

      • so on fm transmiter is the transistor that modulates resonant frequency working on this range
        90000(300) and 9000(3400) Hz or it is working in another way?

      • Aleksandar says: on October 20, 2013 at 11:09 pm

        CAUTION… I made a mistake in explaining the modulation part in my previous post. I started explaining FM and ended up explaining AM or some weird mixture of the two LOL. When I mentioned deviation I ment BANDWIDTH and most of the FM abbr. is ment to be AM. So I apologize if that made some confusions, I was in a hurry to type out the post as quickly as possible.

        And yes, there’s a transistor that does the modulation in the modulator part of the transmiter.

        As amplitude from the microphone (for eg.) changes it drives the input of the modulating transistor that in return varies the power of some oscillator which is essentially a simple transmitter.

        We really shouldn’t change the topic like this! This is against the rules of this forum I think. We should take this convo somewhere else.

    68. Did you mistake at all explaining modulation part or just when you talk about deviation.
      I just want end well with the information you wrote about above 😀

      • Aleksandar says: on October 21, 2013 at 4:16 am

        Yeah, I messed up the whole modulation part. That’s exactly why I’m not a teacher LOL. I sometimes simply suck at explaining things. However the “punchline” still stands about the wavelength and length of the antennas.
        I think it would be better if you read this http://en.wikipedia.org/wiki/Modulation

      • Do not be so hard with you everybody make mistakes.
        Thank you very much for your attention 😀 and Im going study a little on wikipedia :)

      • hello
        I´m trying to build this circuit but when I power it on it TR1 gets very hot, what can it be aleksandar?

      • I reply because Im building this circuit with my friend Andre :)
        he´s circuit worked fine but Im having problems with mine

      • Aleksandar says: on October 23, 2013 at 9:25 am

        It looks like TR1 might have a short. That can happen if you placed TR1 wrong. Check your pins to see if you placed the transistor properly in the circuit. Make sure you properly identified B, C and E of the transistor. If the transistor is placed properly than it’s probably malfunctioning, you might need to replace it.

        Also, make sure that you have proper resistors feeding the current to the TR1 .. it might happen that you maybe misread color bands and put lower value resistor instead of the proper one. Check and recheck everything.

      • Aleksandar says: on October 23, 2013 at 9:27 am

        Also, check the transistor with the multimeter to identify if it has a short. That’s very important. If the transistor is conducting equaly in both ways between to same pins when you try reversing polarity than it most certainly means that it has a short and it’s bad.

    69. Hi
      how can it be possible vr2 do one thing and vr another one if they are set up in the same way at same spot of circuit

    70. sorry I mean whats the fuction of VC1, VC2 adjusts the frequency VR1 adjusts oscillation and VC1?

    71. Aleksandar I did all the connections but it didn´t work:s.
      I have power on speaker but it dont oscillate, I checked all transistors include TR1 and it were all ok.

      What can I do Aleksandar?

      • Aleksandar says: on November 4, 2013 at 10:22 pm

        Measure the voltages between base and emitter (Vbe) and collector-emiter (Vce) for all transistors and post what you measured so we can continue troubleshooting.

    72. base emitter tr1 – 0.6v
      tr2 – 1.10v
      tr3 – nothing
      tr4 – 0.7v

      collector emitter tr1 – 0.6v
      tr2 – nothing
      tr3 – 0.7v
      tr4 – nothing

    73. Those NOTHING’s should be SOMETHING’s.

      It could be a bad solder joint on a pcb or a bad insert on a breadboard.

      Check the connections on resistor R4 and check if you connected your headphones properly.

      TR2 and TR4 MUST have some Vce in order to work properly.

      Check and recheck all the connections around tr2 and tr4 until you get Vce’s on them.

      Check the resistors that supply current to the collectors.

      Measure the voltages on each of them.
      I’m interested in R3,R4,R5,R6,R7. Make sure that your headphones are connected while you are taking measurements.

      If you didn’t have headphones connected while you took Vbe and Vce measurements … then connect headphones and take all those measurements again with the resistor voltages and post again.

      It most certainly looks like a bad connection to me based on those Vce voltages.

      • Aleksandar there´s a strange behavior, from resistor R6 any current can´t pass through, I´ve checked the R6 and it was fine.

        TR2 now is working properly but TR4 needs TR3 to work…

      • Just in case I have sure resistor is inline with positive rail and collector.

      • Aleksandar says: on November 7, 2013 at 6:46 am

        If you’re 100% sure that R6 has a correct resistance and you’re also 100% sure that transistor TR3 and resistors R6 and R5 are properly connected and you still don’t get current going through R6 then there’s something wrong with R6 or TR3 (or the breadboard if you’re using it). Again, recheck connections or even try another R6 and R5 .. if that doesn’t work than switch out TR3. If you’re building this on a breadboard, try using some other holes on it. Breadboards can sometimes fail on their insert holes after some extensive use.

        You’d get the best results if you soldered everything on some proto board or some solderable tin, manhattan od dead bug style.

        If you’re still having problems after this .. I’ll post the schematic with voltages that I measured on my working radio for reference.

      • Aleksandar says: on November 7, 2013 at 6:49 am

        Oh and also you must have 64ohm headphones attached to it in order for TR4 to have current going through. Cause in the final stage, headphones/earphones are behaving like a resistor in the TR4 circuit. It completes the circuit by supplying current through the headphones to TR4.

    74. well now every transistor is receiving voltage from vce and vbe the was a little switch incorrectly inserted, but I still not getting any sound what can be now?

      • Aleksandar says: on November 7, 2013 at 10:17 pm

        Now that you’ve got power. You need to try tuning with VC1 and VR1 at the same time.

        Since it’s a regenerative design, you need to try getting the hissy noise in the headphones. As soon as you do .. you back out from the noise a little and then try tuning into some station. That’s pretty much it. Unless you’re off the frequency band. Then you’d want to adjust the coils in the tank circuit. All that’s left for you know is tinkering with the settings. Assuming that none of the transistors burned out while you were connecting them.

