Orders for the new LimeNET Micro 2.0 all-in-one software-defined radio platform, powered by the LimeSDR XTRX and Raspberry Pi Compute Module 4, are to open soon – in the form of a “Developer Edition” kit.

“LimeNET Micro 2.0 DE (Developer Edition) is a modular radio platform that leverages the Raspberry Pi Compute Module 4 (CM4) and LimeSDR XTRX for their respective computing and RF features,” Lime Micro’s Andrew Back explains of the new platform. “It is based around the new LimePSB RPCM, a planar system – a.k.a. ‘main’ – board, which is significantly more versatile than the previous version of LimeNET Micro, which was limited by its support for a less powerful compute module (CM3) and an integrated SISO radio.”

The radio part of the LimeNET Micro 2.0, which is designed to act as a software-defined base station delivering both edge compute and radio connectivity, is handled by the LimeSDR XTRX, an upgraded redesign of the earlier Fairwaves XTRX. The LimePSB design includes a 2×2 MIMO front-end module (FEM) with Qorvo LNA and driver amplifiers, covering frequencies up to 3.8GHz with over 100MHz of bandwidth.

The RF platform also features a highly flexible reference clock system, which is based around a high accuracy OCXO, which may be disciplined via either the LimeSDR XTRX GNSS receiver, or via IEEE 1588 Precision Time Protocol (PTP) over Ethernet.

The compute side, meanwhile, is powered by a quad-core Raspberry Pi Compute Module 4, which provides a significant performance increase over the CM3. There’s a 20-pin general-purpose input/outout (GPIO) header, two USB 2.0 ports, a gigabit Ethernet port with Power-over-Ethernet support, MIPI DSI display and CSI camera connectors, and two HDMI 2.0 ports with 4k60 display support. USB PD support means that the kit may also be powered via a suitable USB C power supply.

More information on the LimeNET Micro 2.0 Developer Edition is available on the Crowd Supply campaign page, where interested parties can sign up to be notified when orders open.

The popular open-source Lime Suite software stack for LimeSDR devices has been given a major overhaul with the launch of Lime Suite NG, a next-generation rewrite which comes with a new application programming interface (API) – but also boasts a compatibility layer for those migrating from the original version.

“The Lime Suite codebase has grown over the years to incorporate many improvements and become the foundation for various SDR boards and modules that utilise Lime chipsets,” Lime Micro’s Andrew Back explains. “The software collection has also grown to include numerous examples, utilities – such as for testing and programming firmware/gateware – and plug-ins for applications such as the SoapySDR framework and GNU Octave.

“After many years of development it became clear that Lime Suite would benefit from certain architectural changes, such as improved support for boards with more than one transceiver. Furthermore, these improvements would result in breaking API changes, hence it was decided to implement them via a new project, Lime Suite NG (Next Generation).”

Lime Suite NG has launched with support for LimeSDR USB, the LimeSDR Mini and Mini v2, and the LimeSDR XTRX – a board not supported by the original Lime Suite software. The rewrite brings with it a new API, though Andrew advises of a “compatibility wrapper” which allows projects implementing the existing Lime Suite API to work with the new version “largely unmodified.”

More information is available in Andrew’s blog post, while the source code has been published to GitHub under the permissive Apache 2.0 licence; Andrew advises that Lime Suite NG “is still in heavy development,” with additional features to follow.

Pseudonymous YouTuber “sn0ren” has published a video which dives deep into the core concepts behind antenna design and operation – offering advice on how to pick the best antenna for a range of use-cases.

“Which antenna is the best one,” sn0ren says in the introduction to the video. “Well, the short answer is ‘none of these.’ I’ve tried to make the longer answer as short as possible, covering only the basics of antenna theory. First we need to clear something up, and that is that there is nothing magic about antennas. It’s just a piece of metal, and any piece of metal with the same length will be equally as good of an antenna. The second thing we need to clear up is that antennas are like magic: they’re taking the power from electronic circuits and making it disappear into thin air.”

The video walks through core antenna concepts, from resonance frequencies and reflected power to the types of antenna commonly found on the market – then moves into the practical realm with a look at how to measure antenna performance with a vector network analyser (VNA). “We live in an amazing future where what would have been extremely expensive antenna analyser equipment can now be had for next to nothing,” sn0ren explains, while warning that you shouldn’t trust vendor specifications for a given antenna.

The full video is available on sn0ren’s YouTube channel.

Radio ham Helge “LA6NCA” Fykse has put together the hardware for a working radio station with a difference: everything for this “spy transceiver” fits into three matchboxes, while the antennas are hidden on fishing line spools.

“The matchbox[es] contains power, equipment box, and radio station,” Helge explains of the “super small spy transceiver” he has built. The active hardware fits in just one standard-sized matchbox, with a second housing a 9V battery for power. A third matchbox houses the accessories: a headset and a Morse key. “[It] is a complete shortwave radio station,” its creator claims. “It consists of an xtal oscillator at 3592kHz, receiver, and a 0.3 Watt transmitter. The modulation is CW.”

It’s not just for show, either: the first QSO recorded with the transceiver was a 120km contact to Oslo. Three spools, originally housing fishing line, house wire antennas which can be quickly unspooled for use then returned to their pocket-friendly format afterwards.

A full write-up is available on Helge’s website, complete with schematics, with a supporting video on YouTube.

Pseudonymous tinkerer “Qookie Monster” has found an unusual platform on which to display the classic one-bit Bad Apple animation: the waterfall display of SDRangel.

