Sputnik Regenerative Receiver – SSB, CW ,AM, FM

The Sputnik regenerative receiver was designed for the 40m amateur radio band, the perfect project for beginners in homebrew radio receivers.
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Sputnik regenerative receiver has decent receiving capabilities. It’s a simple regenerative receiver for AM, SSB, CW, FM. It was designed for the 40m amateur radio band. It can be adapted to other HF bands as well. It works great on 80m, 40m and 20m as tested by me. It was designed for beginners to help them improve their knowledge in building radio receivers.

THE SCHEMATIC

If you wonder why the receiver it’s called Sputnik, the explanation is somehow simple and also funny. Because of the way the propagation works, after building the very first versions all I’ve heard during the day time were the Russian amateur radio operators. Since I’m a fan of the vintage space era, knowing that Sputnik was the first Russian satellite launched, I decided to call the receiver the same way.

With ought any intention, for some reason it became somehow popular around the world. Different older versions of the receiver are popular on a QRP Forum in Germany and the SolderSmoke BlogCalifornia QRP Club also asked the permission to use it for a kit build, with slight modifications by John Sutter K6JDS. It had some nice words from Peter Parker VK3YE on his Facebook Page. I have loads of emails and photos from the subscribers to the YouTube channel that also built the Sputnik regenerative receiver.

Down bellow you have the latest schematic design. This is the final update as I will no longer make any updates. I wanted a receiver as small and as simple as possible, but with decent performance. To keep it simple and small I did not used an audio preamplifier, but the audio output is good enough for a small speaker or headphones. If outdoors, the speaker is not so loud so headphones are better.

SPUTNIK REGENERATIVE RECEIVER SCHEMATIC

I decided not to use a voltage regulator, as it doesn’t help much when using batteries. If the voltage drops under 12v, the LM386 IC will end up creating that ugly “motorboat” sound. To improve stability in frequency I used D4 9.1v Zener diode. If you want to improve the frequency drift even more, you can use a variable capacitor instead of the diode tuning. This will improve the stability of the receiver even more. I would recommend a variable capacitor with some sort of reduction drive.

I also decided to get rid of all sorts of filters that I used in some of the older versions. There is no more bandpass filter on the input. I tried to get rid of the AM broadcast band interferences by testing the audio amplifier in all sort of configurations. There is no more CW audio filter either. Instead I opted for a sound that makes both CW and SSB signals sound good. This way the schematic is very much simplified.

RF COIL DESIGN

You can build the receiver using a PVC pipe as RF coil form, or a toroid. The terminal marked 1 is the beginning of the coil and the terminal 2 is the end of the coil. L3 is the pickup coil for the external frequency meter if you want to use one. L3 is optional if you want to keep it simple. There is no preamplifier circuit for the pickup coil, so if your frequency counter doesn’t have one, you may have to build a preamplifier for it.

To calculate inductances if you want to use a toroid, I would recommend toroids.info website. If you decide to build the coil on a PVC pipe as I prefer, then you can use Coil32 Software to calculate the desired inductance and also the resonant frequency. There should be a balance between the LC circuit capacitors and the inductance of the coil to have the receiver very stable in frequency. If you go to high with the inductance and too low with the capacitance, the receiver will drift a lot.

Even though a higher inductance allowed me to tune the entire 300Hz on the 80m band with only two 1N4001 diodes. Using a varactor diode will help you have more capacitance swing. That will allow you to have smaller inductances in the coils and more stability in frequency. It’s up to you to experiment. Down bellow you have the RF coil details for the 40m amateur radio band. You can also calculate it for other HF bands as well. I tested it from 80m up to 15m and it works great. I will also put the inductance of L2 down bellow, as that is the only one that matters for each band. When I have time for more tests I will update the info for other bands as well.

RF COIL DETAILS - PVC VERSION

L3 has 3 turns / 0.4mm.

RF COIL DETAILS - T50-2 TOROID VERSION

L3 has 1 turn / 0.4mm.