      • Sorry I made a mistake not all the transistor´s have power TR3 still dont have voltage on collector and I notice when I measure R5 it gives me 8kOhms instead 1M

      • Aleksandar says: on November 8, 2013 at 9:47 am

        I hope you’re not measuring resistor value while it’s in the circuit. Cause that’s wrong.

        Only voltages can be measured in-circuit.

        When I said measure resistor values, I meant take the resistor out and measure it and then put it back.

        Connect the resistor R6 to collector and to positive rail and you should have some voltage then.

        It looks like you have a bad connection on R6 or on the emitter of the transitor. Check and recheck everything.

    75. I took some time to measure voltages across different components in the circuit. I marked them all on the schematic.


      Voltages are in milivolts and are measured with a very cheap voltmeter :)

      I hope this helps.

      • Hello again, thank you very much for your attetion:)
        but I noticed that when insert R6 leg on board and then check with the multimeter it shows me nothing but when I left the leg off It shows me a voltage it looks like something is absorving the voltage to somewhere.

    76. Could be that R6 is faulty. Get another one and put it in, if it continues with the same behaviour than take another tr3 and put it in and see what happens. You might have damaged the tr3 by accident or something.

      Test tr3 (and others just in case) like this

    77. aleksandar When I was checking the circuit I found ot that when I took off R4, R6 let current folow normaly but When R4 is inserted current can´t flow from R6 it´s acting like a switch.
      There´s a very strange behavior :(

      • Aleksandar says: on November 10, 2013 at 7:36 am

        Check C4 for short. In fact, check everything for short. If you find a shorted component, replace it. If all components are fine then you wired your circuit wrong.

      • Aleksandar says: on November 10, 2013 at 7:53 am

        Take a photo of what you built so far and post it here via link. I’d like to see how you built the circuit.

    78. Hello again aleksandar

      I found out that ceramic capacitors were in short and TR4 was inverted and I fix it all and I also tested capacitors and TR4 with multimeter and it were fine, after all the circuit doens´t work -.-
      There is my circuit…
      Ignore circuit below it is isolated from receiver It is a fm transmitter working fine :)

      • Aleksandar says: on November 16, 2013 at 7:06 pm

        Ok, now that you’ve corrected all those errors that you found. Redo all the voltage measurements like from the picture I posted and post them all.

      • I´ve seen the picture you post before but how can I measure the voltage using that information?

      • I mean for instance how it´s possible measure ddp between R4 knowing is that has the same poles + on top and + down It´s only possible measure ddp between +/- it gives me nothing measure ddp on R6

      • sorry I really don´t understund how I will measure

      • Aleksandar says: on November 17, 2013 at 1:54 am

        Voltage is the difference of potentials. You measure it between two points. If you were to measure voltage across a resistor, you would turn on the radio you built and take the (+) terminal and put it on one pin of the resistor and (-) terminal on the other pin of the same resistor. If the current flows through the resistor there must be voltage between those two points. That’s how you measure voltages across resistors.

        If you still don’t understand how to do this, let me know and I’ll make a video on measuring voltages and currents in the circuit.

      • Aleksandar this is what I got

      • Aleksandar says: on November 18, 2013 at 12:53 am

        The readings you took are quite troubling. All those resistor voltages marked “none” look exactly as if they were all shorted out somehow (or perhaps have VERY SMALL VALUE … you should check if you have correct valued resistors). See if you are not by any chance shorting out the resistors. Could be that your transistors are fried. The way you should have built this circuit is stage by stage while measuring if everything works properly after every built stage. Cause the moment you run into a problem it’s much easier to remove it early on. But considering that you might have fried some transistors when you inserted some of them backwards, you might be better off desoldering everything and making the circuit all over again. But this time building stage by stage. And get the datasheets for all transistors so you wouldn’t insert them wrong in the circuit. Also check all transistors for shorts or open circuits. Check all capacitors for shorts and make sure that all resistors have proper values with an ohmmeter. You’ll make it work eventually cause it’s a really simple circuit.

      • I did all the whole circuit again but now Im not geting voltage across first resistor(470k) R3 and R5

      • also R7 have no voltage

    79. can you send me the complete name of every parts of this circuit
      just needed for may project.
      cos i need it to name every part and find the function of this parts.

    80. I did all the whole circuit again but now Im not geting voltage across first resistor(470k) R3 and R5 also R7 have no voltage

      • Aleksandar says: on November 24, 2013 at 12:39 pm

        Ok, I’d like you to answer the following questions as best as you can:

        1. What solder are you using? What type, details.
        2. What temperature is your soldering iron set to.
        3. Are you 100% sure that transistors you are using are functional? (Test the transistors in a simple switch configuration to make sure they’re working properly, at least basic function)
        4. Can you post a close up picture of your solder joints?
        5. Is your soldering iron tip clean?
        6. How many seconds it takes for you to solder one joint?

        And last and most important, I’d like you to describe to me in full detail step by step the way you solder.

        You should know that when you build circuit like this, transistors are soldered LAST so you’d avoid damaging them from excess heat from the soldering iron.

    81. The problem is almost gone 😀 now I’m not having voltage across R1 and R2

    82. hey i have built the circuit and things are not going smooth..:-(

      1.the 1st stage amplifier is working but not the 2nd neither the 3rd.so i skiped the 1st stage amp and used and LM386 audio amplifier where the signal from c3 is the input and the the ouput goes to the speaker..

      2.i have used a 6 volt source. but i am not geting any signal.
      the 10k pot is not responding. plz help

      • Aleksandar says: on January 5, 2014 at 3:30 pm

        You deviated from the schematic, LM386 doesn’t have enough gain for proper amplification. The datasheet for LM386 suggests that the chip has the gain of 20 to 200 while single BC547 transistor has gain ~ 110 to 800. In the circuit three transistors are used for audio stage, which means that it’s amplified three times with possible combined gains of (110~800)^3 which is a lot. So basically, if you were to build the radio properly from the schematic using those three transistors in the audio stage and then in the output (after those three transistors) put LM386 for speaker volume then that would be a nice thing. You could add a volume potentiometer in the input of LM386 and put the entire thing in the box and you’d have a neat little radio that plays music through the speaker. I might do just that with my radio in the future if I find the time to do so. As soon as I do that I’ll post a youtube video and pictures for everyone to see. And a new schematic with the LM386 in the output.

