Lime Microsystems has announced the relaunch of the LimeSDR USB Type-A, the full-size two-full-duplex-channel alternative to the popular LimeSDR Mini and LimeSDR Mini 2.0 – now in stock on Crowd Supply.
“The LimeSDR is based on Lime Microsystem’s latest generation of field programmable RF transceiver technology, combined with FPGA and microcontroller chipsets,” the company writes of the board, which was one of the earliest LimeSDR designs. “These connect to a computer via USB 3 with a Type-A connector. LimeSDR then delivers the wireless data and the CPU provides the computing power required to process the incoming signals, and to generate the data to be transmitted by the LimeSDR to all other devices.”
The LimeSDR USB Type-A is built around the same Lime Micro LMS7002M field-programmable RF transceiver as the LimeSDR Mini and its successor the LimeSDR Mini 2.0, but the larger board provides room for more features: an expanded frequency range from 100kHz to 3.8GHz, more bandwidth at 61.44MHz, double the sample rate at 61.44 mega-samples per second (MSps), and two full-duplex transmit-receive channels rather than one. It’s supported by the same open-source software stack as the Mini variants, including in Lime Suite, and can be plugged straight into a host’s USB 3.0 port.
The relaunched LimeSDR USB Type-A is available on Crowd Supply now, priced at $625; an optional aluminium case with fan is also available to provide active cooling for heavy-duty operation in hot environments.
Community member Adrian M. has shared a video demo of the LimeSDR Mini being used to transmit Digital Mobile Radio (DMR) in repeater mode, using GNU Radio.
“I have a short demo video about transmitting DMR with the LimeSDR Mini (as a subscriber radio – MS, not repeater),” Adrian writes in the MyriadRF Forum. “The transceiver uses GNU Radio for the modulation and demodulation and code from Jonathan Naylor’s MMDVMHost for the data link layer and call control layer. The vocoder used is Codec2, which works seamlessly with MMDVM-based repeaters if the DMR FID is set correctly.”
Digital Mobile Radio (DMR) is an ETSI standard for voice and data transmission in non-pulic networks, and is split into three tiers: Unlicensed, Conventional Licensed, and Trunked. Typically, DMR audio is sent using the proprietary AMBE+2 multiband excitation vocoder – but in this case Adrian has used Codec 2, a low-bitrate speech-focused audio codec developed by David Rowe and made available under a reciprocal open-source licence.
The full video is available on YouTube, while discussions are open on the MyriadRF Forum.
sysmocom, founded to provide commercial support for the Osmocom open-source cellular communications project, has announced its latest creation: an open-source fork of the Asterisk private branch exchange (PBX) software which can make mobile calls – without a mobile.
“During the past year, sysmocom has been developing an open source fork of the popular Asterisk soft switch software which adds IMS Client functionality to it,” the company explains. “IMS is the specification-language term for what is used to implement voice (and video) phone calls over 4G/LTE (VoLTE), 5G/NR (VoNR) as well as WiFi (VoWiFi).
“Using this IMS-enabled version of Asterisk and a SIM card in a smart card reader, you can make and receive voice calls using a cell phone number/subscription – without using any cell phone, cell phone network or even VoWiFi whatsoever. The IMS-enabled Asterisk will establish an IP connection to the ePDG (evolved packet data gateway) of the cellular operator via any form of wired or wireless Internet access.”
The company suggests its ISM-capable Asterisk fork could be used to add cellular capabilities to an existing PBX without the need to have a modem or even be within range of a compatible cellular base station, to ease research projects working on IMS and Voice-over-Wi-Fi (VoWiFi), and to allow alternative non-mainstream mobile operation systems to make calls over VoWiFi without official support.
More information is available on the Osmocom website, while the Asterisk fork itself is available in a git repository under the reciprocal GNU General Public Licence 2.
Daniel Estévez is continuing to investigate signals from spacecraft, this time penning an article on decoding the GMSK telemetry from the Blue Ghost Mission 1 (BGM-1) private lunar lander.
“The [Blue Ghost] mission came to an end on March 16,” Daniel explains, “as night fell on the landing site. During the 14 days that it has been operating on the lunar surface, BGM-1 has been transmitting low-rate GMSK telemetry on S-band at some times, and a high-rate signal on X-band at other times (this is said to be up to 10 Mbps DVB-S2), including some periods of no transmissions, presumably for thermal management.
