A High Performance Regenerative Radio

I have built countless regenerative radio circuits throughout the years and some have worked well – some haven’t. I was inspired by the circuit design of the TEN TEC regenerative radio kit. I used some of the same ideas, but changed the design to better match my design criteria. In this  design, I had eight important design objectives:

Simplicity – this type of radio should not be complicated and I have seen designs on the web that may perform well, but seem unnecessarily complicated.

Tuning/fine tuning – I use a cheap poly variable for main tuning and a junk box rectifier as varactor for fine tuning.

No special inductor required – I have tried all sorts of junk box inductors and they all work great. With this design, no tapped coils or tickler windings are required. This design could easily be made into a multi-band radio

Extremely smooth and stable Regeneration control – I adjust a DC bias point condition instead of RF Feedback to control regeneration and the performance is excellent. There is no hysteresis or abrupt transition from regeneration to oscillation.

Ample Audio Gain with no motorboating or instability – I stayed away from the LM386(which could be used) and chose a TPA301 amplifier IC – which give excellent results.

Antenna Isolation – This is achieved with a simple grounded gate input stage which shares the LC tank with the oscillator.

Excellent sensitivity – This design is the best performing Regen I have ever built

No critical adjustments and easily repeatable results – I have built this circuit now three times with different inductors, for different bands and with different JFET device types on bread-boards, etc. The results have all been the same and I have only had to make minor tweaks to optimize performance for different JFET types and significantly higher or lower frequency bands. The radio currently tunes 7-11MHz.

The basic paradigm of this design is to break up the traditional oscillating detector into a separated regenerative amplifier and detector circuit.

The detector is  a “plate detector”, where RF is fed back to the Amplifier via a partially RF decoupled source(normally bypassed all the way for RF when used as a detector).

schematics:

Version 2: (07/30/2015)

regen_simple

Link to PCB for version 2:(expresspcb format)

https://www.adrive.com/public/NPY7VM/Simple%20Regen.pcb

Version 1 (shown in video):

regen

picture of prototype:

IMG_5001

Video Demo:

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104 thoughts on “A High Performance Regenerative Radio

    • I love the feedback(no pun intended)! I will revisit this. Early on I looked at using an inductor but found it to be a little difficult to “tame” also the small resistor R13 seemed to work reliably over three different builds of the circuit. Can you describe what you find to be better performing about this? I would expect a little more gain in the detector… anything else?

      thanks
      Ray

    • is that correct? Normally output impedance is the parallel of the output impedance of the device and the Drain resistor. Since the drain resistor is 4.7k the total impedance cannot be greater than 4.7k. But to your point, there may be some loss in the circuit due to loading but a higher impedance final amplifier circuit and a larger value volume pot will improve it a couple dB. I found that overall gain was ample so I did not try to hard to optimize.

  1. Hi Ray

    I love your regen! I have a Ten-Tec 1253 that just refuses to oscillate and never goes into regen mode. I’ve heard others have the same problem. Tried everything to fix it. Checked resistor values, soldering, even changed transistors to MFP102 but nothing worked. 😦

    I will modify it to use your circuit, but one question, I note that Q2 in your circuit uses an interesting bias arrangement in that one side of the 10k pot goes to 5V and the other to ground. In the ten-tec it would be more convenient to modify the circuit so that the 10k regen only adjusts the bias to ground. Any ideas if that will work? Just wondering.

    Cheers, Ian

    • Hey there Ian

      Yes the bias to ground will work….but you end up with slightly lower over all gain. I found you can make the source resistor lower and create the negative bias just changing the source reference +/- and the performance is better. One of my goals was to eliminate more stages of amplification so I worked with milking every little bit of gain out that I could from less stages. That having been said a fresh set of eyes and some tinkering with values often leads to improvements- so you should try it! Also someone made a comment that my small value source resistor can be eliminated and a 100uH inductor put in series with the audio bypass cap on the feedback/detecor stage. I had experimented with this early on and just settled with the resistor for simplicity. This mod may work for you and improve performance also. Just a note, I used a range of different FETs and they all worked so anything you got should be fine.

