A receiver built from just junk I had in the shack.
One of Radio ham friends, Alex, M0UKR once joked, “You could probably build a working receiver with the components and crap that’s on the floor of your shack”. I’m not a naturally tidy person, I concur, but it did get me wondering if I could build one not just with crap of the floor but what I had in the shack. Without cannibalising other projects. This started out as an attempt to do just that but finished by costing me a few quid but it gave me a lot of enjoyment. Say hello to the Sproutie General Coverage Regenerative Receiver.
I like going to radio rallies, local and sometimes not so local. I don’t go for the big stalls; the major manufacturers and the big distributors, oh no, I go for the guys who have a shack clear out. I love a good rummage and regularly come home with some little gems and what might be called other people’s junk. So was the case with this find. A beautifully engineered 36:1 reduction drive for the princely sum of two quid.
Many years ago I made a valve regenerative receiver and although it worked it needed headphones and was never very good. I still had a hankering to build another one and get it to work properly. I love the simplicity of the regen and although they take a bit more effort to drive they’re a lot of fun to both build and use. If you’ve never built one, you’re missing out on a lot of fun. A regenerative receiver can be used to listen to AM transmissions such as short wave broadcast stations, CW (morse) and with a delicate touch, SSB ( Single Side Band) transmissions. CW and SSB of course are used by amateur radio. AM is as well but that’s a bit rarer. FM can also be detected but it’s very rare on the bands the sproutie can receive.
Armed with my lovely reduction drive, that incidentally has anti-backlash gears and everything, I set about finding a suitable regen design that uses FET’s instead of valves. There’s tons of them on line but many use loads of variable capacitors and while I try and buy those too when I see them them at a respectable price, I didn’t fancy using 3 or 4 of them in one little receiver. I settle on the Sproutie. It was designed (not quite all of it but he does make that clear on his site) by Dave Richards, AA7EE. Here’s the link to his page which has full construction details, circuit diagrams and everything you will need to build your own. So, with that in mind I see little point in duplicating my efforts here.
Mine doesn’t look anywhere near as good as Dave’s but then it didn’t cost me very much either as I had most of the components and fabricated the chassis.
The only decent capacitor I had to hand was 2 x 500pF which is far too big for the Sproutie even with it’s reduction drive. With the two in series it was still very coarse tuning. I wasn’t able to find the exact capacitor that Dave uses in his build and prices for similar on line are ridiculous. If I find a more suitable one at this year’s crop of rallies then I’ll swap it but for now I simply pulled out several of the vanes from the rotor. It was like extracting teeth! It works much better now with smoother, finer tuning.
I designed the decal on the front in Publisher which is how I knew where to drill the front panel holes. I then printed the decal onto paper and laminated it. For some reason that gave this mottled wood grain effect. By then I couldn’t be bothered to do it all again and in truth it’s kind of grown on me. I stick the decal to the front panel with my wife’s crafting double sided sticky thingies.
I finally found the valve bases that Dave uses in his build on Ali Express. So far I’ve only made a couple of coils, one for the 40M band and another for 80M. The first covers one of the broadcast bands as well and the Sproutie pulls in some great AM stations from loads of different countries. It really is fun. I also found that the caps from old 35mm cans fit very well on the valve bases and really finish of the look of the coils. I only had one T50-6 torpid in the shack so I actually had to buy a few more! Not quite the receiver only from junk I had in the shack I was hoping for.