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 6 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.

Tackling Trunked Radio With Software

June 16, 2020 by Bryan Cockfield 12 Comments

For those starting to wade into radio as a hobby, one of the first real technical challenges is understanding trunked radio systems. On the surface, it seems straightforward: A control channel allows users to share a section of bandwidth rather than take up one complete channel, allowing for greater usage of the frequency range. In practice though it can be difficult to follow along, but now it’s slightly easier thanks to software defined radio.

This guide comes to us from [AndrewNohawk], who is located in San Francisco and is using his system to monitor police, fire, and EMS activity. These groups typically used trunked radio systems due to the large number of users. For listening in, nothing more than an RTL-SDR setup is needed, and the guide walks us through using this setup to find the control channels, the center frequency, and then identifying the “talk groups” for whichever organization you want to listen in on.

The guide goes into great detail, including lists of software needed to get a system like this started up, and since [AndrewNohawk] is a self-identified “radio noob” the guide is perfectly accessible to people who are new to radio and specifically new to trunked systems like these. Once you get the hang of it, it’s not too hard to scale up, either.

Hackaday Links: June 7, 2020

June 7, 2020 by Dan Maloney 7 Comments

For many of us who were in college at the time, the 1989 release of Will Wright’s classic SimCity sounded the death knell of our GPAs. Being able to create virtual worlds and then smite them with a tornado or a kaiju attack was the stuff of a procrastinator’s dreams. We always liked the industrial side of the game best, and took great pains in laying out the factory zones, power plants, and seaports. Those of a similar bent will be happy to know that Maxis, the studio behind the game, had a business simulations division, and one of their products was a complete refinery simulator the studio built for Chevron called, unsurprisingly, SimRefinery. The game, which bears a striking resemblance to SimCity, has been recovered and is now available for download, which means endless procrastination by playing virtual petrochemical engineer is only a mouse click away.

Speaking of time wasters, we stumbled upon another simulation this week that sucked away a couple of hours of productivity. As RTL-SDR.com reports, YouTuber called Information Zulu has a 24/7 live stream showing arrivals and departures at Los Angeles International Airport. That may sound boring, but the cameras used to watch the runways are virtual, and the planes are animated based on ADS-B data being scooped up by an RTL-SDR dongle. We pinged Information Zulu and asked for a rundown of the gear behind the system, but never heard back. If we do, we’ll post a full article on what we learned, because the level of detail is amazing. The arriving and departing planes sport the correct livery for the airline, the current weather conditions are shown, taxiing is shown in real time, and there’s even an audio feed from air traffic control.

If you’re looking to gain back a little of the productivity lost to the last two items, Digi-Key might be able to help with their new PCB Builder service. All you have to do is upload your gerbers and select your materials, and they’ll give you options for a bunch of different quick-turn fabrication houses. Looks mighty convenient.

Steve Mould dropped a video this week about vibration analysis. That might not sound very exciting, but the fascinating bit is how companies are now using motion amplification video techniques to show how and where industrial equipment is moving, even if those motions are too subtle to be seen by the naked eye. It’s frankly terrifying to see how pipes flex and tanks expand and contract, and how pumps and motors move relative to each other. The technique used is similar to the way a person’s pulse can be detected on a video by the subtle color change as blood rushes into capillaries. We’d love to see someone tackle a homebrew version of this so we can all see what’s going on around us.

And finally, we want to remind everyone that the Hackaday Prize is back, and that you should get your entries going. What’s new this year is the Dream Team challenges, where four worthy non-profits organizations will each assemble a three-person team to work on a specific pain-point in their process. The application deadline has been extended to June 9, and there are two $3,000 microgrants, one in June and one in July, for each team member. So look through the design briefs and see if your skills match their needs.

A Dual Screen Luggable With Integrated RTL-SDR

June 3, 2020 by Tom Nardi 23 Comments

It’s been fascinating to watch the development of bespoke mobile computers go from a few sheets of foam board and a Raspberry Pi into hardware that looks like it’s actually been transported here from an alternate reality. Granted a Raspberry Pi is more often than not still onboard, but the overall design and construction techniques of these very personal computers has improved by leaps and bounds.

The latest of these cyberdecks, a dual screen “luggable” reminiscent of classic computers like the Compaq Portable or Kaypro, comes our way from [dapperrogue]. Powered by the Raspberry Pi 4 and featuring a scratch-built mechanical keyboard to perfectly fit the machines’s specific dimensions, this is easily one of the more practical builds we’ve seen. As visually striking as they may be, few would argue that the small offset display that seems characteristic of most decks are ideal from a usability standpoint.

While the keyboard plate was milled out on a CNC, [dapperrogue] says the design of the HDPE body panels and rear polycarbonate viewing window were simple enough they could be done by hand on a band saw. The PETG internal frame uses a Voronoi pattern that not only reduces the amount of time and material required to print it, but maximizes airflow. The fact that it looks like some kind of alien biological life form only helps the retro-futuristic aesthetics.

There’s still plenty of room inside the enclosure, which is good, as [dapperrogue] says there’s more goodies to come. Adding internal battery power is a logical next step, and now that the Pi 4 can boot to external drives, and SSD is also on the list of future upgrades.

For readers who might be getting a sense of déjà vu from this project, [dapperrogue] notes this design was inspired by the phenomenal Reviiser that [Dave Estes] released earlier this year.