[ZXGuesser] has pulled off a true feat of Meccano engineering: building a Meccano Hellschreiber machine. The design is a close replica of the original Siemens Feld-Hell machine as documented here. What is Hellschreiber, you might ask? It’s a very neat method of sending written messages over the air by synchronizing a printing wheel on the receiving end with pulses generated on the transmitter. By quickly moving the print wheel up and down, arbitrary figures can be printed out. If you want to learn more about Hellschreiber, check out this excellent Hackaday post from almost a decade ago!

The Mastodon thread linked above goes into more detail about the difficulty in building this behemoth — and the slight regret of sticking with the authentic QWERTZ keyboard layout! In order to use the Hellschreiber mode, you have to keep up a steady rhythm of typing at about 2.5 characters per second, otherwise, the receiving end will see randomly spaced gaps between each letter. So while having to type at a steady speed [ZXGuesser] also had to work with a slightly different keyboard layout. Despite this difficulty, some very good quality output was generated!

Incredibly, the output looks just like the output from the original, century-old design. We think this is an absolutely incredible accomplishment, and we hope [ZXGuesser] doesn’t follow through on disassembling this amazing replica — or if they do, we hope it’s documented well enough for others to try their hand at it!

Thanks [BB] for the tip!

In the days before integrated circuits became ubiquitous, providing advanced functionality in a single package, designers became adept at extracting the maximum use from discrete components. They’d use clever circuits in which a transistor or other active part would fulfill multiple roles at once, and often such circuits would need more than a little know-how to get working. It’s not often in 2024 that we encounter this style of circuit, but here’s [Maurycy] with a cheap microwave radar module doing just that.

On the board is an RF portion with a single transistor, some striplines, and an SOIC chip. Oddly this last part turns out to be an infra-red proximity sensor chip, so what’s going on? Careful analysis of the RF circuit reveals something clever. As expected, it’s a 3.18 GHz oscillator, but how is it functioning as both transmitter and receiver? The answer comes in the form of a resistor and capacitor in the emitter circuit, which causes the transistor to also oscillate at about 20 kHz. The result is that at different times in the 20 kHz period, the transistor is either off, fully oscillating at 3.18GHz and transmitting, or briefly in the not-quite-oscillating state between the two during which it functions as a super-regenerative receiver. This is enough for one device to effectively transmit and receive at the same time with the minimum of parts, there’s no need for a mixer diode as you might expect if it were it a direct conversion receiver. Perhaps in RF terms, it’s not particularly pretty, but we have to admit to being impressed by its simplicity. He goes on to perform a few experiments with the board as a transmitter or as a more conventional radar.

This isn’t the first such radar module we’ve looked at, here’s one designed from scratch. And we love regens, since they are so simple to build.

Morse code, often referred to as continuous wave (CW) in radio circles, has been gradually falling out of use for a long time now. At least in the United States, ham radio licensees don’t have to learn it anymore, and the US Coast Guard stopped using it even for emergencies in 1999. It does have few niche use cases, though, as it requires an extremely narrow bandwidth and a low amount of power to get a signal out and a human operator can usually distinguish it even if the signal is very close to the noise floor. So if you want to try and learn it, you might want to try something like this Morse trainer from [mircemk].

While learning CW can be quite tedious, as [mircemk] puts it, it’s actually fairly easy for a computer to understand and translate so not a lot of specialized equipment is needed. This build is based around the Arduino Nano which is more than up for the job. It can accept input from any audio source, allowing it to translate radio transmissions in real time, and can also be connected to a paddle or key to be used as a trainer for learning the code. It’s also able to count the words-per-minute rate of whatever it hears and display it on a small LCD at the front of the unit which also handles displaying the translations of the Morse code.

If you need a trainer that’s more compact for on-the-go CW, though, take a look at this wearable Morse code device based on the M5StickC Plus instead.

OK, it’s official: the Quansheng UV-K5 is the king of hackable ham radios — especially now that a second version of the all-band hardware and firmware mod has been released, not to mention a new version of the radio.

If you need to get up to speed, check out our previous coverage of the all-band hack for the UV-K5, in which [Paul (OM0ET)] installs a tiny PCB to upgrade the radio’s receiver chip to an Si4732. Along with a few jumpers and some component replacements on the main board, these hardware mods made it possible for the transceiver, normally restricted to the VHF and UHF amateur radio bands, to receive everything down to the 20-meter band, in both AM and single-sideband modulations.