      Ray

  2. I find your method of regeneration control interesting, compared to the original Ten-Tec design.

    Let’s say you wanted to build a general-coverage receiver using your design, and bandswitching the coils for coverage from 3 to 30 MHz. Does your method of regeneration control allow regeneration adjustment over such a wide frequency range?

    • I think the answer is yes but it may need some adjustment of values. For what its worth I used it from about 2MHz to 18MHz with just changing the inductor. In terms of the regen control – you have a pretty large range of gain control but you are changing the gain of the active device – not the feedback level so it is different.

      • Could you expand upon why you decided to alter the stage gain instead of altering the amount of feedback (as in the Ten Tec design)?

        I haven’t yet built a regen based on this Ten Tec/Butler-oscillator-style topology yet, so I’m curious about how it works in practice. Regarding the original design (with the regeneration control tapping off a variable amount of RF from the source follower stage), some people say it’s great, while some people say it’s terrible.

  3. I find the source follower approach works very well – it also can be done with bipolar transistors(at low voltages). What I find that is tricky is that when improperly adjusted the circuit will go into super-regeneration and sound like an exploding garbage can.The TEN TEC design has a lot of components to lower gain and or feedback and tank Q over the wide frequency range. In general, the design has more parts than required(my opinion). My approach was to keep the basic oscillator topology but use a dc operating point control instead of feedback for the regen control. It reduced my parts count, is very stable and provides extremely smooth transition in and out of regeneration. It seems more tolerant with a variety of tank circuits. Did you check out my video demo – it gives a good representation of the circuit performance.

  4. I checked out the videos. Looks nice.

    There seems to be a bit of “growling” (frequency modulation or detector pulling) in your videos when listening to CW at low beat note frequencies. Is your current design better than, worse than, or equal to other designs in this regard?

    Also how’s the long-term frequency stability? I must admit that operating point stabilization against temperature changes is an area I am still studying, but I wonder about if changing the oscillator’s operating point (when adjusting regeneration) might have any detrimental effects on long-term frequency stability.

    • One of the videos uses a varactor diode for tuning and drifts because of that. The other version used a cheap temperature sensitive inductor which also was near the unshielded front panel. It suffered temperature and hand capacitance drift. You are correct that this oscillator topology may not be optimum for stability but in my case the issues in the video were sloppy layout and temperature sensitive tank circuits.

      Ray

      On Mon, Mar 11, 2013 at 4:05 AM, Circuit Salad

      • Meu amigo, eu moro no brazil, me chamo Rogério, eu tentei por muitas vezes faer o ten tec 1253 oscilar além dos 20 mhz, mas para mim parece impossível, tentei todas as maneiras com tanque lc, indutores comerciais, toróides etc… voce poderia alterar esse seu projeto para sintonizar entre 26 e 28mhz????? 11/10m ?? se possivel poderia me mandar essas alterações??? grande abraço e 73!!!!

  5. I’m thinking about building a varactor-only version of this circuit. Which capacitors are crucial for frequency stability? Clearly C2 must be a high-Q, temperature-stable capacitor as it is directly connected to the tank. How about C4, which grounds the inductor at RF? And what about the feedback-related caps C9 and C10, or the bypass caps C7, C8, C11?

    Also I notice you don’t have a small-value resistor on the gate of Q3, unlike the Ten-Tec design. My understanding is that this resistor helps prevent parasitic oscillations of the source-follower stage, so it might be a good idea to include it.

  6. Hello Ray, in the last few weeks sart building your receiver. Last Monday complete the construction and it works great!. Changing the inductor and using a triming capacitor for C2 is now covering both 80 an 40m bands and I listen many QSO’s in SSB and AM. A very good and fun to operate receiver!
    I use MPF102 for Q1, Q2 and Q3, and as I don´t have a TPA301 put a LM386 stage for audio amp.
    Thanks a lot for sharing your project!
    Bruno.

