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?

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.

Slow Death

As demand has dwindled, post offices worldwide have quit selling IRCs. As of last year, Australia still did. But Germany, Britain, the United States, and many other countries gave up on them long ago. In fact, Britain’s Royal Mail claimed that the average post office sold less than one IRC per year at the time it threw in the towel.

UPU decided to end IRCs altogether by December 31, 2026. The end of an era and, apparently, not just for radio hobbyists. It is telling that the UPU’s recent editions of IRCs had print runs of 1,000 or even 500. So they obviously weren’t selling very many.

IRCs Other Claim to Fame

If you’ve heard of these before and you aren’t interested in radio, then it might have been in economic history. Have you heard of the Ponzi scheme? It has become a generic term for any business scheme that relies on raising money from new investors to service debt owed to old investors.

However, the original Ponzi scheme dates back to 1920, when Charles Ponzi realized he could buy IRCs in a country where they were cheap and sell them for more in another country. He was happy to accept investors, of course.

The problem is that profits are thin, and the costs of acquiring and transporting large numbers of IRCs quickly swamp most potential profits. Fluctuations in currency exchange rates take the rest.

Goodbye!

So the end of the IRC marks a closed chapter for ham radio and swindling. There were probably other uses, too, that are now consumed by electronic mail, payment systems, and the like.

You have to wonder what adventures IRCs went on during their global travels. The video below shows one’s story.

These days, it is easy to think you always have access to the Internet. But some wonder if — in spite of its ARPANET, nuclear-war-planning heritage — you can actually count on it to be there when things go pear-shaped. [The Tech Prepper], as you might imagine, is quite concerned with that last question, and is flogging Reticulum over high-frequency radio as a post-internet network in a video embedded below.

Reticulum is a cryptographic network stack, fully decentralized and amazing from a cyberpunk/hacker/survivalist perspective. Unfortunately for [The Tech Prepper], until the you-know-what hits the ventilation unit and the FCC and its counterparts in other countries are too busy to be concerned with such trifles, encrypted signals are banned on ham radio bands just about everywhere. That’s why his demo is using a dummy load on the Mercury HF modem instead of an antenna: the feds don’t care if the signal doesn’t leave the building. The video shows how to replicate the setup using his EmComm Tools suite on Ubuntu.

Perhaps more interesting is his vision of a Post-Internet network, be it in a disaster scenario, as he envisions, or simply because we get sick of what the internet has become. The idea of easily hooking an open-source radio modem to a PC running modem73, open-source SDR software, has a certain appeal. Reticulum isn’t your only option there: modem73 will let you run a BBS in the clear — that is, unencrypted and legal to transmit — and let’s face it, wasn’t life online more fun in BBS days?

This isn’t the first time we’ve seen the Reticulum network stack, but last time it was operating at considerably shorter ranges over LoRA. 

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.

Here’s a typical session:

                What band will have the best propagation to Japan from my QTH right now?

The best band for Japan from your QTH right now is 30 meters, which shows good propagation reliability. 20 meters is also active and providing a viable path.

Real-time data confirms activity on both bands, primarily using FT8. While the path is open, the signals are relatively weak (typical for this long-haul path), making digital modes like FT8 or CW your best bet for a successful contact.

Would you like me to check if your current antenna setup is suitable for these bands, or perhaps help you calculate dimensions for a 30m or 20m antenna?

In addition, bubbles at the bottom of the screen showed me the busiest band in my area and how many repeaters were nearby.

In all fairness, we asked ChatGPT the same question, but did say “ham radio band” just to give it some idea of scope. It gave a much more detailed answer with sources, even provided headings, and made a suggestion about another location I sometimes operate from because it remembers things from previous unrelated chats.

We understand reactions will be mixed. If you’ve been a ham for a long time, you probably could have guessed that a path from the US to Japan in the morning was likely to be on 20 or 30 meters. You probably also know how to look things up yourself.

We didn’t try any more sophisticated queries that might make it more worthwhile. For example, what if you could send it an ADIF log file and ask it what awards you qualified for? Or to process contest logs for duplicates and fill out a scoring worksheet? What would you like a ham radio-aware AI to do for you?

Ham radio — at least parts of it — has become inextricably linked with computers.

There are plenty of radios you can buy that pick up MW and SW bands if that’s what you’re into. Or, you can follow [mircemk]’s example, and whip one up yourself instead.

The build employs an ESP32 as the brains of the operation. It’s hooked up to a rotary encoder and a small colour TFT screen, which displays an old-school style tuning dial for choosing the desired frequency. This setup is paired with an Si5351—a capable clock generator chip that can deliver just about any frequency from <8KHz up to 150+ MHz on command. There’s naturally a bunch of supporting analog hardware for the radio end of things, plus a NE612 mixer IC and a PAM8403 class D audio amplifier board, hooked up to a small 0.25W speaker for audio output. [mircemk] has set up the rig to act as a simple radio set, or, with the flick of a switch, it can be configured for SDR use with an attached computer.

It’s a handsome build, and one that likely proves a pleasant way to browse the MW and SW bands on a rainy afternoon. We’ve looked at other hardware in this category before, too. Video after the break.

We’re all used to satellite navigation systems such as GPS or GLONASS, sheer magic in which the combination of a set of reference transmitters and super-accurate timing information can be used to calculate a position to an astounding precision. They had land based predecessors such as LORAN and Decca Navigator which worked in a similar fashion but with fixed land-based reference transmitters. Terra is an attempt to do the same thing without a network of dedicated transmitters, instead using FM broadcast transmitters as its fixed points.

This might seem like an impossible task without access to the transmitters, but they have a workaround using the Internet as a backhaul. Instead of transmitting their timing information like the systems mentioned above, they rely on a set of reference receivers sharing it online to the client’s receiver software. So far they have a demo running in Denver.

The interesting thing about this system is that it’s open-source, and requires only a relatively inexpensive software defined radio receiver and a computer to operate. Now anyone with a group of internet-connected friends to set up reference receivers can have their own positioning system, it’s no longer the exclusive preserve of governments. We like this idea, and we look forward to seeing it being tested more widely.

If you’d like to know where we’ve come from, we’ve taken a look at LORAN before.