radio

562 Articles

Radio Apocalypse: Survivable Low-Frequency Communication System

November 12, 2025 by 12 Comments

In the global game of nuclear brinksmanship, secrets are the coin of the realm. This was especially true during the Cold War, when each side fielded armies of spies to ferret out what the other guy was up to, what their capabilities were, and how they planned to put them into action should the time come. Vast amounts of blood and treasure were expended, and as distasteful as the whole thing may be, at least it kept armageddon at bay.

But secrets sometimes work at cross-purposes to one’s goals, especially when one of those goals is deterrence. The whole idea behind mutually assured destruction, or MAD, was the certain knowledge that swift retaliation would follow any attempt at a nuclear first strike. That meant each side had to have confidence in the deadliness of the other’s capabilities, not only in terms of their warheads and their delivery platforms, but also in the systems that controlled and directed their use. One tiny gap in the systems used to transmit launch orders could spell the difference between atomic annihilation and at least the semblance of peace.

During the height of the Cold War, the aptly named Survivable Low-Frequency Communication System was a key part of the United States’ nuclear deterrence. Along with GWEN, HFGCS, and ERCS, SLFCS was part of the alphabet soup of radio systems designed to make sure the bombs got dropped, one way or another.

Continue reading “Radio Apocalypse: Survivable Low-Frequency Communication System” →

The Singing Dentures Of Manchester And Other Places

October 12, 2025 by 39 Comments

Any radio amateur will tell you about the spectre of TVI, of their transmissions being inadvertently demodulated by the smallest of non-linearity in the neighbouring antenna systems, and spewing forth from the speakers of all and sundry. It’s very much a thing that the most unlikely of circuits can function as radio receivers, but… teeth? [Ringway Manchester] investigates tales of musical dental work.

Going through a series of news reports over the decades, including one of Lucille Ball uncovering a hidden Japanese spy transmitter, it’s something all experts who have looked at the issue have concluded there is little evidence for. It was also investigated by Mythbusters. But it’s an alluring tale, so is it entirely fabricated? What we can say is that teeth are sensitive to sound, not in themselves, but because the jaw provides a good path bringing vibrations to the region of the ear. And it’s certainly possible that the active chemical environment surrounding a metal filling in a patient’s mouth could give rise to electrical non-linearities. But could a human body in an ordinary RF environment act as a good enough antenna to provide enough energy for something to happen? We have our doubts.

It’s a perennial story (even in fiction), though, and we’re guessing that proof will come over the coming decades. If the tales of dental music and DJs continue after AM (or Long Wave in Europe) transmissions have been turned off, then it’s likely they’re more in the mind than in the mouth. If not, then we might have missed a radio phenomenon. The video is below the break.

Continue reading “The Singing Dentures Of Manchester And Other Places” →

Smart Bulbs Are Turning Into Motion Sensors

October 7, 2025 by 33 Comments

If you’ve got an existing smart home rig, motion sensors can be a useful addition to your setup. You can use them for all kinds of things, from turning on lights when you enter a room, to shutting off HVAC systems when an area is unoccupied. Typically, you’d add dedicated motion sensors to your smart home to achieve this. But what if your existing smart light bulbs could act as the motion sensors instead?

Continue reading “Smart Bulbs Are Turning Into Motion Sensors” →

Building A Ham Radio Data Transceiver On The Cheap

October 3, 2025 by 19 Comments

Once upon a time, ham radio was all about CW and voice transmissions and little else. These days, the hobby is altogether richer, with a wide range of fancy digital data modes to play with. [KM6LYW Radio] has been tinkering in this space, and whipped up a compact ham radio data rig that you can build for well under $100.

Radio-wise, the build starts with the Baofeng UV-5R handheld radio. It’s a compact VHF/UHF transceiver with 5W output and can be had for under $25 USD if you know where to look. It’s paired with a Raspberry Pi Zero 2W, which is the brains of the operation. The Pi is hooked up to the All-In-One-Cable which is basically a soundcard-like interface that plugs into USB and hooks up to the mic and speaker outputs of the Baofeng handheld. The final pieces of the puzzle are a USB PD battery pack and a small OLED screen to display status information.

What does that kit get you? The capability to transmit on all sorts of digital modes with the aid of the DigiPi software package. You can send emails, jump on APRS, or even chat on the web. You can configure all of this through a web interface running on the Raspberry Pi.

We’ve looked at some interesting digital ham projects before, too. Video after the break.

