It’s Numbers All The Way Down With This Tape Measure Number Station Antenna

September 6, 2023 by 12 Comments

For all their talk of cooperation and shared interests, the nations of the world put an awful lot of effort into spying on each other. All this espionage is an open secret, of course, but some of their activities are so mysterious that no one will confirm or deny that they’re doing it. We’re talking about numbers stations, the super secret shortwave radio stations that broadcast seemingly random strings of numbers for the purpose of… well, your guess is as good as ours.

If you want to try to figure out what’s going on for yourself, all you need is a pair of tape measures and a software defined radio (SDR), as [Tom Farnell] demonstrates. Tape measure antennas have a long and proud history in amateur radio and shortwave listening, being a long strip of conductive material rolled up in a convenient package. In this case, [Tom] wanted to receive some well-known numbers stations in the 20- to 30-meter band, and decided that a single 15-meter conductor would do the job. Unlike other tape measure antennas we’ve seen, [Tom] just harvested the blades from two 7.5-meter tape measures, connected them end-to-end, and threw the whole thing out the window in sort of a “sloper” configuration. The other end is connected to an RTL-SDR dongle and a smartphone running what appears to be SDRTouch, which lets him tune directly into the numbers stations.

Copying the transmissions is pretty simple, since they transmit either in voice or Morse; the latter can be automatically decoded on a laptop with suitable software. As for what the long strings of numbers mean, that’ll remain a mystery. If they mean anything at all; we like to think this whole thing is an elaborate plan to get other countries to waste time and resources intercepting truly random numbers that encode nothing meaningful. It would serve them right.

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Finally, A Machine To Organize Resistors!

September 6, 2023 by 37 Comments

Perhaps it’s a side-effect of getting older, but it seems like reading the color bands on blue metal-film resistors is harder than it was on the old brown carbon ones. So often the multimeter has to come out to check, but it’s annoying. Thus we rather like [Mike]’s Resistorganizer, which automates the process of keeping track of the components.

At its heart is a fairly simple concept, with the microcontroller reading the value of a resistor by measuring the voltage from a potential divider. The Resistorganizer extends this using an array of analogue multiplexer chips, and is designed to plug into one side of a breadboard with the idea being that each line can have a resistor connected to earth through it. Of course it’s not quite as simple as that, because to maintain a readable range a set of resistors must be switched in and out to form the other half of the divider for different ranges. Thus another multiplexer chip performs that task.

Finally a set of digital multiplexers handles an LED to see which of the many resistors is currently selected through a pair of buttons, and a dot-matrix LCD display delivers the value. We want one already!

Streaming Video From An ESP32

September 5, 2023 by 11 Comments

The ESP32, while first thought to be little more than a way of adding wireless capabilities to other microcontrollers, has quickly replaced many of them with its ability to be programmed as its own platform rather than simply an accessory. This also paved the way for accessories of its own, such as various sensors and even a camera. This guide goes over taking the input from the camera and streaming it out over the network to multiple browsers.

On the server side of things, the ESP32 and its attached camera are set up with MQTT, a lightweight communications protocol which uses a publish/subscribe model to send information. The ESP32 is configured to publish its images only, but not subscribe to any other nodes. On the client side, the browser runs a JavaScript program which is able to gather these images and stitch them together into a video.

This can be quite a bit of data to send out over the ESP32’s compact hardware, so there are some tips and tricks for getting more out of these little devices, including using an external antenna for better Wi-Fi signal, or omitting it entirely in favor of Ethernet. As far as getting a lot out of a tiny microcontroller, though, leveraging MQTT really helps the ESP32 go a long way. These chips have come along way since they were first introduced; they’re powerful enough to act as 8-bit gaming consoles too.

Thanks to [Surfskidude] for the tip!

Electro-Optical Control Of Lasers With A Licorice Twist

September 5, 2023 by 8 Comments

You’ve got to hand it to [Les Wright]; he really knows how to dig into optical arcana and present topics in an interesting way. Case in point: an electro-optical control cell that’s powered by ouzo.

OK, the bit about the Greek aperitif may be stretching things a bit, but the Kerr Cell that [Les] builds in the video below does depend on anethole, the essential component of aniseed extract, which lends its aromatic flavor to everything from licorice to Galliano and ouzo. As [Les] explains, the Kerr effect uses a high-voltage field to rapidly switch light passing through a medium on and off. The most common medium in Kerr cells is nitrobenzene, a “distressingly powerful organic solvent” with such fun side effects as toxicity, flammability, and carcinogenicity.

