A two valve regenerative receiver for 40m from Stephen, VK2BLQ

Home brew master, Stephen, VK2BLQ has been at it again and has created a two valve regen a la 1967 All Wave Two, using two 6BL8 or 6U8 triode pentodes (heaters in series), and it still works with a 12 V HT supply instead of the 90 V used previously:

Stephen writes: 

"The receiver sort of works, but the 12 V supply limits the audio output, so is only good for headphones or feeding to an external amplifier. The stability on 40 m is Ok but overloads on strong signals, so I think an antenna pot might be better than the volume control, doing double duty, but it does combine the glamour of thermotron technology with the safety of low voltage.

For the makeshift vernier dial I used an old audio CD , which as fortune would permit, possesses the magic of Soldersmoke so is destined for greatness. Hacking an old variable pot and two grommets seems to function as a vernier drive.

Audio quality on the 39 m AM shortwave band seems to me more pleasant than one of the superhets and 40 m SSB and CW sounds "mellow". (Click to enlarge image).

I did make some circuit changes to suit the lower voltage: I changed the pot and resistors for the Regen control and I did use a 230v to 6v mains transformer for the speaker. Valves are great, the 6U8 worked with the same components even though I didn't have a 6GW8.

Next version gets the upgrades and a heterodyne converter, and if I can quote a line from the TV series "The Nevers":

"It's a prototype". 

If anyone actually has questions, I'm happy to help."

Here it is in action:

-- It's a fine looking prototype if you ask me. Thanks Bill for the link from Soldersmoke!