      • StellarRat says: on June 24, 2015 at 2:11 am

        I’ve used the LM386 on several radio circuits and it will usually drive headphones straight off the detector (no pre-amp). I’m not sure it would work for driving a speaker with super low input though. A different OP AMP such as a OPA227 would probably work fine for lower inputs as it was designed with a FET front end and is highly sensitive. HOWEVER, the big problem with using any kind of OP AMP in this circuit is that 1.5v is too little voltage to run any of the common OP AMPs. Even the low power OP AMPs usually require 5v min. So, I’m fairly certain the LM386 simply won’t run on 1.5v. You could fix that by change the RF transistor biasing resistors and using a 9v battery, maybe.

    83. http://www.electroschematics.com/5150/tiny-fm-radio/

      i have build both this and the one in the link USING BREAD BOARD BUT NO RESULT i am recieving response like a whistle but i seeeee no effect when chage with the vc1. is the shapeand size of L1 VERY IMPORTANT? I made it but its a bit irregular… please help i cant hold on much longer should i directly solder it and see whether it work?

      • Aleksandar says: on January 5, 2014 at 3:06 pm

        Whistling means that there’s too much feedback in some part of your circuit. Try adjusting resistances in the RF stage.

    84. Hello dude i like this idea verymuch hats off to you
      i have one doubt i bought bf 200 instead of bf 199 bcoz itz not available in my area can i use dat ?? a sooner reply will be usefull it will be gud if u also reply to my email address

      thanks in advance 😀

    85. L2 is not critical. However, if you think that the value on the schematic might not work for you, you can always change it and try a different one until you find a value that works for you. When I built mine I just put in a random choke that I found and it worked. I didn’t even pay attention to the L2 value.

    86. Sir, speaker of what wattage and resistance should should I connect?

    87. Sir I have a speaker of 80 watt. Will I be able to hear sound through it or shall I buy a headphone? Then please mention the specifications of it

      • Aleksandar says: on January 11, 2014 at 3:25 pm

        You won’t be able to hear much through your speaker, because speakers usually have impedance of 4 Ohms or 8 Ohms etc, which is too low for this circuit.
        This circuit is meant to be used with small regular headphones with impedance of 64 Ohms or more. If you want speaker power you need to use an output power amplifier. Or you could try experimenting and using a matching transformer on the output to match impedances. I believe that matching ratio of
        output:speaker = 8:1 should work. Google “speaker matching transformers” and experiment a little.

    88. Sir I have another question to ask.. Maybe its a very silly one. What type of capacitance is C7? I mean I havent seen such a symbol of capacitance. And another question is the polarity of the capacitors are not mentioned in the circuit diagram. Can you please help me with this??

    89. Thank you sir. Bt what about the polarity of the capacitors of c1, c2 and others? I mean where should I connect the positive terminal and where the negattive terminal in the above circuit?

      • Aleksandar says: on January 17, 2014 at 1:49 am

        C1 and C2 don’t have polarity. You connect them as shown on the schematic. Only C7 has polarity because it is electrolytic.

      • Thank you sir.. Its working now though the sound is quite low.. But it has been a really great learning Experience.. Thank you sir once again

      • Aleksandar says: on January 18, 2014 at 7:38 pm

        You’re welcome. Post some pictures or youtube videos of the working radio so that others can see what you made.

    90. hello sir i have made this finally but not working what shall i do pls tell me a suggesstion 😀

    91. I would like to make an receiver for 161 MHz. How can i design it?

      • wnh I take L as 4 turns,18swg and .5cm dia thn value is 55.637nH thn i need to take C as 17.5pF. how can I provide a fine tuning??

      • Aleksandar says: on February 7, 2014 at 9:27 pm

        Add an additional variable capacitor parallel to C with a value of couple of pF .. maybe ~1-3 pF, depending on how precise you want your fine tuning to be. Optionally you might want to use varicaps with voltage regulation and a potentiometer instead of mechanical variable capacitors to improve tuning and stability.

      • Thank you sir, and how can I setup a receiver for 161 MHz?
        I designed the values for L and C as 55.637nH and 17.5pF. it satisfies f=161MHz. what will be the other changes thet I need to make for the same?

      • Aleksandar says: on February 10, 2014 at 6:14 pm

        If you plan on receiving narrowband FM, it’ll be insanely difficult to tune in with regular capacitors. You’d most definitively want to have some sort of mechanical reduction gear attached to it to provide an additional fine tuning. And some rediculously small variable capacitors in parallel with the main tunning capacitor .. or maybe some varicaps with fine variable regulated voltage. As for the frequency you’d want to have a high frequency transistor to support that frequency. Most BF’s would do. You just do couple of experiments and find the one that suits you best. It would be very useful if you had some sort of oscillator or a signal generator to make sure that you’re receiving on the right frequency and to test the tunning and maybe add a scale/dial and so on. Making VHF and UHF circuits is tricky mostly because it’s very sensitive. It sometimes changes frequency when you just touch it. Google some guidelines on how to properly design VHF/UHF circuits. You should have your wires as SHORT as possible to avoid any instabilities. Post some photos of what you’re making. And maybe audio recordings of what transmisions you received.

    92. Where is receiving antenna?
      How to receive the signal?

    93. I built this circuit on a bread board and wanted to share my results. So far I am unable to tune in any stations but this circuit by far has given me the best results from any other receiver I built. What I mean is I’m hearing static and various radio sounds which is good! Below is a list of things I want to point out that perhaps may be wrong or may perhaps offer information as to help me (or you if you are building it!)trouble shoot further.

      1. For VR1 I am using a Bournes 10k ohm pot from Digikey (Part Number: 3310Y-025-103L-ND). Good? Bad? I don’t know…

      2. I opted to remove VC1 and use a single variable air capacitor for VC2 with a range of 16pf to 365pf. I left C1 intact. Based on my calculations C1 along with the variable air cap for VC2 should produce the correct pF values for tuning. I may be wrong… Here is a link for the air cap: https://www.midnightscience.com/catalog5.html

      3. For L2 I used a fixed 22uH inductor purchased from mouser electronics (Part Number: 542-70F225-RC) I have heard this refered to as a choke as well. Not sure if this is suitable or not.