Luckily, [Les] found a suitable substitute in the form of anethole — a purified sample, not just an ouzo nip. The solution went into a plain glass cuvette equipped with a pair of aluminum electrodes, which got connected to one of the high-voltage supplies we’ve seen him build before for his nitrogen laser. A pair of polarizing filters go on either end of the cuvette, and are adjusted to blank out the light passing through it. Applying 45 kilovolts across the cell instantly turns the light back on. Watch it in action in the video below.

There’s a lot of room left for experimentation on this one, including purification of the anethole for potentially better results. We’d also be curious if plain ouzo would show some degree of Kerr effect. For science, of course.

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Clean Up Your Resin-Printing Rinse With Dialysis

September 5, 2023 by 64 Comments

There’s a lot to like about resin 3D printing. The detail, the smooth surface finish, the mechanical simplicity of the printer itself compared to an FDM printer. But there are downsides, too, not least of which is the toxic waste that resin printing generates. What’s one to do with all that resin-tainted alcohol left over from curing prints?

How about sending it through this homebrew filtering apparatus to make it ready for reuse? [Involute] likens this process to dialysis, and while we see the similarities, what’s going on here is a lot simpler than the process used to filter wastes from the blood in patients with failing kidneys — there are no semipermeable membranes used here. Not that the idea suffers from its simplicity, mind you; it just removes unpolymerized resin from the isopropyl alcohol rinse using the same photopolymerization process used during printing. Continue reading “Clean Up Your Resin-Printing Rinse With Dialysis” →

Raspi-Powered Typewriter Is A Real MUSE

September 5, 2023 by 4 Comments

Thanks to parenting and life in general, [Brendan] had fallen out of the habit of writing and wasn’t happy about it. If you write anything ever, you already know there are endless distractions when it comes to doing so on a computer. Sure, there always typewriters, but it’s difficult to do anything with the fruits of a typewriter other than scan it in or make copies, and it’s basically un-editable except by hand.

Instead of just sitting down and writing, [Brendan] did what any of us would do — took the time to create an elegant solution. The Most Unusual Sentence Extractor, or MUSE, is a Raspberry Pi-based typewriter with the best of both worlds. It’s essentially a word processor, but it can save to the cloud.

[Brendan] found beautiful inspiration in the Olympia Traveller de Luxe typewriter, a delightfully boxy affair made in the 1960s and 70s with lovely keys. Starting with a 68Keys.io board, [Brendan] set about re-creating the lines of the Traveller de Luxe in Tinkercad.

Since it doesn’t really need a platen, this was the perfect place to mount a screen using black PVC. At first, [Brendan] was going to use an e-ink screen, but a mishap led to a better solution — an LCD touchscreen that makes document navigation a breeze.

We absolutely love the look of this machine, which was obviously a labor of love. And yeah, it does the trick:[Brendan] is writing again. Though it maybe be inconvenient, we agree that it really is nice to have a dedicated workstation for certain things.

Looking for the complete opposite of this project? How about a Chat GPT-assisted daisywheel typewriter?

Spooky Noise Box Has Post-Halloween Potential

September 5, 2023 by 8 Comments

There’s more than one way to scare people on Halloween. Sure, there’s always the low-brow jump scare, but that will generally just annoy the person and possibly cause a heart attack. No, what you need is a sustained soundscape of hellish audio. And where does one find hellish audio? Well, you make your own with a spooky-sounds noise box.

And no, we’re not talking about a soundboard that goes ‘boo’ and ‘ooo-OOO-oooh’ and whatnot. This is a full-on DIY instrument that has potential beyond Halloween. Essentially, the wooden box takes input vibrations from various doodads, and these vibrations are picked up by a piezo disk or two glued to the underside of the lid. The piezos are wired up to a 3.5 mm jack, which runs out to the PC and [SvartalfarQc]’s favorite Digital Audio Workstation (DAW). From there, it’s just a matter of playing around with the sounds — looping them, running them through various instrument voices, adding effects, and so on.

We love the the things that [SvartalfarQc] came up with, including a wind-up walking heart thing, a retractable badge holder, and that noise box mainstay, a sproingy doorstop.

We all know piezos are awesome, but have you ever considered that they can be used to digitize old wax cylinder recordings?