A couple of DIY shortwave radio receivers and a new antenna

[zero cool]

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I've been a ham radio operator for... wow, fuck, 15 years already?! Goodness. I should probably make a ham radio section on here.
Anywhoos. That hobby has been mostly dorment for a number of years, but I got struck by a spark of interest for it lately. So I dug out a pair of my homemade portable (arguably) receivers, only to realize both needed new batteries. They both were built with 12V lead acid batteries for cheapness and ease of use. These are of course all dead after about a decade. The focus got shifted to the left one in the image, since it's easier to modify and upgrade. I built a lithium battery pack for it with a proper BMS and a buck-boost converter to take a varying voltage in for charging, and output a steady 12.6V for the battery pack. This is not a looker by any means, so I wont even take it apart to show it. It's really nothing exciting anyways.
But as these are small portable devices, I've always dabbled with building active, so called 'miniwhip' antennas, that compared to traditional antennas are capacitive rather than magnetic. This means they can be small. I mean, *really* small. Let's say they want to listen to the 80m band (about 3.5MHz) you would ideally want a half-wave antenna, and for portability that would be a longwire. But that would mean you have a 40 meter long wire to hang up, ideally far up and in a straight line. Instead you can have this little active circuit board, where the large copper pad to the left is the actual antenna element.

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These only work for reception however. But it's ideal in my case. As it is an active antenna it also needs a bit of circuitry on the radio end to feed power into the coax to power the antenna through the same cable.
I've hand made several of these antennas in the past with very varying results, so the plan is to finally get around to building one properly, and also modify it a bit to suit my needs.

[zero cool]

Well, this took most of the fucking day, because as it turns out, that antenna design was not great. Well, it's good, but it's picky with what components you use, and I don't have all the exactly right ones. SO! I built another trashy ghetto-looking one that I don't dare to show (also because I don't feel like opening the box, AGAIN. But I can assure you it works fine.
But here is the finished product. I attached a paracord loop at the end so it can be hung up a tree or something.

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As you can see I also added a couple of ferrite cores to the coax. This is because until you start to tinker with RF, you live under the illusion that coax cables actually keep noise and unwanted signals out. HAH! Funny. See, at high frequencies, the outer shield starts to act as an antenna in itself, and the impedance between the radio ground and the length of the cable is enough to induce currents in the shield. These currents travel up the coax and head straight into the antenna. To mitigate this somewhat, ferrite cores are added to the coax, to short out the shield current and stop the noise.
This holds true for all antenna systems, but it's especially important of high sensitivity antennas.

[zero cool]

I have thought about redoing and tidying up the wiring in the radio receiver I'm currently working on ever since I built it really.. It had always been an ugly hack job because I built it with pretty much no wire to use, so it all turned into a bodge job from the start. And several changes and additions through out the years has not helped the matter.
So I (for some damn reason) got inspired to finally get around to doing something about it. It's by no means extremely tidy afterwards either, but it's done on purpose because it's an ever evolving project with tweaks, mods and tests. The DC-DC converter that's being used for charging is such an example. It's hastily mounted and its wiring is not very neat, because I'm not sure it'll even stay in there.

Aaanyways.. Here are some pics.
A small taste of what it was before. Random bits of wire, sloppy solder joints, and no real rime or reason to anything. It was something resembling a slightly melted spaghetti monster.

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And after some three-ish hours of ripping everything out, soldering in new wires, and going to town with lacing the wires using the completely wrong, too thick thread (not recommended) I ended up with this slightly less shit looking thing. Functionally it's identical to before.

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[nathanpc]

That's some amazing craftsmanship. Congratulations!

You're reminding me that I should look into transferring my ham license from Brazil to Portugal, although given the amount of time work is currently occupying, I don't think I'll have enough free time.

[zero cool]

Thanks!
Oh there is a time and place for everything. I'm sure you'll get around to it eventually