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19 Articles

Communicating With Satellites Like It’s 1957

February 3, 2025 by 14 Comments

When the first artificial satellite, Sputnik, was put into orbit around Earth, anyone in the path of the satellite could receive the beeps transmitted by the satellite provided they had some simple radio equipment. Of course, there was no two-way communication with this satellite, and it only lasted a few weeks before its batteries died. Here in the future, though, there are many more satellites in orbit and a few are specifically meant for ham radio operators. And, like the ’50s, it doesn’t take too much specialized equipment to communicate with them, although now that communication can be two-way.

The first step in this guide by [W2PAK] is to know where these satellites are in the sky. The simplest way to do that is to use a smartphone app called GoSatWatch and, when configured for a specific location, shows the satellites currently overhead. After that it’s time to break out the radio gear, which can be surprisingly inexpensive. A dual-band handheld is required since satellite uplink and downlink can be on different bands, and the antenna can be made from simple parts as well as [W2PAK] demonstrates in a separate video. Combined, this can easily be done for less than $100. [W2PAK] also goes over the proper format and etiquette for a satellite contact as well, so a new operator can pick it up quickly.

Using satellites as repeaters opens up a lot of capabilities when compared to terrestrial communications. Especially for operators with entry-level licenses who are restricted to mostly VHF and UHF, it adds a challenge as well as significantly increased range compared to ground-based repeaters and line-of-sight communications. There are plenty of activities around satellites that don’t require a license at all, too, like this project which downloads weather imagery from weather satellites.

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Retrotechtacular: Another Thing Your TV No Longer Needs

October 2, 2024 by 23 Comments

As Hackaday writers we don’t always know what our colleagues are working on until publication time, so we all look forward to seeing what other writers come up with. This week it was [Al Williams] with “Things Your TV No Longer Needs“, a range of gadgets from the analogue TV era, now consigned to the history books. On the bench here is a device that might have joined them, so in taking a look at it now it’s by way of an addendum to Al’s piece.

When VHF Was Not Enough

In a Dutch second-had store while on my hacker camp travels this summer, I noticed a small grey box. It was mine for the princely sum of five euros, because while I’d never seen one before I was able to guess exactly what it was. The “Super 2” weighing down my backpack was a UHF converter, a set-top box from before set-top boxes, and dating from the moment around five or six decades ago when that country expanded its TV broadcast network to include the UHF bands. If your TV was VHF it couldn’t receive the new channels, and this box was the answer to connecting your UHF antenna to that old TV.

It’s a relatively small plastic case about the size of a chunky paperback book, on the front of which is a tuning knob and scale in channels and MHz, on the top of which are a couple of buttons for VHF and UHF, and on the back are a set of balanced connectors for antennas and TV set. It’s mains powered, so there’s a mains lead with an older version of the ubiquitous European mains plug. Surprisingly it comes open with a couple of large coin screws on the underside, so it’s time to take a look inside. Continue reading “Retrotechtacular: Another Thing Your TV No Longer Needs” →

Emails Over Radio

April 9, 2024 by 38 Comments

The modern cellular network is a marvel of technological advancement that we often take for granted now. With 5G service it’s easy to do plenty of things on-the-go that would have been difficult or impossible even with a broadband connection to a home computer two decades ago. But it’s still reliant on being close to cell towers, which isn’t true for all locations. If you’re traveling off-grid and want to communicate with others, this guide to using Winlink can help you send emails using a ham radio.

While there are a number of ways to access the Winlink email service, this guide looks at a compact, low-power setup using a simple VHF/UHF handheld FM radio with a small sound card called a Digirig. The Digirig acts as a modem for the radio, allowing it to listen to digital signals and pass them to the computer to decode. It can also activate the transmitter on the radio and send the data from the computer out over the airwaves. When an email is posted to the Winlink outbox, the software will automatically send it out to any stations in the area set up as a gateway to the email service.

