Thank you to Josef (OE3JJS) for writing in and sharing with us the release of his new open-source software called SDROxide, an SDR client designed for HAMs and SWLs (short-wave listeners), written in Rust. The software supports Linux, Windows, macOS, and also has a web client. As it supports SoapySDR, RTL-SDR dongles are supported for RX. Josef writes about SDROxide:
It's a completely new project written in Rust, supporting many SDR interfaces (CAT/Audio, CAT/IQ, SoapySDR, HPSDR, TCI) and with loads of features built in that used to require extra programs: FT8/FT4, SSTV, RTTY, PSK, OLIVIA, THOR, FSQ, a CW/RTTY/PSK skimmer, there's dx cluster and sota/pota spotting, a logbook with integrations for QRZ.com, HamQTH, eQSL, LoTW, there's neural-network noise reduction, a 3D "hamclock" that visualizes QSOs, satellites, Aurora, CME cones, with up-to-date images of the sun's surface, and you can run the client locally, remote with native binary, or remote via the web (WASM).
Over on X @lambdaprog, (aka Youssef Touil), the developer of SDR#, has been teasing development of a new web client called "WebSpy" for Airspy software-defined radios. The web client allows users to tune in to a remote Airspy SDR via a web browser interface that mimics the SDR# Windows software. Before WebSpy, it has only been possible to access Airspy devices remotely via the SpyServer server software and the SDR# Windows application.
While the software is still in development and not yet available for download, you can access a demo version (HF server) (Broadcast FM server) that Youssef has currently set up on his own server in France. From the X posts on the development of the software, it seems that WebSpy boasts some impressive efficiency in terms of the low 6 kB/s network bandwidth required. This means that even over slow connections, the FFT and audio should be smooth and clear. The web interface also works well on mobile, providing a touch-optimized interface.
Youssef wrote in and wanted to share some additional information about how SharpIQ and SharpFFT work:
Under the hood, WebSpy streams both the radio signal and the spectrum display using two purpose-built compression codecs: SharpIQ for the channel data and SharpFFT for the FFT display.
A key design choice is what gets streamed: unlike most web receivers, which demodulate on the server and send you compressed audio, WebSpy sends the raw IQ signal of the tuned channel and does all the demodulation right in your browser — the same DSP chain as the gold standard SDR#. This matters more than it might sound: with server-side audio you're listening to a lossy rendition of what the server decided to demodulate, with voice-codec artifacts baked in; with local IQ, the actual signal arrives at your machine, so demodulation, filtering and mode changes happen instantly and the audio quality is limited only by the signal itself, not by an audio codec.
Unlike general-purpose compressors, SharpIQ and SharpFFT were designed from the ground up for radio: they adapt in real time to what's actually happening on the band, spending bits only where there is information worth keeping, while preserving the weak-signal fidelity that SDR users care about — a CW signal buried near the noise floor comes through intact.
The result is that a complete listening session — channel IQ, live spectrum, waterfall and all — typically fits in about 5 kB/s, a fraction of what conventional audio streaming would need. That's low enough to comfortably operate a remote receiver over a modest mobile connection, which is precisely what makes a full SDR experience in a browser tab practical — nothing to install, nothing left behind, just a tab you can close; and at 5 kB/s the stream itself hides in the noise of ordinary web traffic. Discreet SIGINT, if you're so inclined.
Thank you to Simone Spadino (SWL ID I8926BA), who wrote in to share his low-cost WSPR setup. WSPR (Weak Signal Propagation Reporter) is an amateur radio mode designed to test propagation paths using very low-power transmissions, with receiving stations reporting spots in real time to the WSPRnet map.
Simone's setup consists of a Raspberry Pi 3B+, which can be made to modulate a square wave RF signal on one of its GPIO pins via the WsprryPi software. Because a square wave generates many harmonics, he used the 20m WSPR shield from TAPR, which provides a low-pass filter to remove them. A dipole made from simple electrical monopole wire was connected to the shield via 50 ohm coax, and the signal was transmitted at 14.0971 MHz.
