The LimeSDR family is set to get a new, more flexible gateware for its on-board field-programmable gate array (FPGA) chips – in a complete rewrite which will unify all the various models together.
The LimeSDR GW Project, launched this month for the LimeSDR Mini v1 and v2 and the LimeSDR XTRX, looks to deliver a single gateware platform which is compatible with all models of LimeSDR – regardless of the model of FPGA used on board, or which vendor produced the FPGA. It will, it’s hoped, reduce fragmentation and make maintaining the gateware easier, but those are far from the only advantages.
The project, launched by Lime Micro in partnership with Enjoy Digital and using the latter’s open-source LiteX platform combined with building-block-like components dubbed the Lime Digital Function Blocks (LimeDFB), also aims to make it easier to add custom code to the gateware to take advantage of otherwise-unused resources on the FPGAs. The first in a planned series of demonstration projects showcases this, implementing a hardware fast Fourier transform (FFT) engine on-device – without requiring any resources from the host. It’s also possible to switch out the CPU cores used, with the initial release supporting the user’s choice of VexRiscV and PicoRV32.
“At Lime Micro, we’ve long expressed our desire to democratise radio access infrastructure with our field-programmable RFIC [Radio-Frequency Integrated Circuit] products and LimeSDR devices,” says Lime Micro chief executive Ebrahim Bushehri. “This partnership with Enjoy Digital is a significant step forward in that mission, opening up the LimeSDR family for new use cases. We are eager to see what the community will do with the new gateware code, and look forward to seeing the implementation of new functionality we have never even considered — unlocking the true potential of our technology for all.”
More information is available on the Lime Micro website; links to the source code are available on the official project site.
Radio operators working at the Dwingeloo radio telescope have announced its first successful signal-bounce from the surface of the planet Venus – marking only the second-ever amateur Earth-Venus-Earth bounce.
“On 22 March 2025, we used the Dwingeloo telescope to successfully bounce a radio signal off the surface of Venus,” the team explains. :At the time, Venus was in its closest approach to Earth at about 42,000,000km. Such a conjunction happens when Venus is between the Sun and the Earth, and happens approximately every 580 days.
“‘Earth-Venus-Earth’ (EVE) bounces were extensively performed in the ’60s and ’70s to make radar images of Venus. More recently, in 2012, the Arecibo telescope in combination with the Green Bank telescope made a very detailed map of Venus. The first, and only until now, amateur EVE was achieved in 2009 by AMSAT-DL from the 20m Radio telescope at the Bochum Observatory (Sternwarte Bochum).
“The Dwingeloo telescope was commanded to transmit a 278 second long tone at a frequency of 1299.5MHz,” the team continues. “Since the light travel time to Venus and back was about 280 seconds, we could receive the reflection of our own signal afterwards. We repeated this cycle four times. We were planning to send complex modulated signals to perform more analysis on the correlations between transmitted and received signals. Unfortunately the transmitter, mounted in Dwingeloo’s focus box for the occasion, started failing after four successful transmissions. We will postpone these other experiments to the next Venus conjunction in October 2026.”
The full write-up is available on the CAMRAS website; the group has also published raw data from the experiment.
Ciprian “YO6DXE” Popica has built possibly the smallest baby monitor around, an FM-transmitting “spy bug” designed to easily fit in a nightlight.
“I tried building it as a small as possible, because I was told I have to install it in a desk lamp, the one that sits next to the baby,” Ciprian says of the device’s ultra-compact form factor, despite being built on prototyping board. “I think you can build it even smaller if you’re trying, but it works fine [like this]. I’m going to power it from the batteries that are already inside that desk lamp.
“The power consumption is somewhere around 14, 15 milliamps, so the [lamp] battery should last quite a bit, it shouldn’t drain. It’s a very simple schematic: one microphone, one transistor, you have four capacitors – three if you don’t want to use the 100nF one on the power rail – and two resistors and a small inductor.”