The new mod featured in the video below does all that and more, all while making the installation process slightly easier. The new PCB is on a flexible substrate and is considerably slimmer, and also sports an audio amplifier chip, to make up for the low audio output on SSB signals of the first version. Installation, which occupies the first third of the video below, is as simple as removing one SMD chip from the radio’s main board and tacking the PCB down in its footprint, followed by making a couple of connections with very fine enameled wire.

You could load the new firmware and call it a day at that point, but [Paul] decided to take things a step further and install a separate jack for a dedicated HF antenna. This means sacrificing the white LED on the top panel, which isn’t much of a sacrifice for most hams, to make room for the jack. Most of us would put a small SMA jack in, but [Paul] went for a BNC, which required some deft Dremel and knife work to fit in. He also used plain hookup wire to connect the jack, which sounds like a terrible idea; we’d probably use RG-316, but his mod didn’t sound that bad at all.

Keen to know more about the Quansheng UV-K5? Dive into the reverse-engineered schematics.

Thanks to [Sam] for the heads up on this one.

We’ve said it before and we’ll say it again: being able to build your own radios is the best thing about being an amateur radio operator. Especially low-power transmitters; there’s just something about having the know-how to put something on the air that’ll reach across the planet on a power budget measured in milliwatts.

This standalone WSPR beacon is a perfect example. If you haven’t been following along, WSPR stands for “weak-signal propagation reporter,” and it’s a digital mode geared for exploring propagation that uses special DSP algorithms to decode signals that are far, far down into the weeds; signal-to-noise ratios of -28 dBm are possible with WSPR.

Because of the digital nature of WSPR encoding and the low-power nature of the mode, [IgrikXD] chose to build a standalone WSPR beacon around an ATMega328. The indispensable Si5351 programmable clock generator forms the RF oscillator, the output of which is amplified by a single JFET transistor. Because timing is everything in the WSPR protocol, the beacon also sports a GPS receiver, ensuring that signals are sent only and exactly on the even-numbered minutes. This is a nice touch and one that our similar but simpler WSPR beacon lacked.

This beacon had us beat on performance, too. [IgrikXD] managed to hit Texas and Colorado from the edge of the North Sea on several bands, which isn’t too shabby at all with a fraction of a watt.

Thanks to [STR-Alorman] for the tip.

[via r/amateurradio]

Making a software defined radio (SDR) receiver is a relatively straightforward process, given the right radio front end electronics and analogue-to-digital converters. Two separate data streams are generated using clocks at a 90 degree phase shift, and these are passed to the software signal processing for demodulation. But what happens if you lack a pair of radio front ends and a suitable clock generator? Along comes [Mordae] with an SDR using only the hardware on a Raspberry Pi Pico. The result is a fascinating piece of lateral thinking, extracting something from the hardware that it was never designed to do.

The onboard RP2040 ADC is of course far too slow for the task, so instead an input is used, with a negative feedback arrangement from another GPIO to form a crude 1-bit ADC. A PIO peripheral is then used to perform the quadrature mixing, resulting in the requisite pair of data streams. At this point these are sent over USB to GNU Radio for demodulating, mainly for convenience rather than necessarily because the microcontroller lacks the power.

The result is a working SDR front end, demonstrated pulling in an FM broadcast station. The Pico has to be overclocked to reach that frequency and it’s more than a little noisy, but we’re extremely impressed with how much has been done with so little. Oddly it isn’t the first Pico SDR we’ve seen, but the previous one was a much more conventional and lower-frequency affair for the European Long Wave band.

Everyone who deals with electronics knows that grounding is important. Your house has a copper rod in the ground. But [Kristen K6WX] has news: the idea of ground is kind of a myth. She explained at a talk at the recent ARRL National Convention, and if you didn’t make it, you can watch it in the video below.

The problem is analogous to finding something that is standing still. You really can only talk about something standing still relative to something else. Sure, you might be standing still outside a building, but seen from the moon, you and the building are spinning around at about one revolution per day. If you were sitting on the sun and not burning up, you’d see lots of motion of everything, and, of course, the sun itself is moving in the right frame of reference.

So what’s ground? Just a common reference between two things. [Kristen] gets into RF grounds, DC grounds, and phasors. If you’ve ever wanted to ground your antenna or deal with RF interference, you’ll find a lot of information in this 45-minute video.

