Requiem For Long Wave, As The BBC Goes Silent

June 27, 2026 by Jenny List 1 Comment

Something happened this morning which will have been unnoticed by many, but which for a certain breed of radio enthusiast marks the end of an era. The BBC stopped broadcasting Radio 4 on their 198 kHz Long Wave frequency, ending over a century of transmission in the band. For now the transmitter carries a recorded message telling listeners that the service has ended, but it’s expected that this will soon be turned off.

A pair of very large transmitting masts against a cloudy grey sky. — The main 198kHz BBC transmitter, at Droitwich. Bob Nienhuis, Public domain.

American readers may be unfamiliar with Long Wave as it’s a band not allocated in their region. Covering 153 to 279 kHz, it’s a relic from the earliest days of high-power broadcasting in the 1920s, used because of the enormous distances that could be covered with its lower frequencies. The main long wave transmitter for the BBC is at Droitwich, and its demise comes because there are no more spares for its high-power transmitter tubes. It joins many Medium Wave, or AM, as it is commonly known, stations in leaving the airwaves, as increased interference from switch mode electronics and the availability of higher quality alternatives took away their listeners. It’s fair to say that there will be few whose lives are inconvenienced by the switch-off in 2026, but it’s worth taking a moment to remember.

The first BBC Long Wave transmissions in the mid-1920s were on a 1600 metre wavelength, or 187.5 kHz. A series of international agreements saw them move to 193 kHz, and then 200 KHz or 1500 metres in 1934. They stayed on that frequency until another shift down 2 KHz to 198 kHz in 1988. They were atomic-controlled, and thus usable as a frequency standard. The programming started with station names redolent of their era, first the BBC National Service, then the Light Programme you’ll see on the dial in the header image, and finally the more modern-sounding Radio 4. A famous BBC programme tied to Long Wave is the Shipping Forecast, a weather bulletin for deep-sea fishermen which became cult listening on land and now features on FM and digital services too, and there’s even a probably-apocryphal tale that British nuclear submarine captains would once use its presence or absence to judge whether nuclear war had occurred.

In an Oxfordshire farmhouse not far short of fifty years ago, a young child who would later become a Hackaday writer heard a radio show like nothing before, which made an impression that continues to this day. The show was one of the earliest airings of the original Hitchhikers Guide To The Galaxy radio series, through a 1970s ITT radio tuned to BBC Radio 4 on (then) 200 kHz Long Wave. So long, Droitwich, and thanks for all the fish.

A drone is shown flying above some trees and a building. A pink cloud of dots appears above the drone, and a purple cloud below the drone. Grey crosshairs are to the right of the drone.

Seeing The World In Radio Waves With The QuadRF

June 20, 2026 by Aaron Beckendorf 38 Comments

Although the basic principle of radio direction finding is easy to understand (measure the phase difference between different antennas, then calculate the angle of arrival from this difference), the radio hardware to actually implement this has historically been hard for hackers to access. The QuadRF project aims to change this by building a phase-coherent four-channel SDR which makes direction mapping easy (GitHub repository).

The QuadRF uses two boards: one to receive and pre-process radio waves, and a Raspberry Pi 5 for additional processing. The RF board has four patch antennas, each capable of either transmitting or receiving in the 4.9 GHz to 6.0 GHz range, with switchable right- or left-hand polarization. For on-device processing, it uses a Lattice ECP5 FPGA, which uses two MIPI cables to connect to the camera and display interfaces on the Raspberry Pi. These form a very high-speed data exchange, and after further processing, the Pi can pass data on over Ethernet or Wi-Fi. Individual QuadRF boards can connect together in a lattice grid to form larger phased arrays.

The QuadRF’s software shows off its real strength: it’s compatible with standard programs like GNU Radio, but it also hosts a few of its own programs. The most striking of these is an “RF camera” which scans its entire frequency range at 30 fps, tracking the direction of detected signals and visualizing them on a spatial plot. When overlaid on a camera feed, this plot lets one easily see the radio signals emitted from electronics; as an example, the creators tracked a drone in flight, even distinguishing the two radio transmitters on the drone.

This isn’t the first multi-antenna SDR we’ve seen, though this is the first that could transmit. It’s important to be careful, though: some applications of this kind of hardware run afoul of arms regulations.

Thanks to [Swake] for the tip!

A Peek Inside The Secret Lagercrantz Suitcase Radio

June 12, 2026 by Al Williams 7 Comments

What counts as portable is somewhat a matter of opinion, especially over the years. [Helge Fykse] has a portable spy radio of Swedish origin. For its time, it was considered very portable, crammed into a good-sized suitcase.

You can see the large crystal that sets the transmit frequency and a key to send Morse code. The receiver has a VFO, so it was more agile. Based on the regenerative knob, it appears the receiver was of the regenerative type. The suitcase had its own battery, and with tubes, it could probably put out some kind of signal if connected to anything metal, like bedsprings, a clothesline, or anything. There was a lightbulb to let you see when you were transmitting maximum power.

Speaking of tubes, there were five inside, two for the transmitter and three for the receiver. The radio had storage for spare tubes, and the agent could maintain the radio in the field.

You not only get a peek inside the suitcase, but a look at the schematic. The radio is a model of simplicity, but we are certain it did its job.

We love looking at exotic spy gear, especially radios.

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Mechanical Stability For Your Coils

June 11, 2026 by Jenny List 8 Comments

If you work with radio, the chances are that before too long you’ll be winding an inductor. At radio frequencies these won’t be big chunky transformer style chokes, but often air-cored affairs supported by their own rigidity. As grizzled old radio amateurs will tell you though, relying on such a coil for stability is a fool’s errand. It will shift inductance from the slightest movement, thermal expansion, or even sound. Luckily [SolderSmoke] is here to remind us of the trusty fix, in the form of Q-dope, or a polystyrene solution that dries to form a rigid low-dielectric coating.

Where this is being written it wasn’t on the market so it was more usual to use nail lacquer, but reading the piece it seems American hams swore by the stuff. That’s in the past tense because it seems it’s no longer on the market. Even there though help is at hand, because dissolving packaging polystyrene in solvent yields an acceptable substitute. There’s even an 11-year-old how-to video linked from the SolderSmoke post, should you fancy making some of your own. We suggest you proceed with caution though, polymers dissolved in solvents sounds a lot like home-made napalm, and probably puts out fumes you don’t want to breathe.

Meanwhile should you fancy experiments of your own with inductors, we’ve got you covered.

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

June 4, 2026 by Tyler August 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 Jenny List 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 Maya Posch 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.