On the AMRAD mailing list, Andre, N4ICK, posted a link to the YouTube video, “12AU7 regenerative radio on a tin bake plate” (see photo at right) It’s a very cool regenerative radio made with a single 12AU7 vacuum tube. The only problem is that there are no links to the schematic for the radio.
So, I Googled a bit, and came up with this circuit. The cool thing about this circuit is that it uses a 12V power supply, not the high voltage power supply normally required for a tube circuit.
Over the weekend, I went to a big rummage sale sponsored by the local Kiwanis club. They had quite a few aluminum baking pans there for very little money. I should have picked up a couple of them. :)
VK3YE has also posted a YouTube video of his experiments with a similar circuit. Unfortunately, he also doesn’t include a link to a schematic.
Another related YouTube video is for a one-transistor radio. This is actually a very well-done video. It shows you step-by-step how to build the radio. This is something that we may actually be able to do down at the museum with some kids.
At the very least, watching the videos is amusing. At best, maybe they’ll inspire you to do a little experimenting.