OTA: OpenLST, Radiosonde Guidance, Wi-Fi Weapon Detection, and More

Planet Labs OpenLST

Satellite communications specialist Planet Labs has announced its entry into the open-source radio community, with an open-hardware device dubbed the OpenLST built exclusively using widely-available commercial off-the-shelf (COTS) parts.

“Radio system design is often viewed as a ‘black box’ that is out of reach to all but the most experienced of engineers. This leads many educational groups to commercial radio solutions, which are often very expensive, difficult to integrate, and can unintentionally drive other elements of design,’ explains Planet’s Bryan Klofas of the inspiration behind the project. “A poorly understood radio subsystem can be fatal to any project. For example, communications subsystems contribute to at least 29 percent of CubeSat failures in the first 90 days on-orbit.

“OpenLST is designed with an existing and proven radio using inexpensive and widely available commercial, off-the-shelf parts. Planet releases it today with the goal of lowering the barriers to entry for engineers and engineering projects of all kinds. The OpenLST transceiver is approximately six by five centimetres with a mass of 20 grammes. This radio operates on the UHF band and provides 3.5 kilobit per second user data rates. The design also provides time-of-flight ranging that can be used to estimate link distance.”

The design files and software, licensed under the Creative Commons Attribution Share-Alike 4.0 (CC-BY-SA 4.) and GNU General Public Licence (GPL) respectively, are available from Planet’s own Git repositories. More information, including the repositories to clone, can be found on the company’s official website.

Rowetel’s David Rowe, meanwhile, has been adding radio support where none existed before, working with Evariste Courjaud’s rpitx to transmit data over the GPIO pins of a Raspberry Pi single-board computer (SBC).

“In many parts of the world it’s still very difficult (and expensive) to move an IP packet over the ‘last 100 miles,'” David explains. “So, armed with some new skills and technology, I feel it’s time for another look at developing world and humanitarian communications. I’m exploring the use rpitx as the heart of HF and UHF data terminals.”

Using Evariste’s beta branch of the software, which improves performance and adds features over the initial release, David was able to transmit 100 bits per second of data on a 7.177MHz carrier frequency. “It works really well,” David concludes, having measured a bit error rate (BER) of 1 percent – “right on theory for a 2FSK modem.” Surprisingly, given the Pi’s GPIO port was never designed to generate radio traffic, the signal was also clean: “At 7.177 MHz it’s clean to the limits of my spec analyser,” David notes, “and exceeds spectral purity requirements (-43dBc + 10log(Pwatts)) for Amateur (and I presume other service) communications.”

More information is available on David’s blog post, while rpitx v2beta is available from Evariste’s GitHub repository.

RTL-SDR has gathered together a selection of talks from the New England Workshop on Software Defined Radio (NEWSDR), which took place in May, picking out the most interesting from a jam-packed playlist.

The eighth annual NEWSDR event, organised by the Boston SDR User Group (SDR-Boston), NEWSDR’18 took place Atwater Kent Laboratories Building of the Worcester Polytechnic Institute. Talks highlighted by RTL-SDR includes remote sensing of space environment using software defined radio by MIT’s Frank Lind, DeepSig’s Nathan West on how deep learning technology can reinvent wireless communications, and SDR optimisation for wireless access, actuation, and attacks from Northeastern University’s Kaushick Chowdhury.

Other talks available on the YouTube playlist include a talk on personal wireless testbeds for software defined radio use by octoScope’s Nandini Venkatraman and sponsor presentations from octoScope, Mediatek, Mathworks, and Ettus Research.

RTL-SDR has also brought our attention to Igor Yatsevich’s recently-released open-source mini-whip antenna and upconvertor project, designed to convert high frequencies (HF) into very high frequencies (VHF) for use with low-cost SDR hardware.

Igor’s documentation, part of a wider SDR project, includes instructions and implementations on creation an active mini-whip antenna with a frequency range of 10kHz to 30MHz and a high-frequency upconverter which allows low-cost SDR hardware with a high minimum tuning frequency to receive signals that would otherwise be out of range. Both designs include variants which use through-hole technology or surface-mount technology (THT or SMT) components, depending on how comfortable the user feels with soldering smaller SMT parts.

More information, and the design files themselves, is available from Igor’s GitHub repository, as well as RTL-SDR’s original write-up.

Members of the Student Kreativity and Innovation Laboratory (SKIL) at the École polytechnique fédérale de Lausanne (EPFL) have worked out a way of guiding the descent of a radiosonde, telemetry units carried into the upper atmosphere on weather balloons which eventually burst and send them back to the ground in often inconvenient locations.

While dozens of radiosondes are released daily, few are recovered: predicting where they might fall when the balloon bursts is not easy, and they can often end up in inaccessible locations including at the bottom of rivers and lakes. The students’ bachelor’s project aims to solve this, adding a guideable parachute to the payload.

“Our system controls the exposed surface area of the parachute, directing the radiosonde towards air currents that will guide it to an accessible landing spot,” explains Hugo Cruz, a student in Environmental Sciences and Engineering at the EFPL, who came up with the idea with colleagues Julie Reznicek, Lorenzo Donadio, Simon Léo Albers, and Guillem Rivas Castellá. “The main thing is to make sure the radiosonde doesn’t end up on the side of a mountain, at the bottom of a lake or in some no man’s land,” adds Lorenzo.

While the project has undergone only a single test flight so far, with telemetry information having been limited through the use of an underpowered microcontroller, initial results are promising and a second flight is planned for September. More information is available from EFPL.

Researchers at Rutgers and Binghamton Universities, meanwhile, have released a study on the use of commonplace Wi-Fi signals to detect suspicious objects inside sealed bags – including, they claim, weapons and bombs.

