LimeSDR users can now enjoy the first officially-tagged release of Lime Suite NG, the next-generation software stack – delivering a range of improvements over the legacy Lime Suite bundle.
“Lime Suite NG was first announced back in May of last year and amongst other things provides greatly improved support for SDRs with multiple transceivers, while also making it possible to aggregate multiple physical SDRs into a single logical device,” Lime Micro’s Andrew Back explains. “Other improvements include that plug-ins for key applications and frameworks, such as the Amarisoft cellular network stack and GNU Radio, are now developed as part of the same source tree.”
The first tagged release, made available this month, builds on the initial testing release from May and its subsequent updates with a range of further improvements: the source is now a modular build, you can build the source offline, there’s Debian packaging support, the LimePCIe driver now includes DKMS and UART support, there’s better handling of direct memory access on Arm platforms, the GNU Radio plugin has been refactored so it can coexist with the legacy gr-limesdr, and there’s improved PCI Express data streaming performance on Raspberry Pi family single-board computers and systems-on-modules.
Other enhancements include support for the Fairwaves XTRX Rev5 SDR so long as it’s running Lime Micro’s gateware, improved legacy API wrapper functionality, a new library of LMS7002M field-programmable RF controls designed for use in embedded systems, improvements to the support for LimeSDR X3 and LimeSDR X8 boards, and additional unit tests.
In addition to the source code and tagged release, available under the permissive Apache 2.0 license on GitHub, Lime Suite NG is now also available in package repositories for Ubuntu 22.04 on x86-64 hardware and on Debian Bookworm for Arm64 and Raspberry Pi devices; instructions on how to set up the repositories with apt are available on the Lime Suite NG wiki. Support for more distributions is planned “in due course,” Andrew adds.
The LibreCelullar project continues apace with the release of a new software stack configuration, providing support for Voice over LTE (VoLTE) and SMS – and there’s a new base station design too.
Launched back in May 2021, LibreCellular is an ongoing project to provide a fully-tested and validated hardware platform and software stack for 4G Long Term Evolution (LTE) cellular networking building atop open-source projects including srsRAN (formerly srsLTE) and Open5GS, OsmoGSMTester, the LimeSDR family of software-defined radio devices, and LimeRFE.
In the latest project update Andrew Back has shown off points of progress include a new “standard” software stack which uses PyHSS for HSS and PCRF, Open5GS for all other EPC functions, and Kamailio for IMS to provide VoLTE and SMS services – building atop Supreeth Herle’s docker_open5gs project. Changes over the original project include an upgrade to the latest Ubuntu Long-Term Support (LTS) release, upgraded software, a move to upstream images for dependencies, the use of configuration files in place of environment variables, using a single HSS for EPC and IMS instead of independent HSSes, and the use of Ansible for deployment.
At the same time, Andrew has unveiled a new base station reference design, dubbed the CSRAN1. “This integrates a host computer for baseband processing,” he explains, “SDR, the LibreCellular RFE and two Band 3 Medium Power RF PAs, plus two cavity duplexers.” The design offers 2×2 MIMO LTE-FDD with a modulated RF power output of around 33dBm. “It could easily be modified for other bands,” Andrew notes, “by selecting different RF PA modules and duplexers, since the SDR and LibreCellular RFE together support operation from 500MHz – 3.8GHz. Similarly, different power output PA modules might be selected, or perhaps omitted entirely for reduced coverage range.”
More information is available in Andrew’s project update.
The Dwingeloo Radio Telescope (CAMRAS) has been to make two-way contact via a geostationary satellite for the first time, Jan “PA3FXB” van Muijlwijk has reported – bouncing a signal off Inmarsat GX-5.
“In an exciting first, we managed to successfully complete a two-way contact by bouncing a signal off a geostationary satellite,” Jan writes of the achievement. “The satellite in question, Inmarsat GX-5, is stationed at an altitude of over 35,000 kilometres, and together with Dan, HB9Q, in Switzerland, we alternated between transmitting towards the satellite and receiving reflections. This first ever amateur QSO over geo satellite the remarkable capabilities of modern amateur radio technology when paired with large, high-gain dishes.
“Our journey towards this milestone began in 2015 with a QSO with Andreas, DJ5AR, utilising a satellite in a polar orbit at 650 kilometres altitude. Encouraged by this initial success, we set our sights on the more challenging goal of achieving reflections from a geostationary satellite. The successful contact over a geostationary satellite was made possible using the recently introduced digital mode Q65, part of the WSJT-X software suite. Q65 is specifically designed for extremely weak signal communication, making it particularly well-suited to overcoming the significant path losses inherent in satellite reflections.
“The signal levels of the QSO were -21dB/-32dB,” Jan reports. “WSJT-X manages to decode this by applying averaging. After initial success, we directly tried another satellite, Inmarsat 4A F4 (Alpha). This satellite gave even stronger reflections: -15dB/-24dB. Two other satellites we tried did not work, highlighting that some luck is involved – possibly involving the orientation of the solar panels towards us. This milestone opens up exciting new possibilities for experimentation and technical advancement within the amateur radio community. We look forward to exploring even greater challenges in the future and continuing to push the boundaries of weak signal communication.”