Like the cellular network, the does rely on having an infrastructure of receiving stations that can send the emails out to the Winlink service on the Internet; since VHF and UHF are much more limited in range than HF this specific setup could be a bit limiting unless there are other ham radio operators within a few miles. This guide also uses VARA, a proprietary protocol, whereas the HF bands have an open source protocol called ARDOP that can be used instead. This isn’t the only thing these Digirig modules can be used for in VHF/UHF, though. They can also be used for other digital modes like JS8Call, FT8, and APRS.

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Getting To The Heart Of A Baofeng

November 15, 2022 by 32 Comments

In amateur radio circles, almost no single piece of equipment serves as more of a magnet for controversy than the humble Baofeng handheld transceiver. It’s understandable — the radio is a shining example of value engineering, with just enough parts to its job while staying just on the edge of FCC rules. And at about $25 a pop, the radios are cheap enough that experimentation is practically a requirement of ownership.

But stripped down as the Baofeng may be, it holds secrets inside that are even more tempting to play with than the radio itself. And who better than [HB9BLA], a guy who has a suspiciously familiar Swiss accent, to guide us through the RF module at the heart of the Baofeng, the SA818. For about $8 you can get one of these little marvels off AliExpress and have nearly all the important parts of a VHF or UHF radio — an SDR transceiver, a power amp, and all the glue logic to make it work.

In the video below, [Andreas] puts the SA818 module through its paces with the help of a board that pairs the module with a few accessories, like an audio amp and a low-pass RF filter. With a Raspberry Pi and a Python library to control the module, it’s a decent imitation of the functionality of a Baofeng. But that’s only the beginning. By adding a USB sound card to the Pi, the setup was able to get into every ham’s favorite packet radio system, APRS. There are a ton of other applications for the SA818 modules, some of which [Andreas] mentions at the end of the video. Pocket-sized repeaters, a ridiculously small EchoLink hotspot, and even an AllStar node in an Altoids tin.

Of course, if you want to get in on the fun, you’re going to need an amateur radio license. Don’t worry, it’s easy — we’ll help you get there.

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A Few Of My Favorite Things: Amateur Radio

January 21, 2021 by 50 Comments

Hackaday has among its staff a significant number of writers who also hold amateur radio licenses. We’re hardware folks at heart, so we like our radios homebrew, and we’re never happier than when we’re working at high frequencies.

Amateur radio is a multi-faceted hobby, there’s just so much that’s incredibly interesting about it. It’s a shame then that as a community we sometimes get bogged down with negativity when debating the minutia. So today let’s talk about a few of my favourite things about the hobby of amateur radio. I hope that you’ll find them interesting and entertaining, and in turn share your own favorite things in the comments below.

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GPU Turned Into Radio Transmitter To Defeat Air-Gapped PC

April 24, 2020 by 31 Comments

Another week, another exploit against an air-gapped computer. And this time, the attack is particularly clever and pernicious: turning a GPU into a radio transmitter.

The first part of [Mikhail Davidov] and [Baron Oldenburg]’s article is a review of some of the basics of exploring the RF emissions of computers using software-defined radio (SDR) dongles. Most readers can safely skip ahead a bit to section 9, which gets into the process they used to sniff for potentially compromising RF leaks from an air-gapped test computer. After finding a few weak signals in the gigahertz range and dismissing them as attack vectors due to their limited penetration potential, they settled in on the GPU card, a Radeon Pro WX3100, and specifically on the power management features of its ATI chipset.

With a GPU benchmarking program running, they switched the graphics card shader clock between its two lowest power settings, which produced a strong signal on the SDR waterfall at 428 MHz. They were able to receive this signal up to 50 feet (15 meters) away, perhaps to the annoyance of nearby hams as this is plunk in the middle of the 70-cm band. This is theoretically enough to exfiltrate data, but at a painfully low bitrate. So they improved the exploit by forcing the CPU driver to vary the shader clock frequency in one megahertz steps, allowing them to implement higher throughput encoding schemes. You can hear the change in signal caused by different graphics being displayed in the video below; one doesn’t need much imagination to see how malware could leverage this to exfiltrate pretty much anything on the computer.

It’s a fascinating hack, and hats off to [Davidov] and [Oldenburg] for revealing this weakness. We’ll have to throw this on the pile with all the other side-channel attacks [Samy Kamkar] covered in his 2019 Supercon talk.

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