Back in March, we posted about GridDown, an open-source Android tablet-based situational awareness system designed to operate without an internet connection, which uses sensors such as an RTL-SDR, a SARSAT receiver and an ESP32-S3/SX1262 LoRa radio.
Recently, GridDown developer Cameron wrote in again and shared with us that the LoRa firmware for GridDown has now been released as an open-source project called "GridDown Secure Messenger" (main website).
The project uses a LILYGO T-Deck CYPHER-M8K (an ESP32-S3 with SX1262, 2.8" display, keyboard, and GPS) to implement secure, encrypted off-grid text messaging, and it also doubles as a 900 MHz drone scanner, with the ability to decode drone Remote ID.
Cameron has also provided two YouTube shorts [1] [2], showing the firmware in action.
Example Renders of the GridDown Secure Messenger Running on a LILYGO T-Deck CYPHER-M8K.
AI Disclaimer: The renders appear to have been AI-generated.
Thank you to Luis Lopez Martinez for writing in and sharing the release of his open-source software, IC-SDR, a new multi-mode SDR application for Windows written in Gowith a focus on performance and efficiency. Luis writes:
IC-SDR supports AM, NFM, WFM, LSB and USB demodulation, along with several integrated digital decoders:
AIS
ADS-B (1090 MHz and UAT 978 MHz)
Radiosondes
APRS
RTL_433
DMR
SSTV
TETRA
It also includes a memory bank, real-time spectrum and waterfall displays, an audio recorder with automatic silence removal, and a frequency-segment scanner with instant triggering.
Instro is an open-source Python library designed to talk to test instrumentation such as power supplies, multimeters, electronic loads, DAQs, oscilloscopes, and PLCs from a unified, typed API. The maintainers describe the goal as follows: "Code against an instrument category once, then swap vendors with a single configuration change. When you want to capture the data, attach a publisher to stream it to a file, Nominal, or a destination of your own." A library like this saves engineers from having to write custom drivers for each piece of equipment.
Recently, Alexander Arsenovic, the original author of the excellent scikit-rf RF engineering Python library, wrote and wanted to share that he has added RTL-SDR support to Instro. He has uploaded a video showing it in action with an RTL-SDR Blog V3.
SDR++ is a popular general-purpose SDR receiver program, commonly used by RTL-SDR enthusiasts. It works on all platforms, including Android; however, the original author has not expressed interest in officially publishing it on the Google Play Store, so sideloading the APK has been the only way to get it on Android.
Recently, we've learned of an unofficial SDR++ fork called "SDR++ iak" that is now on the Google Play Store. The iak fork by OK1IAK includes several improvements, notably a touch-friendly UI overhaul, various crash fixes, KiwiSDR world-map directory, radiosonde decoder, and support for the QRP Labs QMX transceiver.
Thank you to Efe (TA1EEI) for writing in and sharing an HTML web tool he created that uses a PC monitor to transmit Morse code. The tool works by modulating the monitor's pixel clocks to intentionally generate EMI leakage in the form of a Morse code signal. It transmits at 148.5 MHz.
Efe's work appears to be a much simpler version of TrojPix, a University research project that we posted about back in July. TrojPix is a more advanced system that introduces imperceptible pixel modulations into the screen, making high-bandwidth wireless data transfer possible via monitor EMI leakage.
The GitHub project page for Efe's VHF Monitor RF Transmitter explains exactly how the project works, including the video pixel clock and how it can be modulated and transmitted wirelessly. Efe has also provided a link to a Reddit post where there is a video, and discussion.
Back in July, we posted about VibeSDR, an AI vibecoded open-source mobile SDR client for rtl_tcp and UberSDR/KiwiSDR/OpenWebRX servers developed for iOS and Android. In that post, Stuart also mentioned that he was developing an Apple Watch app version of VibeSDR that runs directly on an Apple Watch, allowing you to view and listen to the spectrum on your wrist.
The Apple Watch version, called VibeSDR Jr, is now available as a full standalone Apple Watch App, meaning that no iPhone is required. The app costs £0.99 (~US$1.35). As before, Stuart has provided us with 20 free giveaway codes for the VibeSDR Jr App, so be sure to comment on either this post, the Facebook post, or the X post for a chance to win one of the codes.