The original project write-up was unavailable on the CAMRAS website at the time of writing, but can be read via the Internet Archive.
Anyone looking for a classic crystal earpiece but struggling to find stock now has a do-it-yourself option, thanks to a 3D-printable design by pseudonymous maker “tsbrownie.”
“Quality crystal earphones have become a bottleneck in making crystal radios. But as of today, NO MORE! You can now make an earphone with equal sound quality, because it uses the same piezoelectric element, AND I have made an option to have a rubber earpiece for (GREATLY) improved comfort,” tsbrownie writes by way of introduction to the project. “[I have made] multiple designs for a crystal earphone. One type is the historical plastic ear insert part. The other uses a popular rubber insert. You need to supply the sound element and wire.”
Released under a Creative Commons Attribution-NonCommercial licence, tsbrownie’s designs are designed around a 20mm-diameter piezoelectric element with either a hard plastic casing, like the crystal earpieces of old, or a more comfortable rubber tip using an off-the-shelf part for Xiaomi’s Mi in-ear headphones. The earpieces offer 20k Ohm impedance and 20M Ohm resistance, 15,000pF capacitance, and a 57dB sensitivity at 1kHz plus a 200-8,000Hz frequency range.
“IMPORTANT NOTE: 3D Printed parts are porous and not hygienic,” tsbrownie warns for anyone looking to make their own using the 3D-print files. “They may also be rough and, depending on your printer, may have sharp edges and protrusions that need to be taken care of before using. It you have any doubts, DO NOT USE THEM.”
The project is documented in tsbrownie’s YouTube video, with the 3D print files on Thingiverse for free download – with the creator advising to use “low toxicity, flexible filament.”
Øystein Schrøder “LB8IJ” Elvik is working to build a low-cost motorized antenna tuning coil, dubbed the “Magic Antenna Coil” – targetting “one coil to rule them all.”
“I just built a Ham Radio Antenna system Compatible with the Yaesu ATAS (Active Tuning Antenna System) for less than $20,” Øystein explains. “This antenna system can remotely tune to any of the HF bands using an ATAS compatible transceiver or an external ATAS Controller. The flexible system consists of a 0-50uH Loading Coil Compatible with ATAS and can be combined with a variety of antennas and ground plane to produce the best compromise in effectiveness and agility/flexibility. Quickly jumping between bands and getting a perfect match in seconds.
“[It can also] be used with other transceivers using an extra control box. It has some great benefits: effortless tuning, you can tune while sitting down, no need to get up to manually adjust coil position or antenna length; tuning close to the antenna so you don’t lose effect to heat in the co-ax cable; with no externally moving parts it may be sealed and is protected from the environment; you can use the same antenna for multiple bands.
“I have tested it for 80 to 10m,” Øystein says of the prototype, “but I don’t see why it wouldn’t take on other bands in some configuration because it is flexible in that you can connect any length of radials and radiating elements. And it’s cheap, if you build it yourself. That’s the thing: you can not buy this pre-built, and it is not an easy build – but if you have what it takes and are determined you will harvest the benefits.”
The project is documented in a series of videos on Øystein’s YouTube channel.
Steve “VE6WZ” Babcock has been waxing lyrical on a cable-related mission: to replace classic co-ax antenna cables with CAT6 twisted pair Ethernet cables instead.
“With the computer and internet explosion this stuff is ubiquitous,” Steve explains of the allure of CAT6 twisted pair cabling, “and therefore it’s mass-produced and generally quite affordable – although buyer beware, you get what you pay for. As an RF feed line these twisted pairs are really excellent since they are a balanced transmission line, so inherently less susceptible to noise ingress compared to unbalanced co-ax.
“These same CAT6 cables running through your house and office towers carry data between computers and are running at somewhere between 20 to 200MHz, you know, they can certainly handle our low frequency ham signals. Another plus for CAT6 is we have eight wires to use. With one cable to the antenna we have multiple balanced feed lines as well as DC control lines for powering amplifiers and switching.
“To match the 100 Ohm CAT6 pair to the antenna,” Steve notes, “we can build a passive matching transformer. They’re easy to design and build yourself, you don’t need to buy them – roll your own to suit your needs. Now, if you want to add gain to your antenna I’ve redesigned the LMH6622 transimpedance amplifier to be used with CAT6. The modification is simple, really, just replacing the 75 Ohm R4 resistor with a 100 Ohm unit.”
Steve’s full video is available on his YouTube channel, with a link to download a Gerber PCB production file for the modified transimpedance amplifier.
Author, educator, and radio amateur Bill Meara has launched a project aiming to get highschool students into the hobby – by building their own fully-functional radio receiver.
“At a local high school, students get a lot of exposure to digital high tech, but there was a gap in the area of analogue electronics,” Bill explains. “Radio amateurs were asked to teach students how to build something analogue. A direct conversion receiver was chosen: it had the right mix of simplicity and usefulness.
“The instructors decided to make this a true homebrew project: students would build the four stages of the receiver on copper-clad boards using the Manhattan technique. The ultimate in open-source projects, all components would be discrete and analogue (no ICs). The students would understand the purpose of every part in the receiver.