    • I am happy that it works and really appreciate the info. I had not tried the MPF102 – so it is nice to have verification that it works. Also the LM386 info is good. I used the chip I did just for the fun of it, but I use LM386’s all the time. Did you do anything special with the LM386 portion of the circuit? I am sure others would like to use that IC as well.

      • Hello Ray, nothing especial with the LM386 for now. Used the gain 50 configuration suggested in the datasheet and is working very good.
        I’m really happy with the receiver results and like I say is very fun to operate.
        Thank you Ray and 73´s!

  7. Hi Ray I would like to build this circuit into an old AM valve superhet radio.
    In other words use it as the RF stage and feed it into the existing audio stage.
    Do you think the circuit would work using the existing Am tuning capacitor and coil

    • Yes It should —- Your tank will be pretty high Q so may have to fiddle with R13 and C10 to keep the regen smooth. I did use the circuit in the AM range with a big multiturn loop tank/antenna and got it to work. Let me know how it goes… sounds like a neat idea.

  8. At http://transistor.aax7.de/frames/rf/regenerative_rx.htm and http://transistor.aax7.de/frames/rf/regenerative_rx.gif you see a regenerative receiver with the same topology as described here. But a BJT is used for controlling the regeneration, also by changing the bias.

    There are many topologies for regenerative receivers. I have built a regen with two distinctive blocks, a Q-Multiplier and a separate detector stage. The Q-Multiplier can consist of a JFET Hartley oscillator and the detector can consist of of a drain bend detector with a JFET. Schematic: http://www.uploadarchief.net/files/download/modifiedbeast-01regen.gif In this schematic I use a BJT emitter follower to control the regeneration by changing the Drain voltage of the Q-Multiplier. It is in fact a cascode circuit.

    Another approach is by using a differential pair as a Q-Multiplier and a separate BJT detector. Both are connected onto a tap of the main tuning coil, see http://www.b-kainka.de/bastel3.htm.

    • Love the links you have provided. Yes I think the idea of separating out the Q multiplying from detection and using bias to control regen is the way to go. There is definitely more than one way to skin a cat

      • I think that a regenerative receiver in which Q-Multiplying and detection are separated, perform much better than those receivers in which detection and Q-multiplying are combined in one single stage. Combining more functions in one stage always means compromises which affects performance. Doing each function in a separate stage means optimizing each stage for its function.

  9. Hello from Argentina! I just finish this circuit but something is wrong because cant hear anything but a hum from my power supply. I use a wall charger as power supply, add some filter…. maybe tomorrow will test again with a 9v battery. Also cant buy a J310, but find 2N3819; this can be a possible cause of the problem? The circuit refuses to oscillate. Any advice? Thanks! I will post the problem cause when I found it!

      • I just try a 9v batt, nothing change… so right now I am reuilding the whole circuit. Was a “ugly” style of course!; maybe have some component placed wrong?; now is not so ugly because taking care of everything. Only to be sure; in the schematic were are placed the FETs, always is Drain in top and source in bottom right? Thank you very much!

      • When remove C8, starts oscillating; and audio level very low. The R13: 220 and R8: 33K; and C8: 0.1uF and works much better, this afternoon will play one more time with these 3 values to make it work better. Thank you for your support!

      • Why not using a truely separated detector stage? You leave the original circuit for Q-Multiplying alone and you connect onto the tank circuit a drain bend detector with a J-FET which has been biased near its pich-off point. In this case the source resistor of the separate drain bend detector should be around 10k to 30k, which must be bypassed for RF and AF by a capacitor and an elco. See my contribution at #22 by DrM on August 21, 2013 – 5:29 am

      • Thanks DRM! Your circuit seems to be a little more complicated but certainly a will give it a try just for fun and to learn more about reg receivers. Best regards

  10. I am glad you got it to start working.. I am thinking 1K for R13 and lower R8 down some maybe 22K and increase C8 so that audio(as well as RF) is bypassed. The 1uF should work. Sorry it hasn’t been that easy but I guess that is what makes it fun.