Stuart has also noted that he now has a live VibeSDR demo running at demo.vibesdr.net, allowing users to see VibeSDR's DSP and server functionality in action. Stuart writes, "There is an RTL-SDR V4C, SDRPlay RSP1B, and AirSpy HF running on that demo server, all connected to the same AirSpy YouLoop with LNA antenna setup. The RSP1B is locked to 2.8MHz - 10.8MHz and can handle 10 users and the RTL-SDR & AirSpy are unlocked frequencies but 1 user at a time, each user gets a 30 minute time slot to play with. All the built in decoders are available and for the FM-DXers there is a full advanced RDS suite measured against a professional broadcast analyser too."
He also notes the following to avoid confusion with the software in the VibeSDR family:
VibeSDR + Buddy: The Main VibeSDR app and the Apple Watch Remote control companion app for that app. VIbeSDR Jr: The full standalone Apple Watch SDR client no iPhone required VibeServer: Built in to Android and standalone apps which allow you to quickly and easily share your SDR’s on a network
Use VibeServer to connect your radio and serve it and then use Jr to listen to it on your wrist, or if you don’t have your own radio Jr is compatible with almost all the same servers as the main VibeSDR app, the only thing it cannot do due to bandwidth/processing requirements is anything that is RAW IQ such as RTL-TCP or SpyServer.
Finally, Stuart notes that the Android version is coming soon and is currently just pending acceptance on the Google Play Store.
Thank you to Cees for writing in and sharing his Android app, "Carshepherd," which is currently in the pre-release stage. Carshepherd works with a connected RTL-SDR and TETRA antenna to give drivers early awareness of nearby emergency-service activity (such as police, ambulance, fire) by detecting the TETRA uplink signal.
Cees notes that this is essentially the same as what hardware devices like 'Target Blu Eye' do to detect emergency services. Laser/radar detectors are illegal in most European countries, and while not advertised as such for legal reasons, Carshepherd could be a legal alternative for detecting laser/radar speed traps, detecting ProViDa video-based pacing vehicles, or just for general awareness.
The app works by continuously sweeping the TETRA bands, looking for the signature of a TETRA carrier. Once it detects a confirmed uplink carrier, it estimates proximity, which then triggers a readout and audible alert. The TETRA uplink is not always active, but emergency service vehicles often send bursts of uplink data every few seconds with GPS position updates, and, of course, during voice PTT.
The algorithm is based on a large labeled dataset from dozens of real-world test drives. The dataset trains an AI classifier that can even tell you whether an emergency unit is keeping pace with you (e.g., traveling down the same stretch of motorway as you) or whether you are approaching a stationary unit.
Carshepherd currently only works in countries whose emergency services use the TETRA communications protocol, which includes most of Europe and various other countries, but notably not the USA. However, Cees notes that they are working on a US version that will listen to the P25 network.
While Carshepherd has not yet been released, the pricing is indicated as €3.99 per month. You can sign up for the waitlist at www.carshepherd.nl.
After nearly being hit by a tornado that NEXRAD didn't see coming, Koakno decided to build his own DIY self-contained mobile weather radar built from a $5 salvaged RV satellite dome, a HackRF or PlutoSDR, and open-source software.
Koakno notes that NEXRAD (the US weather radar system) data is typically 4-6 minutes old, and from a radar station that is often 100+ miles away, resulting in warnings coming in too late or not being detected at all. Only professional local mobile Doppler radar trucks have the capability of detecting local tornadoes rapidly enough to take action. Koakno set out to recreate this capability on a budget.
His antenna consists of a salvaged Winegard Carryout Anser GM-5000 automatic satellite dome built for RV motor homes. The dish carries an LNB that radiates an 850 MHz signal at 10.4 GHz, which is a perfect wavelength for weather radar. The SDR hardware can either be a HackRF or PlutoSDR. As the HackRF is only half-duplex, it uses pulsed timing, whereas the full-duplex PlutoSDR uses a continuous FMCW chirp. Open-source Python software processes the results, producing a live radar display showing color-scaled reflectivity.
Importantly, Koakno addresses the licensing concerns around this project. He notes there are clauses in the amateur radio FCC legislation that support the use of automatically controlled beacons for the observation of propagation, and experimental activities in the 3cm 10.0 - 10.5 GHz amateur radio band, but he is not an attorney, so this activity may still exist in a grey area.
The screenshot below was generated via the simulation the software provides for testing the UI.
