Category: Amateur Radio

Advanced FT8/FT4 DX Decoder: A Native FT8/FT4 Decoder Plugin for SDR++Brown on macOS

Thank you to ReLLL for writing in and sharing news about the release of his "Advanced FT8/FT4 DX Decoder", a free and open-source plugin for SDR++Brown running on Apple Silicon Macs. SDR++Brown is a popular unofficial fork of SDR++ that already includes some built-in FT8 decoding capabilities. This plugin builds on that and adds a full DX monitoring workspace directly inside the SDR software, so there is no need to pipe audio out to WSJT-X just to see who you’re hearing.

The plugin decodes FT8 and FT4 and plots received stations on a DX map. It also displays tables of unique stations, all decoded messages and countries heard, along with receiver SNR and approximate distances calculated from grid locators. Other features include table filtering and sorting, persistent CSV reception logging, optional waterfall notifications, and a WSJT-X format UDP output that can feed GridTracker directly. Decoding also continues in the background even when the plugin window is closed.

We note that the latest release also adds decoding for WSPR, FST4, FST4W and Q65. Note that the plugin is not intended for use with standard SDR++, or on Windows or Linux. Installation instructions are on the GitHub page, and a user guide is also available.

Advanced FT8/FT4 DX Decoder plugin for SDR++Brown
Advanced FT8/FT4 DX Decoder plugin for SDR++Brown

OnAir Adds Decoder Support for Almost Every Signal

Just last week we posted about OnAir, a new open-source program that started out as an easy-to-use digital and analog TV decoder for software-defined radios. It also had support for a few digital modes like ADS-B, GNSS and DMR.

In the last week, with the obvious help of Claude AI, OnAir has added experimental support for almost every single analog and digital signal and application out there. Support ranges from digital voice modes like P25 and NXDN, to HF digital modes like HFDL, to aircraft signals like ACARS and VOR/ILS, to ocean radar, to a radio astronomy integrator, to satellite decoders like Iridium and Inmarsat, to cell tower metadata decoders to Wi-Fi and many many more.

Obviously, with these decoders all being vibecoded so quickly, there is no guarantee yet that they will all work as expected. However, we did give some decoders in the program a test with an RTL-SDR. A DMR control channel was successfully decoded, and it read the calls; ADS-B showed aircraft; LTE PCI values were detected with the LTE decoder; and POCSAG messages came in cleanly.

From our own experience with Claude, Opus 5.5 is very capable of vibe-coding decoders, so there is a high chance that most, if not all, of the decoders implemented in this software will work. 

OnAir Updated to Add Almost Every Decoder Possible
OnAir Updated to Add Almost Every Decoder Possible

AI Disclaimer: This software was coded with Claude AI.

SDR– Updated to V2.2: Many New Decoders, Tools and KrakenSDR Direction Finding and Beamforming Support Added

Last month we posted about the release of SDR-- (SDR minus minus), an open-source app that lets you visually wire together a receiver on a canvas. Since that time, Julian, the developer of SDR--, has been busy adding support for many decoders, various tools, and improving performance. Julian has also added KrakenSDR support, with radio direction-finding and beamforming blocks. Julian shares the following update for SDR-- V2.20:

New Decoders

  • Aviation and satellite: VDL2, HFDL, Inmarsat Aero and STD-C, Iridium, Drone Remote ID, 406 MHz beacons
  • Voice: TETRA, Tetrapol, GSM downlink, DECT, D-STAR, FreeDV, NXDN, dPMR
  • Data: LoRa (LoRaWAN, Meshtastic, MeshCore), ISM sensors, End-of-Train, DSC, BLE, Wi-Fi survey
  • Weather: NOAA APT, Meteor LRPT, WEFAX, radiosondes with landing forecast
  • Broadcast: DVB-T/T2, DVB-S2X, DAB packet mode, DRM with xHE-AAC

Coherent and mobile

  • Direction finding, beamforming and passive radar on the KrakenSDR
  • An iOS app with CarPlay for DF while driving is in TestFlight. Android is coming soon.