The antenna is a simple length of wire kept away from prying hands within the body of the lamp, and the inductor has a hand-wound coil. Its range, Ciprian estimates, could be anything from a few feet to a few hundred feet, depending on how much power the radio is given.
The project is documented in Ciprian’s YouTube video, with a link to download the project files under the reciprocal Creative Commons Attribution-NonCommercial-ShareAlike 3.0 licence in the video’s description.
A research team led by Daniel Reardon from the ARC Centre of Excellence for Gravitational Wave Discovery and Swinburne University of Technology has been performing a CT scan of the night sky — and finding out what makes bow shocks tick.
“The ionized interstellar medium contains astronomical-unit-scale (and below) structures that scatter radio waves from pulsars, resulting in scintillation,” the team explains of its findings. “Power spectral analysis of scintillation often shows parabolic arcs, with curvatures that encode the locations and kinematics of the pulsar, Earth and interstellar plasma. Here we report the discovery of 25 distinct plasma structures in the direction of the brilliant millisecond pulsar, PSR J0437−4715, in observations obtained with the MeerKAT radio telescope.”
The team’s work is based on using a scintillating pulsar to perform what is, effectively, a CT scan of the interstellar medium – peering inside to find previously-unseen layers of plasma. Of particular interest: the make-up of a structure called a bow shock. “Travelling at Mach 10,” Daniel explains, “the pulsar and its energetic wind of fast-moving particles create a shock wave of heated gas” – like the wave at a ship’s bow.
“To our surprise,” Daniel continues, “the scintillation arcs revealed multiple sheets of plasma inside the shock, including one unexpectedly moving towards the front of the shock.” Other findings turned previous understanding on its head, too: “These scintillation arcs revealed an unexpected abundance of compact solar-system sized blobs of plasma within our Local Bubble,” the scientist adds, “which was thought to be more smooth.”
The full paper has been published in the journal Nature Astronomy, under closed-access terms; a preprint is available under open-access terms on Cornell’s arXiv server.
A number of Polar Operational Environmental Satellites (POES) operated by the National Oceanic and Atmospheric Administration are set to end official transmissions in June this year, though some will continue to send data until being permanently decommissioned.
“Please be advised that NOAA will officially end the delivery of all data from these three POES satellites on June 16, 2025, at 18:00 UTC,” a notice from NOAA Operations reads, referring to the NOAA-15, NOAA-18, and NOAA-19 satellites in the POES constellation. “In the interim, all users should make plans to discontinue use of POES data from NOAA-15, NOAA-18, and NOAA-19 as these data and services will no longer be made available after Jun 16, 2025 1800 UTC.”
Carl “USRadioguy” Reinemann reached out to NOAA for clarification on exactly what that means, receiving an update attributed to Office of Satellite and Product Operations NOAA Satellite Operations Facility Physical Scientist J. Jankot: “Advanced Picture Transmission (APT) and Low Resolution Picture Transmission (LRPT) services will continue until the decommissioning of the respective POES satellites.
“High Resolution Picture Transmission (HRPT) services will also continue until the decommissioning of the respective POES satellites,” Jankot’s update continues. “However, please be advised that POES data products generated after June 15, 2025, are no longer approved for operational use. This critical notification applies to all users of Advanced Very High Resolution Radiometer (AVHRR) and APT direct broadcast data.”
More details are available on the USRadioguy blog.
Researchers from Bilkent University and Nanyang Technological University have come up with a new approach for creating next-generation radio-frequency devices: deep-trench 3D printing.
“This work bridges a critical gap between 3D printing and functional RF devices,” claims senior author Hilmi Volkan Demir of the team’s work. “By achieving sub-10 micron resolution in high-aspect-ratio metal structures, we’ve unlocked new design freedoms for miniaturised, high-performance components. The ability to tune resonance frequencies and Q-factors through geometric control offers exciting opportunities for next-generation sensors and communication systems.”
