Satellite communications engineer Phil Crump has published an open-source design for an external TCXO frequency reference board for the LimeSDR Mini and other devices in the LimeSDR family.
“This PCB provides an external, thermally separate, TCXO Frequency Reference to the LimeSDR Mini board,” Phil explains of the project. “I built this as even though the onboard TCXO is well-specced, being next to the high-power FPGA & RF components was causing noticeable thermal drift, especially in amplitude-modulated (eg. SSB) outdoor use.”
Designed to be easy to assemble, the board is based on a 40MHz TCXO and is a plug-in replacement with no software or hardware reconfiguration required. The board also includes a 12-turn potentiometer, allowing for manual calibration.
The design files are available on Phil’s GitHub repository under the permissive MIT licence.
Radio amateur and software developer Charles Brain has shown off a project to take video from a webcam and transmit it over a LimeSDR on an Nvidia Jetson Nano – taking advantage of its hardware acceleration capabilities.
Launched two years ago, the Jetson Nano is a maker-friendly low-cost entry in the Nvidia Jetson family of deep-learning-focused computers-on-modules. Like its more expensive brethren, its main focus is a powerful graphics processor used to accelerate a range of workloads – and, in Charles’ case, video encoding.
“Webcam [to] HW accelerated FFmpeg [to] Lime [SDR] running on a Jetson Nano transmitting 500 KHz DVB-T on 437 MHz,” Charles writes of his experiment. “Small enough footprint to run on the cheaper Nano too,” he adds – referring to the Jetson Nano 2GB launched late last year, which offers a reduced cost but with less RAM and more restricted IO options.
Charles has posted images of the experiment to his Twitter account.
Developer Martyn van Dijke has released a GNU Radio implementation of a LoRa transceiver, claiming it allows software defined radios to connect to LoRa networks at even very low signal to noise ratios.
“In the GNU Radio implementation of the LoRa Tx and Rx chains the user can choose all the parameters of the transmission, such as the spreading factor, the coding rate, the bandwidth, the presence of a header and a CRC, the message to be transmitted, etc,” Martin explains.
“In the Tx chain, the implementation contains all the main blocks of the LoRa transceiver: the header- and the CRC-insertion blocks, the whitening block, the Hamming encoder block, the interleaver block, the Gray mapping block, and the modulation block.
“On the receiver side there is the packet synchronization block, which performs all the necessary tasks needed for the synchronization, such as the necessary STO and CFO estimation and correction. The demodulation block follows, along with the Gray demapping block, the deinterleaving block, the Hamming decoder block and the dewhitening block, as well as a CRC block.”
The project is based on earlier work by Pieter Robyns, Peter Quax, Wim Lamotte, and William Thenaers, along with a paper published by J. Tapparel, O. Afisiadis, P. Mayoraz, A. Balatsoukas-Stimming, and A. Burg.
The code, and instructions for getting started, are available on Martyn’s GitLab repsitory under the GNU General Public Licence 3.0.
Radio enthusiast and developer Luigi Cruz has published an updated version of his PiSDR, now up to v5.0, which bundles a range of software packages and drivers for popular software defined radios into a single SD Card image for the Raspberry Pi family of single-board computers.
Among the new features of PiSDR v5.0 are the inclusion of the LimeSDR Toolbox, the FoxTelem and Hamlib packages, Universal Radio Hacker, VaporTrail, and dump1090. As with prior releases, all variants of the Raspberry Pi family are supported: the Raspberry Pi Zero, original, Raspberry Pi 2, Raspberry Pi 3, and Raspberry Pi 4, along with the embedded Compute Module variants.
The latest release can be downloaded from the project GitHub repository now; once downloaded, the image needs to be flashed to a microSD card – or, where compatible, USB storage device – and inserted into a Raspberry Pi where it will automatically boot into a graphical user interface.
The project is published under the permissive MIT Licence.
The GNU Radio project has announced the release of GNY Radio 3.9.0.0, which includes the work of brand-new contributors – a sign, the maintainers claim, of how maintainable the latest code base truly is.