Hardware

  • Native Support: KrakenSDR, RTL-SDR Blog V4 Lite, AntSDR, PlutoSDR, SDRplay, Airspy, bladeRF and ESP-SDR
  • NanoVNA and antenna rotators
  • rtl_tcp and ADS-B Beast output for other apps

Tools

  • A satellite node with Doppler correction, plus a map with footprints and tracks
  • A spectrum monitor that classifies signals automatically, and a scanner with priorities and lockouts
  • Antenna calculator, noise figure, PER tester, SID monitor
  • Audio denoise, call recording, and a decoder log grouped by station
  • Event outputs: CSV, desktop notifications, PostgreSQL, InfluxDB

App

  • A redesigned UI with a unified look for every node
  • Multi-user editing, remote access from a browser, built-in HTTPS
  • An MCP server, so an AI assistant can build and tune a canvas

Performance

All measured on an M4 Max, full results at https://sdrmm.com/benchmarks:

  • DSP against GNU Radio:
  • FIR is 3.5x faster
  • NCO is 3x faster
  • FM demod is 4x faster
  • DDC is 1.6x faster
  • A 4096-point FFT is 1.6x faster than FFTW
  • Decoding rate in noise (48 trials per decoder across an SNR range):
  • ADS-B: 68%, against 56% for readsb and 50% for dump1090-fa
  • POCSAG: 73%, against 50% for multimon-ng
  • DMR: 81%, against 60% for dsd-fme
  • NXDN: 67%, against 23% for dsd-fme

(feel free to verify yourself with cargo xtask compare dsp)

The speed comes from hand-written SIMD kernels (NEON, AVX2, AVX-512), one shared downconversion for all channels on a radio, and a DSP path that never locks or allocates. The noise gains come from decoding IQ directly with
coherent receivers and soft decisions.

SDR-- Screenshot
SDR-- Screenshot

AI Disclaimer: This software is likely to be AI-assisted or vibe-coded.

esp32-sdr-trx: Use an ESP32-S3 as a Receiver for SDR++ and as an FM/SSB Voice Transmitter on 13cm

Thank you to Jochen (DA2JH) for writing in and sharing with us his project, esp32-sdr-trx,  a software-defined transceiver built from a single ESP32-S3 dev board and two USB cables.

esp32-sdr-trx uses the same undocumented I/Q dump that we posted about previously, which was first discovered by h0m3us3r. To be able to get the data off the ESP32 and into the PC via the ESP32's limited USB streaming bandwidth, it is necessary to decimate the IQ data oln the chip down to 250 or 333 ksps. Then to keep things simple, the espdr-rx tool presents itself as an rtl_tcp server, allowing any RTL-SDR compatible software like SDR++ and GNU Radio to receive data within 1.84 to 2.79 GHz.

On the transmit side, the espdr-tx tool is used to transmit narrowband FM or SSB voice in the 13cm amateur band via a WAV file, audio pipe or sound card. Jochen notes that the ESP32 has no I/Q input so the PHY's test-tone carrier is steered in frequency and amplitude 40,000 times a second (polar modulation).

Jochem notes that there are several limitations to be aware of with this software and hardware "one board and one Linux host tested; the transmitter's power is not calibrated and its harmonics were not measured; transmitting needs an amateur radio licence (the tool asks for confirmation, and the firmware only sends in 2320 to 2450 MHz)".

The ESP32-S3 (Top) | SDR++ receiving a PlutoSDR through the ESP32 (Left) | SDR++ receiving SSB voice transmitted by the ESP32 with a HackRF. (Right)
The ESP32-S3 (Top) | SDR++ receiving a PlutoSDR through the ESP32 (Left) | SDR++ receiving SSB voice transmitted by the ESP32 with a HackRF (Right)

AI Disclaimer: Jochen notes that much of the code and documentation for this project was written with Claude.

ChronAlert: Live Dashboard for Radio, Weather, Alerts with RTL-SDR Integration for APRS, ADS-B and AIS

Thank you to Danny from brokensignal.tv, who wrote in and shared the release of his new project, 'ChronAlert'. Danny describes ChronAlert as "a free PC-based live dashboard for radio, weather, alerts, and other live information". 

ChronAlert appears to be a situational awareness dashboard that combines multiple live feeds into one screen. It includes feeds like weather and emergency, ham radio & propagation, hazards & infrastructure, and local radio & tracking.

