The LimeSDR family has grown a little larger with the unveiling of the LimeRFE, an open hardware software-definable front-end add on for the LimeSDR, LimeSDR Mini and LimeNET Micro.

Due to launch on Crowd Supply in the near future, the LimeRFE includes power amplifier, filter, and support circuitry, is programmable using the Arduino IDE, and integrates with Lime Suite. It’s designed with real-world use-cases in mind, from custom HAM radio to cellular and wideband network use – and even amateur satellite communications.

“We’re not aware of any other solution which, when paired with a LimeSDR, gives ready-to-run use on this combination of amateur radio bands, and in particular the more exotic 23 cm, 13 cm and 3.5 GHz bands,” says Lime’s Andrew Back. “Here people typically resort to buying surplus commercial power amplifiers and filters and assembling a custom solution for each band, so this is a major improvement in convenience.”

More information on the new board can be found on the Crowd Supply campaign page, or you can join the discussion in the Myriad-RF forum.

LimeSDR users are being asked to submit short summaries of what they’re doing with their hardware as part of a Field Report Contest, with a LimeSDR Mini as the grand prize.

“Did you do something unique, difficult, or unexpected with your Lime product? Are you looking for alien signals from deep space? Setting up a private cellular network for you and your friends in the middle of the wilderness? Let the community know,” an update on the LimeSDR Mini campaign page explains. “Or maybe you’ve done something less glamorous but nonetheless of potential use to Lime users, like a particular configuration with universal application, or a solution to a knotty technical problem? Share a ‘Field Report’ with us and we’ll share it with the world!”

Those interested in participating can send a 300-word-plus summary of their project, which can be based on any member of the LimeSDR or LimeNET family or any other device using Lime Microsystems technology, via the Crowd Supply contact page. Entries close on the 21st of May, and one will be randomly selected to win the LimeSDR Mini.

Backers of the LimeNET Micro have been introduced to a new case, designed to modify the original aluminium case in order to support the improved features of the revised LimeNET Micro hardware.

Following the news that all LimeNET board-only and acrylic-case bundles have been sent to Crowd Supply and will begin their journey to backers soon, Lime announced a revision to the aluminium case. Designed to support the new LimeSDR Micro version, which adds ports and features not present on the original design, the revised case is a hybrid which has a plastic body and an aluminium lid – and backers who would prefer to design or otherwise source a whole-metal case of their own can contact Crowd Supply to downgrade to an acrylic-case or board-only pledge, or cancel their order altogether, if the change or resulting delay to shipment is unwelcome.

Pantacor, meanwhile, has announced a device image for the LimeNET Micro which includes everything backers need to run a cellular GSM network.

Designed to tie into Pantacor’s Pantahub website for configuration, management, and monitoring, the device image comes ready-to-run with the open-source Osmocom CNI GSM network software stack. Those looking to use the LimeNET Micro for other purposes will find support for additional applications announced in the coming weeks, allowing quick installation of software and reconfiguration for a variety of roles.

A demo of the Pantacor device image and Pantahub configuration website can be seen on the LimeNET Micro Crowd Supply campaign page.

Forum-goer Shao Zhuyuan has shared his build of a high-powered Long Term Evolution (LTE) base station based around the LimeSDR.

Announced in a forum post linking to a YouTube video, Zhuyuan’s build is housed in a rack-mount casing and boasts impressive specifications: “The coverage is now 1km in a sector of 65 degree,” he explains. “The throughput is 15Mbps DL 6Mbps UL.”

More information on the build, in Chinese, can be found on the project blog.

Maker-oriented HackSpace Magazine continues to introduce new users to the joys of software defined radio and satellite communication technologies, publishing a piece on building a SatNOGS ground station using a Raspberry Pi.

Following on from its tutorial on slow-scan TV (SSTV) reception, discussed in a previous OTA, HackSpace Magazine has detailed how to build a ground station for the SatNOGS amateur satellite communication programme.

“Most of the time a satellite will not be overhead of a single ground station; in fact, it may only pass over a ground station once every few days, massively reducing the amount of information or data we can receive,” the magazine explains. “So we need a network of ground stations. The SatNOGS network solves this by creating a global network of stations that can work together to increase coverage. SatNOGS is an open-source project that has numerous designs for satellite ground stations, but whichever design you pick, you can join the network that links them all via the web.”

The full article is available on the Raspberry Pi website, or in print in HackSpace Magazine Issue 18.

The Signals Everywhere YouTube channel is branching out into podcasting, and in its second episode has published details on common SDR mistakes – and, more importantly, how to fix them.

Best known for its video content, which has included a tutorial on using a LimeSDR to transmit DVB-S video signals using DATV Express on Windows as featured in an earlier OTA, the Signals Everywhere podcast brings the same passion to an audio-only format.

Its second-ever episode is one of interest to anyone new to SDRs, covering common mistakes and their resolutions from setting the correct gain and sample rate to choosing the right antenna. It follows on from an initial episode discussing communication with the amateur radio transponders on the Es’hail-2 (QO-100) satellite.

Both episodes are available now on the Signals Everywhere website.

Hobbyist electronics site Hackaday has highlighted a homebrew electromagnetic compatibility (EMC) probe based around an SDR.