“[The video was] encoded and played on the PC audio [output], then upconverted on a generic mixer, and received on [an SDR],” Qookie explains of the project, which takes as its source a one-bit black-and-white video which has become the go-to for demonstrating playback on unusual platforms. “Since the audio output doesn’t output much above 20kHz, the video can be high quality with a very low fps [frames per second] (~0.1) or low quality with 5 fps.”

The video itself is converted into audio frequencies, rather than being transmitted in a decodable data format — making it visible as an image on the waterfall view in popular software-defined radio package SDRangel. As a result it needs no additional software to view, though there’s no accompanying audio.

More information, including links to videos of the low- and high-resolution versions, is available in Qookie’s Reddit post.

Internet of Things (IoT) connectivity startup Hubble Network has announced a major milestone: its first successful Bluetooth transmission reaching from the ground to an orbiting satellite – without modifying the underlying hardware.

“We’ve disproved thousands of skeptics,” claims Hubble Network co-founder and chief executive Alex Haro of the company’s achievement. “By showcasing that we can send signals directly from Bluetooth chips and receive them in space 600km away, we’ve opened a new realm of possibilities.”

The idea behind the company’s offering is to make it possible for existing Bluetooth-capable devices to communicate with a network of orbital satellites, using only a firmware modification – delivering, it claims, global connectivity at one-twentieth the power and one-fiftieth the operating costs of current satellite communication offerings.

“Our innovative approach allows existing Bluetooth-enabled devices to be retrofitted to transmit data to the Hubble Network without any hardware modifications,” co-founded and chief technology officer Ben Wild adds, “ushering in a new era of connectivity.”

More information on the company’s offerings is available on the Hubble Network website.

Radio ham Barbaros Aşuroğlu has designed an antenna tuner in the footprint of a credit card, antenna connectors notwithstanding, for QRPp and QRP portable operations: the Pocket Tuner.

“[For] almost a year now I work QRPp on HF digital modes with a highly portable QRPp HF transceiver with sub-500mW RF output from parks, backpack hikes, and from my car,” Barbaros explains. “I work mostly on 10m to 17m with my rig. [It’s] all working great except with one minor issue, lacking a highly portable antenna tuner to accompany my setup in my backpack. ATU type tuners such as ATU-10 or so fail to tune below 500 mW!

“My go-to tuner is a 4State QRP tuner which I grabbed from a hamfest as a second hand. This tuner [was] designed by David Cripe, NM0S, and works like a charm! The only issue I have is its size! I wanted something the size of a credit card as a tuner! So I took this challenge upon me and designed a T-match tuner similar to David Cripe’s excellent 4State QRP Tuner with a twist and way smaller than that.”

Built with David’s approval, the miniaturised tuner is the footprint of a credit card, if you discount the switches and antenna connects which stick out from the circuit board, and is suitable for use on 10m to 40m bands. “[It] struggles on 80m in this current configuration of inductance,” Barbaros admits, “though it can be set to work on lower-end bands by playing with inductance values. I can tune up to 5 watts with this tuner, though my aim was more in [the] QRPp zone which is sub-1W.”

The full write-up, including schematic, is available on the Ankara Telsiz ve Radyo Amatörleri Kulübü Derneği website.

Developer Youssef Touil has released a new version of the popular SDR# software-defined radio software, which brings with it strong claims for major performance improvements – dropping memory requirements by 85 per cent, he claims.

“The latest, greatest, lightest, and fastest SDR# release [brings] many performance improvements, new native modern UI, improved plugin compatibility, and a state-of-the-art DSP for difficult signal scenarios,” Youssef says of SDR# Revision 1920. “This release slashes the memory usage by 85 per cent and CPU utilisation by 50 per cent, [and] improves the scalability for both high sample rates and number of spectrum slices.”

Other improvements in the new build include a revamped user interface, improved plugin compatibility — and an updated plugin software development kit (SDK) which targets .NET 8 – along with a package size reduction from 92MB to just 2.7MB. This latter feature, though, comes with a fairly important disclaimer: it now relies on having the .NET runtime already installed, hence the space savings.

More information on the new release’s features, including demos of noise reduction and co-channel cancellation, is available in Youssef’s Twitter thread; the latest versions of SDR# and the plugin SDK are available on the official download page.

Finally, systems engineer Nathan Misaghi has released an open-source tool for turning a software-defined radio into a real-time passive radar for aircraft tracking: blah2.

“[blah2 is] a real-time radar which can support various SDR platforms,” Nathan explains of the project. “[The software features] two-channel processing for a reference and a surveillance signal. [It’s] designed to be used with external RF source (for passive radar or active radar) [and] outputs delay-Doppler maps to a web front-end. [You can] record raw IQ data by pressing spacebar on the web front-end [and it] saves delay-Doppler maps in a JSON array.

“On [my] roof I have my radar surveillance antenna, which is a 3m-long Yagi with seven directors, a driven element, and a reflector. I [also] have the ADSB ‘truth’ antenna, and on the other side I have my reference antenna which is a telescopic monopole.

“Detections from the radar software are given by orange dots, whereas detections from the truth [antenna] are given by the green dots,” Nathan continues in a demonstration video which shows the radar spotting commercial flights – including identifying a helicopter based on the movement of its rotor.

The demonstration video is available on Nathan’s YouTube channel, while the blah2 source code is published on GitHub under the permissive MIT license; a live demo is also available on Nathan’s website.