Continue reading “Building A Ham Radio Data Transceiver On The Cheap” →

Hard Hat Becomes Bluetooth Direction Finder

September 30, 2025 by 10 Comments

Have you ever wanted to find a Bluetooth device out in the wild while looking like the comic relief character from a science-fiction series? You might like Dendrite, the direction-finding hat from [SolidStat3].

Dendrite is intended for hunting down Bluetooth devices. It’s capable of direction estimation based on signal strength readings from four ESP32 microcontrollers mounted on an off-the-shelf hard hat. Each ESP32 searches for BLE devices in the immediate area and reports the apparent signal strength to a fifth ESP32, which collates readings from all units. It then runs a simple multilateration algorithm to estimate the direction of the device. This information is then displayed via a ring of addressable LEDs around the perimeter of the hat. White LEDs marking the direction of the detected device. The only problem? You can’t see the LEDs while you’re wearing the hat. You might need a friend to help you… or you can simply take it off to see what it’s doing.

Ultimately, this project is a useful direction-finding hard hat that would also make a perfect prop from an episode of Inspector Spacetime. We’ve covered direction finding in other contexts before, too. Meanwhile, if you’re cooking up your own innovative hard hat (or radio) hacks, don’t hesitate to let us know!

A Ham-Adjacent Portable Radio Repeater

September 26, 2025 by 45 Comments

Although ham radio offers a wide array of bands to transmit on, not to mention plenty of modes to communicate with, not everyone wants or needs to use all of this capability. For those needing simple two-way communication services like FRS or GMRS are available (in North America) with much less stringent licensing requirements, and GMRS even allows repeaters to be used to extend their range beyond the typical mile or so. [Dave] aka [N8DAV] has built an off-grid simplex repeater that can travel around with him wherever he goes.

The repeater itself is based on a pre-built simplex repeater module, which means that it has to record an incoming signal and then play it back on the same frequency. Compared to a split frequency repeater which uses different frequencies for transmit and receive this can be a bit cumbersome but simplifies the design and the use. A Baofeng UV-5R is used to perform the actual radio duties paired to a 40 watt amplifier to extend the range as much as possible. It’s all packed into a Pelican-like case and set up with a large battery that could power it for a number of days, making it useful for camping, rescue, or other off-grid activities.

For those wondering why [Dave] is using his ham call sign instead of his GMRS one, all of the equipment in this build will work in either the UHF ham bands or the channels reserved for GMRS with minor adjustments, so it’s perfectly possible to use the setup for one’s preferred license. And, for those in other parts of the world without GMRS there’s a similar class of radio called UHF CB which might be able to support similar builds, but be sure to check your local jurisdiction’s laws before hooking something like this up. For an even longer-range radio repeater using similar equipment we’d recommend looking to the skies.

Continue reading “A Ham-Adjacent Portable Radio Repeater” →

Hackaday Links Column Banner

Hackaday Links: September 21, 2025

September 21, 2025 by 7 Comments

Remember AOL? For a lot of folks, America Online was their first ISP, the place where they got their first exposure to the Internet, or at least a highly curated version of it. Remembered by the cool kids mainly as the place that the normies used as their ISP and for the mark of shame an “@aol.com” email address bore, the company nevertheless became a media juggernaut, to the point that “AOL Time Warner” was a thing in the early 2000s. We’d have thought the company was long gone by now, but it turns out it’s still around and powerful enough of a brand that it’s being shopped around for $1.5 billion. We’d imagine a large part of that value comes from Yahoo!, which previous owner Verizon merged with AOL before selling most of the combined entity off in 2021, but either way, it’s not chump change.

For our part, the most memorable aspect of AOL was the endless number of CDs they stuffed into mailboxes in the 90s. There was barely a day that went by that one of those things didn’t cross your path, either through the mail or in free bins at store checkouts, or even inside magazines. They were everywhere, and unless you were tempted by the whole “You’ve got mail!” kitsch, they were utterly useless; they didn’t even make good coasters thanks to the hole in the middle. So most of the estimated 2 billion CDs just ended up in the trash, which got us thinking: How much plastic was that? A bit of poking around indicates that a CD contains about 15 grams of polycarbonate, so that’s something like 30,000 metric tonnes! To put that into perspective, the Great Pacific Garbage Patch is said to contain “only” around 80,000 metric tonnes of plastic. Clearly the patch isn’t 37% AOL CDs, but it still gives one pause to consider how many resources AOL put into marketing.

Continue reading “Hackaday Links: September 21, 2025” →