A Direct Conversion Receiver Anyone Can Build

January 15, 2025 by 26 Comments

A couple of years ago one of the Hackaday Prize finalists was a project to take highschoolers through building a direct conversion radio receiver for the 40 metre amateur band. It was originated by the SolderSmoke podcast, and we’re pleased to see that they’ve recently put up an overview video taking the viewer through the whole project in detail.

It’s a modular design, with all the constituent building blocks broken out into separate boards on which the circuitry is built Manhattan style. Direct conversion receivers are pretty simple, so that leaves us with only four modules for oscillator, bandpass filter, mixer, and audio amplifier. We particularly like that it’s permeability tuned using a brass screw and an inductor, to make up for the once-ubiquitous variable capacitors now being largely a thing of the past.

A point that resonated was that most radio amateurs never make something like this. Arguments can be made about off-the-shelf rigs and chequebook amateurs, but we’d like to suggest that everyone can benefit from a feel for analogue circuitry even if they rarely have a need for a little receiver like this one. We like this radio, and we hope you will too after seeing the video below the break.

Need reminding? See the Hackaday.io project page, and the Hackaday Prize finalists from that year.

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All The Attacks On The RP2350

January 15, 2025 by 29 Comments

Raspberry Pi’s new microcontroller, the RP2350, has a small section of memory that is meant for storing secrets. It’s protected by anti-glitching and other countermeasures, and the Raspberries wanted to test it. So this summer, they gave them out, pre-programmed with a secret string, as part of the badge for DEFCON attendees. The results of the cracking efforts are in, and it’s fair to say that the hackers have won.

First place went to [Aedan Cullen], who also gave a great talk about how he did it at 38C3. One of the coolest features of the RP2350, from a hacker perspective, is that it has dual ARM and dual RISC-V cores onboard, and they can be swapped out by multiplexers. The security module has a critical register that has disable bits for both of these processors, but it turns out that the ARM disable bits have priority. When [Aedan] glitched the security module just right, it disabled the ARM cores but left the RISC-V cores running in the secure context, with full debug(!), and the game was over. As of yet, there is no mitigation for this one, because it’s baked into the secure boot module’s silicon.

[Marius Muench] managed to pre-load malicious code into RAM and glitch a reboot-out-of-secure-mode on the USB module. This one is possibly fixable by checking other reboot flags. [Kévin Courdesses] has a sweet laser fault-injection rig that’s based on the 3D-printable OpenFlexure Delta Stage, which we’ve seen used for microscopy purposes, but here he’s bypassing the anti-glitching circuitry by exposing the die and hitting it hard with photons.

Finally, [Andrew Zonenberg] and a team from IOActive went at the RP2350 with a focused ion beam and just read the memory, or at least the pairwise-OR of neighboring bits. Pulling this attack off isn’t cheap, and it’s a more general property of all anti-fuse memory cells that they can be read out this way. Chalk this up as a mostly-win for the offense in this case.

If you want to read up on voltage glitching attacks yourself, and we promise we won’t judge, [Matthew Alt] has a great writeup on the topic. And ironically enough, one of his tools of choice is [Colin O’Flynn]’s RP2040-based Chip Shouter EMP glitcher, which he showed us how to make and use in this 2021 Remoticon talk.

Forget The Coax, Wire Up Your Antennas With Cat 6 Cable

January 15, 2025 by 65 Comments

These days, anything with copper in it is expensive. If you doubt that, a walk into any Home Depot electrical department, where the wire is locked up tighter than Fort Knox, will prove otherwise. Coaxial cable is a particularly expensive species, which is a pity for hams and other radio enthusiasts since it’s the only thing we can use for antenna feedlines.

Or is it? [Steve (VE6WZ)] has found a way to use ordinary Cat 6 Ethernet cable for antenna feed lines that seems pretty clever. As he points out, Ethernet cables are designed to handle frequencies that coincide nicely with most of the interesting amateur radio bands, and their insertion losses are acceptably low, especially for Cat 6 cable. The twisted pairs are also a balanced system that’s good at rejecting common mode noise. Cat 6 cable also has four pairs of conductors, allowing you to feed multiple antennas with one cable, or to distribute power to amplifiers and switches along with antenna feeds.

The downside? Cat6 conductor pairs have a characteristic impedance of around 100 ohms, which isn’t a match for the 50-ohm feedline impedance universally expected by ham radios. Also, the relatively small wires probably aren’t up to the job of carrying much current, limiting their use to feedlines for receive-only antennas. That works for [Steve] since he uses Cat 6 to support his massive Beverage antenna farm (Beverage antennas are non-resonant horizontal antennas that live close to the ground and point in the direction of the signal, rather than broadside to the signal as with a resonant antenna like a dipole.) Each antenna in his farm has a transimpedance amplifier that needs to be powered, plus switching relays so he can turn the correct antennas on for the signals he wants to receive. He describes the amps in detail in the video below, along with the custom impedance-matching transformers he uses and the combining gear.

