The VLF Transformation

August 19, 2025 by Al Williams 6 Comments

People have long been interested in very low frequency (VLF) radio signals. But it used to be you pretty much had to build your own receiver which, luckily, wasn’t as hard as building your own VHF or UHF gear. But there is a problem. These low frequencies have a very long wavelength and, thus, need very large antennas to get any reception. [Electronics Unmessed] says he has an answer.

These days, if you want to explore any part of the radio spectrum, you can probably do it easily with a software-defined radio (SDR). But the antenna is the key part that you are probably lacking. A small antenna will not work well at all. While the video covers a fairly common idea: using a loop antenna, his approach to loops is a bit different using a matching transformer, and he backs his thoughts up with modeling and practical results.

Of course, transformers also introduce loss, but — as always — everything is a trade-off. Running hundreds of feet of wire in your yard or even in a loop is not always a possibility. This antenna looks like it provides good performance and it would be simple to duplicate.

Early radio was VLF. Turns out, VLF may provide an unexpected public service in space.

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Sniffing 5G With Software-Defined Radio

August 18, 2025 by Fenix Guthrie 3 Comments

The fifth generation mobile communications protocol (5G) is perhaps the most complicated wireless protocol ever made. Featuring wildly fast download speeds, beam forming base stations, and of course non-standard additions, it’s rather daunting prospect to analyze for the home hacker and researcher alike. But this didn’t stop the ASSET Research Group from developing a 5G sniffer and downlink injector.

The crux of the project is focused around real-time sniffing using one of two Universal Software Radio Peripheral (USRP) software-defined radios (SDRs), and a substantial quantity of compute power. This sniffed data can even be piped into Wireshark for filtering. The frequency is hard-coded into the sniffer for improved performance with the n78 and n41 bands having been tested as of writing. While we expect most of you don’t have the supported USRP hardware, they provided a sample capture file for anyone to analyze.

The other main feature of the project is an exploitation framework with numerous attack vectors developed by ASSET and others. By turning an SDR into a malicious 5G base station, numerous vulnerabilities and “features” can be exploited to with results ranging from downgrading the connection to 4G, fingerprinting and much more. It even includes an attack method we preciously covered called 5Ghull which can cause device failure requiring removal of the SIM Card. These vulnerabilities offer a unique look inside the inner workings of 5G.

If you too are interested in 5G sniffing but don’t have access to the hardware needed, check out this hack turning a Qualcomm phone into a 5G sniffer!

Walter Is A Tiny Cellular Modem For Your Projects

August 16, 2025 by Tyler August 21 Comments

It wasn’t that long ago that projects with cellular connectivity were everywhere, but with 2G no longer universally available, glory days of cheap 2G modules seem to be on their way out. So when [Data Slayer] titled his video “You’ve Never Seen Cellular Like This” about a new GSM radio module, we couldn’t help but think that we have — and that we’re glad to see it back.

The module is the Walter, by DPTechnics out of Belgium. It’s fully open-source and contains a ESP32-S3 for WiFi and BLE plus a Sequans Monarch chip for GSM and GNSS connectivity. It’s not the blazing-fast 5G you’re paying your phone carrier for: this is an IoT modem, with LTE-M and NB-IoT. We’re talking speeds in the kbps, not Mbps– but we’re also talking very, very low power usage. Since it’s LTE-M rather than full LTE, you’re probably not going to be bringing back the golden days of Arduino Cellphones, (since LTE-M doesn’t support VoLTE) but if LoRa isn’t your jam, and you hang out around cell towers, this level of connectivity might interest you.

Walter is actually a drop-in replacement for PyCom’s old GPy module, so if you had a project in mind for that and are frustrated by it being EoL — well, here you are. [Data Slayer] seemed impressed enough with its capabilities as a GPS tracker. We’re impressed with the 9.8 µA consumed in deep sleep mode, and the fact that it has already been certified with the CE, FCC, IC, RCM and UKCA. Those certs mean you could go from prototype to product without getting tangled in red tape, assuming Walter is the only radio onboard.

Our thanks to [Keith Olson] for phoning in the tip. If you have a tip and want to connect, operators are standing by. Continue reading “Walter Is A Tiny Cellular Modem For Your Projects” →

[Ben] at workbench with 3D-printed sea scooter

Watertight And Wireless In One Go: The DIY Sea Scooter

August 11, 2025 by Heidi Ulrich 26 Comments

To every gadget, tool, or toy, you can reasonably think: ‘Sure I could buy this… but can I make it myself?’ And that’s where [Ben] decided he could, and got to work. On a sea scooter, to be exact.