Play Video about How To Quickly Calculate Inductors And Resonant Circuits

When I started playing around with receivers schematics, I did not know how to calculate the circuits to resonate on the frequencies I wanted. I learned the hard way and at first I discovered how to do it by trial on error. Later I discovered that using some really simple online calculators, can save me a lot of time and also enameled copper wire.

PCB DESIGN AND PARTS LAYOUT

Here you have the PCB design and also the parts layout of the Sputnik regenerative receiver . I’m not a master in PCB design, but I did my best to keep it as small as possible. The “Print This” PDF file found in the downloaded folder contains a print for two PCB boards of the receiver ( PCB Design and Parts Layout ). Just in case you mess up one board, you have an extra print to repeat the process. I may improve the board design in the future, so on the PCBWay Shred Projects I will always have the latest version. I try to design the boards both for ordering from PCBWay and also for homebrewing using the toner transfer method.

SPUTNIK REGENERATIVE RECEIVER PCB BOARD

RF ATTENUATOR

The RF attenuator will help you to adjust the signal level entering the receiver. It will also stop the RF generated by the regeneration stage of the receiver leak back into the antenna. This RF attenuator stage was borrowed from another regenerative receiver designed by N1TEV. This is not an RF preamplifier as many people think. It does amplify the signal but only a little. Is nothing but a buffer stage.

REGENERATIVE RECEIVER STAGE

This is a simple regenerative stage. The level of regeneration it’s adjusted using the 10K regeneration potentiometer. I wanted to bring the receiver to a stage where the regeneration control is really smooth and easy to use. It can also be used as fine tuning. Some people like using a 10K multiturn potentiometer instead.

For a good stability in frequency C11, C12 C13 and C16 should be the NP0 type capacitors. If you have too much capacitance, or not enough and you can’t get the receiver into the desired band, you can either increase or decrease the value of C16.  For C16 you have two spots on the PCB board ( A and B ). This is in case you want to split the value of the capacitor in two. Using two 47pF capacitors instead of a single 100pF capacitor, will help a little in frequency stability. 

With the help of the trimmer capacitor C15, set the receiver in the higher part of the band ( ex 7.2MHZ ), with the multi turn potentiometer all the way at the end. Then with the help of the 10K trimmer resistor, set the receiver at the beginning of the band ( ex 7.00MHz ), with the multi turn potentiometer all the way at the beginning. Or if you want you can simply set the receiver just for the CW or the SSB part of the band.

DIODE TUNING

The diode tuning was used in the design to replace the variable capacitor. These days is hard to get your hands on a good variable capacitor. If you do have a variable capacitor, replace the diode tuning with the variable capacitor as the receiver is more stable and there is no frequency drift when the battery goes low. With the two 1N4001 diodes I can cover the entire 40m band. One of the reasons I used regular diodes instead of varactor diodes, is that they are really easy to find. If you want you can replace them with BB405 or similar.

The diode tuning stage is formed from multi turn 10K potentiometer, the 10K trimmer resistor, C13, C14, D2, D3, and R8. If you want to replace the diode tuning with a variable capacitor, you can connect it in the spot designed for C13. Replace D2 with a jumper wire. The value of the variable capacitor should be at least 20pF. The trimmer resistor has holes so you can fit either a 12mm or a 6mm trimmer resistor, depending on what you have available.

AUDIO AMPLIFIER

Initially the intention was to use an audio amplifier based on transistors only. The LM386 amplifier can be anytime replaced with another audio stage if you want to. I wanted to use the LM386 because of it’s simplicity and because the IC it’s easy to find. The receiver presented here does not include an audio preamplifier, but the audio level on the output is strong enough to power headphones. Is also good enough for a speaker if listening in a quiet room. Not loud enough if listening outdoors. Try using a larger speaker as it gives a better sound.

POWER INPUT

This is a simple stage powered by 12v for the LM386 audio amplifier and 9.5v for the regenerative receiver stage, RF preamplifier and the diode tuning stage. R3 it’s used to lower the voltage to about 9.5V. C7 is used to filter the voltage for the 9.5v stages. The voltage is slightly stabilized by the Zener Diode D4, to 9.1v.