“I will show how to decode the GMSK S-band telemetry signal with GNU Radio. I will use the IQ recording done by CAMRAS with the Dwingeloo 25 m radiotelescope during the landing as an example, since this dataset is publicly available. The signal is 15360 baud GMSK, with the usual precoder that allows coherent demodulation as OQPSK. The coding is CCSDS concatenated coding with a Reed-Solomon interleaving depth of 4. The frame size is 892 bytes (4 times 223). The frames are CCSDS TM Space Data Link frames, but there is a bug in how the Reed-Solomon interleaving is implemented.”
Blue Ghost Mission 1 was launched by Firefly Aerospace on the 15th of January 2025, and landed on the moon on the 2nd of March – becoming, in process, the first commercial lunar lander. The craft continued to transmit data from its ten experimental scientific payloads until night fell and its batteries emptied, with the mission end being called just before midnight on the 16th of March.
Those transmissions, naturally, were captured, and Daniel has been working on decoding them – and by downloading an IQ recording and following along, you can do the same. There’s only one catch, though: “The contents of the Space Data Link frames are encrypted,” Daniel notes, “probably using CCSDS SDLS.”
The full write-up is available on Daniel’s website, with Jupyter notebooks and GNU Radio files available on GitHub. The IQ recordings, meanwhile, can be downloaded from CAMRAS.
A mononymous radio enthusiast going by the initials “JJ” has shown off a software-defined radio with a difference: the user interface is a Casio programmable calculator.
“I recently challenged myself to build a radio without buying anything, just recycling some old parts I had in my toolbox,” JJ explains. “So I came up with the calcRADIO! A standalone, portable, FM / DAB+ / INTERNET / MP3 radio. The user interface, both for input and output, is made of a Casio fx-CG20 graphical calculator (also compatible with the fx-CG10 and fx-CG50) and it runs all day non-stop on a 5V / 18000 mAh power-bank.
“This calculator is great because (1) it has a 3-wire serial port built-in that is used to clone two calculators together, so I can use it to connect to the UART port on my Strong SRT 2023 Android board, previously flashed with Armbian + Ubuntu. I just had to solder the wires (send, receive, ground) and voila, I can easily exchange data between the two systems. And (2) this calculator can be programmed in C with the non-official CASIO SDK. Finally (3) it has a beautiful colour display and I can even play games while listening to the news!”
The project is written up towards the bottom of JJ’s website, with source code and supporting files available on GitHub under an unspecified licence.
Hackaday has brought to ourattention a proejct by Georg “DG6RS” Seegerer to generate an SSB signal through unusual means: combining AM and FM modulation.
“The signal source works on 35-4400MHz and produces various narrow band modulation schemes (2.7kHz maximum) via polar modulation: SSB/CW/FM/FT8/PSK31/etc.,” Georg explains. “The concept to produce the signal via combination of amplitude and phase modulation is similar to the uSDX by DL2MAN. However the power amplifier is not part of the signal source. Output power is approx. 0dBm. Intention was to build a signal source for the narrow band transponder of the QO-100 satellite, without the need of a 2m/70cm allmode transceiver as would be necessary for a usual upconverter.
“Why polar modulation is quite unknown? For stationary devices using small TX power, like base stations for cellular radio, the efficiency of the PA was never a big topic because other components like digital processing or air conditioning dominate the power consumption. In cases with high TX power and small bandwidths, e.g. medium and short wave broadcast transmitters, polar modulation was always employed. For pure AM, it was not called polar modulation, it was rather modulation of the anode voltage.
“The modulation got polar,” Georg continues, “when the transmitter was used for ‘Digital Radio Mondiale’ (DRM), that is an OFDM modulation (Orthogonal Frequency-Division Multiplexing) with 9kHz bandwidth. The signal generator was used for the phase part of the modulation, and the AM was done by modulating the anode voltage as usual. HAM radio operators use a 2.7kHz wide SSB signal even at frequencies in the GHz range. This is a narrowband signal which is possible to be generated with polar modulation. In this application polar modulation can find a niche.”
