Radio Repeaters In The Sky

April 30, 2025 by Bryan Cockfield 10 Comments

One of the first things that an amateur radio operator is likely to do once receiving their license is grab a dual-band handheld and try to make contacts with a local repeater. After the initial contacts, though, many hams move on to more technically challenging aspects of the hobby. One of those being activating space-based repeaters instead of their terrestrial counterparts. [saveitforparts] takes a look at some more esoteric uses of these radio systems in his latest video.

There are plenty of satellite repeaters flying around the world that are actually legal for hams to use, with most being in low-Earth orbit and making quick passes at predictable times. But there are others, generally operated by the world’s militaries, that are in higher geostationary orbits which allows them to serve a specific area continually. With a specialized three-dimensional Yagi-Uda antenna on loan, [saveitforparts] listens in on some of these signals. Some of it is presumably encrypted military activity, but there’s also some pirate radio and state propaganda stations.

There are a few other types of radio repeaters operating out in space as well, and not all of them are in geostationary orbit. Turning the antenna to the north, [saveitforparts] finds a few Russian satellites in an orbit specifically designed to provide polar regions with a similar radio service. These sometimes will overlap with terrestrial radio like TV or air traffic control and happily repeat them at brief intervals.

[saveitforparts] has plenty of videos looking at other satellite communications, including grabbing images from Russian weather satellites, using leftover junk to grab weather data from geostationary orbit, and accessing the Internet via satellite with 80s-era technology.

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British wartime periscope on a workbench

British Wartime Periscope: A Peek Into The Past

April 22, 2025 by Heidi Ulrich 4 Comments

We all know periscopes serve for observation where there’s no direct line-of-sight, but did you know they can allow you to peer through history? That’s what [msylvain59] documented when he picked up a British military night vision periscope, snagged from a German surplus shop for just 49 euros. Despite its Cold War vintage and questionable condition, the unit begged for a teardown.

The periscope is a 15-kilo beast: industrial metal, cryptic shutter controls, and twin optics that haven’t seen action since flares were fashionable. One photo amplifier tube flickers to greenish life, the other’s deader than a disco ball in 1993. With no documentation, unclear symbols, and adjustment dials from hell, the teardown feels more like deciphering a British MoD fever dream than a Sunday project. And of course, everything’s imperial.

Despite corrosion, mysterious bulbs, and non-functional shutters, [msylvian59] uncovers a fascinating mix of precision engineering and Cold War paranoia. There’s a thrill in tracing light paths through mil-spec lenses (the number of graticules seen that are etched on the optics) and wondering what secrets they once guarded. This relic might not see well anymore, but it sure makes us look deeper. Let us know your thoughts in the comments or share your unusual wartime relics below.

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Building A 3D Printed Phone Handset With Mil-Spec Style

December 28, 2024 by Tom Nardi 14 Comments

In general, military gear is designed to be rugged and reliable. A side effect of this is that the equipment usually has a distinct visual look that many people find appealing. You might not need a laptop that can survive being in a war zone, but plenty of hackers have picked such machines up on the second hand market anyway.

Case in point, the H-250 telephone handset. [Tobias] didn’t actually need a combat-ready phone handset, but loved the way it looked. Technically you can pick these up on eBay for a reasonable price, but then you’ve still got to deal with the weirdo military components inside it. So why not design a look-alike and 3D print it?

[Tobias] came up with a design in OpenSCAD that has a very close resemblance to its military counterpart. Not only has he made the source code for the 3D model available for others who might want to print their own look-alike handset, but the Hackaday.io page also includes a breakdown of the hardware that needs to be added to the printed parts to make it a functional handset.

If you think the H-250 handset looks familiar, it’s probably because it comes standard issue on the TA-1042 field telephone — another very slick looking piece of military gear that we’ve covered previously.

RC Submarine Build Starts With Plenty Of Research

August 13, 2024 by Orlando Hoilett 19 Comments

[Ben]’s a 15-year-old who loves engineering and loves taking on new challenges. He’s made some cool stuff over the years, but the high water mark (no pun intended) has to be this impressively documented remote controlled submarine.