MORE ABOUT ON THE RECEIVER

The receiver in the video was built based on the first schematic designs I tested, trying all sort of configurations. Here in this video you have a little more info and details on the receiver.

Play Video about Sputnik Regenerative Receiver - 40m Band

ORIGINAL VIDEO

This was the first modified version of the receiver. At the same time, my very first video on the YouTube channel. I am happy that I learned a lot thanks to this receiver and happy the way it turned out.

Play Video about Simple Regenerative Receiver

BUILDING TIPS

If you decide to build it Manhattan style or dead bug style, try to keep the connections between parts as short as possible. Built well with attention to detail it can end up as a really nice receiver. As a radio receiver project, it could be better. I tried keeping it simple for beginners. It was also designed as a portable receiver with a minimum battery consumption. Also using a variable capacitor instead of diode tuning ( one with a reduction drive ), can make the receiver even more stable. I hope you like it and you have success in building it.

73 DE YO6DXE

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34 Comments

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  1. Great jobs!
    I built a regenerative radis designed by N1TEV.
    I want to add a frequency display.
    Could you tell me the detail of your frequency display?
    Thanks!

    • I have built a Sputnik Regenerative Receiver. I add a pre-amlifier using 9018 transistor before frequency counter.
      The frequency counter display successfully.
      Thanks for your awesome design.

    • Ciao Giancarlo. Finora non ho provato alcun circuito squelch. Non ero davvero interessato a questo. Adesso però mi hai incuriosito e probabilmente proverò a cercare qualcosa. Spero solo di non dimenticare che ho tanto lavoro (ah). Nel caso in cui non mostrassi più segni ricordamelo per favore.

      73, YO6DXE

  2. Good morning from Mario
    I ask if it is possible to have 5–10 pieces of the printed circuit of the excellent super regenerative RX Sputnik, I would not like to build it on a millefore hi..; of course I will pay the correct cost requested via PayPal. mbeelettronica@libero.it
    In the meantime I congratulate you on the excellent achievement and thank you,
    73 by i2mbe Mario

  3. Hi, Ciprian… Love the progress of your business in the DX experiments and project! Bravo…

    Do I miss the dimensions of the Sputnik PCB board? Many thanks for the schematics and PCB layout you’ve sent by email long time ago. ????????????????️✨

    Success to you…
    73

    YD2UBK

    • Good morning from Transylvania. Thank you so much. I should have a little more time soon both for projects and also to update the blog. The dimensions of the PCB board… I am not at home now, but if I remember well, when you download the files folder in the txt info file usually I put the dimensions of the PCB if the circuit has a PCB design. Have a look there if not let me know so I can update the file. I don’t have access to the computer now to check.
      73, YO6DXE

  4. Hi,
    A friend of mine sent me a layer file called Sputnik-40_ReWork_Ghost_D_2021. I made the circuit but it didn’t work. I need the schematic. I couldn’t find this on your pages. It says dxexplorer.com on the top silk layer. Is this one of your projects? I would be happy if you inform me. Best wishes.
    Ali

    • Hi Ali, can you send me an email when you have the time ? Send me a photo of what you have so I know what version it is. I used to have the Sputnik 40 as an older version but meanwhile I simplified the circuit so is easy to be built by beginners. I no longer have the schematic but if I see the PCB I will tell you what to do and draw you a quick schematic.
      73, YO6DXE.