    • No doubt! if it has been easy I would do not learn anything. (sorry for my english). In a few days I will post some pictures in my facebook; of course the credits will be yours!

  11. Well yes you could do that and in fact you are correct – I am trying to provide feedback in the source and then utilize the drain as a plate detector of sorts. Trying to do both is not optimal. But when I built it – it seemed to operate well and I always like to see how simple I can make the design so i just left it that way. Ironically, if i did as you suggest,it would probably be less critical with regard to the values used in the feedback circuit and easier for other builders to reproduce reliably.

    thanks for the suggestion – it makes perfect sense

  12. I’m attempting to try circuit with a 4 inch coil wound for the AM broadcast band. ( ~30 turns of #30). It seems to be working, however I can’t get the regeneration it to go below the threshold of oscillation. Any thoughts on reducing the feedback a bit? Maybe R13 to 1K and R8 to 22K as you suggest? Thanks.

  13. The circuit now is working and this weekend tune a CW contest! But sometimes when moving the main tunning cap (100pF) I think the bandwith seems to be not enough becouse the audio signal is “croped”… or maybe the signal is too strong for the detector? What do you think?

  14. That’s great! With all that effort – lets not settle for mediocre performance here. If you feel something is not working well …. I will help try and get it better. Sounds like you are close.

  15. yes the circuit looks neat – I will have to try it. Have you built it? How do you know how well it performs? One thing I don’t like is adjusting the regen with the B+ being varied. I fined is the tuning pulls and you can’t get as smooth a regen control.

    • Today I found something interesting. The audio distortion reported earlier its not from a remote AM broadcast nor local AM harmonic; is local FM!!. Maybe my receiver is going to superregenerative? maybe is because not having a good ground to earth?. Also I try a diferent coils and what happends; when the coil is 5uH and air core (like the pictures posted yesterday)… the oscilator works fine and can tune a lot of AM remotes broadcast, but when I try a toroidal ferrite core (always 5uH) the oscillator stops oscilating; I think the higher Q makes more load to the oscilator. What do you think Ray? Any idea, what can I change? Y try with different values in R12, R13 and R8 and nothing. Another thing is I have to remove R2, to make it work; I forget to mention that in my first report. Thanks!

  16. I am getting some 2n3819’s to try myself.
    The R2 issue—- probably just has too much voltage drop across it. You can try using more than 5 V for supply (maybe you already are). Also you can use 100ohms instead of 1K. R2 is just decoupling, is not that important. As far as the inductor with a core not working – not sure what this is about. I use all kinds of air core and ferrite core inductors. Is it specifically a RF inductor or is it a power supply inductor? Just any old inductor with a core may be too lossy for RF at that frequency. As far as the FM not sure what this is about. I doubt you are in a superregen mode. Especially since the radio is not tuned to the station. I assume it is some sort of overloading.

    • Yes I am using 5v at this moment, I will change the vreg to 9v regulator and 13.8v power supply input and test it!. The inductors are made myself and tested with a digital inductor meter and the core is toroidal. The idea is minimize the coil size since I’m using a switch to change the bands. For the overloading a will use a pair of 1n4148 as limiter after RF amplifier. Thanks for trying 2n3819! I really appreciate that effort. Thanks again.

      • This weekend add two diodes and convert a 7805 to 6.3v regulated. Add the limiter with the 1n4148 and found the FM issue, was the audio amplifier with poor RF filtering (ups!). Still using low Q coils; right now this is my main challenge. Best regards

      • Forget to mention that really works!!, outstanding perfomance. No microphonics and great stability… listen 40m at night was a beauty; listen CW and LSB QSOs and a lot of broadcasts. When finished it; will film a video to show how its works. Thanks Ray for share this circuit!

  17. So you are saying increasing the supply voltage helped the performance? “Add the limiter with the 1n4148”. What is the limiter with the diode you speak of? I am interested in your modifications.

  18. Hi Ray, seems like a nice design! Is there a way to calculate the size of the tuning inductor for various frequency ranges utilizing the varactor approach?

