software-defined radio

123 Articles

Use Your RTL, In The Browser

December 13, 2024 by 14 Comments

The web browser started life as a relatively simple hypertext reading application, but over the 30+ years since the first one displayed a simple CERN web page it has been extended to become the universal platform. It’s now powerful enough to run demanding applications, for example a full software-defined radio. [Jtarrio] proves this, with an application to use an RTL-SDR, in HTML5.

It’s a fork of a previous Google-Chrome-only FM receiver, using the HTML5 WebUSB API, and converted to TypeScript. You can try it out for yourself if you have a handy RTL dongle lying around, it provides an interface similar to the RTL apps you may be used to.

The Realtek digital TV chipset has been used as an SDR for well over a decade now, so we’re guessing most of you with an interest in radio will have one somewhere. The cheap ones are noisy and full of spurious peaks, but even so, they’re a bucket of fun. Now all that’s needed is the transmit equivalent using a cheap VGA adapter, and the whole radio equation could move into the browser.

Supercon 2023: Receiving Microwave Signals From Deep-Space Probes

October 10, 2024 by 5 Comments

Here’s the thing about radio signals. There is wild and interesting stuff just getting beamed around all over the place. Phrased another way, there are beautiful signals everywhere for those with ears to listen. We go about our lives oblivious to most of them, but some dedicate their time to teasing out and capturing these transmissions.

David Prutchi is one such person. He’s a ham radio enthusiast that dabbles in receiving microwave signals sent from probes in deep space. What’s even better is that he came down to Supercon 2023 to tell us all about how it’s done!

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Portable Multi-SDR Rig Keeps Your Radios Cool

September 3, 2024 by 12 Comments

With as cheap and versatile as RTL-SDR devices are, it’s a good idea to have a couple of them on hand for some rainy day hacking. In fact, depending on what signals you’re trying to sniff out of the air, you may need multiple interfaces anyway. Once you’ve amassed this arsenal of software defined radios, you may find yourself needing a way to transport and deploy them. Luckily, [Jay Doscher] has you covered.

His latest creation, the SDR SOLO, is a modular system for mounting RTL-SDRs. Each dongle is encased in its own 3D printed frame, which not only protects it, but makes it easy to attach to the base unit. To keep the notoriously toasty radios cool, each frame has been designed to maximize airflow. You can even mount a pair of 80 mm fans to the bottom of the stack to really get the air moving. The current design is based around the RTL-SDR Blog V4, but could easily be adapted to your dongle of choice.

In addition to the row of SDR dongles, the rig also includes a powered USB hub. Each radio connects to the hub via a short USB cable, which means that you’ll only need a single USB cable running back to your computer. There’s also various mounts and adapters for attaching antennas to the system. Stick it all on the end of a tripod, and you’ve got a mobile radio monitoring system that’ll be the envy of the hackerspace.

As we’ve come to expect, [Jay] put a lot of thought and effort into the CAD side of this project. Largely made of 3D printed components, his projects often feature a rugged and professional look that really stands out.

DIY Passive Radar System Verifies ADS-B Transmissions

April 29, 2024 by 5 Comments

Like most waves in the electromagnetic spectrum, radio waves tend to bounce off of various objects. This can be frustrating to anyone trying to use something like a GMRS or LoRa radio in a dense city, for example, but these reflections can also be exploited for productive use as well, most famously by radar. Radar has plenty of applications such as weather forecasting and various military uses. With some software-defined radio tools, it’s also possible to use radar for tracking aircraft in real-time at home like this DIY radar system.

Unlike active radar systems which use a specific radio source to look for reflections, this system is a passive radar system that uses radio waves already present in the environment to track objects. A reference antenna is used to listen to the target frequency, and in this installation, a nine-element Yagi antenna is configured to listen for reflections. The radio waves that each antenna hears are sent through a computer program that compares the two to identify the reflections of the reference radio signal heard by the Yagi.

Even though a system like this doesn’t include any high-powered active elements, it still takes a considerable chunk of computing resources and some skill to identify the data presented by the software. [Nathan] aka [30hours] gives a fairly thorough overview of the system which can even recognize helicopters from other types of aircraft, and also uses the ADS-B monitoring system as a sanity check. Radar can be used to monitor other vehicles as well, like this 24 GHz radar module found in some modern passenger vehicles.