“GNU Radio 3.9 packs a whole bunch of power when it comes to transforming the way GNU Radio and its ecosystem can be developed in the future,” the project maintainers claim in the release announcement. “Not only did we have great progressions from old dependencies that proved to be all too problematic (SWIG, Python2), but also did we see an incredibly influx of people actively working on how maintainable this code base is. This will nurture the project for years to come.”
There’s an improvement beyond the accessibility of the code base which may explain the influx of contributors, too: The removal of the Contributor Licence Agreement (CLA). “If you’re contributing code upstream, we no longer need you to submit a CLA,” the maintainers explain. “Instead, we ask you to just certify, yourself, that you’re allowed to contribute that code (and not, e.g. misappropriating someone else’s code). That’s what the DCO (Developer Certificate of Origin) is: just a quick, ‘hey, this code is actually for me to contribute under the project’s license;’ nothing more.”
Full release notes, and links to the latest release, can be found on the GNU Radio website.
The SdrGlut software-defined radio player utility, designed for minimal resource usage, has been upgraded with dramatically improved recording capabilities in its v1.21 release.
“The latest release extends the audio recording capabilities of SdrGlut,” pseudonymous project creator RightHalfPlane explains. “It can be programmed to record any frequency in any mode at any time. The 48,000 Hz 16-bit raw mono audio files can be imported into Audacity and played or exported as another type of audio file.”
The new release also includes a “send” function, transferring the I/Q stream to external programs over TCP/IP – including to Listen, a bundled program which can decode AM, FM, NBFM, USB, and LSB then output the decoded audio to another program or your system’s speakers.
The latest release, and all source code, can be found on RightHalfPlane’s GitHub repository under the permissive MIT Licence.
LuaRadio, the lightweight flow graph signal processing framework built on LuaJIT, has been upgraded to v0.9.1, bringing a range of bug fixes along with new blocks.
The major changes made in the LuaRadio v0.9.0 release include the addition of PulseMatchedFilterBlock, PulseAmplitudeModulatorBlock, and QuadratureAmplitudeModulatorBlock, fixed support for Lua file handles in the PrintSink and BenchmarkSink blocks, a refactoring of read and write multiplexing of Pipes into the PipeMux class, new control sockets in blocks to allow for a graceful shutdown, a reimplemented flow graph stop for faster shutdowns, automatic termination of unresponsive block processes during shutdown, and a bug fix for blocking in flow graph wait when running multiple flow graphs.
The release of LuaRadio v0.9.0 was followed just four days later by the LuaRadio v0.9.1 point-release, the latest version at the time of writing. This release fixes a bug in shutdown handling on Apple’s macOS X operating system and a spurious warning regarding downstream block termination on shutdown.
The latest version, including full source code, is available under the permissive MIT Licence.
Maker Daniel Nikolajsen has published details of an affordable, small-footprint satellite-tracking antenna mount built from 3D-printed parts and controlled via smartphone: SATRAN.
“This is a continuation of an old project of mine, when I built a simple satellite antenna tracker with an android app that calculates the position of any satellite using its ‘Kepler elements,’ and controlling the Az-El antenna rotator to track it across the sky,” Daniel explains. “During a few late nights together with two other ham operators, we built a crappy but functional prototype from spare parts. Now some years later, I decided to redesign it from the ground up as an affordable and easy to use kit.
“The onboard microprocessor is an ESP8266 NodeMCU board with wifi-capability that can be controlled manually in a web-interface or automatically through an android app. Motion will happen with the help of two Nema17 stepper motors, and the rotator has a platform that allows for many different kinds of antennas or a small satellite dish.”
Daniel is looking to release the SATRAN as a kit of parts within the next couple of months, but is also making the STL files and code available free of charge for home printing. More details are available on the SATRAN Hackaday.io project page.
Developer Pavel Milanes has released a software recipe to turn single-board computers and SDR devices into what he calls a Fully Automatic Amateur Satellite Ground Station: FAASGS.
“[FAASGS is] a setup to build a satellite ground stations that can tune, record and generate images for FM and APT weather satellites,” Pavel explains. “This is the software recipe, in the hardware part I used an Orange Pi Prime Board but you can use any single board computer, including Raspberry Pis, Odroids, and even a normal PC or Server.