On the local radio side, we see that RTL-SDR is supported for receiving and tracking aircraft and ships via ADS-B and AIS, and for receiving APRS messages.  The dashboard also supports Meshtastic radios, allowing users to see heard Meshtastic nodes and messages.

ChronAlert is free at the basic level, which allows 2 saved panels and 1 watch zone. A one-time fee of US$39.99 unlocks 10 panels and 10 watch zones, as well as various other features.

If you want more information, Danny has also published a detailed article with screenshots about ChronAlert on his blog.

ChronAlert: Weather, Ham Radio, Alerts & More in One Free Dashboard

HamRadioWeb FT8 WSJTx JTDX Remote Control Android App

Thank you to Patricio (LU5AKF) for sharing with us the release of HamRadioWeb.com's new FT8 WSJTx JTDX remote control Android app. Previously, we posted about HamRadioWeb's browser-based remote FT8 and FT4 receiver, and this Android app seems like a natural continuation of their software.

Patricio writes:

The app allows amateur radio operators to remotely control their JTDX or WSJT-X station from any Android phone or PC — no VPN, no port forwarding required.

What operators can do with it:

  • Monitor real-time FT8/FT4 decodes and band activity, just like sitting in front of JTDX or WSJT-X
  • Respond to CQ calls and transmit CQ remotely
  • Check where your signal is being heard via PSKReporter
  • Explore a worldwide activity map and a public DX spot page
  • Keep a contact log — auto-detected or manually added/imported
  • Follow community rankings and chat with other operators

The station connection is handled by a free Windows companion app (HamRadioWeb Companion) that links JTDX or WSJT-X to the user's account.

No radio at hand? The app opens in demo mode with simulated data so anyone can explore before creating an account.

Screenshots from the HamRadioWeb.com FT8 Remote Control App.
Screenshots from the HamRadioWeb.com FT8 Remote Control App.

SDR–: A Software-Defined Radio Application with Visual Signal Path

Thank you to Julian for writing in and sharing with us his interesting project called SDR-- (SDR minus minus). SDR-- is an open-source app that lets you wire devices, decoders, and displays together on a desktop window or browser-based canvas. It is described as "a software-defined radio application with a visual signal path. Connect devices, decoders, displays, and recorders on a canvas, then pin the controls you use to a rack."

A separate Rust server, which can sit on the same PC or a remote computer (like a Raspberry Pi), handles the DSP. Julian notes that SDR-- has native RTL-SDR support, and decoders for ADS-B, AIS, POCSAG, FT8, SSTV, and RDS are already implemented, with more in progress. The app also has a built-in signal generator and a repository of IQ recordings that can be used for experimentation and testing the various decoders.

The project releases are available on GitHub releases, and they cover Windows, Linux, and MacOS. 

SDR-- Screenshot
SDR-- Screenshot

Claude VOACAP Skill: Ask Claude About Live Ionospheric Propagation Predictions to Optimize DX

Thank you to Reid Crowe for submitting his project, "voacap-skill." This skill for Claude Code AI (a frontier LLM) lets Claude access and use the latest VOACAP ionospheric propagation data in conversations.

Instead of manually filling out a form for each prediction and analyzing the results yourself, with the voacap-skill, users can ask Claude questions like, "What's the best band to reach Tokyo from Columbus, Ohio around 0300Z in October?" and Claude will run a VOACAP prediction in the background and return an answer. Reid explains:

If you've ever used VOACAP, VOACAP Online, or watched a contest DXpedition plan its band schedule, you already know the engine underneath this: it's the same NTIA/ITS point-to-point HF prediction model that's been the industry standard for propagation forecasting since the 1980s. It takes a transmitter location, a receiver location, a month, and a sunspot number, and tells you — for every hour of the day and every frequency you care about — how reliable that circuit is likely to be.

voacap-skill takes that engine (via voacapl, the modern Linux/GFortran port, on macOS/Linux, or the native NTIA/ITS Windows engine on Windows) and wires it into Claude Code as a "skill" — a capability Claude can reach for on its own.

The skill is free and open-source, with the code available on GitHub. Below, Reid provides some more examples of what you can ask Claude once it has access to VOACAP data.