      4. I tried powering the circuit with 3.7 volts lipo battery (have single cell lipo laying around) I have also powered it with the recommend 1.5 volts by adding a 39 ohm resistor to the lipo battery to drop the voltage. I didn’t notice any difference and I am not sure if it should even be powered with more then 1.5 volts.

      5. For L1 I gathered the 20 awg copper center from a coaxial cable. I wound 8 turns on a round number 2 pencil (roughly 6mm in diameter).

      6. For TR1 I used a RF NPN transistor from Digikey (MPSH10GOS-ND). Not sure if this is/was suitable but it was one of the closest RF NPN transistor I could find for TR1.

      7. Grounding. Not sure if this is grounded correctly in that I have no earth ground. Any thoughts?

      8. I need to use a plastic knob on my variable air cap and move the ground (black wire on front) so its not near my finger as I tune.

      9. Other then the above mentioned points I did not deviate from any other part listed in the circuit.

      I have my work cut out for me.

      Here are some pictures: one, two and three.

      • The problem with building any kind of high frequency circuit on a breadboard is that those long connections (in your case the jumper wires) will affect the performance of the circuit because the long wires change the values of the components. It is well knowns that long wires, even long terminals have inductive properties at high frequencies (I am a former radio pirate). My recommendation is to make the connections as short as possible especially where the RF signal passes through (the first stage up to T2).

    94. What P.Marian said… Long wires in the RF section are a deal breaker. I’m pretty sure that your circuit works as it is but you should replace those jumper wires with a shorter ones (maybe the bendable telephone wire used in wall installations).Also, you could try tinkering a little with a coil by spreading or compressing the windings with your fingers. And also playing with the regeneration control. When I built mine I had to mess arround with the regeneration controll A LOT! while I was tuning and it would only work in certain positions on the regeneration pot, so try tunning like this… Examine all possible combinations of positions of your variable cap with regeneration pot and when you find the best regeneration position (you’ll know when, typicially you’ll receive some station).. you mark it with a pen. And then when you tune in to stations you’ll have to move the regen pot just slightly back or forth to improve the volume and quality of reception.

      BTW, congratz on building the prototype circuit on the breadboard. It’s the way to go. As soon as you make the circuit work the way you want it you could than move on to a pcb and make the “real deal” :)

      • Thank you both so much for your replies and suggestions. I can’t tell you how much fun this has been and now I feel like part of a larger community because I shared by work. I can’t wait to try the suggestions. I don’t have telephone wire but I have lots of ethernet cable. I will go ahead and build the shortest possible jumper wires for the breadboard. I am also going to try a higher quality variable pot…I think that little plastic cheapy is ok..but not ideal.

        I did move the ground tap on the var cap last night (and I’m getting better resuls). I also added a plastic shaft extender to it so my fingers don’t have to touch the metal post when I tune.

        I will report back soon!

      • Just wanted to report back on my progress. Things are coming along well and I’m able to tune in a lot of stations! I’m learning a lot also and experimenting as Aleksandar had suggested in previous posts. Here is a summary of what I have done so far.

        1. I decided I needed a solid surface to work on and mount various parts. I used an old wood plaque I had lying around. I mounted the breadboard to it as well as my 10K ohm linear pot from the midnight society and my variable air cap (referenced in my above posts). Doing this allows me to make adjustments without moving the actual parts around and wires and thus causing interference and unwanted noises! I found this to be very important. Hot glue is great for mounting parts(in my n00b opinion). I used it to mount a small block of wood as a base for the 10k pot..I then hot glued the pot to the small block.

        2. I decided it was best to use an AC to DC wall adapter to power the circuit. I didn’t have to worry about batteries. I salvaged a 9VDC power adapter and a power jack I had laying around in a junk box from an old phone charging base. I hot glued the power jack to the wood plaque so I had a firm place to plug in power. I connected the power jack to my Bournes 10k pot (referenced in an earlier post) and measured the voltage output of the pot as I rotated the dial. Once it read 1.5 or 1.6 volts I stopped. Now..this 1.5 volts I routed to the 10k pot that I had previously mounted. Now I can control that 1.5 volts being fed to the tank circuit! As Aleksandar said many times..this variable pot is what REALLY helps tune in the stations. He wasn’t kidding when he said how sensitive it is and that you use two hands to tune the radio. You seriously feel like you are Lieutenant Uhura on Star Trek :)

        3. Now this is weird. For some crazy reason I had to NOT ground the variable air cap. I can’t figure out why but when it was connected in parallel(I think??) with the tank circuit I couldn’t tune anything. As soon as I disconnected the air cap ground wire I was able to tune. Can anybody tell me what is up here??

        4. I wanted the ability to use various headphones and what not at the output. I took a 1/4″ gold plated headphone jack and soldered 3 wires to each of the sections on it. I then hot glued the jack onto my wood plaque for stability. I then connected the soldered wires to the circuit. Now I have a nice headphone jack I can plug 1/8″ plugs into….SO I took my jambox speaker and connected it to the headphone jack. Now I had a really nice loud powered speaker to hear with. This also really helped with tuning in stations. Without the speaker I had to run the circuit close to 9 volts to hear anything in the headphones.

        5. As P. Marian and Aleksandar said in a previous post I eliminated as many jumper wires as possible (especially in the RF section) and used some 22 awg solid wire to make my own small jumper wires. This really helped with the noise. My recommendation is to make short custom jumper wires for anything and everything if you make this on a breadboard like me. I’m still working on eliminating ALL non custom jumper wires from this circuit.

        Here are some photos of the work in progress:


      • Aleksandar says: on February 20, 2014 at 10:29 am

        Great work! See if you can record a youtube video and post the links for it with you tuning into stations and such. It would be great demo video. I think Marian should put your pictures and possibly video (if you upload it) right next to mine at the beginning of this article. Everyone should see how it should be done and in what ways things like this can be built. Once again, you’ve done a beautiful job building this circuit the proper way and doing tests and experiments and taking care of all the bits and pieces and “gotchas” on the way. Looking forward to hear more updates on your progress.

