Lime Microsystems has announced a new entry in the LimeSDR XTRX family, a front-end adapter which combines a 2×2 multiple-input multiple-output (MIMO) radio-frequency front end (RFE) with a full-size PCI Express carrier: the LimeFEA mPCIe.
The LimeFEA mPCIe is designed to accept the LimeSDR XTRX mini-PCI Express software-defined radio module and adapt it for use in a full-size x4-or-larger PCI Express slot, bringing compatibility with a broad range of desktops, workstations, servers, and single-board computers.
It’s not just a simple adapter board, though, but includes an integrated 2×2 MIMO RFE with low-noise amplifiers (LNAs) in the receive paths and power amplifiers (PAs) in the transmit paths. It includes a SIM card slot for cellular network operation, time division duplex (TDD) switching controlled by a general-purpose input/output (GPIO) pin on the LimeSDR XTRX, pulse-per-second (PPS) and reference frequency connectors, a JTAG header for programming and debugging, and acts as a passive heatsink to improve the radio’s stability in hot environments.
For those who don’t need the extra features, Lime has confirmed a variant dubbed the LimeFEA Lite which drops the RFE, SIM slot, PPS/reference IO, and other features while still providing conversion from mPCIe module to full-size PCIe add-in board and the JTAG connectivity.
For more information see the LimeFEA mPCIe documentation and orders can be placed now via Crowd Supply.
A team of researchers at the University of British Columbia and Drexel University have come up with a new way to create compact yet tunable antennas: by applying kirigami, the art of paper-cutting, to MXene-printed plastic sheets.
“For wireless technology to support advancements in fields like soft robotics and aerospace, antennas need to be designed for tunable performance and with ease of fabrication,” explains co-author Yury Gogotsi of the thinking behind the team’s work, which uses origami’s cutting-based cousin kirigami. “Kirigami is a natural model for a manufacturing process, due to the simplicity with which complex 3D forms can be created from a single 2D piece of material.”
The flat antennas are created by printing MXene material onto a plastic substrate, which is then cut in a particular pattern. By adjusting the tension of the plastic sheet, the cut sections can be raised or lowered to turn the flat antenna into a three-dimensional shape — tuning its reception, with prototypes showing a 400MHz shift which could also make the design usable as a strain-sensor for infrastructure monitoring.
“Frequency selective surfaces, like these antennas, are periodic structures that selectively transmit, reflect, or absorb electromagnetic waves at specific frequencies,” adds co-lead Mohammad Zarifi of the project. “They have active and/or passive structures and are commonly used in applications such as antennas, radomes, and reflectors to control wave propagation direction in wireless communication at 5G and beyond platforms.”
“Our goal here was to simultaneously improve the adjustability of antenna performance as well as create a simple manufacturing process for new microwave components by incorporating a versatile MXene nanomaterial with kirigami-inspired designs,” concludes co-author Omid Niksan. “The next phase of this research will explore new materials and geometries for the antennas.”
The team’s work is available in the journal Nature Communications under open-access terms.
Maker, researcher, and radio amateur Ricardo Caratti got tired of having to get up to control his FM transmitter — so turned an Espressif ESP32 microcontroller into a host for a web-app remote control system accessible from a mobile phone.
“[This is] a prototype of an FM transmitter based on the [Quintic] QN8066, controlled via a mobile phone,” Ricardo explains. “For this, I use an [Espressif] ESP32 programmed to function as a [Wi-Fi] Access Point, providing a self-contained network connection, as well as acting as an HTTP server. This allows both computers and mobile phones to access the QN8066 through a web browser.”
The QN8066 is a popular FM transceiver chip often paired with a microcontroller for low-cost custom radio projects, controlled over an I2C bus. It’s a very familiar device to Ricardo, who is the author and maintainer of a library designed to make it easier to use with Arduino-compatible microcontrollers – but his latest creation goes one step further.
Using an Espressif ESP32 microcontroller with built-in Wi-Fi radio, Ricardo’s latest project creates a wireless access point to which any other Wi-Fi device can connect. Once connected, an on-board web server provides a web app which allows for the radio chip to be configured on-the-fly – without having to get up and physically interact with the hardware.
The project is demonstrated on Ricardo’s YouTube channel, while the library is available on GitHub under the permissive MIT licence.
Radio ham Stephen “KD2WTU” Talbot has a trick for saving some money on your amateur radio setup – by opting to use cheap TV-grade co-axial cable instead of anything more expensive.
“For the past year I have been using 75 Ohm cable, television [grade] RG6 coax cable, in my amateur radio station,” Stephen explains. “If you want to use 50 Ohm coax that’s going to perform better than RG6 75 Ohm coax in your station, you’re going to have to purchase RG213 – that’s how good the performance of RG6 is. It has great performance and low loss, comparable to RG213 for about a quarter of the price.
