Radio Hacks

1476 Articles

Make Your Ceiling Disappear With ADS-B And Short-Throw Projector

June 4, 2026 by 15 Comments

If you’re into airplanes, you’ve probably had the experience of hearing an unusual aircraft and rushing outside to try and catch a glimpse of it, all while fumbling with a smartphone to open a flight-tracking app. If your home was equipped with [cpaczek]’s Skylight project, which combines ADS-B data with a short throw projector, that little dance would have been totally unnecessary.

ADS-B or the “Automatic Dependent Surveillance-Broadcast”, is the standard by which aircraft broadcast their position and other flight information from onboard transponders. In most of the world, every commercial aircraft has an ADS-B transmitter, and they’re slowly creeping into general aviation as well. The signals aren’t hard to pick up with software-defined radio — like perhaps this RP2040 based unit we featured — or the RTL-SDR v4 this project calls for.

Using data from ADS-B, the Skylight software runs on Raspberry Pi 5 and renders icons of the aircraft exactly where they would appear above you, if that pesky ceiling wasn’t in the way. You get the flight’s code, destination and flightplan with a nice icon representing what type of airplane it is. Thanks to specifying a Pi 5, the projection is a smooth 60 FPS at 1080p. Airplanes aren’t the only things plotted, though — this is also a planetarium, giving you a full view of the stars and any satellites passing overhead. That’s obviously via an API, not SDR, and if you like you can configure it to track aircraft that way to — allowing you to set your Skylight for anywhere in the world, if you aren’t near an interesting airport.

ADS-B isn’t just for pilots and plane nerds — if you’re flying drones, you probably should keep an eye on it, too. In that case, though, you probably won’t be looking at your ceiling.

Thanks to [Thinkerer] for the tip!

Web-Based Control For A CB Radio

June 3, 2026 by 20 Comments

There was a time when a CB radio was a simple affair: a small box with a channel selector, volume, and squelch controls. No longer it seems, because they can now be multi-mode devices that equal the capabilities of amateur radio rigs if not surpass them. [ThatCrazyDcGuy] has one, an Albrecht AE-5900, which has the interesting feature that it can be entirely controlled from its microphone. This led to a web-based interface for the rig, through clever emulation of the microphone.

The communication between rig and microphone is a serial line, for which an FT232 USB-to-serial interface is pressed into service. A USB sound card handles the audio along with some little transformers for isolation, and a USB hub joins everything together. The whole is mounted on perfboard in a small enclosure, and plugged into a Raspberry Pi which acts as a server. This is running a Python script that expose a web front end to control the rig. We like the way this has been done, with minimal intrusion into the radio itself.

Far less so than this CB to 6 meter conversion we featured a while back.

Decoding The Tianwen-2 Sample Return Mission’s Telemetry Signal

May 27, 2026 by No comments

China’s Tianwen-2 asteroid sample return mission launched on 28 May of 2025 and is scheduled to arrive at its target – near-Earth asteroid 469219 Kamo’oalewa – in June 2026. This gives folk back on Earth plenty of time to listen in on the probe’s communication with its home base, such as [Daniel Estévez] who recently had a poke at this telemetry as captured by the Dwingeloo radio telescope in the Netherlands.

With not a lot of public information on its trajectory it’s a hard probe to track, but now that it’s nearing its destination there’s an obvious part of the sky to aim for. This is X-band telemetry, broadcast at 8428.19 MHz, with the same basic modulation as its predecessor Tianwen-1.

Where it differs is in the coding, with Tianwen-2 also using concatenated coding, but having a frame length that’s better suited to submitting full Reed-Solomon codewords and does not require omitting bytes to make things awkwardly fit.

After analyzing the telemetry data itself, there doesn’t seem to be anything exciting contained within this capture. This does seem to be as expected considering that the probe is still in its coast phase where it doesn’t have to do much and likely is in a low-power state most of the time. Once its orbital insertion burn begins is when this knowledge can likely be used to track the mission in fine-grained detail, which is an event that we’re definitely looking forward to.

