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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122 thoughts on “A High Performance Regenerative Radio

  1. Hi Ray !
    Always wanted to build a regen. I think your design will be my first. I have most of the parts and will start pulling them together tomorrow. Very nice thread and you follow up well. I will let you know when I get started.
    Thanks and Merry Christmas to you and All the regen buffs !
    Jim WB4ILP

      • Hi Ray !
        Thanks for the reply. I was wondering how the plastic cased polyvaricons compare to standard air variables. I have read that they are far inferior to a good air variable but I’ve also read that they work well. ??? They obviously work well in small transistor radios and they’re available for cheap on eBay. I ordered some last night.. I have a couple of table top AM/FM radios picked up at yardsales that contain a nice air variable. Also, how well would a PTO work in your design? A variable core inductor with fixed capacitance, maybe switched fixed caps. This might help some builders work around the need for a variable cap.
        Jim

  2. I am unable to open the .pcb file . Could you please help post or email me a copy of the pcb for Laser printing?

    Many thanks!

  3. The Poly caps work well for me…They are inferior for applications requiring high voltage tolerance, high power such as in transmitting loops. They also have more drift but they work fine for receivers. They best place to make improvements is in the construction of nice RF coils. Yes a well constructed air variable is better but it seems a waste to invest in a really nice one for a regen!

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