“RG6 is excellent for receive-only antennas, like your beverage or loop on ground antennas, because of its low attenuation, and there’s a wide variety of cables readily available and [cheap] – like direct-burial, UV-resistant, riser-rated, quad-shield, there’s a whole bunch of stuff you can get in RG6.
“If RG6 is so great why isn’t everyone using it in their station,” Stephen asks. “There are some drawbacks to using it in your station. It’s true that RG6 will handle less power than RG213, and that makes sense when we’re comparing a $110 cable to a $20 cable. Anecdotally, I can attest to the fact that RG6 will handle 100W of whatever you want to pull into it. You can transmit 100W FT8 into RG6 as much as you want – I’ve done it, it’s fine, I haven’t had a problem.”
A full run-down of the pros and cons is available in Stephen’s YouTube video.
Hackaday’s Al Williams has designed a Simple Add-On (SAO) standard badge accessory tailored to radio amateurs – acting as an automatic ASCII to Morse code converter.
“I’ve been a ham radio operator for a very long time. In fact, July was my 47th anniversary in the radio hobby,” Al explains. “Well, that’s not true. It was my 47th year with a license. I had been listening to shortwave long before then. So, I wanted to do something with Morse code. You don’t have to know Morse code to get a license these days, but a lot of hams enjoy it.
“I set out to do a simple board that would play some Morse code messages. But that’s just another blinking light LED with a buzzer on it, too. So, naturally, I decided it would also provide Morse code output for the I2C host. That is, the SAO could be used to convert ASCII to Morse code. Sounds simple, right?”
Al’s initial plan was to build around the Raspberry Pi Pico microcontroller board, which proved too bulky. Switching to a third-party alternative based on the same RP2040 microcontroller got the size down, and the firmware was written in MicroPython. After some difficulty in getting the hardware to act as an I2C device, rather than a host, Al’s badge add-on was ready to turn any text sent to it over the I2C bus to audible Morse.
More information is available on Hackaday, with the source and design files on Hackaday.io. Additional details are available in Al’s YouTube video.
Developer Marco Greco has come up with a “media centre quality” FM and DAB receiver package, built around Qt – offering a clean user interface and MPRIS controller support.
“Guglielmo implements a simple FM and DAB receiver based on Qt and the Qt-dab and sdr-j-fm packages,” Marco explains. “The primary reason it is being developed is there is a lack of media centre quality open source software defined radios: most of the packages out there focus more on hobbyist features, such as signal and content monitoring, leaving out media features like a volume slider or MPRIS control.
“Yes, I have blown the ribbon tweeter fuses on my maggies because my previous go to SDR DAB receiver started at full blast, and I run my media centre headless: I don’t really want to scramble for a VNC session when I want to stop the music, when I could simply use KDE connect on my phone. There is also a distinct lack of FM SDR receivers, which is disappointing, since, at least in the UK, for reasons of cost, most stations transmit at a fairly poor bitrate, if not downright in mono, and FM stations seem to still be a better proposition in terms of sound quality.
“In DAB mode, top to bottom, there’s the channel name, a list of all the services (AKA stations) in the current channel, a channel selector, and the previous and next buttons. FM mode sports a frequency display, and a large, old style, frequency knob. Turn it either way to select the frequency. The knob turns several times, much like in the analogue days of old. Below there’s a scan down, scan up and stop scan buttons, which can be used to find the previous or next FM station.
“Guglielmo can send slides to MPRIS controllers and accept volume changes, play, pause, stop signals, as well as skip to next and skip to previous. Mpris-qt5 does not implement playlists, and even if it did, I haven’t found a single MPRIS controller that handles them. For this reason I haven’t currently implemented my plan of having playlists for presets and skip previous and next for stations, and unless matters change, I am unlikely to implement it ever.”
Guglielmo is available on GitHub under the reciprocal GNU General Public Licence 2.
Security engineer Matthew Rogers has turned an Espressif ESP32 and an Analog Devices AD8317 demodulating logarithmic amplifier into a portable gadget for tracking down sources of radio signals: the RFHunter.
“This project is an RF [Radio-Frequency] signal scanner built using an [Espressif] ESP32, [Analog Devices] AD8317 RF detector, and various other components,” Matthew writes of his gadget. “It’s designed to detect and measure RF signals in the environment and display the signal strength on an OLED display. It’s useful to find hidden cameras, wiretapping devices, and other RF-enabled devices.
“I had people talk to me about selling it, making it as a side project. I’ve decided this isn’t something I’m interested in doing. I believe people ought to have privacy so I’m releasing the build instructions and the source code.
“You’ll need a few things to put this together. It took me about 1/2 hour to make the second unit. The first one might take you 45 minutes if you’re good, it probably took me an hour. You can print the case on any 3D Printer, it’s not very big and should fit on almost any bed.”