The name ground is, perhaps, unfortunate. You do want earth grounding for lightning protection, but what most of us think of as ground is just a convention. Need a -9V battery? Just reverse your meter leads, and there you go.

Getting a good common reference can be maddening. We’ve looked at way too many ground loops before.

We’ve all been there. You left your Walkman at home and only have your trusty Game Boy. You want to take a break and just listen to some tunes. What to do? [orangeglo] has the answer now with the Orange FM cartridge.

This prototype cart features an onboard antenna or can also use the 3.5 mm headphone/antenna port on the cartridge to boost reception with either a dedicated antenna or a set of headphones. Frequencies supported are 64 – 108 Mhz, and spacing can be set for 100 or 200 kHz to accomodate most FM broadcasts setups around the world.

Older Game Boys can support audio through the device itself, but Advances will need to use the audio port on the cartridge. The Super Game Boy can pipe audio to your TV though, which seems like a delightfully Rube Goldberg-ian way to listen to the radio. Did we mention it also supports RDS, so you’ll know what that catchy tune is? Try that FM Walkman!

Can’t decide between this and your other carts? Try this revolving multi-cart solution. Have a Game Boy that needs some restoration? If it’s due to electrolyte damage, maybe start here?

Stay in the amateur radio hobby long enough and you might end up with quite a collection of antennas. With privileges that almost extend from DC to daylight, one antenna will rarely do everything, and pretty soon your roof starts to get hard to see through the forest of antennas. It may be hell on curb appeal, but what’s a ham to do?

One answer could be making one antenna do the work of two, as [Guido] did with this diplexer for dual APRS setups. Automatic Packet Reporting System is a packet radio system used by hams to transmit telemetry and other low-bandwidth digital data. It’s most closely associated with the 2-meter ham band, but [Guido] has both 2-meter (144.8-MHz) and 70-cm LoRa (433.775-MHz) APRS IGates, or Internet gateway receivers. His goal was to use a single broadband discone antenna for both APRS receivers, and this would require sorting the proper signals from the antenna to the proper receiver with a diplexer.

Note that [Guido] refers to his design as a “duplexer,” which is a device to isolate and protect a receiver from a transmitter when they share the same antenna — very similar to a diplexer but different. His diplexer is basically a pair of filters in parallel — a high-pass filter tuned to just below the 70-cm band, and a low-pass filter tuned just above the top of the 2-m band. The filters were designed using a handy online tool and simulated in LTSpice, and then constructed in classic “ugly” style. The diplexer is all-passive and uses air-core inductors, all hand-wound and tweaked by adjusting the spacing of the turns.

[Guido]’s diplexer performs quite well — only a fraction of a dB of insertion loss, but 45 to 50 dB attenuation of unwanted frequencies — pretty impressive for a box full of caps and coils. We love these quick and dirty tactical builds, and it’s always a treat to see RF wizardry in action.

In the 1960s, if you were a teenager in the United States, a big part of your life was probably music. There was a seemingly endless supply of both radio stations and 45s to keep you entertained. In the UK and other countries, though, the government held a monopoly on broadcasting, and they were not always enthralled with the music kids liked. Where there is demand, there is an opportunity, and several enterprising broadcasters set up radio stations at sea, the so-called pirate radio stations. In 1964, Irish businessman [Ronan O’Rahilly] did just this and founded Radio Caroline. Can you imagine that 60 years later, Radio Caroline is still around?

Not that it has been in operation for 60 years in a row. There were a few years the station’s ship had been impounded by creditors. Then, the ship ran aground on the Goodwin Sands and was damaged. You can see a news short from 1965 in the video below (Radio Caroline shows up at about the 1:50 mark).

True, Radio Caroline isn’t quite the same as it was. They operate mostly from a legal onshore studio now. But one weekend a month, a crew operates from the ship now in British waters.

Back in 1964, you might have had problems picking up Radio Caroline from far away. Now, the pirate station is as close as your web browser. The other big pirate station was RNI, and they are still around, too.

