Real Spectrum Analysis Goes Virtual

November 24, 2020 by Al Williams 4 Comments

One of the hard things about electronics is that you can’t really see the working parts without some sort of tool. If you work on car engines, fashion swords, or sculpt clay, you can see with your unaided eye what’s going on. Electronic components are just abstract pieces and the real action requires a meter or oscilloscope to understand. Maybe that’s what [José] was thinking of when he built a-radio. This “humble experiment” pipes a scan from a software-defined radio into VR goggles, which can be as simple as a smartphone and some cardboard glasses.

The resulting image shows you what the radio spectrum looks like. Granted, so will a spectrum analyzer, but perhaps the immersion will provide a different kind of insight into radio frequency analysis.

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Easy-SDR Gets Updates

October 30, 2020 by Al Williams 1 Comment

Back in 2018, we covered [Igor’s] Easy-SDR project that aimed to provide open hardware extensions for the chap RTL-SDR receivers. If you haven’t been there for a while, it’s worth a look as there have been many recent updates. According to the author’s Reddit post:

Most of the devices are now prepared for installation in a metal case measuring 80 x 50 x 20 millimeters.
There’s a completely redesigned LNA design. Now, Bias Tee powered amplifiers are housed in a 50 x 25 x 25mm metal case and have N-type connectors.
There’s an added amplifier based on the PGA-103 microcircuit.
Added is the ability to install filters in final amplifiers (a separate printed circuit board, depending on the filter used).
A new device – SPDT antenna switch for receiving antennas.
The upconverter has been redesigned. Added intermediate buffer stage between the crystal generator and mixer.
RF lines in all devices were recalculated to correspond to the characteristic wave impedance of 50 Ohm.
Reduced size of PI attenuator PCB.

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Tracking Boats And Ships In Real Time At The Same Time

October 22, 2020 by Bryan Cockfield 15 Comments

Software-defined radio came on the hacker scene in a big way less than a decade ago thanks to the discovery that a small USB-based TV tuner dongle could be used for receiving all kinds of radio transmissions. Two popular projects from that era are tracking nearby airplanes and boats in real time. Of course, these projects rely on different frequencies and protocols, but if you live in a major port city like [Ian] then his project that combines both into a single user interface might be of interest.

This project uses an RTL-SDR dongle for the marine traffic portion of the project, but steps up to a FlightAware Pro dongle for receiving telemetry from airplanes. Two separate antennas are needed for this, and all of the information is gathered and handled by a pair of Raspberry Pis. The Pis communicate with various marine and air traffic databases as well as handles the custom user interface that knits both sets of information together. This interface was custom-built from a previous project of his and was repurposed slightly to fit the needs of this one.

This is a great project that goes into a lot of interesting detail about how the web traffic moves and how the UI works, so even if you’re not into software-defined radio it might be worth a look. However, it’s also worth noting that it hasn’t been easier to set up a system like this thanks to the abundance and low price of RTL-SDR dongles and the software tools that make setting them up a breeze.

Teardown: Mini GPS Jammer

September 8, 2020 by Tom Nardi 142 Comments

If you spend enough time trolling eBay for interesting electronic devices to take apart, you’re bound to start seeing suggestions for some questionable gadgets. Which is how I recently became aware of these tiny GPS jammers that plug directly into an automotive 12 V outlet. Shipped to your door for under $10 USD, it seemed like a perfect device to rip open in the name of science.

Now, you might be wondering what legitimate uses such a device might have. Well, as far as I’m aware, there aren’t any. The only reason you’d want to jam GPS signals in and around a vehicle is if you’re trying to get away with something you shouldn’t be doing. Maybe you’re out driving a tracked company car and want to enjoy a quick two hour nap in a parking lot, or perhaps you’re looking to disable the integrated GPS on the car you just stole long enough for you to take it to the chop shop. You know, as one does.

But we won’t dwell on the potentially nefarious reasons that this device exists. Hackers have never been too choosy about the devices they investigate and experiment with, and there’s no reason we should start now. Instead, let’s take this piece of gray-area hardware for a test drive and see what makes it tick.

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Comparing Shortwave Antennas With RTL-SDR And Python

September 5, 2020 by Danie Conradie 7 Comments

Measuring the performance of antennas in absolute terms that can involve a lot of expensive equipment and specialized facilities. For practical applications, especially when building antennas, comparing performance in relative terms is more practical. Using cheap RTL-SDR dongles and Python, [Eric Urban] was able to compare the performance of two shortwave/HF antennas, and documented the entire process.

The two antennas in question was a single band inverted-L and smaller broadband T3FD antenna. [Eric] first gathered performance data for each over few days, connected to separate PCs with RTL-SDRs via low-pass filters. These were set up to receive FT8 transmissions, a popular digital ham radio mode, which allowed [Eric] to automate data collection completely. GQRX, a software receiver, converted the signals to audio, which was then piped into WSJT-X for demodulation.

Data for each received FT8 transmission was recorded to a log file. [Eric] also modified GQRX and WSJT-X to give him all the remote control features he needed to automatically change frequencies. Between the two antenna setups, more than 100,000 FT8 transmissions were logged. Using the recorded data and Python he compared the number of received transmissions, the distance, and the heading to the transmitters, using the location information included in many FT8 transmissions. Where the same transmission was received by both antennas, the signal-to-noise ratios was compared.

From all this data, [Eric] was able to learn that the inverted-L antenna performed better than the T3FD antenna on three of the four frequency bands that were tested. He also discovered that the inverted-L appeared to be “deaf” in one particular direction. Although the tests weren’t perfect, it is impressive how much practical data [Eric] was able to gather with low-cost hardware. Continue reading “Comparing Shortwave Antennas With RTL-SDR And Python” →

Virtual Software Defined Radio

August 7, 2020 by Al Williams 5 Comments

Software defined radio or SDR has changed the radio landscape forever. But to use one you need to buy some kind of hardware right? Maybe not. As [Tech Minds] shows in a recent video there are plenty of SDRs publically available on the Internet. We know that isn’t news, but the video does cover several different methods of finding and using SDR receivers including many that run totally in the browser.

Of course, there are a lot of reasons you might want to borrow an alien radio receiver, even if you have your own hardware. Maybe you don’t have a great antenna or maybe you want to hear a signal — maybe even your own — from a different location.

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Lightning Analysis With Your SDR

August 7, 2020 by Jenny List 19 Comments

Perhaps it’s just one of those things adults dream up to entertain their children, but were you ever told to count slowly the time between seeing a lightning flash and hearing the rumble of thunder? The idea was that the count would tell you how far away the storm was, but from a grown-up perspective the calibration accuracy of a child saying “one… two…three…” in miles seems highly suspect. It’s a valid technique though, and it can be used to monitor thunderstorms by the radio emissions created through the electrical discharge. It’s an area the SAGE project has been working in, and they’ve posted some details including a fascinating run-down of the software techniques , on how lightning can be detected with an RTL-SDR.

A lightning strike produces a characteristic wideband burst that shows up in the time domain as a maximum point that can easily be detected but could also be confused with radio interference from another source. Thus after identifying maxima they zoom in and perform a Fourier transform to spot the wideband burst. It’s all done in Python, and the pleasant surprise is how straightforward to understand it all is.

SAGE are working on a distributed sensor network, so we hope this work might one day give us real-time open lightning data. The FFT approach should ensure that it won’t be fooled by false positives as a traditional detector might be.

Via RTL-SDR.com.