Well, it's taken me a while to make a post about this one. It was a goal of mine after I completed the simple foxhole radio and one I set out to complete over the Christmas break. I decided since the crystal set was the simplest radio to build, what's the next step? The one-tube regenerative circuit was the answer.
Lately I've been reading quite a bit about radio history and have read about the huge leaps in receiver technology with the advent of the "audion" or vacuum tube. A lot of initial growth in radio reception is thanks to this circuit designed by Edwin Armstrong while still a junior in college in the early 1900s.
I scoured the net looking for parts (chiefly the 3S4 tubes) and kept coming back to Borden Radio Company. Rather than drop alot of money on shipping from various sources, I purchased a kit from Borden. It also happens that he doesn't live too terribly far from my parent's so I was able to meet up with the owner/operator, Lance Borden, over the Christmas holiday.
I pieced the kit together in two evenings. The first evening was spent winding the coils and mounting the hardware. The next night was spent meticulously wiring the components as outlined in the directions. (Maybe color coding the wires would have made the instructions a little clearer, but I can't complain.) The radio worked right from the get-go. It's tuned for broadcast AM reception and works like a charm. As you can see in the picture it requires quite a few batteries to power the tube, but it is 100 times louder than the crystal set and much more sensitive. I've heard stations all over the nation on this little set. This evening alone I was able to quickly tune into WWL 870 from New Orleans as well as KOA 850 out of Denver, Colorado.
The controls are finicky and not really what the casual listener would want, but the sensitivity and simplicity makes it worth the effort. Aiding reception is the clear audio produced by the old high-impedence Allied Radio headset that I purchased with the kit. The owner of Borden Radio assured me I wouldn't be disappointed with the headset as it works so much better than the old ear piece I had been using - boy was he right!
So, if you're following my steps through the old style radio setups, this is a step you definitely don't want to skip.
Another shot of the radio is here. (I tried to get a shot of the dim glow of the tubes, but the camera just wasn't able to capture the almost imperceptible light from within the tube.)
Next up: Super-regen? Super-het? FM ? (the passive FM is almost too tempting)