The full write-up, in considerable technical detail, is available on Georg’s website; source code is available on GitLab under an unspecified license.
NASA and the Italian Space Agency have announced a successful test of the LuGRE experiment – designed to receive Global Navigation Satellite System (GNSS) signals on the Moon, from satellites in orbit around Earth.
“On Earth we can use GNSS signals to navigate in everything from smartphones to airplanes,” says NASA’s Kevin Coggins. “Now, LuGRE shows us that we can successfully acquire and track GNSS signals at the Moon. This is a very exciting discovery for lunar navigation, and we hope to leverage this capability for future missions.”
The LuGRE payload – the Lunar GNSS Receiver Experiment – was one of ten scientific payloads sent to the Moon on board the Blue Ghost Mission 1 lander from Firefly Aerospace, discussed above. Effectively, it’s little different to any GNSS receiver used on Earth – except that instead of being beneath the orbiting satellites it’s tuning into, it’s about 225,000 miles above them. In the future, the project’s staff hope, it could lead to using GNSS signals for autonomous navigation on the Moon without the need to give it its own constellation of orbiting satellites.
The official announcement is available on NASA’s website, along with links to more information on the LuGRE project.
The Emerging Technologies Institute (ETI) has published a webinar which spends an hour walking through that most important of radio technologies: the antenna.
“The DoD [US Department of Defense] mission is increasingly conducted in the electromagnetic spectrum (EMS) which is a heavily utilised, contested, dynamical, high-dynamic range domain,” the ETI explains by way of background to its webinar. “Typical EMS missions include communications, active and passive sensing, electronic warfare, and directed energy.
“The antenna is the central component between electronic systems and the electromagnetic spectrum, thus it’s characteristics and limitations play a significant role in the overall success of EMS operations. Professor Jonathan Chisum from the Wireless Institute at the University of Notre Dame will provide an overview of antenna technologies including fundamentals of operation and a survey of various antenna technologies for use in wide-ranging EMS applications.”
The webinar is available on-demand on YouTube now.
Google Research has announced the successful launch of the first in a planned constellation of satellites designed to spot small wildfires before they grow out of control: FireSat.
“The first satellite for the FireSat constellation officially made contact with Earth. This satellite is the first of more than 50 in a first-of-its-kind constellation designed to use AI to detect and track wildfires as small as a classroom (roughly 5×5 meters),” the company says in its announcement.
“Currently, many wildfire authorities depend on satellite imagery that’s low-resolution or only updated a few times a day. FireSat will advance the science and practice of fighting wildfires by providing high-resolution imagery updated globally every 20 minutes, helping emergency responders catch wildfires before they become destructive.”
FireSat is a collaboration between Google Research, Muon Space, Earth Fire Alliance, Moore Foundation, wildfire authorities, and others,” the company continues. “Funding for the constellation’s first satellites comes in part from Google.org, which has provided $13 million through the AI Collaborative: Wildfires, an initiative to harness AI’s potential in reducing the economic, humanitarian and environmental damages from catastrophic wildfires.”
More information on the project is available on the Google blog.
Finally, pseudonymous YouTuber “Tech Minds” has published a walkthrough review of the sdrberry project – a graphical front-end for SoapySDR-compatible software defined radios running on a Raspberry Pi single-board computer.
“You must admit this graphical user interface looks absolutely stunning,” Tech Minds says in the video walkthrough of the software. “It looks really nice, and it’s actually really pleasant to use. sdrberry does support touch to select features, like changing bands, changing mode of modulation, and altering volume and other sliders – however I find it easier to use a mouse to change frequency. You can literally just point and click, or use the thumbwheel on a mouse to fine-tune.
“[There’s also a] web interface, and when enabled you’re able to open a web browser on a computer which is on the same network as the sdrberry,” Tech Minds continues. “Now I believe this is still under active development so don’t expect everything to be working right now, but it does give you an idea of how well this software has been put together and the possibility of future features.”
The full video is available on the Tech Minds YouTube channel; sdrberry itself, which is designed for use with a Raspberry Pi 4 Model B or Raspberry Pi 5 single-board computer with touchscreen display, is available on GitHub under the reciprocal GNU General Public Licence 3.