Transmitting from his rooftop in the center of Bari in southern Italy, Simone had his beacon received in England, Finland, Cyprus, and the Canary Islands, all more than 3100 km away. He repeated the experiment a week later with similar results. This is a reminder of how far low-cost hardware can transmit with a resilient protocol like WSPR.
Simone's WsprryPi SetupWSPR Range with the Raspberry Pi 3
Thank you to Christophe (F4DAN) for writing in about his new project called Wavelingo, an AI real-time shortwave radio translator. The software currently works with the KiwiSDR web SDR network. Christophe has a live public example running at wavelingo.app, however, with a 60-second timeout due to hosting cost constraints. Christophe writes:
Are you listening to a QSO in a foreign language on your transceiver? Click on the closest SDR (KiwiSDR fleet for now, more SDR to come in the future), and get real-time translations.
I opened a telegram channel to share updates and feedbacks on this projects - and provide support.
VLF (Very Low Frequency) refers to signals in the 3–30 kHz range. Software-defined radios like the SDRplay RSPdx can pick up these signals with an appropriate antenna.
Over on YouTube, @electronics.unmessed has uploaded a video showing how you can build a high-performing VLF loop using a single loop of wire and a balun. The one-turn design results in a naturally low impedance at low frequencies. A balun is then added to step up the impedance, resulting in impedance compatibility with an SDR.
The video explains the concepts behind VLF loops using an equivalent circuit model and shows how conductor thickness offers little benefit above 10 kHz (though wide sheet conductors can add ~3 dB), larger loops scale with area but 2 m is a good indoor compromise, extra turns help small loops but underperform a single turn with a proper transformer, and alternative ferrite mixes give little improvement over standard choke cores. Ultimately, it is concluded that a one-turn loop with a well-chosen balun is one of the most effective designs.
If you're interested in similar content, there are also several other interesting videos on the @electronics.unmessed channel about VLF antennas, mag loop antennas, SDR reception, and more.
Over on YouTube Amateur Radio VK3YE has uploaded a video showing his 'HF Helper' project. The HF Helper is a tunable HF filter and attenuator that helps improve HF reception when in the presence of strong overloading signals. VK3YE writes:
Using an RTL-SDR.COM dongle (genuine model V4) and a computer with SDR Sharp you can get quite good reception of HF signals. However reception can sometimes be spoiled by overload from signals on or away from the desired reception frequency. The 'HF Helper' presented here can reduce these problems. And you can use it in conjunction with a QRP transmitter to form a simple transmitting station.
RTL SDR HF Helper improves reception
Also as a bonus, in a related video VK3YE also shows the RTL-SDR Blog V4 being used on SDR Touch on an Android phone for portable HF, VHF and UHF reception.
The latest August edition of the RadioWorld Magazine has included an article by James Careless about the use of software defined radios for shortwave radio listening. RadioWorld is a magazine targeted towards radio broadcast owners, managers and engineers all over the world. The article explores SDRplay and RTL-SDR Blog V4 units from the perspective of a shortwave listener new to software defined radios, comparing them to his high-end Sangean ATS-909X2 shortwave digital receiver.
Thank you to Ihar Yatsevich for writing in and sharing with us his open-source WSPR beacon project. The WSPR beacon consists of a custom PCB with ATMega328 microcontroller, GPS module, single transistor amplifier, and Si5351 with TCXO.
The result is a very simple, portable WSPR beacon that can be heard all over the world. However, it appears that no band filters are built into this, so you will need to add a bandpass filter for the WSPR band that you are using.
WSPR (Weak Signal Propagation Reporter) (pronounced "whisper") is an amateur radio digital HF mode designed to be decodable even if the signal is received with very low power. Because of this design, even low-power transmitters can be received from all over the world. It can also be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet.
If you are interested, Ihar has written about his project in more detail over on Reddit.