      • Thank you for the kind words and encouragement! I am planning on taking a video for sure. Just want to clean up a few more things. Good times!

      • StellarRat says: on June 24, 2015 at 2:40 am

        You can buy 10+ turn 10K wire wound pots from Digikey, BUT they are expensive! I’ve used them on several radio projects and they are very good for making fine adjustments to tuning and regeneration. Obviously, if it takes 10 full turns of the pot to work through the range you’ll have 10x as much fine control of your resistance value.

    95. Aleksandar, are you from Serbia or ex YU regione? Muzika je naša:)

    96. Aleksandar,

      This FM receiver circuit works properly, I’ve done one (my first one ever) few days ago.

      I’ve also read all the tread, and really astonished by your enthusiasm and the help you’ve kindly provided. Your posts was really helpful for me as well as for others.

      Photos: https://www.dropbox.com/sc/3nmm5du93iiucs7/5_zM9C1QFz
      Video: http://youtu.be/g2sNFVRBuCw

      I read that usage of air capacitor instead of ceramic one (VC1) is highly recommended for super-regenerative circuits, isn’t it? It will be nice to get your expert comments.

    97. Nicelly done on the build! Variable small pF air caps are good for vhf/uhf stuff cause they’re easy to make and they’re cheap. They’re great for manual tunning (if they’re variable that is :) ). You can very easily experiment with all types of caps to see what suits you best for your situation. For eg. if you needed a very small picofarad value cap you could make a gimmick capacitor out of two bendable telephone wires and just twist them together :) .. that’s probably the simplest capacitor that you can make and very low level caps are very often used in the vhf/uhf filters and oscillators and such.

      Here’s some examples about what I’m talking about regarding gimmick caps.

      Also you could try experimenting with variable screw type caps that are also very easy to build!


      And also variable cap made out of Al-foil and cardboard :)

      All are very great solutions for experimentation and I’ve personally had lots of fun building radio circuits using homemade variable capacitors, inductors and other components. LOTS OF FUN! 😀

      Check out the links and enjoy.

    98. Pošto smo iz Srbije možemo na srpskom:)? Nadam se da se ostali članovi neće ljutiti :). Početnik sam u radio tehnici, pa bi mi pomoć dobrodošla, ako imaš vremena i nerava za početnike:)..?

      • Aleksandar says: on March 23, 2014 at 9:51 am

        Aleksandar2, this is an English speaking website. So it’s not recomended that we speak in our native tongue here. What you should do is you should register here on this website and then you’ll be able to communicate with me here via private messages. And then all the questions that you might have you can ask me privately and I’ll do my best to answer them as accurate as I can.

        Aleksandar2, ovo je sajt na kome se govori iskljucivo engleski jezik. Stoga nije preporucljivo da pricamo na nasem jeziku ovde. Ono sto bi trebalo da uradis je da se registrujes ovde na sajtu i onda cemo moci da komuniciramo ovde preko privatnih poruka. Onda cu moci da ti odgovorim na bilo koje pitanje koje imas sto je tacnije moguce s moje strane.

    99. I’m sorry, I didn’t know the site rules about language. Thanks for the advice about it. In any case, I will be registered on site. Thanks for your patience Aleksandar:).

    100. absolutely fantastic for us beginners.
      I have made a number of radio circuits mostly not working but the making is the pleasure to me.
      I will be giving this one a go next.

      Thank you

    101. I have got all the bits together for this project but I was short of a 56k resistor so had to put two together and ended up with 56.4k.I hope this is close enough to work.Also I was short of a 470k resistor and ended up putting three together with a total of 468k.I have all the capacitors needed and a am/fm polyvaricon tuning capacitor,just got to figure out which two terminals to use for fm.
      I will probably build this circuit on a piece of wood as you have done but I also like the dead bug construction so may give this a go.
      I have wound the 8 turn coil and plan to use a plug in amp/speaker for the output.

      Looking forward to this one.
      Keep you posted on my progress.


    102. hey! whose not working plz contact

    103. Brother can you give me circuit schematic diagram for this

      • Aleksandar says: on May 16, 2014 at 2:10 am

        Sure, scroll up to the beginning of this page and then right click on the schematic and click “save image as”.

    104. Sorry for the Stupid question, I mean the PCB Layout for this circuit and also do tell me that Which Transistor I’ve to use from this list http://www.datasheetcatalog.com/datasheets_pdf/B/F/1/9/BF199.shtml

    105. And please can you provide me your any other contact,Where we can share more about this project, Because this project is much important for me, Can you give me your Facebook or Skype A/C name please
      Thanks :) :)

      • Aleksandar says: on May 20, 2014 at 1:04 am

        I don’t use Facebook nor Skype.
        I’m registered here on the site. You can send me private messages here if you register. I’d be happy to answer all your questions.

      • mudassir says: on May 20, 2014 at 11:38 am

        I’m registered now,I didn’t found option for sending private message here so,I replied here!
        Actually I’m working on FM SPY BUG RECEIVER PROJECT!!!,Which can fit in my Ear,I found this circuit to be done firstly and shift all of my components to SMD with the smallest Packages
        My question is
        1: I’ve three pin Variable capacitor VC1 value is 0-22pf, How can i use this instead of 2 pin VC.??
        2: I don’t find 5pf Variable capacitor VC2 in my Area, any other value which can replace this,

      • mudassir says: on May 20, 2014 at 12:01 pm

        And I’m using 10K potentiometer for VR1…

      • Aleksandar says: on May 20, 2014 at 2:04 pm

        I remember that there used to be an option for sending private messages. It looks that the admins might have changed/removed that options because now I can’t find it either. I’ll ask the admin about it.