The researchers’ manufacturing approach relies on a multi-stage workflow building atop two-photon polymerisation (2PP) 3D-printing – capable of nanometre-scale object creation. This is used to create a device with deep trenches, which are later filled with copper through an electroplating process before being dry-etched to functionalise them into radio-frequency resonators with frequencies tunable between 4-6GHz.
“The findings of our experiments,” the team says in conclusion, “indicate that the method we proposed, involving the creation of deep trenches through 3D-printing, presents a promising avenue for the fabrication of intricate metal-based structures with high aspect ratios.”
The full paper is available under open-access terms in the journal Microsystems & Nanoengineering.
Pseudonymous developer “Imagineer7” has released SignalAtlas, a browser-based tool designed to present an interactive visualisation of “the entire known radio frequency spectrum.”
“SignalAtlas is an interactive, zoomable web visualisation of the entire known radio frequency spectrum,” Imagineer7 explains of the project. “It allows users to explore frequency bands, navigate through standard band regions (like VHF/UHF), search specific frequencies, and view allocations sourced from publicly available spectrum charts.
“With current SignalAtlas features, you can: browse through frequency bands with detailed usage information; zoom into specific ranges and see sub-band details like CW, FM, Digital, and more; search for certain frequencies or bands. Tech behind it: React.js for the front-end; D3.js for interactive visualisations. The data is currently powered by static JSON files, but I’m open to expanding it further!”
The tool is designed to run entirely in-browser, with a live version available for immediate use without having to install anything locally. The software is also under active development, with bug fixes and additional features planned.
The project’s source code is available on GitHub under an unspecified licence.
The SETI Institute is looking to get a new generation interested in astronomy, radio science, and, yes, the search for extra-terrestrial intelligence, with the expansion of its ARISE Lab programme.
“Hands-on experiences are proven to improve student engagement and retention,” explains project lead Vishal Gajjar, a radio astronomer at the SETI Institute. “With ARISE, we’re combining cost-effective tools like GNU Radio with one of the most captivating topics in science — the search for life beyond Earth — to spark curiosity and build skills across STEM disciplines.”
“Whether it’s detecting a signal from a Mars orbiter or analysing pulsar data, students are gaining real experience with tools used in both professional astronomy and industries,” adds lead research assistant Joel Earwicker of the programme, funded through a grant from the Amateur Radio and Digital Communication (ARDC) Foundation. “It’s about making science feel real, relevant, and achievable.”
After a pilot run last year, the programme has now been expanded to include 15 additional labs on topics including astronomy, digital communications, signal modulations, and data science, two hands-on workshops, and on-site lab sessions across 10 community colleges, plus virtual workshops on the first Monday of every month beginning in June.
More information is available on the SETI Institute website.
Finally, Gabe Emerson has used a homebrew radio telescope to capture images of geosynchronous satellites via their radio emissions – with the twist that the images are captured over time and turned into animations which reveal they’re not quite as still as you might think.
“Back in December user [Chris] Davidson on my Discord came up with a really cool improvement to some of my Winegard portable satellite antenna computer code,” Gabe explains. “My version takes a static picture of the sky where you can see radio sources like geostationary orbit TV satellites, but his version does a continuous sweep of the sky – and it runs faster than mine, so he can basically get animations or time-lapses of what’s going on out in space.
“You might notice […] we have some stuff in the geostationary satellite belt, the Clarke belt, that looks like it’s moving up and down. We have some wobbling satellites. Those are geosynchronous, but not geostationary satellites – so they are in a 24-hour orbit aligned with the ground, [and] they move up and down in the same longitude […] because they are in something of an inclined orbit, or a figure-eight orbit.
“The next thing you might notice,” Gabe continues, “is we’ve got this zippy blob going overhead once every 24 hours – and that is the sun, because the sun puts out microwave energy. The sun shows up as an oblong blob because by the time that the scan gets all the way across the sun the sun has moved a little bit.”
The full video is available on Gabe’s YouTube channel; Chris’s source code is available on GitHub under the permissive MIT licence.