This sea scooter was to be a fully waterproof, hermetically sealed 3D-printed underwater personal propulsion device, with the extreme constraint that the entire hull and mechanical interfaces are printed in one go. No post-printing holes for shafts, connectors, or seals. It also meant [Ben] needed to embed all electronics, motor, magnetic gearbox, custom battery pack, wireless charging, and non-contact magnetic control system inside the print during the actual print process.

As [Ben] explains, both Bluetooth and WiFi ranges are laughable once underwater. He elegantly solves this with a reed-switch-based magnetic control system. The non-contact magnetic drive avoids shaft penetrations entirely. Power comes from a custom 8S LiFePO₄ pack, charged wirelessly through the hull. Lastly, everything’s wrapped in epoxy to make it as watertight as a real submarine.

The whole trick of ‘print-in-place’ is that [Ben] pauses the builder mid-print, and drops in each subsystem like a secret ingredient. Continuing, he tweaks the printer’s Z-offset, and onwards it goes. It’s tense, high-stakes work; a 14-hour print where one nozzle crash means binning hundreds of dollars’ worth of embedded components.

Still, [Ben] took the chance, and delivered a cool, fully packed and fully working sea scooter. Comment below to discuss the possibilities of building one yourself.

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A photo of the circuit board with components soldered on

A Solar-Only, Battery-Free Device That Harvests Energy From A BPW34 Photodiode

August 10, 2025 by John Elliot V 21 Comments

Normally when you think solar projects, you think of big photovoltaic cells. But a photodiode is just an inefficient, and usually much smaller, PV cell. Since [Pocket Concepts]’s Solar_nRF has such a low power budget, it can get away with using BPW34 photodiodes in place of batteries. (Video, embedded below.)

The BPW34 silicon PIN photodiode feeds a small voltage into a BQ25504 ultra-low-power boost converter energy harvester which stores power in a capacitor. When the capacitor is fully charged the battery-good pin is toggled which drives a MOSFET that powers everything downstream.

When it’s powered on, the Nordic nRF initializes, reads the current temperature from an attached I2C thermometer, and then sends out a Bluetooth Low Energy (BLE) advertising packet containing the temperature data. When the capacitor runs out of energy, the battery-good pin is turned off and downstream electronics become unpowered and the cycle begins again.

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Hands On: The Hacker Pager

July 31, 2025 by Tom Nardi 27 Comments

It should come as no surprise that the hacker community has embraced the Meshtastic project. It’s got a little bit of everything we hold dear: high quality open source software, fantastic documentation, a roll-your-own hardware ethos, and just a dash of counterculture. An off-grid communications network cobbled together from cheap parts, some of which being strategically hidden within the urban sprawl by rogue operators, certainly sounds like the sort of thing you’d read about it in a William Gibson novel.

But while the DIY nature of Meshtastic is one of its most endearing features for folks like us, it can also be seen as one of its weak spots. Right now, the guidance for those looking to get started is to pick a compatible microcontroller development board, 3D print a case for it, screw on an antenna from AliExpress, flash your creation with the latest firmware, and then spend some quality time with the documentation and configuration tools to actually get it on the air. No great challenge for the average Hackaday reader, but a big ask for the weekend adventurer that’s just looking for a way to keep in touch with their friends while camping.

Quality hardware that offers a turn-key experience will be critical to elevating Meshtastic from a hobbyist’s pastime to something that could actually be fielded for applications such as search and rescue. Plus, let’s be honest, even those of us who like to put together our own gadgets can appreciate a more consumer-oriented piece of hardware from time to time. Especially if that hardware happens to be open source and designed to empower the user rather than hold them back.

Enter the Hacker Pager from exploitee.rs. As the name implies, it’s still very much a device intended for hackers — a piece of hardware designed for the halls of DEF CON rather than trekking through the wilderness. But it’s also an important step towards a new generation of Meshtastic hardware that meets the high standard of quality set by the software itself.

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Legally Distinct Space Invaders Display WiFi Info

July 30, 2025 by Bryan Cockfield 23 Comments

In the early 00s there was a tiny moment before the widespread adoption of mobile broadband, after the adoption of home WiFi, and yet before the widespread use of encryption. For this brief time a unique practice arose called wardriving — where people would drive around, document, and use these open wireless networks.

Although the pursuit has diminished with the rise of mobile broadband and WPA encryption, there are still a few use cases for the types of hardware a wardriver would have used. [arduinocelentano] recently built a Wi-Fi strength monitor in this style but with a unique theme.

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