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Breadboard SDR Doesn’t Need Much

March 19, 2024 by 10 Comments

[Grug Huhler] built a simple Tayloe mixer and detector on a breadboard. He decided to extend it a bit to be a full-blown software defined radio (SDR). He then used WSJT-X to monitor FT8 signals and found that he could pick up signals from all over the world with the little breadboard system.

A Raspberry Pi Pico generates a quadrature clock that acts as the local oscillator for the radio. All the processing of the input signal to a quadrature signal is done with a 74LV4052A, which is nothing more than an analog multiplexer. In principle, the device takes a binary number from zero to three and uses it to connect a common signal to one of four channels. There are two common lines and two sets of four channels. In this case, only half of the chip is in use.

An antenna network (two resistors and a capacitor) couples the antenna to one of the common pins, and the Pi generates two square waves, 90 degrees out of phase with each other. This produces select signals in binary of 00, 01, 11, and 10. An op amp and a handful of passive components couple the resulting signals to a PC soundcard, where the software processes the data. The Pi can create clocks up to about 15 or 20 MHz easily using the PIO.

The antenna is a 20-meter-long wire outside, and that accounts for some of the radio’s success. There are several programs than can work with soundcard input like this and [Grug] shows Quisk as a general-purpose receiver. If you missed the first video explaining the Tayloe mixer design, you can catch it below the first video.

This isn’t the first breadboard SDR we’ve seen, but they all use different parts. We’ve even seen a one-bit SDR with three components total (not including the microcontroller). Seriously.

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Long-Distance Wi-Fi With Steam Deck Server

June 16, 2023 by 11 Comments

It’s no secret that the Steam Deck is a powerful computer, especially for its price point. It has to be capable enough to run modern PC games while being comfortable as a handheld, all while having a useful amount of battery life. Thankfully Valve didn’t lock down the device like most smartphone manufacturers, allowing the computer to run whatever operating system and software the true owner of the device wants to run. That means that a whole world of options is open for this novel computer, like using it to set up an 802.11ah Wi-Fi network over some pretty impressive distances.

Of course the Steam Deck is more of a means to an end for this project; the real star of the show is DragonOS, a Debian-based Linux distribution put together by [Aaron] to enable easy access to the tools needed for plenty of software-defined radio projects like this one. Here, he’s using it to set up a long-distance Wi-Fi network on one side of a lake, then testing it by motoring over to the other side of the lake to access the data from the KrakenSDR setup running on the Deck, as well as performing real-time capture of IQ data that was being automatically demodulated and feed internally to whispercpp.

While no one will be streaming 4K video over 802.11ah, it’s more than capable of supporting small amounts of data over relatively large distances, and [Aaron] was easily able to SSH to his access point from over a kilometer away with it. If the lake scenery in the project seems familiar at all, it’s because this project is an extension of another one of his DragonOS projects using a slightly lower frequency to do some impressive direction-finding, also using the Steam Deck as a base of operations.

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Passionate Hams Make Their Mark On The Hack Chat

June 12, 2023 by 63 Comments

Let’s be honest — there are some not very pleasant stereotypes associated with amateur radio, at least if you ask outsiders. Hams are often thought of as being in two camps: old guys who can’t figure out modern technology or conspiracy theorists who think their knowledge of radio will give them an edge after the world becomes a post-apocalyptic hellscape. We’ll leave it to you to decide which is the worse brush to be painted with.

As is often the case, the best way to fight such ignorance is with education and outreach. Events like our weekly Hack Chat are a perfect platform for that, as it allows the curious to ask questions and get answers directly from subject matter experts. This is precisely why we invited Mark Hughes and Beau Ambur to helm last week’s Chat. The fact that they’re both relatively recent licensees makes them uniquely qualified to shed some light on what it’s like to become part of the ham radio community in the 21st century. As an added bonus, they’re both sharp and articulate technologists — about as far as you can get from the mental image of the doddering old granddad who prefers the simplicity of the Morse key to those newfangled smarty-phones.

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