Author: Al Williams

4547 Articles

Postal IRCs Are Almost A Thing Of The Past

July 21, 2026 by 18 Comments

Have you ever found out that something you remember from your youth is now gone, and you didn’t even notice? If you are a certain age, you might feel that way when I deliver the news: You haven’t been able to buy International Reply Coupons (IRCs) at a US Post Office since early 2013. By the end of 2026, you won’t be able to buy them anywhere. The age of the IRC is over.

What’s an IRC?

An IRC from 1978 (public domain).

If that didn’t mean anything to you, you might be too young to remember, or maybe you just weren’t into shortwave listening or ham radio. Although there were other reasons to get IRCs, a radio hobby is the most likely reason a Hackday reader would have bought an IRC.

For radio purposes, here’s the problem. You’ve worked on your station for months, and one winter night, you finally pull in that rare station from Luxembourg. They’ll send you a QSL card to verify that you heard them. You only have to send them a letter telling them what time you heard them, what frequency, and some details about the program you heard. But they probably don’t want to pay the postage required to send hundreds or thousands of cards overseas.

While this is a radio-specific problem, you might find the same issue with pen pals or when trying to buy things from an overseas company.

SASE

If everyone were in the same country, the solution would be easy. Take a stamp, put it on an envelope that has your address on it, and stuff it in with the letter. Or, you could just drop a stamp or two in the letter you sent.

The problem is, US postage won’t help Radio Luxembourg. On the other hand, the effort required for you to buy postage that works in Luxembourg would have been a nightmare.

Enter the UPU

The Universal Postal Union is a UN agency that is effectively an association of post offices in 192 countries. Their charter is to facilitate mailing things worldwide.

The IRCs date back to 1906. The idea is you buy an IRC at your post office. You send it to Radio Luxembourg, or wherever. There, the mail person at the radio station could go to their post office and trade the coupon for enough local postage to send a surface letter worldwide.

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Tired Of Xargs?

July 21, 2026 by 32 Comments

What if you want to do something in Linux for a lot of files? [Numerator] was tired of using xarg and other ways to handle this job and created bashumerate.

Some examples in the post of the “other ways” include:

find . -name '*.log' | xargs rm
find . -name '*.sh' -exec wc -l {} \;

You can, also, use a for loop, and if you are a programmer at heart, you may well do this:

for f in *.txt; do
  wc -l "$f"
done

Bashumerate handles all of the common cases in one tool and uses the same syntax for multiple kids of enumerations.

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Your AI Ham Radio Buddy

July 18, 2026 by 12 Comments

AI chatbots are everywhere these days, and they seem to “know” about everything. But while that is a strength, it can sometimes be a weakness because it isn’t laser-focused on one topic. Not so with this Ham-radio-centric chatbot called HamGPT. The service is clearly built on another GPT engine but understands how to retrieve data from common ham radio sources, such as the FCC database, propagation reports, and the like. It didn’t, however, seem to have access to ham radio-related books, magazine articles, or other “static” data that we could tell.

You do have to sign up for an account, which includes providing your callsign and location. There is a free tier that allows a limited number of queries per day, so you can try it to see if it is useful for you without subscribing.

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A USB Port By Any Other Color…

July 16, 2026 by 34 Comments

[Dr. Gough] bought a generic USB 3.0 hub on an Asian website. Surely, USB 3 is mature enough that even the cheapest hub will have some IC in it that will work well, right? You’d think so, but a little exploratory surgery showed that the only thing about this hub that was USB 3 were the blue port connectors.

We have a few problem USB hubs ourselves, so it might be worth doing this to any you have lying around. The first clue: most of the connectors on the PCB only have four pins. On closer examination, the hub appears to be a USB 3.0 extension cable with a USB 2.0 hub made from two HS8836A chips.

Not only are these USB 2-only, but all the ports on an HS8836A also share the same USB 1.1 bandwidth. Some hubs can provide multiple ports full 1.1 bandwidth, using the higher-speed USB protocol to the PC as a backhaul.

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Chromatography As Art

July 15, 2026 by 7 Comments

You may or may not remember in some ancient chemistry class studying or even performing chromatography. The short definition is using media like paper or powder to separate a mixture. It is an old technique, but [Suchir2004] is using it as an art form.

