I've designed this radio circuit, it's made to work on the 80m and maybe 40m band.


Regen is controlled using a pot in the tickler coil. Tube is ECF82, coil is air cored on a 30mm former. Will it be able to receive LSB and CW, or just AM? Can you recommend any good literature on the topic of regen receivers?

  • \$\begingroup\$ It's rare to see such a retro design here. Might I ask why you're using a regenerative receiver instead of a less oscillation-prone design? \$\endgroup\$ – Hearth Apr 6 at 17:00
  • \$\begingroup\$ @Hearth Well, the whole point of regens is to oscillate, thats how they detect CW. I want to use it because of their simplicity. \$\endgroup\$ – thegamebusterpl Apr 6 at 17:28
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    \$\begingroup\$ Does this circuit actually work? I'd be surprised if you hear much. That single tube does 3 functions (oscillate, mix down, amplify audio). That last one seems to be missing: at audio frequency, plate impedance is near zero. A high impedance at audio frequency should exist between plate and +88V DC. Something like a big iron choke, or at least a resistor. I think C5 could be much larger too. \$\endgroup\$ – glen_geek Apr 7 at 2:00
  • \$\begingroup\$ So C5 470nF and a 1mH inductor between 88V and L2? \$\endgroup\$ – thegamebusterpl Apr 9 at 9:21

I certainly don't have enough experience with radio circuits to say much here, but one problem sticks out to me immediately: your potentiometer R2 doesn't have its third terminal connected. Since turning a pot (or sliding, if it's a slide pot) can cause the wiper to bounce up off the track, it's usually recommended to connect the "unused" terminal to the wiper to prevent internal arcing when turning it, especially with an inductor on the other side of it.

  • \$\begingroup\$ I recall hearing Morse on the Hallicrafters S-38, with or without the BFO enabled. \$\endgroup\$ – analogsystemsrf Apr 6 at 18:05
  • \$\begingroup\$ @analogsystemsrf I'm afraid I don't know enough about radio to know what half the words in that sentence mean! \$\endgroup\$ – Hearth Apr 6 at 18:16
  • \$\begingroup\$ @Hearth The BFO is a "beat frequency oscillator." A regen uses positive feedback to enhance its sensitivity (and there are other benefits.) I don't recall ever applying a BFO, but I would assume that the BFO might be operated at half the regen frequency such that the 2nd harmonic can be used to avoid pulling or blocking the detector, itself. But I'm sure there are still more creative approaches with BFOs in a regen. \$\endgroup\$ – jonk Apr 6 at 18:56
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    \$\begingroup\$ @jonk . You don't use a BFO with a regenerative receiver. Adjusting the pot until just barely self oscillation begins. It brings out the Morse code nicely. \$\endgroup\$ – Marla Apr 6 at 20:35
  • \$\begingroup\$ @Marla Like I said, I've never considered (nor tried) to apply a BFO to a regen (never crossed my mind.) I just tried to use my imagination about it, since "analog" mentioned "with or without BFO." He made my mind wander a bit. \$\endgroup\$ – jonk Apr 6 at 21:34

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