      • Aleksandar says: on May 20, 2014 at 2:10 pm

        I just got a reponse from the admin. The option for sending private messages has been removed for some reason unfortunately. So, we can talk here I suppose. It’s better for more people to see our chats cause that way more people can jump in if they think they can help or share some ideas :)

      • Aleksandar says: on May 20, 2014 at 2:26 pm

        mudassir, I’ve never seen anyone attempt building this project as a small receiver the size of an ear plug. It most certainly would be an interesting project. As for PCB, I could try designing it for you. But you need to give me the exact specs for the parts you intend to use. Me personally I’d use double sided pcb. I think it can be done. But the only problem is how we’d fit the antenna inside. If it were on higher frequency .. small printed loop antenna would do. One more thing, this is a VHF REGEN receiver which means that it’s insanely sensitive to body capacitances and loads of other stuff, it’s difficult to use it even in normal size let alone smd ear plug size.

        Now when I think about it I think your best bet would be to use an IC like TDA7010T instead of this regen project. TDA7010T is basically the entire receiver, you just need to add couple of capacitors and inductors and you’re done. And it’s much more stable since it’s an industry standard IC. I think it would be perfect if you did it like that. I’d like to hear from others what they think about it. It’s a really interesting idea.

    106. Alexzandar, Yes Sir.! That’s what I’m too thinking about,Let us do Chat here so that other peoples would understand & respond with better Ideas

    107. TDA7010T is Little big which can fit in the ear,and with it we’ve to give some capacitor and resistors along with it Ofcourse it should be double sided PCB, but the size of TDA7010T is not suitable! Instead I’ve planned to amplify the sound with BC847 NPN Transistor from NXP (SOT883), Which is the smallest Transistor known if I’m not wrong,And Instead of BF199 We can use BF799 (SOT23) and all the resistors & other local components should be in 0201 Packages
      And if we talk about the battery we can use DOT battery, Which the size of 3mm in diameter and 2mm of height Which can provide 1.5V

    108. BC847AM I mean

      • Aleksandar says: on May 20, 2014 at 10:37 pm

        You could leave out the sound amplification if you use a small piezo speaker for the ear bud. Piezo speakers are very high impedance and are super sensitive. So you could theoretically build the entire radio with just two transistors .. maybe even one. It’s highly debatable and needs to be tested. I think that it would be a good idea if admin made a new “folder” for this topic. SMD ear bud size radio receiver. :)
        Also the capacitors and the coils for the resonance tank could be printed onto the PCB itself on some fixed frequency.

    109. Yeah that’s a good Idea if admin started a new forum on this project.! It will be glad if you talk with him about this. :)

    110. Sir ,Alex I’ve builded the circuit of this page and its working well,But the problem is the sound is much cracky and How can i tune to the different station, If i Shake the wire of my Headphone the station is changing it self.
      And do tell me how can i set one station for permanently.

      • Aleksandar says: on May 21, 2014 at 7:27 pm

        The reason why sound is “cracky” and why the radio is so unstable is because it’s regenerative and this particular one is very low tech. You cannot expect high quality sound from it because it relies on the envelope demodulation technique for FM demodulation. The point of this project was to allow beginners build it hence the simplicity of the circuit as you can see on the schematic. In order to fix “random changes of stations” you need to use short connections everywhere (including long headphone wires) as much as possible because it’s a VHF circuit. One long connection can act as a tank circuit and an antenna and everything else and can ruin your day. The best solution is to build it in some kind of grounded box with an speaker audio amplifier. And let it sit on the table somewhere and listen to the stations. I built mine on the wood plank as you can see on the video and pictures that I posted before. I built this just for fun cause I had some junk parts laying around. Always a fun to build something.

    111. Ohh i see, it’s unstable due to Regenerative.!!!, How could i make this more stable and fix to one particular Station or frequency i need

    112. I mean how can i make this circuit into Super Regenerative.?

      • Aleksandar says: on May 21, 2014 at 9:19 pm

        I think this is already a super regenerative design because performance is outstanding for one transistor receiver .. especially for VHF. The RF amplification is very good. As for fixed frequency all you have to do is pick a frequency and then calculate fixed values for the capacitor and inductor that make up a tank circuit. You put fixed value components instead of that variable capacitor.
        I already described this in earlier posts, scroll up and read. I posted a link to an online calculator and couple of formulas for calculating the values in those posts.

      • Aleksandar says: on May 21, 2014 at 9:21 pm

        Of course I’m referring to the RF part of the circuit when I say one transistor receiver.

    113. I can hear lots of noises and crackling sound while listening to some of the station,Should i use any Op-Amp in the circuit like Lm386,.??? What is the euivalent for BF199 in SMD.??I Found BF799 in SOT-23 Package, Is this gonna work.??,I’ve planned to make it on PCB and with as much as small and use of Piezo speaker!!!!
      And about fixed frequency and station, You’re right!!! I should try as you’ve told me 😉
      I’ll do it by tomorrow, It’s time for Bed now :) :)

      • Aleksandar says: on May 21, 2014 at 10:43 pm

        I don’t have much experience with SMD components so I can’t help you much there. If the transistor you selected has similar or same characteristics like the through hole version then it should work. As for Audio amplification I personally would go for an op amp. It’s like my personal preference. You know, this receiver would do wonderful job at receving AM modulation imho. It doesn’t have to be FM. If you wanna receive a signal from some transmitter you could just build an AM transmitter (which is super easy) and go with that. You’d have much clearer sound in that case.

    114. I can make a transmitter ,But the problem is receiver is not much stable and not fixing to particular frequency,I’ve to keep holding my screwdriver on 5pf VC, and keep my hand on antenna to fix to one station, If i release my screwdriver and my hand its moving to another frequency & to another station, it’s quite irritating,
      Between I’m using a 3 inch insulated wire for antenna and a Alligator clip test lead which came with my Multimeter, Is this is reason I can’t able to receive proper signals/.??

    115. And about Bf799 is quite similar to Bf199 but the VCEO,VCES,VBEO, Frequency is around 800Mhz

    116. Or i should use any Antenna Booster Circuit./??

      • Aleksandar says: on May 22, 2014 at 4:05 pm

        The receiver is not stable because it’s a regen. It’s too simple. If you want stability you’d be better of with a superheterodyne instead which is a little more complicated but a lot more stable then regen. Or you could just simply try isolating antenna, and other leads as well as putting it inside a box and taking care of parasitic capacitances by grounding it and adding a small balun transformer for the antenna.