Chromatography works because the parts of the liquid mixture travel through the media at different speeds. While experimenting, [Suchir2004] noted that black ink and water perfused into constituent pigments. A butterfly ensued.

Is it art? Yes! Is it science? Well, sort of. Especially since the post does talk about how the effect works and even does some simple tests to start. This would be an excellent project for a class where some students are more motivated by art and others by science. Even with an individual kid, it might show you where their interests lie.

There’s nothing particularly difficult. A sketch pen, some paper, a coffee filter, a glue stick, and a few other household items are all you really need to get started.

Want something more practical? How about measuring caffeine content?

Putting Some Zig In A Linux-Based 3D Printer

July 15, 2026 by 17 Comments

Having Linux on so many devices is both a blessing and a curse. Sure, it is great that you can hack on things and modify them or even totally repurpose them. But it also means you have a fleet of Linux devices you have to manage and keep track of.

My current “main” 3D printer is a Flashforge AD5X: a nice, cheap machine that does four colors with the purge/exchange method. It sort of runs Klipper. I say sort of because Flashforge has Klipper running on a Linux host in the box, but it is massively crippled and modified. I’m sure it works for most folks. I’m also sure that if you know nothing about Linux, Klipper, or 3D printing, the experience is probably better thanks to all the cloud point-and-click interfaces. But, of course, I check none of those boxes.

I’ve had the printer for probably a year or more. Almost immediately, I put a “mod” on the printer to give it a more true Klipper interface and gave me things like shell access. There are several that I think will do this, but I used Zmod, which doesn’t totally replace the printer’s firmware; it just sort of patches it and extends it. You can easily bypass or even remove it and go back to the stock printer, although I would not want to.

In my case, the issue was a printer, but the same idea might apply to any embedded Linux system, from a router to a thermostat. Sure, it runs Linux, but is it Linux you can change?

The Problem

The AD5X runs Linux… sort of.

The Flashforge firmware and Zmod both will run on the AD5X’s little sister, the AD5M. However, the AD5M has a significantly less capable processor board than the AD5X. That means that Linux on the boxes is very stripped down. From Flashforge’s point of view, no one should be in the Linux OS anyway, and the author of Zmod probably figures every byte used is a byte taken away from the user or other advanced Zmod features.

It may seem like a first-world problem, but there were two things that irked me about the printer’s Linux. There was no less or more command for poking around files. There was also only vi as an editor. I did a few hacks to make myself happy. I wrote a pager in shell script, for example. I would try to remember to use my desktop emacs and tramp to edit files on the box. But it was a shame that there were some very basic tools lacking. Besides that, even the tools that were there like ls lacked help commands in case you want some strange option you can’t remember.

No Install

To save space, the printer doesn’t really have programs like ls, cat, and grep. Instead, it has a single busybox executable. This is common on small systems. You get one copy of the libraries and a single executable that will do all the work you need. You can invoke, for example, grep by running “busybox grep” or, if you make a symlink to busybox named grep, the user may never realize that you don’t really have grep installed.

However, busybox has to be built. You can’t easily install packages to it. So I couldn’t just run some package manager and install less or anything else. My plan was to produce a new busybox package myself to supply at least the missing commands and maybe some of the more basic ones, too. How hard could it be?

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Newton’s Cradle Isn’t Really Perpetual

July 13, 2026 by 20 Comments

If any astute Hackaday reader saw [dongvua90]’s Newton’s cradle go on without human intervention all day long, they’d probably suspect the truth: there’s a battery and a magnet involved. But it is a nice desk piece, and you might be able to fool your less enlightened friends that you’ve discovered perpetual motion. Watch the resulting faux perpetual motion machine in action in the video below.

The trick is to sense the ball’s travel and inject a little electromagnetic pulse at just the right time. No problem for an ESP32 and a proximity sensor like the ones you find on some 3D printers. In fact, there’s very little custom circuitry. Everything is a module, and even the Newton’s cradle is cut out of a premade toy. A printed case and some software are really the heart of the design.

We can imagine this might be an interesting science demonstrator. Show the class the cradle with the electronics turned off, then subtly turn it on and ask the class what changed. You could even make the point by having students do it normally, while only you can get it to keep going forever, and challenge them to deduce what’s going on.

You might correctly imagine that this isn’t the first one of these we’ve seen. You can also build one that is sort of simulated.

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