Something that all radio amateurs encounter sooner or later is the subject of impedance matching. If you’d like to make sure all that power is transferred from your transmitter into the antenna and not reflected back into your power amplifier, there’s a need for the impedance of the one to match that of the other. Most antennas aren’t quite the desired 50 ohms impedance, so part of the standard equipment becomes an antenna tuner — an impedance matching network. For high-power hams these are big boxes full of chunky variable capacitors and big air cored inductors, but that doesn’t exclude the low-power ham from the impedance matching party. [Barbaros Aşuroğlu WB2CBA] has designed the perfect device for them: the credit card ATU.

The circuit of an antenna tuner is simple enough, two capacitors and an inductor in a so-called Pi-network because of its superficial resemblance to the Greek letter Pi. The idea is to vary the capacitances and inductance to find the best match, and on this tiny model it’s done through a set of miniature rotary switches. There are a set of slide switches to vary the configuration or switch in a load, and there’s even a simple matching indicator circuit.

We like this project, in that it elegantly provides an extremely useful piece of equipment, all integrated into a tiny footprint. It’s certainly not the first ATU we’ve brought you.

Thanks [ftg] for the tip!

[Alex R2AUK] has been busy creating version two of a homebrew all-band ham radio transceiver. The unit has a number of features you don’t always see in homebrew radios. It covers the 80, 40, 30, 20, 17, 15, 12, and 10 meter bands. The receiver is a single-IF design with AGC. The transmitter provides up to 10W for CW and 5W for single sideband operations. There’s a built-in keyer, too. A lot of the documentation is in Russian (including the video below, which is part of a playlist). But translation tools are everywhere, so if you don’t speak Russian, you can still probably figure it out.

The VFO for both transmit and receive is an Si5351. The transmit chain is straightforward. The receiver reuses many of the same filters.

Like many projects these days, an attractive 3D-printed case gives the radio a polished look. If you prefer using a straight key to a keyer, the transmitter will use either. The microphone amplifier has built-in compression for good audio levels.

If you don’t want to roll your own, you can get similar ham gear that is ready-built. If you want to go minimal. we’ve seen a less-capable transceiver built with only seven transistors.

The Altoids tin has long been the enclosure of choice for those seeking to show off their miniaturization chops. This is especially true for amateur radio homebrewers — you really have to know what you’re doing to stuff a complete radio in a tiny tin. But when you can build an entire 80-meter transceiver in a matchbox, that’s a whole other level of DIY prowess.

It’s no surprise that this one comes to us from [Helge Fykse (LA6NCA)], who has used the aforementioned Altoids tin to build an impressive range of “spy radios” in both vacuum tube and solid-state versions. He wisely chose solid-state for the matchbox version of the transceiver, using just three transistors and a dual op-amp in a DIP-8 package. There’s also an RF mixer in an SMD package; [Helge] doesn’t specify the parts, but it looks like it might be from Mini-Circuits. Everything is mounted dead bug style on tiny pieces of copper-clad board that get soldered to a board just the right size to fit in a matchbox.

A 9 volt battery, riding in a separate matchbox, powers the rig. As do the earbud and tiny Morse key. That doesn’t detract from the build at all, and neither does the fact that the half-wave dipole antenna is disguised as a roll of fishing line. [Helge]’s demo of the radio is impressive too. The antenna is set up very low to the ground to take advantage of near vertical incidence skywave (NVIS) propagation, which tends to direct signals straight up into the ionosphere and scatter them almost directly back down. This allows for medium-range contacts like [Helge]’s 239 km contact in the video below.

Banging out Morse with no sidetone was a challenge, but it’s a small price to pay for such a cool build. We’re not sure how much smaller [Helge] can go, but we’re eager to see him try.

If you don’t know Morse code, you probably think of a radio operator using a “key” to send Morse code. These were — and still are — used. They are little more than a switch built to be comfortable in your hand and spring loaded so the switch makes when you push down and breaks when you let up. Many modern operators prefer using paddles along with an electronic keyer, but paddles can be expensive. [N1JI] didn’t pay much for his, though. He took paperclips, a block of wood, and some other scrap bits and made his own paddles. You can see the results in the video below.

When you use a key, you are responsible for making the correct length of dits and dahs. Fast operators eventually moved to a “bug,” which is a type of paddle that lets you push one way or another to make a dash (still with your own sense of timing). However, if you push the other way, a mechanical oscillator sends a series of uniform dots for as long as you hold the paddle down.