  19. Hey, I think your blog might be having browser compatibility
    issues. When I look at your website in Opera, it looks fine but when opening in Internet Explorer,
    it has some overlapping. I just wanted to give you a quick heads up!
    Other then that, great blog!

  20. OK, I was going to build this, but I have a problem. The MCP1804,TPA301, and SMV1212 are so tiny I have no idea how I’m going to get them into my breadboard. It appears I’ll need to use a magnifying glass and tweezers to solder some larger leads on them. How are you working with these parts? As far as I can tell they are only available as surface mount parts. I’m sort of a beginner in electronics and didn’t realize what I was ordering. However, I called Mouser and they said this is the only size available.

      • I can suggest a better part for the amp but you will have to give me a day or so. You can use various rectifers or zener diodes as varactors- but otherwise get a variable cap out of an old am radio. The regulator can be anything so I will give suggestions for that and the amp. I may have to provide a modified schematic.

      • I can buy some larger varactors from Amazon or somewhere else. I’ll need to know what specs to get though. Also have the Elenco Diode kit which contains these: 1n4001,1n4004,in4007,1n5404,1n5408(5pcs),6ao1, 6a08(2pcs), 1n751,1n4733,1n4735,1n4742, 1n4150,1n4148,1n914(5pcs), wo1, wo2,(2pcs) 1n60(5pcs), 1n34a(3pcs),fv1043,1n5818(2psc). If one of those will work let me know.

        I have an LM386 amp and an LM317 voltage regulator in my existing parts stash if those would work. Otherwise I’ll just buy whatever you think is best.

  21. you can use anything that will give you 5V. For example the digikey part number: LM340LAZ-5.0/NOPB-ND is a 5V TO92 type transistor case leaded part that would work well. for the amp use a TDA7052A(comes in a DIP or SOIC. You can get these from mouser I am sure.

    you can look at the my last blog post for the bipolar regen to see how I use that amplifier

    The varactor needs to be adjustable from 10pf to 30pf or 30pf to 100pF something like that…you can parallel them if need be but the diodes you have will nut be good candidates. 1 watt, 12 or greater volt zeners often work well.

    • yes I did not include that but I figured builders can make that addition based on experience or other designs. The main point was to use a more “beef stew” generic amplifier IC and eliminate some of the regulators, etc.

  22. Got it. I built this circuit and am going to add fine tuning, probably later today sometime.

    It works very well. I used J310s. Not quite as much audio as I’d like, but I have an amplified speaker I can use.

    • Interesting on the volume…not sure I have built a couple and had pretty good volume…you can fiddle with R8, R7 and R9 and maybe squeak out some more gain that way or add a really simple 1 stage audio amp between the the detector and the tda7052 if you are using that. Fine tuning really helps

      • I can’t find exactly 5.0 uH for L1 in my local electronic store.So I bought the nearest value, which is a 5.2uH toroidal inductor to replace it. For C6 I used a general AM plastic tuning capacitor CBM-223 and offset the value to 5-150pF (I’ve verified that using a capacitance meter)

  23. cool …toroid – that can work well or very badly. The reason is the type of inductor. Is it an RF type inductor or for power supply applications? Tell me a little more about the toroid. Also you can try upping the supply voltage to 9v – bypassing the regulator. At least initially it might get it oscillating. From there we we can tweak..

    • You got it!! The toroidal inductor really cause the problem. After I googled “toroid inductor color code”,I found that the one I bought from my local electronic store seems to be a “power choke”,and has a T50-52 (Blue/Green) color code. So I replaced it with my hand wind coil (on a T37-6), it turn out to work correctly.
      Thanks a lot!

      • great! Yes I design a lot of switch mode power supplies so I run into issues with magnetics all the time. Very happy you got it running. Let me know if you get it working well.