Described in the paper Towards In-Baggage Suspicious Object Detection Using Commodity Wi-Fi, the team’s work has resulted in the creation of a system for detecting potentially dangerous objects in sealed bags with a 99 percent accuracy rate using nothing more than a pair of low-cost two- or three-antenna Wi-Fi radios which, they claim, can be easily integrated into existing Wi-Fi networks without signal degradation.

“This could have a great impact in protecting the public from dangerous objects,” says Yingying “Jennifer” Chen, study co-author and a professor in the Department of Electrical and Computer Engineering in Rutgers–New Brunswick’s School of Engineering, of the project. “There’s a growing need for that now.”

The 99 percent “dangerous object” detection dropped to just over 95 percent for common backpack types, rather than thinner carrier bags, and around 90 percent when the object is wrapped as a means of concealing its nature. The team plans to continue working to refine the system, including adding the ability to identify objects based on their shapes and estimate the volume of liquid inside containers.

More information is available in the paper itself (PDF warning).

Popular freeware Windows-based software defined radio application HDSDR has reached version 2.80, with an impressive list of changes since version 2.76 was released back in February.

Launched to the public earlier this month as a near-final beta, HDSDR 2.80 includes tweaks designed to make it more accessible and flexible – including a fully-integrated band manager support International Telecommunication Union (ITU) regions 1, 2, and 3. Other improvements include automatic local oscillator tuning (auto-LO) , the ability to maintain main tuning when the local oscillator frequency is changed, auto band zoom, the ability to zoom using the mouse wheel, new functions for the fast-forward and reverse WAV control buttons when no WAV file is loaded, more options for digital mode, drag-and-drop WAV file support, a slow speed for the display, and the ability to automatically save the waterfall.

Full details on the changes in this release, and earlier releases, can be found in the official changelog, while the software itself can be downloaded from the main page – being sure to choose the “beta10” release, rather than the 2.76a “stable” release.

India’s Defence Research and Development Organisation (DRDO) has announced successful tests of software defined radios as replacements for existing fixed-purpose communication devices.

The in-development SDR-based communication systems – which include tactical, naval, hand-held, airborne, and manpack variants – are based on a locally-developed operating system and have gone through developer-assisted user evaluation trials, the organisation explains.

“With the indigenous development of SDR, India has come on par with the world for military radio communication. The SDR-NC and SDR-TAC ship-borne radios are contemporary to the similar radios from advanced countries (e.g. Rhode and Schwarz from Germany). The portable radios use latest devices, software tools and architecture (with specific Indian customizations), which are contemporary to radios of Thales (France) and Harris (USA),” the DRDO claims of the project. “The INDESDR radio operating environment and ad hoc networking architecture are contemporary to the best radio operating environment and networking architecture available in the world.”

More information is available in the DRDO August newsletter (PDF warning), pages 19-21.

YouTube channel The Thought Emporium is becoming something of a regular to Over The Air, this issue having published a pair of videos on the subject of building a motorised tracker for satellite communication or radio astronomy use.

“We’ve built a couple radio telescope on this channel over the years. The first took a picture of the sky in microwave frequencies and the second took a picture of Wi-Fi signals in a building,” the Emporium’s Justin Atkin explains by way of introduction. “This time we’re scaling up both the size of the telescope and the quality and utility of the build.

“Part of being a radio telescope is that it also happens to fulfil the role of satellite tracker which will allow us to receive data from more satellites that ever before. We looked previously at getting images from NOAA satellite, but they also put out a higher resolution image at a higher frequency near where the antenna is tuned to. Further, this exact antenna has been used for GOES 16 reception so we’ll give that a try when my new filter arrives.”

Built using off-the-shelf or CNC-milled parts, which “could be made by hand with sufficient patience,” the videos showcase the design and creation of the tracking system. Part 1 and Part 2 are available now on YouTube, with links to source code and design files in the videos’ descriptions.

Technology magazine Wired has published a piece on the impact of radiofrequency spectrum licensing, describing it as a “strange David and Goliath saga.”

“Random Farms, and tens of thousands of other theatre companies, schools, churches, broadcasters, and myriad other interests across the country, need to buy new wireless microphones. The majority of professional wireless audio gear in America is about to become obsolete, and illegal to operate. The story of how we got to this strange point involves politics, business, science, and, of course, money,” David Zweig’s piece begins by way of introduction, following a tale of a plea for funding from his childrens’ theatre group.

“Four years ago, in an effort to bolster the country’s tech infrastructure, the FCC decreed that the portion of the radio spectrum used by most wireless mics would be better utilised for faster and more robust mobile broadband service. Now, as the telecom companies that won the rights to that spectrum begin to use it, the prior tenants are scrambling for new radio-frequency homes.”

The full piece is available on the Wired website.

Finally, eHam.net forum member Joseph ‘NE3R’ Durnal has called for participation in Light Up 2 Metres Night, an event for FM simplex transmission.

“Most Amateur Radio Operators today start out with a radio capable of operating FM on the 2 metre band, so, you probably already have the minimum equipment necessary to participate. The objective is simple – make 2 meter FM simplex contacts, challenge your operating limits, and just get on the air and have some fun,” Joseph writes. “If calling on 146.52MHz, please be considerate of other operators. Your local band plan may differ, so feel free to share with suggested frequencies that would be best in your local area.

“Now all you have to do is get on the air! Of course, you don’t have to stop there, maybe your station needs an upgrade, whether it’s a handheld needing a better antenna, to the 100′ of 30 year old RG8X to your 2 meter vertical on the tower needing replaced, or maybe, a new mobile rig has been on your shopping list.”

More information is available on Joseph’s forum post.

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