“This stupid project is a side project that I’ve done while I was preparing for another stupid project,” creator Dimitris Tassopoulos explains. “Although it’s quite amazing, it’s actually quite useless for most of the home projects and completely useless for professional use.

“In the next project I plan to use a 10 MHz OCXO as a time reference. The idea was to use a rubidium reference, but it’s quite expensive and it didn’t fit in the cost expectancy I have for a stupid project. Of course, both OCXO and the Rb are enormous overkill, but this is the point of making stupid projects in the first place. Well, in my case I needed to measure how my OCXO behaves. Does it leak the 10MHz or harmonics in different places? And if yes, how can I reduce this RF leakage. So, I’ve decided to build an EMC probe myself.”

The build sees a low-cost SDR dongle connected to a semi-rigid co-axial cable modified into a probe for electromagnetic compatibility testing – and while it produced interesting results, Dimitris warns that a calibrated commercial tester is probably more appropriate for most uses. More information is available on the blog post.

Wards Auto has brought up the issue of GPS signal spoofing and the need to develop protections against it, after receivers at the Geneva Motor Show were fooled by an unknown transmitter.

“It just so happened that somebody managed to anger a number of automakers participating in the recent Geneva Motor Show,” Regulus Cyber’s Roi Mit explains on the site. “It’s still an unsolved mystery as to who or why, but the location systems of some cars at the show apparently were spoofed. Spoofing is a smart attack on the sensor’s receivers, allowing an attacker to pose as a legitimate signal, enabling them to manipulate and deceive the target.

“Certainly, a lot of work is taking place to explore and perfect the security requirements for safe satellite-based navigation for driverless technology. Best practices should be implemented for systems that currently exist – cyber defence for sensors, anti-interference, anti-jamming, anti-spoofing systems. There are engineered, end-to-end solutions based on military expertise that are showing promise in ensuring safety and operational robustness of autonomous vehicles.

“But as fast as we can perfect cyber defence for sensors, newer technological developments will create new threats,” Roi concludes. “The rapid growth of real-world attacks happening across multiple sectors will always be highlighted and are expected to further grow as GNSS-dependent systems become more connected and autonomous.”

The full piece can be read over on Wards Auto now.

RTL-SDR has highlighted a post by Priyasloka Arya on receiving and decoding signals from the NavIC Indian GNSS constellation for up-to-20m resolution positioning.

Based on MATLAB code originally developed for high-power rocketry tracking using the Global Positioning System (GPS), Priyasloka’s modified version uses an SDR dongle and antenna to receive the signals from the NavIC (formerly Indian Regional Navigation Satellite System) constellation then MATLAB to decode the data and calculate the receiver’s position.

Priyasloka’s post, which goes into detail about the data format of NavIC and its comparisons to GPS, can be found on

The American Physical Society has proclaimed CubeSats – miniature satellites built and launched at a fraction of the cost of their larger-scale equivalents – a great success for scientific endeavours.

“This work demonstrated that these small, relatively cheap – ranging from $1 million to $2 million for MinXSS [Miniature X-ray Solar Spectrometer] – CubeSats can collect data that fills a specific niche and is consistent with large satellites, which are much more expensive, and contribute to major science investigations,” Professor Christopher Moore told attendees of the American Physical Society’s April Meeting 2019 earlier this month.

“[CubeSats provide] excellent opportunities to train future leaders in technology and science,” Moore continued, “as undergraduate students, graduate students and postdocs commonly have pivotal roles in design, development, testing, mission operations and science analysis. More than 40 graduate students at the University of Colorado Boulder contributed to MinXSS over the project’s lifetime.”

Researchers at the Department of Energy’s SLAC National Accelerator Laboratory have detailed a new, pocket-sized very low frequency (VLF) antenna which they claim could prove invaluable where conventional radio simply doesn’t work.

Designed to take VLF technology away from massive emitters and into something pocket-sized, the four-inch-tall antenna is aimed at rescue, defence, and disaster recovery scenarios where communication is required over radio-hostile media including through water, ground, and extreme distances.

“Our device is also hundreds of times more efficient and can transmit data faster than previous devices of comparable size,” boasts SLAC’s Mark Kemp, the project’s principal investigator. “Its performance pushes the limits of what’s technologically possible and puts portable VLF applications, like sending short text messages in challenging situations, within reach.”

“There are many exciting potential applications for the technology. Our device is optimised for long-range communication through air, and our research is looking at the fundamental science behind the method to find ways to further enhance its capabilities.”

The team’s paper, “A High Q Piezoelectric Resonator as a Portable VLF Transmitter,” is available in the journal Nature Communications now.

Finally, RTL-SDR has showcased a video from Tech Minds which showcases transmission from a Raspberry Pi’s GPIO pins from the UK to Europe without amplification.

Tech Minds’ video is based on the ability to toggle a Raspberry Pi GPIO pin in such a way as to transmit a radio signal. Unamplified, the signal is weak – 10mW – but is nevertheless strong enough to be of use with WSPR, the Weak Signal Propagation Reporter.

Using an unun and high-frequency wire antenna connected to a Raspberry Pi Zero W single-board computer running the WsprryPi software, Tech Minds was able to transmit signals which reached mainland Europe, Iceland, and Morocco from his UK base.

Full details are available on the YouTube video.