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A new open-source radio telescope can see Wi-Fi signals through walls

The XJ9 makes Wi-Fi visible (Image Source: The Though Emporium)
The XJ9 makes Wi-Fi visible (Image Source: The Though Emporium)
In their latest video, The Thought Emporium discusses the science and practical applications of the channel's latest and most advanced open-source radio telescope, the XJ9. Featuring a modular design and a host of radio-focused features, the XJ9 is an enticing project for radio enthusiasts.

Using concepts from radio astronomy, the team at The Thought Emporium has successfully developed an open-source build of a functional radio telescope dubbed the XJ9. Featuring a modular design, the XJ9 can detect 2.4 GHz Wi-Fi frequencies and has a host of attachments to suit different applications, such as an auto dart turret and knife arm. However, the XJ9's capabilities as a radio telescope are by far the most impressive.

Building on a previous project known as Cogsworth, the team created a refined system to detect and visualize the intensity of microwaves released by Wi-Fi routers. The microwaves released by routers oscillate at around 2.4 GHz, and because microwaves are a form of light, it is possible to create a device that can capture these frequencies. This is the same concept used in radio astronomy because many forms of astrological phenomena create electromagnetic radiation as they occur. Common examples include black holes, gas jets, and quasars, all of which have been photographed thanks to radio telescopes measuring the radio frequencies they produce. Similarly, a small version of a radio telescope can do the same thing for Wi-Fi when tuned to the right frequency.

The XJ9 is a primarily 3D-printed radio telescope that features a host of upgrades over the team's previous version, including geared stepper motors, belt drives, and a flat bearing. With an antenna attachment, XJ9 uses a software-defined radio or SDR to turn the radio waves that hit the antenna into usable data. In this case, the team uses the HackRF SDR to capture the radio waves from a router. Then, using GNU radio to process the data, the XJ9 takes measurements of the detected radio waves at various positions to form a scan of its surroundings. Unfortunately, the first tests did not yield accurate results, and the team found that the configuration for GNU radio normalized their readings instead of capturing spikes, causing the scans to be inaccurate. After a simple fix, the XJ9 began to capture accurate hotspots of Wi-Fi radiation.

While this is an impressive accomplishment, the team has bigger hopes for real-world applications of the XJ9. The experiment is effectively a proof of concept for what is known as passive radar. Building on the idea of Wi-Fi radiation as a form of light, the team hopes to use Wi-Fi or an adjacent frequency to illuminate objects in the surrounding area, effectively letting the XJ9 see through walls and build a 3D map of its surroundings. However, the team has considerable work to do before this is possible. Kindly visit the resources below for more information on the build or to access the 3D files for the XJ9.

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> Expert Reviews and News on Laptops, Smartphones and Tech Innovations > News > News Archive > Newsarchive 2024 12 > A new open-source radio telescope can see Wi-Fi signals through walls
Stephen Pereyra, 2024-12-11 (Update: 2024-12-11)