radio

566 Articles

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.

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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.

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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.

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Give Your Band The Music Of The Bands

September 18, 2025 by 3 Comments

The way to get into radio, and thence electronics, in the middle years of the last century, was to fire up a shortwave receiver and tune across the bands. In the days when every country worth its salt had a shortwave station, Cold War adversaries boomed propaganda across the airwaves, and even radio amateurs used AM that could be listened to on a consumer radio, a session in front of the dial was sure to turn up a few surprises. It’s a lost world in the 21st century, as the Internet has provided an easier worldwide medium and switch-mode power supplies have created a blanket of noise. The sounds of shortwave are thus no longer well known to anyone but a few enthusiasts, but that hasn’t stopped [gnd buzz] investigating their potential in electronic music.

There’s very little on the air which couldn’t be used in some form by the musician, but the samples are best used as the base for further processing. One example takes a “buzzer” signal and turns it into a bass instrument. The page introduces the different types of things which can be found on the bands, for which with the prevalence of WebSDRs there has never been a lower barrier to entry.

If you’re too young to have scanned the bands, a capable receiver can now be had for surprisingly little.

Radio dial header: Maximilian Schönherr, CC BY-SA 3.0.

It’s A Variable Capacitor, But Not As We Know It

September 17, 2025 by 22 Comments

Radio experimenters often need a variable capacitor to tune their circuits, as the saying goes, for maximum smoke. In decades past these were readily available from almost any scrap radio, but the varicap diode and then the PLL have removed the need for them in consumer electronics. There have been various attempts at building variable capacitors, and here’s [radiofun232] with a novel approach.

A traditional tuning capacitor has a set of meshed semicircular plates that have more of their surface facing each other depending on how far their shaft is turned. The capacitor presented in the first video below has two plates joined by a hinge in a similar manner to the covers of a book. It’s made of tinplate, and the plates can be opened or closed by means of a screw.

The result is a capacitor with a range from 50 to 150 picofarads, and in the second video we can see it used with a simple transistor oscillator to make a variable frequency oscillator. This can form the basis of a simple direct conversion receiver.

We like this device, it’s simple and a bit rough and ready, but it’s a very effective. If you’d like to see another unusual take on a variable capacitor, take a look at this one using drinks cans.

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6502 Puts On An SDR Hat

September 11, 2025 by 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.