  5. I built the printed circuit board and built the sputnik reaction receiver,but it doesn’t work .By adjusting the reaction subtend a very weak and very critical trigger.What can I do? How can I send you a picture?.Thanks
    Julian

  6. Ciprian
    Very nice blog!!!
    I have just completed the Sputnik Regenerative Receiver. Excellent project and very well documented on the blog. It worked perfectly in the range from 7000 to 7250 kHz. From Buenos Aires (Argentina) I can receive amateur radio stations from Argentina, Brazil and Uruguay in SSB and AM. I have picked up China Radio International (AM) very well. Thank you very much for publishing this project, I have really enjoyed studying the documentation and construction. On my QRZ page you can find some photos.
    I ask you please if you can publish (or send me) two things: i) some good explanation of how the regenerative receiver extracts the “envelope” from the AM signal. I have searched on the Internet but I have not found a clear explanation and ii) the calculation of the resonance frequency of the circuit so that it can be developed for other bands.
    Thank you very much and congratulations for the blog.
    Daniel (LU1BDR)

    • Hi Daniel. Than you so much for the nice words. I am happy that you like it, as I also like this receiver and is really close to my heart. On the info request you made… I have a little bit of some crazy work related days, but I will send you an email as soon as I have a little free time to give you the proper info you need.
      73, YO6DXE

  7. Hola, buenos días.

    Si no me equivoco te compré el kit de componentes, necesito el pcb si me lo envías, te lo agradecería porque no puedo comprarlo en la web. Quería saber si había alguna manera de vender mi juego completamente ensamblado. Te lo agradecería mucho ya que no soy bueno soldando.

    Te felicito por lo que haces, nos das alegría. Me despido con un abrazo y gracias chau.

    • Hola José.

      El kit de componentes de eBay lo vende Graham, el propietario de la tienda eBay, no yo. Me pidió permiso si puede vender el kit de componentes. La página de mi tienda aquí en el sitio web aún no está lista. Sólo abriré la tienda a finales de Diciembre. El kit completo con los componentes soldados está disponible en PCBWay y cuesta alrededor de $40 con la opción de envío más económica. Creo que recibirías 4 placas PCB vacías y una completamente instalada: ( debes hacer clic en PCB + Ensamblaje ). Si no tiene prisa, colocaré algunas placas PCB en la página de la tienda aquí en dxexplorer.com antes de Navidad. No puedo vender kits completamente instalados, pero al menos obtienes la placa PCB.

      Seguimos en contacto, haré todo lo posible para ayudarte.
      73, YO6DXE

  8. Hello, will it be possible to buy a set of components again, the current one is already sold out on ebay, thanks for your reply…

    • Hi Lubor. The kit on eBay is sold by Graham not by me. I will email Graham and try to find out if there will me more available ( I will get back to you if I hear anything ). I have no connection with the kit, but he was really nice and asked for permission if he can sell it. I will also have some kits available here in the shop but only at the end of January. 73, YO6DXE

  9. Hello Ciprian, one detail: you say in the video that C4, C6, C9 should be Mylar capacitor but these show up as ceramic in the BOM. Did you change your mind? This is a nice project, thank you for posting!

    • Hi George. Yes is the BOM there are just ceramic capacitors. The Mylar ones are optional for those that want a little more quality sound. The difference in performance is not big, but to my ear Mylar ones make it sound better. I put ceramic ones in the BOM to keep things simple for everyone.

  10. Dear Friend. Thank you very much for answering my questions about the differences between the PCB and the schematic. Thank you.
    I have two other questions that I would like to ask you.
    The first question is: I have a frequency meter exactly like yours, but the signal generated by coil L3 does not have enough voltage to activate the input of said frequency meter. Do you use any amplifier to activate the frequency meter? Can you tell me how to do it? Adjusting it with an oscilloscope is not possible for me, since I don’t have a digital one.
    My second question: what is the antenna you use? Do you use a 40 m cable? I don’t pick up any stations. Maybe in my residence, in the north of Spain, it is not possible to tune in to any station in said 40m band.
    Forgive my ignorance, radio was never a field of interest to me. A friend of mine says that he believes that there are no stations that broadcast in that band. The truth is that I don’t receive any signal, although I haven’t finished testing yet.
    By the way, I have made the PVC type coil that you indicate in your videos.
    Thank you very much for your work and excuse my ignorance.
    Gracias

