Radio Receiver or Art? Why not Both?

We’ve heard it said before that you should build things twice. Once to learn how to build it and the second time to build it right. [AA7EE] must agree. He was happy with his homebrew regenerative receiver that he called Sproutie. But he also wanted to build one more and use what he learned to make an even better receiver. The Sproutie Mark II was born.

This isn’t some rip off of an old P-Box kit either. [AA7EE] used a four-device RF stage with FET isolation back to the antenna and a regulated power supply. Plug in coils allow reception on multiple bands ranging from about 3 to 13 MHz. There’s an audio stage with multiple selectable audio filters, and–the best part–a National HRO tuning dial that is a work of art all by itself.

You wouldn’t put the Mona Lisa in a wood shed, and [AA7EE] didn’t want that beautiful dial in some makeshift case. Instead he built a chassis that would be at home in a tube radio, a professionally-made front panel, and a gorgeous wooden case. The final result is a beautiful set that apparently performs quite well, too (see the video below).

Even the insides are clean looking. The Manhattan construction is neat (and looks good thanks, in part, to the use of meSQUAREs). Of course, if you are lazy like we are, you might want to stick to one chip and a breadboard. Sure doesn’t look as good as the Sproutie Mark II, though.

Thanks to [jmilldrum] for passing this along.

17 thoughts on “Radio Receiver or Art? Why not Both?

  1. loved the write-up and photos! but I cringed when I saw the 1/4″ jack being used for power ;( those are shorting, as you insert them, and its not suitable for power!

    audio alchemy used to do this with 1/8″ trs jacks and they were known to spark as the box was moved or if the jack was removed without a power-down delay.

    other than that, great job! but please do revisit the idea of using shorting style jacks for power. what I use is a midi 5pin din plug that is keyed, won’t rotate and you can get any length you want. you have extra wires in case you need more voltages, too.

      1. ok, I’ll take your word for it. if that’s the case, then I retract my comment ;)

        I’ve seen more than my share of shorting jacks being used for power. I did that once, as a kid, had it pointed out to me and I never did it again.

        glad this build didn’t do it. sorry if I misjudged.

        again, really great write-up. love the photos, especially. good clear tech photos are somewhat rare, for some reason, on blog posts. I guess camera phones kind of made most people just not care about the photo quality or post processing.

  2. Beautiful project. I had one of those P-Box receivers though, and with the addition of a vernier tuning capacitor in parallel with the main one, it was surprisingly capable. Spent a lot of hours with it on a relatively short “long” wire wrapped around my bedroom listening to foreign newscasts and ham operators.

      1. No doubt. But notice while it’s beautiful, he doesn’t really have anything resembling an accurate frequency display. He gets a beautiful glide across the spectrum, similar to tuning an old Hallicrafters rig, but he hasn’t calibrated it in any way. If it was a superhet he could always stick a frequency counter on the IF oscillator but I really wonder how he’s supposed to know what frequency he’s tuning in. I of course had the same problem with my P-Box, but I put a lot less effort into it.

        1. If he really needs to know the exact frequency then he can listen to the oscillation of the regenerative detector on a nearby receiver with a digital read out.

          Outstanding work.

        2. Hi localroger – with these receivers, I draw up dial calibration graphs, with dial marking on the y axis and frequency on the x axis. At the time of making the video, I hadn’t yet made a graph, which is why I wasn’t too sure where I was in the band. If you look at the blog-post again, you’ll see an example of a partially-completed dial calibration graph. In another post, about an earlier version I made of this receiver, there is a better example of a dial calibration graph. That post is at https://aa7ee.wordpress.com/2014/08/21/the-sproutie-a-general-coverage-regen-receiver-with-plug-in-coils/ – it’s about 2/3 of the way down the page. I use a piece of freeware called “Graph”. PS – the graphs on my blog are reduced in size, so hard to read. The originals are clearer.

          One of the things I have long thought about regens is that many of us don’t consider them as “serious” receivers, because we don’t take them seriously when we build them i.e. we don’t make them physically solid, don’t provide adequate dial calibration, etc. Good dial calibration – either directly on the dial, or on a graph, is not anywhere near as accurate as a frequency counter, but it can get you close enough. On the coils I wind for specific bands, where the frequency coverage is 1MHz or less, I can easily read the frequency to under 5KHz. That sounds a bit broad, but it’s enough to identify which channel you’re on when listening to the international shortwave broadcasters, most of whom operate at 5KHz spacing. When you also consider that the bandwidth is somewhere in the region of 5KHz wide (give or take), if I am waiting for, say the Voice Of Korea to come on a particular frequency at a particular time, I can set the dial and wait – and I’ll hear them when they come on. Even with the more general coverage coils, which cover a 2 or 3MHz span, I can still read the frequency almost as accurately, but it takes a bit more scrutiny.

          Thanks for the kind comments and interest. I was amazed to find that hackaday considered my little project worthy of featuring!

          Dave
          AA7EE

          1. Dave, your radio is totally worthy. The effort, the experimentation, collaboration and perseverance you put into this project is true hacker cred. Of course hams have been doing this since before ‘hacking’ was a thing.

            I grew up on radios and still do the occasional build – regenerative radios are like electronic haiku, and a different kind of kick from working with software or firmware. Great job!

          2. There’s also the fact that absolute frequency calibration is actually a sort of technological confection depending on the application. (_Exactly_ how tall are we? And so knowing [or not knowing] that number matters exactly how?) In Amateur Radio, with few exceptions we expressly need _not_ know our operating frequency exactly–only that we’re operating safely within a given band or license-class-mandated subband. Seeking absolute frequency calibration also forces us to address the issue of exactly what sort of “frequency” we need to be exact about: carrier or suppressed-carrier frequency? Channel center? Emission center? “Mark”? “Space”? What’s beautiful to me about a relatively-calibrated analog dial like Dave’s “HRO” dial (as we’ve called it in hamdom since the 1930s) or the smaller dials either side of it is that such a frequency display both facilitates and encourages mapping to the physical the virtual place/space the frequencies it can tune to, with the different possible frequencies in its coverage band equating to different places on the dial scale. The sense of different frequencies and the bands that contain them as _different places_ is quite strong in those well experienced in worldwide communication via shortwave radio. Best regards, Dave/amateur radio W9BRD, a cookie-and-tea-tins guy: http://dpnwritings.nfshost.com/ej/pictures/pictures1.htm .

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