Radio Hacks

1441 Articles

2025 One Hertz Challenge: Blinking An LED With The Aid Of Radio Time

August 14, 2025 by 3 Comments

If you want to blink an LED once every second, you could use just about any old timer circuit to create a 1 Hz signal. Or, you could go the complicated route like [Anthony Vincz] and grab 1 Hz off a radio clock instead. 

The build is an entry for the 2025 One Hertz Challenge, with [Anthony] pushing himself to whip up a simple entry on a single Sunday morning. He started by grabbing a NE567 tone decoder IC, which uses a phase-locked loop to trigger an output when detecting a tone of a given frequency. [Anthony] had used this chip hooked up to an Arduino to act as a Morse decoder, which picked up sound from an electret mic and decoded it into readable output.

However, he realized he could repurpose the NE567 to blink in response to output from radio time stations like the 60 KHz British and 77.5 KHz German broadcasts. He thus grabbed a software-defined radio, tuned it into one of the time stations, and adjusted the signal to effectively sound a regular 800 Hz tone coming out of his computer’s speakers that cycled once every second. He then tweaked the NE567 so it would trigger off this repetitive tone every second, flashing an LED.

Is it the easiest way to flash an LED? No. It’s complicated, but it’s also creative. They say a one hertz signal is always in the last place you look.

Continue reading “2025 One Hertz Challenge: Blinking An LED With The Aid Of Radio Time” →

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 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.

Continue reading “A Solar-Only, Battery-Free Device That Harvests Energy From A BPW34 Photodiode” →

Screenshot of audio noise graph

Whispers From The Void, Transcribed With AI

August 8, 2025 by 14 Comments

‘Hearing voices’ doesn’t have to be worrisome, for instance when software-defined radio (SDR) happens to be your hobby. It can take quite some of your time and attention to pull voices from the ether and decode them. Therefore, [theckid] came up with a nifty solution: RadioTranscriptor. It’s a homebrew Python script that captures SDR audio and transcribes it using OpenAI’s Whisper model, running on your GPU if available. It’s lean and geeky, and helps you hear ‘the voice in the noise’ without actively listening to it yourself.

This tool goes beyond the basic listening and recording. RadioTranscriptor combines SDR, voice activity detection (VAD), and deep learning. It resamples 48kHz audio to 16kHz in real time. It keeps a rolling buffer, and only transcribes actual voice detected from the air. It continuously writes to a daily log, so you can comb through yesterday’s signal hauntings while new findings are being logged. It offers GPU support with CUDA, with fallback to CPU.

It sure has its quirks, too: ghost logs, duplicate words – but it’s dead useful and hackable to your liking. Want to change the model, tweak the threshold, add speaker detection: the code is here to fork and extend. And why not go the extra mile, and turn it into art?

Real-Time Beamforming With Software-Defined Radio

August 5, 2025 by 13 Comments

It is perhaps humanity’s most defining trait that we are always striving to build things better, stronger, faster, or bigger than that which came before. Taller skyscrapers, longer bridges, and computers with more processors, all advance thanks to this relentless persistence.

In the world of radio, we might assume that a better signal simply means adding more power, but performance can also improve by adding more antennas. Not only do more antennas increase gain but they can also be electronically steered, and [MAKA] demonstrates how to do this with a software-defined radio (SDR) phased array.

The project comes to us in two parts. In the first part, two ADALM-Pluto SDR modules are used, with one set to transmit and the other to receive. The transmitting SDR has two channels, one of which has the phase angle of the transmitted radio wave fixed while the other is swept from -180° to 180°. These two waves will interfere with each other at various points along this sweep, with one providing much higher gain to the receiver. This information is all provided to the user via a GUI.

The second part works a bit like the first, but in reverse. By using the two antennas as receivers instead of transmitters, the phased array can calculate the precise angle of arrival of a particular radio wave, allowing the user to pinpoint the direction it is being transmitted from. These principles form the basis of things like phased array radar, and if you’d like more visual representations of how these systems work take a look at this post from a few years ago.

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Two For The Price Of One: BornHack 2024 And 2025 Badges

August 1, 2025 by No comments

BornHack is a week-long summer hacker camp in a forest on the Danish island of Fyn, that consistently delivers a very pleasant experience for those prepared to make the journey. This year’s version was the tenth iteration of the camp and it finished a week ago, and having returned exhausted and dried my camping gear after a Biblical rainstorm on the last day, it’s time to take a look at the badges. In case you are surprised by the plural, indeed, this event had not one badge but two. Last year’s badge suffered some logistical issues and arrived too late for the camp, so as a special treat it was there alongside the 2025 badge for holders of BornHack 2024 tickets. So without further ado, it’s time to open the pack for Hackaday and see what fun awaits us. Continue reading “Two For The Price Of One: BornHack 2024 And 2025 Badges” →

2025 One-Hertz Challenge: A Software-Only AM Radio Transmitter

July 30, 2025 by 10 Comments

We’ve been loving the variety of entries to the 2025 One-Hertz Challenge. Many a clock has been entered, to be sure, but also some projects that step well outside simple timekeeping. Case in point, this AM transmitter from [oldradiofixer.]

The software-only transmitter uses an ATTiny85 processor to output an AM radio signal in the broadcast band. It transmits a simple melody that you can tune in on any old radio you might have lying around the house. Achieving this was simple. [oldradiofixer] set up the cheap microcontroller to toggle pin PB0 at 1 MHz to create an RF carrier. Further code then turns the 1MHz carrier on and off at varying rates to play the four notes—G#, A, G#, and E—of the Twilight Zone theme. This is set up to repeat every second—hence, it’s a perfectly valid entry to the 2025 One-Hertz Challenge!

It’s a simple project, but one that demonstrates the basics of AM radio transmission quite well. The microcontroller may not put out a powerful transmission, but it’s funny to think just how easy it is to generate a broadcast AM signal with a bit of software and a length of wire hanging off one pin. Video after the break.

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The Power-Free Tag Emulator

July 27, 2025 by 21 Comments

Most of you know how an NFC tag works. The reader creates an RF field that has enough energy to power the electronics in the tag; when the tag wakes up, two-way communication ensues. We’re accustomed to blank tags that can be reprogrammed, and devices like the Flipper Zero that can emulate a tag. In between those two is [MCUer]’s power-free tag emulator, a board which uses NFC receiver hardware to power a small microcontroller that can run emulation code.

The microcontroller in question is the low-power CW32L010 from Wuhan Xinyuan Semiconductor, a Chinese part with an ARM Cortex M0+ on board. Unfortunately, that’s where the interesting news ends, because all we can glean from the GitHub repository is a PCB layout. Not even a circuit diagram, which we hope is an unintended omission rather than deliberate. It does, however, lend itself to the fostering of ideas, because if this designer can’t furnish a schematic, then perhaps you can. It’s not difficult to make an NFC receiver, so perhaps you can hook one up to a microcontroller and be the one who shares the circuit.