    117. Superheterodyne.?? Sir can you tell me what is the Difference between, Regenerative,Super Regenerative,Heterodyne,Superhetereodyne and other FM’s.??

    118. But, Regen = Easy Design
      Superheterodyne = Much Complicated Design .??

    119. Regen < Superhet when compare with stability and good sound Quality .??

      • Aleksandar says: on May 23, 2014 at 7:21 pm

        Yeah, superhet is better then regen regarding stability and sound quality. However stability mostly depends on how the device is built. If you build it on a pcb with supershort paths it will be very stable in that case. Also everything needs to be isolated and put inside the metal box that would be tied to ground. At least the tuning part and the oscilator part should be put inside the metal box. Google radio building guides and gotchas, you can find a lot on that subject. Ham radio operators that’ve been building their rigs for years know this stuff very well, you can send them messages and ask them for specifics. I myself am also new to building radio circuits. I’m an IT and Electronics engineer who specializes in digital systems. So I haven’t had the chance to play with radio and analogue electronics much. Everything that I do as my daily routine is all digital electronics, microcontrollers and processors, programming and that sort of thing :) I recently also obtained a ham radio licence and a radio and got involved in it a bit so I plan on building some stuff in the future and maybe I’ll post my projects here.

    120. I builded your given circuit on BreadBoard with much wires :/ :/ :/ and I didn’t got 5Pf VC in my market so i diveded its capaitance by giving some pfs in Series and came near to 5P value, and i used the Long wire Headphone too :/ :/ :/,
      I know that you will blame me.. : /:/ :/
      But Insha’Allah I’ll build this circuit on smallest Home Made PCB in next day :) :)

      • Aleksandar says: on May 23, 2014 at 10:46 pm

        Oh no no, I’m not blaming you .. It’s a good thing that you did it like that, because you wouldn’t learned it the proper way otherwise. You see in electronics you have to make mistakes sometimes in order to learn. Get it? Learn from your mistakes. All those tiny little things that make your circuit NOT working is what you’ll know next time and that’s what makes the learning experience so great. You can build it on a breadboard to be stable too, you just have to use as short wires as physically possible. Breadboards aren’t the best for VHF circuits because they have very high parasitic capacitances but still it can be done. It’s all about experimenting and testing things. It’s fun :) I personally enjoy it very much. I like building things to test and experiment.

    121. Thank you Sir, :) :)
      Can you give me some Superhet FM Radio Circuit Diagrams..
      And do tell me What if i want a Fm to be tuned above 108Mhz and below 87Mhz

    122. Look Alex Our conversation is going longer here.!! ^_^ Thus i told you give me your alternate contact A/C name :/ :/

      • Aleksandar says: on June 1, 2014 at 12:35 pm

        mudassir, my e-mail address is aleksandar dot electronics at gmail dot com. Make sure you put a subject “electroschematics.com” if you send me a message, otherwise I won’t notice it.

    123. Audio transformers and radio frequency chokes have always been problem factors for hobbiest and radio enthusiasts since they are not easily available. Calculating the values is also a cumbersome task and hence projects having these components are generally avoided. Sometimes their value are very critical and sometimes not. It seem RF Choke used in this project is not very critical as it is used here to restrict the radio frquencies from getting lost to AF stage. If this is so, please tell in simple layman’s terms how many number of turns of thin enammed copper wire should one wind over a plastic 10 to 15mm long with 4mm dia former ( ball pen refill ) to obtain approximate value of 1mH, 5mH and 10mH? I am sure this information will be useful to many not just for this project but for other projects too. Thanks.

    124. I have built this circuit (cannot find BF199 so used SS9018 instead) and I seem to have trouble getting it working. I adjust VR1 to just before the oscillations get audible, but I hear many different stations and adjusting the trim caps (VC1 and VC2) does not tune the receiver, like it has a fixed tuning frequency and very poor selectivity.
      Could you suggest what could be going wrong in my build as I am not familiar with the way a superregenerative receiver works?

    125. L 1
      Several rounds?
      Multi-mili wire?

    126. This circuit is Wonderful and amazing says: on November 21, 2014 at 7:36 pm

      I have built this circuit and it is working. The little two circuits on the picture is the transceiver operating at 27 MHz. I used 5 W amplifier to further increase the signal power since it was attenuated due to geographical area. Remember the FM signals are line of sight therefore buildings blocks the signal.

    127. dear sir,what is the value of l1 inductor

      • Dear Niraj, The L1 inductor is basically in micro-henry (uH). The inductor can though fluctuates as the core is air. when i measured my inductor it was between 1uH to 4uH. I would advice if the inductor is not picking up any frequency, try inserting the screw drive or a ferrite magnetic material (rod) as a core. The is no exact or stable value for that inductor, once you touch it…the frequency changes.

    128. sir what is the equivalent transistor of bf 199 ?

    129. What are the values for TR1, TR2, TR3 and TR4? or they dont really matter? please reply asap

    130. hi
      can i use speker instead of headphone?

    131. NO, U can’t…

      u must be amplifying the Output Of Sound Signal And Then Connect to SpK


      therefore i think , u need an ic that Amplify ….

      u can Use LM386 for Student’s Circuitssss :)))))))))))))

    132. Hi,
      I need your help to build a fm receiver circuit.
      I am living in mysore and I want to catch all fm stations of bangalore which is 140 km from Mysore.
      Mysore also having some fm stations. But I want Bangalore fm reception.
      Please help me. I will be thankful to you.

    133. How much power does this circuit comsume? Can I design a low power fm circuit by modifying it? Cause I need a fm receiver working around 50 mW, but small output power is OK. Low but listenable audio for small headphones will be enough.

    134. Hello Aleksandar, does this circuit really work?
      Because I´ve build it, there is nothing in short I have Colletor Emitter Voltage in all transistors and the same with Base Emitter.
      All I can hear is hissing noise.

      Please Help me.

