Tagged: FT8

SimTX: A Multiplayer Shortwave Radio Simulator with Realistic Propagation and rtl_tcp Support

Recently, we came across SimTX, an open-beta multiplayer shortwave radio simulator. Everyone shares the same simulated band, so whatever one user transmits from their virtual station can be picked up by anyone else, simulated propagation permitting. The website suggests running a pirate station, making your own numbers station, or just tuning around and listening.

For realism, the ionosphere is based on IRI-2020 climatology with live ionosonde data assimilated on top, groundwave and noise follow ITU-R models, and every link passes through a Watterson fading channel with Doppler, multipath and storms. Users can transmit from a mic, an audio file or raw IQ from GNU Radio in modes including AM, SSB, CW, NFM, WFM, WSPR and FT8, and can even launch and track their own satellites.

To receive, the SimTX app runs a local rtl_tcp bridge, so SDR++ or any other rtl_tcp-capable SDR program can tune the simulated band as if it were an RTL-SDR, without any real radio hardware. The app runs on Windows, macOS, and Linux, and accounts are created via Discord. The software does not appear to be open source. The demo video below shows a song broadcast from a simulated Amsterdam and received 1145 km away in Budapest.

This may be useful for playing around with and seeing what different TX/RX variables and propagation effects do to signal reception.

We broadcast a song through a simulated ionosphere

OrcSDR Update: SSTV, ACARS and Offline Maps Come to the Standalone ESP32-P4 RTL-SDR App

Back in September, we posted about OrcSDR, open-source firmware that runs an RTL-SDR directly on the ESP32-P4 microcontroller-based M5Stack Tab5 tablet, with no PC or Raspberry Pi needed. Erik Elfstrom has now written in again to share that OrcSDR v0.5.0-beta.1 (release notes) is out, with several new features and a lot of stability work.

The main additions are SSTV reception and a dedicated ACARS dashboard. SSTV images are drawn directly on the touchscreen and saved to the SD card, and the ACARS dashboard shows live messages and aircraft lists. Erik has tested SSTV with Robot36, PD120, and Scottie S1 on various RTL-SDR models. Offline maps have also been added to the LoRa/Meshtastic, ADS-B, and FT8 dashboards. There is also a new 'Dead Air' dashboard for logging RF and audio activity, and Erik notes that despite the Halloween timing, it is not a ghost detector.

Erik also notes that a lot of work has gone into fixing layout issues, redraw flicker and memory pressure, and there is now a guided first-run setup. The software is still in beta, and Erik says that not every issue is gone yet. The update can be installed with M5Burner or the browser installer, and the code is open source under AGPL-3.0 and available on GitHub.

Some screenshots of new OrcSDR Features
Some screenshots of new OrcSDR Features

AI Disclaimer: The OrcSDR README notes that the project was created with "extensive AI assistance".

SDR++ and SDR# Plugins For: FT8 / FT4 / WSPR / FST4 / FST4W / JS8 / Q65 / CW / RTTY / JS8 / Olivia / PSK31 and PSK63

Thank you to ReLLL for writing in with an update on his decoder plugins, which we previously posted about as the “Advanced FT8/FT4 DX Decoder” just yesterday. 

Kondor Weak Signal Modes Decoder is the renamed and expanded version of the original plugin. It now decodes WSPR, FST4, FST4W, JS8, and Q65 in addition to FT8 and FT4. Its features include: A day/night DX map with SNR colors, station and country statistics, a DX activity bearing display, searchable tables, SQLite and CSV logging and optional forwarding to GridTracker.

ReLLL also added a new plugin called Maverick Text Modes Decoder (formerly CW Notebook) which decodes CW, RTTY, JS8, Olivia, PSK31 and PSK63. It provides a CW transcript with Markdown logs, simultaneous frequency tabs, spectrum discovery, pinned priority signals, and RX SNR readouts.

Both plugins now support standard SDR++ 1.2.0 and SDR++Brown 1.2.1 on Apple Silicon Macs running macOS 15 or later. There is also now a downloadable Windows preview for SDR#.

ReLLL welcomes reception reports, bug reports and UI ideas via GitHub Issues or X @FoxOnTheRunTr.

Kondor Weak Signal Modes Decoder
Kondor Weak Signal Modes Decoder

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

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.

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

HamRadioWeb: A Browser-Based Remote FT8/FT4 Receiver with Live Heatmaps, Performance Metrics and DX Cluster

Thank you to Patricio for writing in and sharing with us his release of HamRadioWeb, a browser-based remote receiver with a focus on FT8 and FT4 reception. If you're not aware, FT8 and FT4 are amateur radio digital fixed-format modes that can be decoded even with very weak signals. 

The software works by running a small server bridge app alongside JTDX/WSJT-X on the shack PC. Users can then log in from anywhere in the world on any device via the browser-based system. Once logged in, you can transmit and monitor, just as if you were sitting in a ham shack.

HamRadioWeb is designed to streamline remote FT8/FT4 operating directly from any mobile browser or PC without requiring complex setups like VPNs or port forwarding. In addition to remote TX/RX control, it features:

  • Live FT8 geospatial heatmaps and signal footprint visualization.
  • Grid-level SNR benchmarking against nearby stations.
  • Azimuthal radar & path telemetry relative to the shack.
  • Automated DXCC and award hunting synchronized with logbook data.

It’s built to make remote digital mode operating visual, data-driven, and easily accessible on the go.

HamRadioWeb is free for unlimited decodes, but limited to 10 TX's per day. Premium is a paid service costing $4.99 per month, which provides unlimited access.

HamRadioWeb: A Demo of the FT8/FT4 Terminal Display
HamRadioWeb: A Demo of the FT8/FT4 Terminal Display