  24. Hi, i’ve a doubt,,, on scheme rev2 fet pins are called 1, 2 and 3.
    3 is gate, but drain and source?
    thanks, and excuse me for english 😛

    • JFETs are constructed on a solid block of N or P type material such that Drain and Source are only defined by the potential across the FET not by the physical structure of the FET. This means they are completely interchangeable with respect to physical pins. In simple terms the data sheet defined source and drain pins are completely interchangable – either pin can be the source or drain. This is only true of JFETS not mosfets.

    • JFETs are constructed on a solid block of N or P type material such that Drain and Source are only defined by the potential across the FET not by the physical structure of the FET. This means they are completely interchangeable with respect to physical pins. In simple terms the data sheet defined source and drain pins are completely interchangable – either pin can be the source or drain. This is only true of JFETS not mosfets.

  25. hi Ray. I made the version 2 of this regen. Unfortunately I am getting lots of motorboating. I’m using fot the tank cap an Alps variable 5 sections. Coil is an air core 16 turns 1 cm diameter with 22 AWG wire. Any suggestions to get rid that motorboating?

    • so two types of motor boating….oscillator is self-quenching by the oscillation being to strong and then shifting the bias point until it turns itself off. The other motor boating type occurs from feedback via the audio chain and is an audio decoupling issue. My first suggestion is eliminate the audio possibility by isolating the audio amplifier independent of the rest of the radio by using a different supply. If that works then we can explore decoupling strategies. If it doesn’t then we need to look at the bias and feedback for the oscillator/detector.

      • Thank you Ray. I’ll look after those suggestions you made. I’ll try to assembly in a protoboard so it will be easier to make modifications and detect the source of the problem.

  26. I don’t get it. There’s a potentiometer (a volume control as I suppose) connected to the TDA7052’s pin 4. There’s nothing about such a solution in the datasheet. The pin 4 is marked as N.C. there.
    Could you explain this, please?

  27. i had same doubt, but i’ve find this:

    in this pin-out 7 is N.C and 4 is VC
    4 is VCA control =)
    it will sound better than audio passing on potentiometer =)

  28. I made two sets using your design using J176 and 2SK193 JFETs. Two more JFETs you can add to the list. I used ugly and tacky construction with clip leads etc. I used a general purpose AF amp too. The next one will be bullt as one unit to be used as my emergency back up. I plan to use an AF amp capable of driving a speaker. The Gulf Coast Hurricane Net meets nightly on 80 meters. I was able to follow some of the net traffic with my piece meal bread boarded receiver. Hopefully the next one will be even better. Thanks for the design.

    • I’m so happy you got it to work reliably. As always there are probably tweaks and adjustment to values one can make to improve performance with a given active device or tank circuit. If you come come with any other insights or suggestions please share! Eliminating tapped and tickler coils was an important design goal…so with a quality air wound coil, a good air variable and a well regulated supply voltage…the sensitivity and stability should pretty darn good. I have a couple version of the circuit on the site…the TDA7052 is a great choice for an audio amp and much easier to make stable then an LM386.

      • I should have said more about the modifications I made. The 2SK193 is made for FM front end service and it worked without modification,
        The J176 had to have about 8.5 volts to oscillate. The J176 is made for switching but works as an amp with a little tweaking. They are $8 a hundred or $25 for five hundred on Ebay. At that price I had to buy some and find a circuit to build with them. Once I got the Butler oscillating I put several coils on it and it worked from broadcast up to about 12 Mhz. I made the AF using SS8050 and SS8550 transistors for the output. They are rated 2 watts but I’m driving a headphone. (plenty of volume there) My plan is a separate oscillator, AF, RF, and product detector or ring mixer.
        My tuner is a slug tuned coil. I used this pattern with a 1/4″ brass screw and 3/8″ sink supply line for the former.
        http://radio.radiotrician.org/2016/02/a-slug-tuned-coil-from-straw-and.html
        I put the frequency counter on it and tuned the slug. About 3.5 Mhz to 4.2 Mhz.