The RFHunter is a handheld tool in a 3D-printed housing with a simple user interface: a knob controls the sensitivity, and an OLED display shows the strength of the received signal. As you move around, the signal strength will change – allowing you, with a little trial-and-error, to pinpoint the signal’s source. When you’re close, an integrated buzzer emits an audible alarm.
More information is available on Matthew’s blog, while design files and source code have been published to GitHub under the reciprocal GNU General Public Licence 3.
Researchers from Sandia National Laboratories and Ohio State University have figured out a way to help planes land in the event of degradation to traditional Global Navigation Satellite System (GNSS) services like GPS – by using cellular phone signals as a navigation tool.
“We’re not trying to replace GPS,” explains Sandia lead researcher Jennifer Sanderson of the project. “We’re just trying to assist it in situations where it’s degraded or compromised. I worry about relying too heavily on it without a backup. The impacts of losing GPS could be felt throughout society.
“Commercial GPS receivers are susceptible to a couple different threats, one being jamming,” Jennifer notes, with the other being spoofing – sending a fake signal, rather than overwhelming the real signal with noise. “There are actual apps you can download that allow you to spoof your location, and entire subreddits dedicated to showing you how to use it for various [location-based] games.”
To provide a backup, the researchers looked to “signals-of-opportunity” – in particular cellular phone signals. To ensure they’re available at the altitudes aircraft are likely to operate, the team sent radio payloads aloft to 80,000 feet using weather balloons – and believe that it could be possible to use these existing signal sources as a less-accurate backup navigation source.
“While we are still processing the flight data,” Jennifer says, “we believe our preliminary findings indicate that we detected cell tower signal beacons at our peak altitude of about 82,000 feet. If these signals are clean enough for navigation, it will significantly change what we thought was possible for alternative navigation.”
The team presented its findings at the Institute of Navigation’s GNSS+ 2024 conference last month.
Wired’s Makena Kelly and Dell Cameron have penned a piece detailing how amateur radio comes into its own during disaster scenarios – and how it has helped in the aftermath of hurricanes Helene and Milton.
“Amateur radio is one of those things you get into because of your love of radio communications and the technical aspects of it or the community and the challenges that you can overcome,” says Thomas Witherspoon, a radio amateur interviewed for the article. “It’s a lot of fun, but underlying all of that is this prime directive with amateur radio that it’s always there as emergency communications when all else fails.”
“As of Monday, telecommunications companies were still putting up temporary towers to restore cell phone connectivity in North Carolina,” Makena and Dell write. “AT&T and T-Mobile have deployed mobile units where residents can drive to connect their phones to Wi-Fi and send messages. For many residents, the simplest method of reaching a loved one is speaking into a handheld radio.”
“Florida amateur radio operators are perfectly equipped to handle Hurricane Milton, even just after Hurricane Helene,” adds Amateur Radio Emergency Service director Josh Johnston. “They have the systems in place and have a well-refined action plan in each county, as well as at the state level. They’re quite accustomed to busy storm seasons, and ready to provide critical information to served agencies as Milton comes through.”
The full article is available on the Wired website.
University of South Carolina professor Allison Marsh has written an article for IEEE Spectrum on a piece of radio history: the Regency TR-1, the first transistor radio.
“Imagine if your boss called a meeting in May to announce that he’s committing 10 percent of the company’s revenue to the development of a brand-new mass-market consumer product, made with a not-yet-ready-for-mass-production component. Oh, and he wants it on store shelves in less than six months, in time for the holiday shopping season,” Allison writes. “Ambitious, yes. Kind of nuts, also yes.
“But that’s pretty much what Pat Haggerty, vice president of Texas Instruments, did in 1954. The result was the Regency TR-1, the world’s first commercial transistor radio, which debuted 70 years ago this month. The engineers delivered on Haggerty’s audacious goal, and I certainly hope they received a substantial year-end bonus.”
The Texas Instruments Regency TR-1 was a departure from the company’s usual fare, with its origin as a seismic instrumentation and military electronics firm, and designed to exploit the company’s recently-acquired licence on transistor technology developed by John Bardeen and Walter Brattain at Bell Labs in 1948. It was developed in just six months, as proof of the broad applicability of transistorisation – putting a portable radio in anyone’s pocket.
“The Regency TR-1 was a success by many measures: It sold 100,000 in its first year, and it helped jump-start the transistor market,” Allison concludes. “But the radio was never very profitable. Within a few years, both Texas Instruments and IDEA left the commercial AM radio business, TI to focus on semiconductors, and IDEA to concentrate on citizens band radios. Yet Pat Haggerty estimated that this little pocket radio pushed the market in transistorized consumer goods ahead by two years. It was a leap of faith that worked out, thanks to some hardworking engineers with a vision.”
The full article is available on IEEE Spectrum.