High-Stakes Fox Hunting: The FCC’s Radio Intelligence Division In World War II

With few exceptions, amateur radio is a notably sedentary pursuit. Yes, some hams will set up in a national or state park for a “Parks on the Air” activation, and particularly energetic operators may climb a mountain for “Summits on the Air,” but most hams spend a lot of time firmly planted in a comfortable chair, spinning the dials in search of distant signals or familiar callsigns to add to their logbook.

There’s another exception to the band-surfing tendencies of hams: fox hunting. Generally undertaken at a field day event, fox hunts pit hams against each other in a search for a small hidden transmitter, using directional antennas and portable receivers to zero in on often faint signals. It’s all in good fun, but fox hunts serve a more serious purpose: they train hams in the finer points of radio direction finding, a skill that can be used to track down everything from manmade noise sources to unlicensed operators. Or, as was done in the 1940s, to ferret out foreign agents using shortwave radio to transmit intelligence overseas.

That was the primary mission of the Radio Intelligence Division, a rapidly assembled organization tasked with protecting the United States by monitoring the airwaves and searching for spies. The RID proved to be remarkably effective during the war years, in part because it drew heavily from the amateur radio community to populate its many field stations, but also because it brought an engineering mindset to the problem of finding needles in a radio haystack.

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Tune In To “Higher Lower”, The Minimal Handheld Electronic Game

[Tommy] has a great write-up about designing and building a minimalistic handheld electronic game called “Higher Lower”. It’s an audio-driven game in which the unit plays two tones and asks the player to choose whether the second tone was higher in pitch, or lower. The game relies on 3D printed components and minimal electronics, limiting player input to two buttons and output to whatever a speaker stuck to an output pin from an ATtiny85 can generate.

Fastener-free enclosure means fewer parts, and on the inside are pots for volume and difficulty. We love the thoughtful little tabs that hold the rocker switch in place during assembly.

Gameplay may be straightforward, but working with so little raises a number of design challenges. How does one best communicate game state (and things like scoring) with audio tones only? What’s the optimal way to generate a random seed when the best source of meaningful, zero-extra-components entropy (timing of player input) happens after the game has already started? What’s the most efficient way to turn a clear glue stick into a bunch of identical little light pipes? [Tommy] goes into great detail for each of these, and more.

In addition to the hardware and enclosure design, [Tommy] has tried new things on the software end of things. He found that using tools intended to develop for the Arduboy DIY handheld console along with a hardware emulator made for a very tight feedback loop during development. Being able to work on the software side without actually needing the hardware and chip programmer at hand was also flexible and convenient.

We’ve seen [Tommy]’s work before about his synth kits, and as usual his observations and shared insights about bringing an idea from concept to kit-worthy product are absolutely worth a read.

You can find all the design files on the GitHub repository, but Higher Lower is also available as a reasonably-priced kit with great documentation suitable for anyone with an interest. Watch it in action in the video below.

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3D Printing A Modular Guitar Means It Can Look Like Whatever You Want

Got some spare filament and looking to build a guitar you can truly call your own? [The 3D Print Zone] has created a modular 3D printable guitar system that lets you easily mix and match different components for the ultimate in customization.

The build is based around a central core, which combines the pickups, bridge, and neck into one solid unit. This is really the heart of the guitar, containing all the pieces that need to be in precise alignment to get those strings vibrating precisely in tune. The core then mounts to a printed outer body via mating slots and rails, which in the main demo is made to look like a Les Paul-style design. This outer body also hosts the volume, tone, and pickup controls. Output from the pickups travels to the controls in the outer body via a set of metallic contacts.

What’s cool about this build is that the sky really is the limit for your creativity. As the video below demonstrates, the main build looks like a Les Paul. But, armed with the right CAD software, you can really make a guitar that looks like whatever you want, while the 3D printer does all the hard work of making it a reality. The files to print the guitar, along with the pickups and other components, are available as kits—but there’s also nothing stopping you from working up your own printed guitar design from scratch, either.

We’ve seen some other great 3D printed guitars before, too.

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A Lego vehicle crossing a gap between two benches.

Making A LEGO Vehicle Which Can Cross Large Gaps

Here is a hacker showing off their engineering chops. This video shows successive design iterations for a LEGO vehicle which can cross increasingly large gaps.

At the time of writing this video from [Brick Experiment Channel] has been seen more than 110,000,000 times, which is… rather a lot. We guess with a view count like that there is a fairly good chance that many of our readers have already seen this video, but this is the sort of video one could happily watch twice.

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Building An Automatic Wire Stripper And Cutter

Stripping and cutting wires can be a tedious and repetitive part of your project. To save time in this regard, [Red] built an automatic stripper and cutter to do the tiring work for him.

An ESP32 runs the show in this build. Via a set of A4988 stepper motor drivers, it controls two NEMA 17 stepper motors which control the motion of the cutting and stripping blades via threaded rods. A third stepper controls a 3D printer extruder to move wires through the device. There’s a rotary encoder with a button for controlling the device, with cutting and stripping settings shown on a small OLED display. It graphically represents the wire for stripping, so you can select the length of the wire and how much insulation you want stripped off each end. You merely need select the measurements on the display, press a button, and the machine strips and cuts the wire for you. The wires end up in a tidy little 3D-printed bin for collection.

The build should be a big time saver for [Red], who will no longer have to manually cut and strip wires for future builds. We’ve featured some other neat wire stripper builds before, too. Video after the break.

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Building An Eight Channel Active Mixer

There are plenty of audio mixers on the market, and the vast majority all look the same. If you wanted something different, or just a nice learning experience, you could craft your own instead. That’s precisely what [Something Physical] did. 

The build was inspired by an earlier 3-channel mixer designed by [Moritz Klein]. This project stretches to eight channels, which is nice, because somehow it feels right that a mixer’s total channels always land on a multiple of four. As you might expect, the internals are fairly straightforward—it’s just about lacing together all the separate op-amp gain stages, pots, and jacks, as well as a power LED so you can tell when it’s switched on. It’s all wrapped up in a slant-faced wooden box with an aluminum face plate and Dymo labels. Old-school, functional, and fit for purpose.

It’s a simple build, but a satisfying one; there’s something beautiful about recording on audio gear you’ve hewn yourself. Once you’ve built your mixer, you might like to experiment in the weird world of no-input mixing. Video after the break.

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Open Source Watch Movement Really Ticks All The Boxes

When you think of open-source hardware, you probably think of electronics and maker tools– RepRap, Arduino, Adafruit, et cetera. Yet open source is an ethos and license, and is in no way limited to electronics. The openmovement foundation is a case in point– a watch case, to be specific. The “movement” in Openmovement is a fully open-source and fully mechanical watch movement.

Openmovement has already released STEP files of OM10 the first movement developed by the group. (You do need to sign up to download, however.) They say the design is meant to be highly serviceable and modular, with a robust construction suited for schools and new watchmakers. The movement uses a “Swiss pallets escapement” that runs at 3.5 Hz / 25,200 vph. (We think that’s an odd translation of lever escapement, but if you’re a watchmaker let us know in the comments.)  An OM20 is apparently in the works, as well, but it looks like only OM10 has been built from what we can see.

If you don’t have the equipment to finely machine brass from the STEP files, Openmovement is running a crowdfunding campaign to produce kits of the OM10, which you can still get in on until the seventh of June.

If you’re wondering what it takes to make a mechanical watch from scratch, we covered that last year. Spoiler: it doesn’t look easy. Just assembling the tiny parts of an OM10 kit would seem daunting to most of us. That might be why most of the watches we’ve covered over the years weren’t mechanical, but at least they tend to be open source, too.