    • Good morning Mariano. Regarding the frequency meter, I will email you a link to a video that shows you how to modify it in order to be able to measure weak signals. Basically it transforms the crystal tester into a pre-amplifier. So the crystal tester will no longer work since is now a pre-amplifier only. On the antenna part, I used a simple six to eight meters wire hanging around the ceiling in my room at first, but the signals were not so strong. Then I installed a longer wire outside… about twelve meters of wire. Much better signal this way. Of course later on I built a proper EFHW antenna and the signal is great now. The problem in the city is that using a simple antenna like a random wire hanging in the balcony doesn’t seem to do the job well. I guess is because there are many interferences as well. I noticed this as well when trying to use it in my sister’s apartment and the signal was really weak. I also tested the tr(u)SDX with the same results. But usually in the evening the signals got stronger. I will email you something else that maybe it would be helpful to you.
      73, YO6DXE

  11. Dear Friend. I think there is an error in your printed circuit that I purchased from PCBway. Coil L1 must be located between the collector and the base of Q1. Likewise, the base is also connected to R9, through which it receives power, as seen in the diagram. In your PCB design one end of L1 goes to the collector, but the other end is connected directly to the voltage of 9.1 V. Please tell me if the schematic or the PCB is wrong.

    Gracias

    • Hi Mariano. Yes I forgot to update the schematic after I updated the PCB design. But it works no worries. I either have to move the resistor in the schematic same as it is in the PCB design, or the other way around. Thanks for reminding me about it. I totally forgot ( ha ). Too much work to do. I want to update the PCB design as I had a request to ad one more hole for the trimmer resistor, so I guess I will just move the resistor back where it was just as in the schematic. 73 my friend. Let me know how it turns out.

  12. Looking in the schematic I can see two voltages:
    One is 12 volts and the other is 9.5 volts
    Also another point with arrow with arrow but not the word (to 9.5 volts)

    My concerns are:
    1)
    The one that not says “to” ins a point of control? (I mean if you measure
    with tester that piont must indicate 9.5 volts? or must be connected to 9.5 volts?

    2) If I use the same power source of rectificated CC 12 volts, could I reduce it
    somehow to obtain 9.5 volts or is convenient use 2 regulated sources?

    3) I am very interested i connecting a frequencimeter, how do you connect it
    and where to find?

    I suppose I got several other questions for the future but this three are Ok for now

    regards
    Ruben (LU8ARM)

    • Good day Ruben… if you build the receiver using the PCB design that you can make for now using the toner transfer method…. you really don’t have to bother with all that it is in the schematic. But… in case you build it from scratch, the reason why the receiver part works on 9v approximate and the audio amp on 12v is to avoid having the LM386 going into oscillation as it often happens. So is really important that the receiver will always work on 9v’ish and the audio amp on 12v. Of course if on battery the voltage will go low slowly, so when you hear the receiver making some ugly sound, is time to replace the battery.

      About the schematic…. because I wanted to avoid drawing some long lines, is the reason you have the arrow with +9.5v and the other two with “to +9.5v”. So basically there two points get connected to the arrow saying +9.5v. To use a frequency counter, you just connect one where is written “count”. L3 is the pickup coil for the frequency counter. Now it depends of the model you want to use. Some work with no issues other may need a little pre-amp in order to work well. One that I really like is THIS ONE. No need to buy it from there is just for you to see the model. That one you just connect to count” and it works like a charm ( of course you also have to power it haha ). Let me know if you need anything else.
      73, YO6DXE

    • Hi Gary… I’ve been playing around with Eagle this week trying to learn it so I can re-design all the circuits on the blog. This coming week I will post the latest and last video about the Sputnik… and I will give some more details in the video as well. This one will be the first on the list to create the project files as a lot of people requested this. I will try to do it as fast as I can. I will email you when is up on the blog. Have an amazing weekend.
      73, YO6DXE

  13. Bună seara! În schema postată aici, L5 are valoarea de 100 milihenry sau 100 microhenry?
    Mulțumesc mult!