  29. First of all, great site! I have attempted to build v2 of the circuit using j310s for Q1,Q2 and Q3.
    I used the pc board layout and etched a board, populated it using all values listed in the v2 schematic and I’m having issues. It seems there is no oscillation happening…Or at least that is my theory, I can hear the background noise floor in my headphones, but nothing more. The tank circuit is a poly cap (15 – 95pf) and a 5uh rf inductor (with core), I also tried a home-made air core inductor (16 turns 22 awg), but no difference.
    Also, the datasheet for the j310s list the pinout as: 1- Drain 2-Source 3-Gate and they are oriented per the silkscreen layout in the v2 pcb.

    • Update: according to my transistor tester…the j310’s I’m using have a different pinout than I initially thought. These were bought from a surplus electronics retailer, so the spec sheet I was referencing did not match the part. This is why you don’t assume things I suppose 🙂 I’ll try rearranging the fets later this evening and hopefully will have good news to report.

      • yes let me know…About ten different builders conveyed to me success building this circuit…so I am pretty sure it can made to work with out much trouble…I will assist if I can..if you continue to have troubles.

    • Also jfets are symmetric, so the Drain and Source can freely swap places. In other words, placement of the terminal defines its function as source or drain, not the actual physical structure of the fet.

      • I eventually ran this issue down and got the circuit to fire up 🙂 It all came down to a messy work area and a fet that wasn’t a j310…so correction: j310 pinout is as described by spec sheet…I accidentally tested another fet I was working with. Root cause was a lifted pad on my homemade board.
        Thanks for the circuit!

  30. Hello, thank you for sharing your experiments. I would like to ask some questions about this regen, have you ever tried using a 400p variable in place of C6? Could it be that if only the variable can replace 80m with the same coil?
    I’ve already set up this one – http://www.qsl.net/pa2ohh/05simrx.htm – which worked very well and I’ve already set up Kitchin’s high performance regen, now I’m interested in putting together your project, I’ve come up with your site for the video on youtube. 73.

    • Everything understood as to the tuning issue, I’m with a variable of 2x360p and I thought of trying to see if it arrives in the range of 80m without the need to replace the inductor.
      The inductor I am going to use has air core, it was wrapped in a porcelain tube that I removed from a power wire resistor, the outside diameter is 10mm by 30mm in length, I used wire 22 and I filled the entire length of the tube, the inductor got a value a little above 5u.

      • Meu amigo, eu moro no brazil, me chamo Rogério, eu tentei por muitas vezes faer o ten tec 1253 oscilar além dos 20 mhz, mas para mim parece impossível, tentei todas as maneiras com tanque lc, indutores comerciais, toróides etc… voce poderia alterar esse seu projeto para sintonizar entre 26 e 28mhz????? 11/10m ?? se possivel poderia me mandar essas alterações??? grande abraço e 73!!!!

  31. Hi Ray

    Very interesting – i am just getting back into radio and electronics after 30 odd years and am playing with regen receivers currently and say your design which i would like to build. Question/s – is layout critical? i want to build it using vero strip board or even point to point tag strips (old fashioned i know!)? I was thinking of making an air wound coil similar to how picco (commenter above) said, on a ceramic former – is that ok? and finally can i simply run it off a 6v battery without the regulator circuit (7805) – many thanks

    • Yes originally built on solder-less breadboard…no problem with any construction method. Air inductor is great…If you look at one of my youtube videos, I show the circuit using a giant 4 inch diameter air coil of 5 turns and no antenna…works fine. 6 volts will work fine but if you go up to 9 volt changes would have to be made…gets trickier to tame. The regulator is preferable from a stability standpoint(tuning drift and critical regen adjustment remaining stable)…doesn’t have to be that particular regulator either.

  32. Interested in your regen receiver but I think I need more details to built it (like the L1 description). Am I looking in the wrong area or is defining that feature …

    • L1 can be anything from 10uH down to 2uH…etc. Big air wound, small air wound, cheap molded inductor, nice toroid…anything will work except low frequency power inductors…just experiment and have fun! Some may work better than others but its not that critical.

  33. Thanks. I am working from your schematic dated 7//1/15. I assume it is the latest.

    Thanks again for the quick (no) very quick response.

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