6502 Puts On An SDR Hat

September 11, 2025 by Bryan Cockfield 11 Comments

The legendary 6502 microprocessor recently turned 50 years old, and to celebrate this venerable chip which brought affordable computing and video gaming to the masses [AndersBNielsen] decided to put one to work doing something well outside its comfort zone. Called the PhaseLoom, this project uses a few other components to bring the world of software-defined radio (SDR) to this antique platform.

The PhaseLoom is built around an Si5351 clock generator chip, which is configurable over I2C. This chip is what creates the phase-locked loop (PLL) for the radio. The rest of the components, including antenna connectors and various filters, are in an Arduino-compatible form factor that let it work as a shield or hat for the 65uino platform, an Arduino-form-factor 6502 board. The current version [Anders] has been working on is dialed in to the 40-meter ham band, with some buttons on the PCB that allow the user to tune around within that band. He reports that it’s a little bit rough around the edges and somewhat noisy, but the fact that the 6502 is working as an SDR at all is impressive on its own.

For those looking to build their own, all of the schematics and code are available on the project’s GitHub page. [Anders] has some future improvements in the pipe for this project as well, noting that with slightly better filters and improved software even more SDR goodness can be squeezed out of this microprocessor. If you’re looking to experiment with SDR using something a little bit more modern, though, this 10-band multi-mode SDR based on the Teensy microcontroller gets a lot done without breaking the bank.

Receiving Radio Signals From Space Like It’s 1994

August 28, 2025 by Bryan Cockfield 19 Comments

For certain situations, older hardware is preferred or even needed to accomplish a task. This is common in industrial applications where old machinery might not be supported by modern hardware or software. Even in these situations though, we have the benefit of modern technology and the Internet to get these systems up and running again. [Old Computers Sucked] is not only building a mid-90s system to receive NOAA satellite imagery, he’s doing it only with tools and equipment available to someone from this era.

Of course the first step here is to set up a computer and the relevant software that an amateur radio operator would have had access to in 1994. [Old Computers Sucked] already had the computer, so he turned to JV-FAX for software. This tool can decode the APT encoding used by some NOAA satellites without immediately filling his 2 MB hard drive, so with that out of the way he starts on building the radio.

In the 90s, wire wrapping was common for prototyping so he builds a hardware digitizer interface using this method, which will be used to help the computer interface with the radio. [Old Computers Sucked] is rolling his own hardware here as well, based on a Motorola MC3362 VHF FM chip and a phase-locked loop (PLL), although this time on a PCB since RF doesn’t behave nicely with wire wrap. The PCB design is also done with software from the 90s, in this case Protel which is known today as Altium Designer.

In the end, [Old Computers Sucked] was able to receive portions of imagery from weather satellites still using the analog FM signals from days of yore, but there are a few problems with his build that are keeping him from seeing perfectly clear imagery. He’s not exactly sure what’s wrong but he suspects its with the hardware digitizer as it was behaving erratically earlier in the build. We admire his dedication to the time period, though, down to almost every detail of the build. It reminds us of [saveitforparts]’s effort to get an 80s satellite internet experience a little while back.

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Hackaday Links: August 24, 2025

August 24, 2025 by Dan Maloney 9 Comments

“Emergency Law Enforcement Officer Hologram program activated. Please state the nature of your criminal or civil emergency.” Taking a cue from Star Trek: Voyager, the Seoul Metropolitan Police Agency is testing a holographic police officer, with surprisingly — dare we say, suspiciously? — positive results. The virtual officer makes an appearance every two minutes in the evening hours in a public park, presumably one with a history of criminal activity. The projection is accompanied by a stern warning that the area is being monitored with cameras, and that should anything untoward transpire, meat-based officers, presumably wearing something other than the dapper but impractical full-dress uniform the hologram sports, will be dispatched to deal with the issue.

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Quieting That Radio

August 22, 2025 by Al Williams 22 Comments

If you are casually listening to the radio, you probably tune into a local station and with modern receivers and FM modulation, the sound quality is good. But if you are trying to listen to distant or low-powered station, there’s a lot of competition. Our modern world is awash in a soup of electronic interference. [Electronics Unmessed] tells — and shows — us how much noise can show up on a SDR setup and what simple things you can do to improve it, sometimes tremendously.

According to the video, the main culprit in these cases is the RF ground path. If you have a single antenna wire, there still has to be a ground path somewhere and that may be through the power line or through, for example, a USB cable, the host computer, and its power supply. Unsurprisingly, the computer is full of RF noise which then gets into your receiver.

Adding a counterpoise makes a marked difference. A low inductance ground connection can also help. The counterpoise, of course, won’t be perfect, so to further turn down the noise, ferrite cores go around wires to block them from being ground paths for RF.

The common cores you see are encased in plastic and allow you to snap them on. However, using a bare core and winding through it multiple times can provide better results. Again, thanks to the SDR’s display, you can see the difference this makes in his setup.

None of this is new information, of course. But the explanation is clear, and being able to see the results in a spectrum display is quite enlightening. Those cores essentially turn your wire into a choke. People think that grounding is simple, but it is anything but.

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Whispers From The Void, Transcribed With AI

August 8, 2025 by Heidi Ulrich 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?

A Repeater For WWVB

August 7, 2025 by Bryan Cockfield 11 Comments

For those living in the continental US who, for whatever reason, don’t have access to an NTP server or a GPS device, the next best way to make sure the correct time is known is with the WWVB radio signal. Transmitting out of Colorado, the 60-bit 1 Hz signal reaches all 48 states in the low-frequency band and is a great way to get a clock within a few hundred nanoseconds of the official time. But in high noise situations, particularly on the coasts or in populated areas these radio-based clocks might miss some of the updates. To keep that from happening [Mike] built a repeater for this radio signal.

The repeater works by offloading most of the radio components to an Arduino. The microcontroller listens to the WWVB signal and re-transmits it at a lower power to the immediate area, in this case no further than a few inches away or enough to synchronize a few wristwatches. But it has a much better antenna for listening to WWVB so this eliminates the (admittedly uncommon) problem of [Mike]’s watches not synchronizing at least once per day. WWVB broadcasts a PWM signal which is easy for an Arduino to duplicate, but this one needed help from a DRV8833 amplifier to generate a meaningfully strong radio signal.

Although there have been other similar projects oriented around the WWVB signal, [Mike]’s goal for this was to improve the range of these projects so it could sync more than a single timekeeping device at a time as well as using parts which are more readily available and which have a higher ease of use. We’d say he’s done a pretty good job here, and his build instructions cover almost everything even the most beginner breadboarders would need to know to duplicate it on their own.

Real-Time Beamforming With Software-Defined Radio

August 5, 2025 by Bryan Cockfield 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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