So Long, CHU, And Thanks For All The Time Signals

May 27, 2026 by 59 Comments

In the long ago, pre-internet days when your clock project wasn’t an ESP32 getting its timing via NTP over WiFi, it was still possible to build a wirelessly-updating clock. All you needed was a shortwave receiver tuned to a time signal — perhaps like the National Research Council of Canada’s CHU, found on the dial at 3330, 7850, and 14 670 kHz. At least, it can be found at those frequencies until June 22nd, 2026, when the station will finally go dark.

Depending where you were on Earth, it might have been easier to tune into CHU than the United States based WWVB, or one of the various European signals like DCF77 or the UK’s MSF. If you’re not into radio, all these time signals have essentially the same job, if you hadn’t guessed: tell the time. This can be done in a variety of ways, and CHU has made use of more than one of them since its establishment in 1923.

Initially, the time was sent in Morse code, but later they added a speaking clock for easier human listening in both Canadian French and English. For synchronizing radio clocks, a series of pulses is given in DUT1 format using 0.3s pulses — which is what older clocks would have been listening to — and nowadays a digital FSK time code for more modern equipment. You can have a listen through the video by [Shortwave Listener] embedded below.

It’s not our place to judge the Government of Canada for trying to save money where they can. It wasn’t so long ago that WWVB was in danger of shutting down for similar reasons. But we’re still going to miss those beeps. If you do tune in before the station goes dark, CHU should still be giving out QSL cards. Get yours before it’s gone forever.

If you do have a clock that relies on this time signal, don’t worry. You can make your own, perhaps with a GPS time source.

Continue reading “So Long, CHU, And Thanks For All The Time Signals” →

A web interface is shown providing information about a cellular network base station.

Running Your Own 3G Network

May 9, 2026 by 14 Comments

CDMA2000 was one of the protocols defined for 3G networks and is now years out of date and being phased out worldwide. Nevertheless, there are still vast numbers of phones that will happily connect to it, creating an opportunity for hackers seeking to run their own cellular networks. [Chrismoos] recently made this endeavour significantly easier by releasing 1xBTS, a Rust implementation of the lower three layers of a CDMA2000 network.

The lowest layer of the stack is an SDR for the actual radio communications. It’s been tested with the USRP B200 and B210, the LimeSDR Mini 2, and the BladeRF Micro 2.0. The code might work with certain other SDRs using the SoapySDR abstraction layer. The SDR is controlled by the base station (BTS) software, which, in turn, is controlled by the base station controller (BSC) over an Abis link. The BSC manages channels and mobile device associations, and exchanges frames with the mobile switching center (MSC), which handles message switching.

Continue reading “Running Your Own 3G Network” →

This Az-El Mount Is Worth Following

May 7, 2026 by 7 Comments

Communication with satellites often involves the use of high-gain directional antennas coupled with careful positioning to find and track the target. With a geostationary satellite the mount is either fixed or a single-axis polar mount, but when the craft is moving in a different orbit it becomes more of a challenge to stay locked on. An azimuth-elevation mount is needed to cover the whole sky, and [Ham Radio Passion] has one as a work in progress. It’s 3D printed and looks straightforward, making it a project to watch.

An az-el mount has two parts, the first being a turntable to set the azimuth, and the second being a horizontal rotating axis to set the elevation. He’s mounting the antenna to a piece of aluminium extrusion and driving it through a set of 3D printed gears driven from a 360 degree servo with a worm drive. He explains why the servo makes more sense to him here.

The result is not yet a finished project, but it shows enough promise to make it worth keeping an eye on. It’s by no means big enough for a huge antenna array, but we can imagine antennas for higher frequencies would be well within its capabilities. Meanwhile it’s certainly not the first az-el mount we’ve seen.

Continue reading “This Az-El Mount Is Worth Following” →

A 1947 Radio Gets A Face Lift

May 6, 2026 by 6 Comments

We’ve all done it. We spy an old radio at a garage sale or resale shop. We know someone should bring it back to life, but it looks like a project, so we pass it by. Not [Ken] from [Ken’s Shop]. He found an Arvin 664A AM radio from 1947 in what appears to be a home-built cabinet and decided to bring it back to life.

From what we could find, the original case was a white plastic, not the wood box it is in today. So the first challenge was simply getting inside to see what was going on. Continue reading “A 1947 Radio Gets A Face Lift” →