“I used Armbian as OS, but you can manage it to make it work with RaspiOS or any other Linux distro with a little of work. The only advice is to use one with a multiple cores and at least 1GB of RAM as some task are resource intensives. This proyect is inspired and heavily based on the work of Luick Klippel and his work on his NOAA Satellite Station repository.”
The software includes a browser interface to access details on upcoming satellite passes and recordings of previous passes, FM reception, recording, and decoding, automatic decoding of APT-format images from NOAA weather satellites, and spectrogram creation for voice FM satellites.
The software is available on Pavel’s GitHub repository under the GNU General Public Licence 3.0.
The Wireless Broadband Alliance (WBA) has released a blueprint for the convergence of 5G cellular and Wi-Fi 6 radio networks – developed, it says, with input from mobile carriers, telecommunications companies, and its own 5G Working Group.
“The convergence of Wi-Fi 6 & 6E and 5G is a win-win scenario for end-users, cellular and Wi-Fi players,” claims WBA CEO Tiago Rodrigues, of the blueprint outlined in the Alliance’s latest paper. “The continued development of 5G and Wi-Fi 6 & 6E networks presents almost limitless potential for industry 4.0, residential connectivity, connected smart cities and more, but convergence is critical for all parties if we are to truly capitalize on the potential this technology has to offer.
“This paper provides a path forward for regulators and industry bodies that stands to benefit all, giving stakeholders the ability to cost-effectively improve performance while also retaining control and maximizing their return on investment.”
The paper is available to download from the Wireless Broadand Alliance website now.
Pseudonymous developer ‘Xerbo’ is publishing a series of articles investigating the output of Transit-5B5, the oldest “working” satellite to still be transmitting a broadcast signal – after launching all the way back in 1964.
“The story starts in the 1960s with a fleet of satellites called NAVSAT, a satellite constellation for military navigation,” Xerbo writes. “While satellites were only launched between 1956 and 1988, one satellite in the constellation has refused to die and entered ‘zombie’ status. Enter Transit-5B5.
“Transit-5B5 (launched in 1964) is the oldest “working” satellite, broadcasting an intermittent signal when not eclipsed in the 137MHz band. Interestingly enough, its actual navigation systems failed with in 19 days of launch, and it only continues to broadcast telemetry.”
Xerbo’s first article, available on their website, includes an analysis of the signal and the creation of a GNU Radio flow graph – available for download – to work with the signal. Additional articles are planned, with Xerbo saying “there is still an awful lot to figure out about Transit.”
Developer Dmitrii Eliuseev has published an article describing how to decode NOAA APT-format satellite imagery in just 50 lines of Python code.
“One of the interesting data protocols developed in the last century is APT (Automatic Picture Transmission). It is used to transmit images of the Earth’s surface from space, and what is much more interesting for us, receiving APT signals is feasible to radio amateurs.
“There have already been several articles on Medium about the NOAA reception like this, but they all usually boil down to ‘plug in the receiver, run the program, get a picture,’ without explanation of how it really works. Let’s try to go one logical level down and see how the data processing works under the hood.”
The article, which walks through receiving the signal with an SDR dongle, decoding it with the scipy library, and processing it with the Python Image Library (PIL) before displaying it on the screen, is available on Dmitrii’s Medium page now.
Finally, Hackaday has brought to our attention an “emergency transmitter” project which uses just eight components – including a single transistor.
“QRP is all about doing more with less. This is more than true, with the construction of this cheap, simplistic transmitter presented here,” writes project creator Kostas Giannopoulos. “It is designed primarily as an emergency transmitter (EMTX) that can be built or serviced in the field or at any home. However, it can be used as a ham radio transmitter as well.
“Do not judge by it’s low components count though. This transmitter is powerful, more powerful than anything the QRPers would dream of. It is just remarkable how 8 components can lead in so much output power, that lets you communicate with a big part of the world, when propagation conditions are right. It is very difficult for a circuit to match that kind of simplicity in balance with such performance.”
A full schematic for the project, along with details of its design and creation, can be found on Kostas’ website.