Modern paddles tend to work with electronic “iambic” keyers. Like a bug, you push one way to make dots and the other way to make dashes. However, the dashes are also perfectly timed, and you can squeeze the paddle to make alternating dots and dashes. It takes a little practice, but it results in a more uniform code, and most people can send it faster with a “sideswiper” than with a straight key.

Don’t like radio? Use Morse Code as your keyboard. Want to learn code? It isn’t as hard as you think.

Like most waves in the electromagnetic spectrum, radio waves tend to bounce off of various objects. This can be frustrating to anyone trying to use something like a GMRS or LoRa radio in a dense city, for example, but these reflections can also be exploited for productive use as well, most famously by radar. Radar has plenty of applications such as weather forecasting and various military uses. With some software-defined radio tools, it’s also possible to use radar for tracking aircraft in real-time at home like this DIY radar system.

Unlike active radar systems which use a specific radio source to look for reflections, this system is a passive radar system that uses radio waves already present in the environment to track objects. A reference antenna is used to listen to the target frequency, and in this installation, a nine-element Yagi antenna is configured to listen for reflections. The radio waves that each antenna hears are sent through a computer program that compares the two to identify the reflections of the reference radio signal heard by the Yagi.

Even though a system like this doesn’t include any high-powered active elements, it still takes a considerable chunk of computing resources and some skill to identify the data presented by the software. [Nathan] aka [30hours] gives a fairly thorough overview of the system which can even recognize helicopters from other types of aircraft, and also uses the ADS-B monitoring system as a sanity check. Radar can be used to monitor other vehicles as well, like this 24 GHz radar module found in some modern passenger vehicles.

Over the past century or so we’ve come up with some clever ways of manipulating photons to do all kinds of interesting things. From lighting to televisions and computer screens to communication, including radio and fiber-optics, there’s a lot that can be done with these wave-particles and a lot of overlap in their uses as well. That’s why you can take something like a fairly standard Wi-Fi antenna meant for fairly short-range communication and use it for some other interesting tasks like downloading satellite data.

Weather satellites specifically use about the same frequency range as Wi-Fi, but need a bit of help to span the enormous distance. Normally Wi-Fi only has a range in the tens of meters, but attaching a parabolic dish to an antenna can increase the range by several orders of magnitude. The dish [dereksgc] found is meant for long-range Wi-Fi networking but got these parabolic reflectors specifically to track satellites and download the information they send back to earth. Weather satellites are generally the target here, and although the photons here are slightly less energy at 1.7 GHz, this is close enough to the 2.4 GHz antenna design for Wi-Fi to be perfectly workable and presumably will work even better in the S-band at around 2.2 GHz.

For this to work, [dereksgc] isn’t even using a dedicated tracking system to aim the dish at the satellites automatically; just holding it by hand is enough to get a readable signal from the satellite, especially if the satellite is in a geostationary orbit. You’ll likely have better results with something a little more precise and automated, but for a quick and easy solution a surprisingly small amount of gear is actually needed for satellite communication.

In the world of cheap amateur radio transceivers, the Quansheng UV-K5 can’t be beaten for hackability. But pretty much every hack we’ve seen so far focuses on the firmware. What about the hardware?

To answer that question, [mentalDetector] enlisted the help of a few compatriots and vivisected a UV-K5 to find out what makes it tick. The result is a (nearly) complete hardware description of the radio, including schematics, PCB design files, and 3D renders. The radio was a malfunctioning unit that was donated by collaborator [Manuel], who desoldered all the components and measured which ones he could to determine specific values. The parts that resisted his investigations got bundled up along with the stripped PCB to [mentalDetector], who used a NanoVNA to characterize them as well as possible. Documentation was up to collaborator [Ludwich], who also made tweaks to the schematic as it developed.

PCB reverse engineering was pretty intense. The front and back of the PCB — rev 1.4, for those playing along at home — were carefully photographed before getting the sandpaper treatment to reveal the inner two layers. The result was a series of high-resolution photos that were aligned to show which traces connected to which components or vias, which led to the finished schematics.

There are still a few unknown components, mostly capacitors by the look of it, but the bulk of the work has been done, and hats off to the team for that. This should make hardware hacks on the radio much easier, and we’re looking forward to what’ll come from this effort. If you want to check out some of the firmware exploits that have already been accomplished on this radio, check out the Trojan Pong upgrade, or the possibilities of band expansion. We’ve also seen a mixed hardware-firmware upgrade that really shines.