“We went with just four boards, four subcircuits: bandpass filter; mixer; RF oscillator; audio amplifier,” Bill explains. “Understanding these four circuits allows students to understand almost all RF devices. Circuits were chosen for their simplicity and understandability: Nothing exotic or overly clever. Students were required to actually BUILD the circuits. This was a challenge. This was not easy. This was NOT a kit-build. Students would layout their own boards and acquire parts from a central parts source. The receiver they built is a real receiver, capable of real long-distance communications. It has been used on the airwaves in a two-way contact.”
The project is documented, with schematics, on Hackaday.io; the first in a planned series of introductory videos is available on YouTube.
Engineer and radio amateur Ido “4X6UB” Roseman has built a pocket-sized “All Band Receiver,” designed for picking up transmissions between air traffic control and the air traffic which they are controlling.
“While it may be tempting to use a simple off-the-shelf walkie-talkie style receiver or scanner to listen in on air traffic communications, doing so in or near an airport can be problematic. More importantly, airport security and aviation authorities generally view the use of such devices with suspicion,” Ido explains. “In some cases, they may even be prohibited in certain areas of an airport due to concerns about security and interference with official communications. Even if your intentions are pure and have the proper equipment, trying to explain that to a concerned security officer can turn to be a headache. Enter the All Band Receiver.
“In technical terms, it’s basically a diode detector followed by a high-gain audio amplifier, which makes it safe to use without a risk of spurious harmonics or any other emissions from the (non existent) local oscillator. The downside is that the signal needs to be very strong to be detected. That means I should be physically very close the the transmitter to hear anything. You can also hear any other electromagnetic energy such as atmospheric cracks, cell phones (not switched to flight mode) searching for a tower, and engine roar, among others. If you’re at home you might want to try things like car remote key fobs or your microwave oven.
“When finally got on an airplane I was very happy with this little gadget,” Ido notes. “Unlike ‘normal’ receivers, background noise is very minimal and no squelch is needed. I might even say it masks nicely the engine noise and I was able to stay with the headphones throughout the flight. Just don’t expect any rug chewing. These are very busy people, so communication is kept at a minimum like altitude changing or headings, but you might get the heads up on avoiding bad weather, occasional close by airplanes, or what’s going on at the gate.”
The project is documented on Ido’s blog, with PCB design and production files – based on a circuit designed by Paul “G7VAK” Beaumont – available on GitHub under an unspecified open source licence.
Maker Gabe Emerson has showcased a freely-available 3D-printed antenna designed targeting reception from weather satellites including NOAA and Meteor – describing it as working just as well as a considerably larger off-the-shelf L-band dish and being easier to use for handheld tracking of low Earth orbit satellites.
“While I’ve used a variety of antennas – everything from TV satellite dishes to umbrellas coated in tin foil – not all of those antennas are easy or cheap for folks to get their hands on,” Gabe says by way of introduction to the project, “and a lot of them are big, clunky, and take up a lot of space. Now,w hat if you could 3D-print a small, portable, convenient satellite antenna that you could use on L-band?”
“I didn’t invent anything,” says the pseudonymous “t0nito,” the designer of the files printed by Gabe, “as this type of antenna and its dimensions already existed. I just wanted to make a design for myself (with the very little knowledge I have 3D designing) that could be printable in any standard 3D printer and decided to share it.”
“I think it’s fantastic,” Gabe concludes after side-by-side testing with his usual L-band antenna. This thing is much better than any of my other antennas as far as size, weight, ease of use – I can wave this around, I can lock right on to a satellite on-handed, I don’t have to juggle some giant dish over my head, I don’t have to balance something on a tripod and try to get it aligned just right.”
Gabe’s full video is available on his YouTube channel, while t0nito’s 3D-print files are available on Thingiverse under a Creative Commons Attribution-NonCommercial-NoDerivatives licence.
Finally, Jon Dawson has designed a low-cost standalone Slow Scan TV (SSTV) decoder, powered by a Raspberry Pi Pico microcontroller board – adding SSTV support to any radio receiver.
“Slow Scan Television (SSTV) is a fascinating way to transmit images over radio, commonly used by amateur radio enthusiasts,” Jon explains. “Traditionally, decoding SSTV signals requires a PC and a soundcard, but this project demonstrates a simpler, more accessible solution. Using a Raspberry Pi Pico microcontroller and an affordable TFT display, you can build a compact SSTV decoder that doesn’t require a PC. With just a few resistors and capacitors, the decoder interfaces directly with the headphone output of any radio, making it highly versatile and easy to set up.
“I have managed to receive quite a few SSTV images using very simple hardware. In future, I would like to consider expanding the range of SSTV modes that can be received,” Jon adds. “It should be possible to add SD card support to allow images to be automatically saved as they are downloaded. I also think it should be possible to decode a much wider range of signals using identical hardware. With appropriate software, I believe that the hardware should be capable of receiving FAX, CW, RTTY, PSK31, and FT8.”
A full project write-up is available on Jon’s blog, while source code and 3D-print files for an enclosure are available on GitHub under the permissive MIT licence.