His new build starts off with more research than the actual building. [Ben] spent a ton of time investigating the design of the submarine from its shape, to the propeller system, to the best way to waterproof everything, keeping his sub in tip-top shape. He decides to go with the Russian-style Akula submarine, which is probably the generic look that most of us would think of when we hear the word submarine. He had some interesting thoughts on the propeller system (like the syringe ballast we’ve seen before), and which type of motor to use. In the end, he decided with four pumps that would act essentially as thrusters. ~~fill a chamber with water, allowing the submarine to submerge, or fill with air, making the submarine buoyant, allowing it to resurface.~~

However, what we found most interesting about his build is how he explains the rationale for all his design decisions and clearly documents his thought process on his project page. We really can’t do [Ben]’s project justice in a short post, so head over to his project page to see it for yourself.

While you’re at it, check out some of these other cool submarine builds that we’ve featured here on Hackaday

Retrotechtacular: How Not To Use Hand Tools

May 6, 2024 by Dan Maloney 48 Comments

Whatever you’re doing with your hand tools, by the US Army’s lights, you’re probably doing it wrong. That seems to be the “Green Machine’s” attitude on pliers and screwdrivers, at least, the main stars of this 1943 War Department training film on the horrors of tool abuse.

As kitschy as the film might be, they weren’t wrong. That’s especially true about the dreaded slip-joint pliers, which seem to find their way onto everyone’s list of unloved tools and are shown being used for their true purpose — turning nuts and bolt heads from hexagons into circles. Once that gore is wrapped up, we’re treated to the proper uses of pliers, including the fascinating Bernard-style parallel jaw pliers. We can recall these beauties kicking around the bottom of Dad’s tool kit and being entranced by the mechanism used to keep the jaws parallel and amplify the force applied. Sadly, those pliers are long gone now; Tubalcain did a great review of these pliers a few years back if you need a refresher.

A selection of screwdrivers gets the same treatment, complete with dire warnings against using them as prybars and chisels. Also against the Army Way is using the wrong size screwdriver for the job, lest you strip the head of the screw or break the tool itself. It has to be said that the Plomb Tool Company of Los Angeles, which produced the film, made some fantastic-looking screwdrivers back in the day. The square shanks on some of those straight screwdrivers are enormous, and the wooden handles look so much more comfortable than the greebled-up plastic nonsense manufacturers seem to favor these days. Also interesting is the reference to the new-fangled Phillips screw, not to mention the appearance of a Yankee-style spiral ratcheting screwdriver, another of Dad’s prized acquisitions that thankfully is still around to this day.

What strikes us about these military training films is how many of them were produced. No subject seemed too mundane to get a training film made about it, and so many were made that one is left wondering how there was any time left for soldiering after watching all these films. But really, it’s not much different today, when we routinely pull up a random YouTube video to get a quick visual demo of how to do something we’ve never tried before. The medium may have changed, but visual learning is still a thing.

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Computer Gear With — Um — Gears

November 21, 2023 by Al Williams 10 Comments

Analog computers have been around in some form for a very long time. One very obvious place they were used was in military vehicles. While submarine fire computers and the Norden bombsight get all the press, [msylvain59] has a lesser-known example: an M13A1 ballistic computer from an M48 tank that he tears down for us in the video below.

The M48, known as a Patton, saw service from 1952 to 1987. Just looking at the mechanical linkage to the tank’s systems is impressive. But inside, it is clear this is a genuinely analog computer. The thing is built — quite literally — like a tank. What was the last computer you opened that needed a hammer? And inside, you’ll find gears, bearings, and a chain!

We don’t pretend to understand all the workings. These devices often used gears and synchros (or selsyns, if you prefer) to track the position of some external thing. But we are guessing there was a lot more to it than that. It’s probably an exciting process to see something like that designed from scratch.

We did think of the Norden when we saw this. Hard to imagine, but there were “general purpose” analog computers.

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China Plans Its Own Megaconstellation To Challenge Starlink

June 22, 2023 by Lewin Day 39 Comments

Satellite internet used to be a woeful thing. Early networks relied on satellites in geostationary orbits, with high latency and minimal bandwidth keeping user demand low. That was until Starlink came along, and provided high-speed, low-latency internet access using a fleet of thousands of satellites in Low Earth orbit.

Starlink has already ruffled feathers due to concerns around light pollution and space junk in particular. Now, it appears that China may be readying its own competing constellation to avoid being crowded out of low orbits by the increasingly-popular service.

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