      • Im using a breadboard and 64ohm speaker

      • Aleksandar says: on March 2, 2015 at 8:12 am

        Hissing means that the circuit is working (probably oscillating). Now, what you need to do is play with the regeneration control until the regenerative circuit stops oscillating and picks up a station. Tuning this radio is done with regeneration control and variable capacitor at the same time. First you adjust regeneration control on the edge of the oscillation (hissing changes/stops or reduces in volume) and then you try to find a station .. and if it’s bad audio signal you try to adjust the regeneration control some more until you get it “perfect”. It’s all about fiddling and tinkering. You’ll get it working I’m sure of it.

      • Aleksandar says: on March 2, 2015 at 8:15 am

        also try using headphones/earphones instead of speakers, because it will give you a better volume without an amplifier. Using just speakers on their own is not recommended because the amplification is not good enough. You’ll get a very low volume. Either use headphones/earphones or an additional amplifier with a speaker (perhaps a PC amplified speaker).

      • also for L2 i´ve used a encapsulated inductor with 2.2uH, does this matter?

      • Aleksandar says: on March 3, 2015 at 7:29 am

        2.2uH for L2 is exactly what’s on a schematic. When I was building my radio I just picked a random RF choke of unknown value.. and it worked with it. So obviously it’s not that important for L2 to be THAT exact value. But since you got one, it’s fine. VC1, VC2, L and VR1 are the components with values that should be adjusted in case you’re having trouble making it work. VC1, VC2 and L is the tank circuit which dictates which frequency the radio is receiving and VR1 is the regeneration control.

      • could the problem being my local radio stations?
        I´ve been using a normal radio and I can listening radio stations with no problem.
        Maybe this radio has low sensibility… I don´t know

      • Aleksandar says: on March 4, 2015 at 8:30 am

        Try changing the values in the tank circuit. In my case my build came out pretty sensitive, could receive even the remote stations pretty good.

    135. I make this circuit on bread board. At turning on and off, it shows noise. Otherwise it is completely silent. What should i do ?

    136. When i vary the VR1, after some displacement i listen a whistle for a moment…. What should i do ?

    137. is dit met een rekenmachine gefilmd

    138. Here are some suggestions for future improvements if you want to experiment. I think using a couple of varactors and small pots to tune the radio would make the circuit more user friendly. It will eliminate a lot of hands/tools capacitance problems and make the radio far less “touchy” to tune. You’ll need to change your circuit to run on 9v to do this. You can still run the RF on 1.5v by using 1.5v voltage regular IC. You can eliminate all of the audio amp transistors with an LM386 IC and get a lot more volume, probably enough to drive a small speaker. Alternately, a high speed OP AMP could be used if you want to just run headphones with a high sound quality, OPA227 maybe?.)

    139. Shelton Burrup says: on July 9, 2015 at 10:40 pm

      Next time I read a blog, Hopefully it won’t fail me just as much as this particular one. I mean, Yes, it was my choice to read, but I genuinely thought you’d have something helpful to say. All I hear is a bunch of complaining about something you could possibly fix if you weren’t too busy searching for attention.


    140. I appear to be a couple years late with this post but I am building this circuit. I am struggling to understand the variable capacitors. I have read and reread the comments. I understand how to use them as far as tuning but as far as why we are using two and their ranges are kind of confusing me. I have all the components required except for VC1 and VC2. I can purchase a 5 pF to 108 pF or 5 pF to 68 pF and a bunch of other variations. Is the range critical as long as it gets down to 5 pF?

      In a comment earlier you mention that theoretically its equivalent to a 25 pF capacitor. Can i just get that instead? I love to tinker and plan on doing so but obviously the tuning circuit has to work so i wanted to stick to the planning.

      I look forward to your response, any help/direction would be much appreciated. And if it is easier, I can provide my email for more efficient communication. Thank you for your time and consideration of this issue.

      • Aleksandar says: on July 21, 2015 at 4:22 am

        5 pF to 68 pF sounds about right.
        Here’s the thing.
        VC1 and VC2 are both part of the LC tank circuit that allows you to change/set frequency of the radio.

        VC1 for eg. can be the MAIN tunning capacitor while VC2 would be FINE TUNE capacitor.

        So for eg. VC1 could be 5-68pF while VC2 could be something smaller. You could use larger value variable capacitors in series with small fixed value to get a small value variable capacitor.

        Use the Thompson formula to calculate the LC circuit frequency and use the Parallel and Series capacitor connections formula to calculate the possible values of capacitors using different combinations of values to get what you need. You might have the appropriate part in your junkbox without even knowing it.

        Happy tinkering :)

    141. Thank so much for the response. So if I understand correctly, if I were to get say a 5pF – 322pF and a 3.6pF – 68pF it just widens the range of frequencies I can tune the resonance to? Because I was thinking about having the L1 specified for FM and then putting in a switch that could change the path to a different coil in parallel to L1 for AM or some other range. So depending on what I wanted, I could toggle between them with a switch at the node between L1,C1, and C2?

      • Aleksandar says: on July 22, 2015 at 10:00 am

        5pF – 322pF and a 3.6pF – 68pF in parallel would add up making a single variable capacitor in which you’d use the larger one for main tuning and the smaller one for fine tunning. Yeah basically you can expand the frequency range or shift the frequency band. Band switching with the switch between the coils in the tank circuit should work. imho your logic is sound :) Try it, test it, document it and post it here so we can see what you’ve done. Pics and videos would be nice. Make a demonstration video or something like that :)

    142. It works! :)
      Have a great time constructing this one. Here is my video contribution: https://www.youtube.com/watch?v=6c4zOPvlZvQ
      Cheers! Greets from Serbia 😉

    143. How do I tune it to receive signals before 87 MHz ?

    144. You should be able to adjust VC2, the high-pass filter (rectifies low-frequency signals and allows high ones to pass), to allow lower frequencies through. For example, a 100pF capacitor used with a 32-ohm resistor passes frequencies higher than ~50MHz. This http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php calculator makes figuring out filters easy.
      In other words, maybe try a higher value for VC2. I hope that helped.

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