Coax will probably still be the cable of choice for most feedline applications, but it’s nice to know there are alternatives. And who knows—if you stick to QRP work, maybe Cat 6 could even be used for transmitting.

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Avian-Inspired Drones: How Studying Birds Of Prey Brings More Efficient Drones Closer

January 15, 2025 by 17 Comments
The EPFL LisRaptor with adjustable wings and tail.
The EPFL LisRaptor with adjustable wings and tail.

Throughout evolution, the concept of powered flight has evolved and refined itself multiple times across both dinosaurs (birds), mammals (bats) and insects. So why is it that our human-made flying machines are so unlike them? The field of nature-inspired flying drones is a lively one, but one that is filled with challenges. In a recent video on the Ziroth YouTube channel, [Ryan Inis] takes a look at these efforts, in particular those of EPFL, whose recent RAVEN drone we had a look at recently already.

Along with RAVEN, there is also another project (LisRaptor) based on the Northern Goshawk, a bird of prey seen in both Europe and North-America. While RAVEN mostly focused on the near-vertical take-off that smaller birds are capable of, this project studies the interactions between the bird’s wings and tail, and how these enable rapid changes to the bird’s flight trajectory and velocity, while maintaining efficiency.

The video provides a good overview of this project. Where the LisRaptor differs from the animal is in having a rudder and a propeller, but the former should ideally not be necessary. Obviously the kinematics behind controlled flight are not at all easy, and the researchers spent a lot of time running through configurations aided by machine learning to achieve the ideal – and most efficient – wing and tail configuration. As these prototypes progress, they may one day lead to drones that are hard to differentiate from birds and bats.

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Game boy with custom cartridge mounted on car dashboard

A Game Boy Speedometer, Just Because You Can

January 15, 2025 by 10 Comments

From a practical standpoint, [John] may be correct that his recent creation is the “world’s worst digital dash”, but we’re still oddly enamored with the idea of using a Nintendo Game Boy as a digital speedometer. Pulling it off meant interfacing the handheld with the vehicle’s CAN bus system, so whether you’re into retro gaming or car hacking, this project has something to offer.

Showing real-time vehicle speed on the Game Boy sounds like it should be relatively easy, but the iconic game system wasn’t exactly built for such a task. Its 2 MHz CPU and 160×144 pixel dot-matrix screen were every kid’s dream in 1989, but using it as a car dashboard is pushing it. To bridge that gap, [John] designed two custom circuit boards. One interfaces with the Game Boy, intercepting its memory requests and feeding it data from a microcontroller. The other processes the CAN bus signals, translating speed information into a form the Game Boy can display. [John] used inexpensive tools and software to read the CAN bus data, and used GBDK-2020 to write the software in C. His video goes in great detail on how to do this.

Months of work have gone into decoding the Game Boy’s data bus and creating a schematic for the interface board. Tricking the Game Boy into thinking it was loading a game, while actually displaying incoming speed data. The screen’s low resolution and slow refresh rate rendered it barely readable in a moving vehicle. But [John]’s goal wasn’t practicality — it was just proving it could be done.

Want to dive deep into the Game Boy?  Have you seen the Ultimate Game Boy talk?

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No Ham License? Listen Anyway In Your Browser

January 15, 2025 by 53 Comments

Full disclosure: ham radio isn’t for everyone, and there are many different facets to it. What appeals to one person might bore another to death. One area of ham radio that has changed a lot in the last few years is more or less local and typically mobile operation on VHF or UHF. Not long ago, hams used HTs (walky-talkies or handi-talkies) or mobile radios via repeaters to talk to each other and — the golden prize back then — make phone calls from their cars. Cell phones have made that much less interesting, but there is still an active community of operators talking on repeaters. However, the traffic has gone digital, the Internet is involved, and people with inexpensive, low-powered radios can talk to each other across the globe. This is nothing new, of course. However, having digital services means that operators with special interests can congregate in what amounts to radio chat rooms organized by region or topic.

There’s a long history of people listening to ham radio conversations with shortwave radios, SDRs, and scanners. But with so much activity now carried on the Internet, you can listen in using nothing more than your web browser or a phone app. I’ll show you how. If you get interested enough, it is easy enough to get your license. You don’t need any Morse code anymore, and a simple Technician class license in the United States is all you need to get going.

A Quick DMR Primer

There are several digital ham networks around and like real networks, you can have different physical transport layers and then build on top of that. For the purposes of this post, I’m going to focus on DMR (digital mobile radio) on the Brandmeister network which is very large and popular ham network. You won’t need a license nor will you need to sign up for anything as long as you are content to just listen.

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