Clever Quest Lab: Free Browser-Based Decoders for RTTY, Weather Fax, SSTV, NAVTEX, APRS and More

Thank you to Simpli for writing in and sharing a set of free radio decoders that run entirely in the browser. There are pages for Morse, RTTY, PSK31, SSTV, weather fax, NAVTEX, APRS and the DCF77/MSF time signals, plus a signal identifier that tries to name an unknown mode and links to the matching decoder.

Audio can come from your SDR program via a virtual audio cable, a microphone, a WAV or MP3 recording, or a WebSDR playing in another browser tab (this needs a desktop browser with screen sharing), so no hardware is needed to try them. Simpli tested them on DWD RTTY on 4583 kHz and DWD weather fax on 3855 kHz via the Twente WebSDR, as well as on live PSK31 and an ISS SSTV recording in PD120 mode.

Simpli writes:

A detail you might find interesting: the WebSDR player inserts 128 zero samples about once a second, and its playback speed wanders by up to half a percent. That's enough to tear a fax picture apart. The fax decoder cuts those gaps out and tracks the speed from the white tone, so the chart comes out straight. The RTTY page also switches to reversed polarity by itself when it sees too many framing errors.

All decoding happens locally with nothing uploaded, and the tools are free with no sign-up. This is similar in spirit to OFFgrid-SDR, which we just posted about, as both run in the browser and can automatically identify a mode. However, OFFgrid-SDR connects directly to an RTL-SDR via WebUSB and is open source under the GPLv3, while Clever Quest Lab's decoders work on audio from any receiver and do not appear to be open source.

Clever Quest Web Browser Weather Fax Decoder
Clever Quest Web Browser Weather Fax Decoder

ErgissVAG F16: An F-16 Cockpit-Style Android Car Dashboard with RTL-SDR ADS-B and Airband Receivers

Thank you to Gabriel Diaconu from Iasi, Romania, for writing in and sharing ErgissVAG F16, an Android car dashboard app that shows OBD2 data on a head-up display styled like an F-16 cockpit. Its latest release adds two RTL-SDR pages for car head units and phones, which allow it to receive the AM airband and ADS-B.

The AM airband receiver covers 118-137 MHz with 25 and 8.33 kHz channel spacing and includes active/standby frequencies, scanning with squelch, and a live spectrum. The ADS-B page uses a 1090 MHz decoder written from scratch and shows aircraft on a radar-like display. Gabriel saw several airliners near Iasi sending altitude and speed but no position, consistent with the GNSS interference reported in Gabriel's region, and the app flags these as "GNSS-x" (we've previously posted about mapping GNSS interference through ADS-B data).

Rather than relying on a separate driver app, ErgissVAG F16 talks to the dongle directly through Android's USB Host API using a port of librtlsdr, with no root needed, and rtl_tcp is supported as an option. Gabriel tested it with an RTL-SDR Blog V3 on a powered USB hub, as it drops out on bare OTG. The app is available on Google Play with a free 7-day trial, then a one-time €9.99 Pro unlock.

ErgissVAG F16 Airband Tuner & ADS-B TCAS-Style Traffic Display
ErgissVAG F16 Airband Tuner & ADS-B TCAS-Style Traffic Display

OFFgrid-SDR Updated to V2.1: Adds DAB, DAB+ and DRM xHE-AAC Decoding in the Browser

Back in October, we posted about OFFgrid-SDR, a fully offline RTL-SDR receiver program that runs in a WebUSB-compatible browser from a single index.html file. Richard Didd has now written in again to let us know that the project has passed 10,000 downloads and views, and that version 2.1 adds DAB, DAB+ and DRM digital radio support.

The DAB decoder is written in JavaScript directly from the standard, while DAB+ (HE-AAC) and original DAB (MP2) audio are decoded by FAAD2 and pl_mpeg compiled to WebAssembly. DRM also now supports xHE-AAC audio via Android's libxaac decoder. Richard tested DAB off-air on the BBC National DAB multiplex, but can't receive any xHE-AAC DRM stations from the UK, so reception reports from anyone in range would be welcome.

Richard also points out the AUTO mode, which listens to a signal for a couple of seconds, identifies it, and switches to the right mode or decoder. It recognizes CW, RTTY, PSK, NAVTEX, weather fax, SSTV, FT8/FT4/WSPR, ACARS, APRS, AIS, DRM and DAB, among others. OFFgrid-SDR is open source under the GPLv3 licence and available on GitHub, with more technical details in the Hackaday.io project log.

OFFgrid-SDR Receiving the BBC National DAB Multiplex
OFFgrid-SDR Receiving the BBC National DAB Multiplex

ESPica32: A Standalone ESP32 Radio for Tuning Any KiwiSDR with No PC or Phone

Thank you to Ivan (LU8MIL) from the ‘Radio Bunker’ YouTube channel for writing in and sharing ESPica32, a standalone ESP32-based radio that tunes into any public KiwiSDR in the world with no PC or phone needed. The name is a tribute to the Spica, a pocket transistor radio that was hugely popular in Argentina.

The build uses just four parts: an ESP32-WROOM-32, an SH1106 OLED display, a rotary encoder, and a MAX98357A I2S amplifier with a small speaker. A single encoder controls frequency, volume and mode (LSB, USB, AM, CW and FM). A web page served by the ESP32 handles Wi-Fi setup, KiwiSDR server selection and full remote control, and also includes a diagnostic for tracking down audio dropouts.

Ivan notes that distant KiwiSDRs initially cut out because the ESP32 couldn’t keep up with uncompressed audio. Switching to the KiwiSDR’s ADPCM compression fixed this, and a Kiwi in Argentina now plays cleanly from Germany at about 260 ms ping. The Arduino IDE sketch and wiring diagram are available on Ivan’s Todo-SDR blog, and the Spanish-language video below shows the build and a demo (English subtitles are available).

🎯 EL PROYECTO DIY QUE TODO RADIOESCUCHA DEBERÍA CONOCER: ESPica32

VMA Radio Lab: DecSAT Extended into a Multi-SDR Receiver with DVB-T/T2, DAB+ and Analog PAL TV

Last week we posted about DecSAT, an open-source program by CasualArclamp that turns a HackRF One into a DVB-S/S2/S2X satellite receiver and analyzer. Now Vitor Martins Augusto has written to share his fork, 'VMA Radio Lab' (initially called DecSAT-VMA), which extends DecSAT into a general-purpose broadcast receiver and measurement tool.

The biggest difference between DecSAT and VMA Radio Lab is multi-SDR operation. VMA Radio Lab can run several SDRs at once, each with its own VFOs, including the HackRF, PlutoSDR, USRP B210, RTL-SDR, SDRplay RSP1 and Airspy. One SDR can be dedicated to a sweeping wideband overview, such as the full 950 - 2150 MHz satellite IF. It also pulls in DVB-T/T2, DAB/DAB+ and TETRA decoding from CasualArclamp's sibling projects DecDVB-T, DecDAB and DecLAB, and adds analog radio, PAL color TV with teletext, measurement tools such as a vectorscope and transport stream analyzer, and control of CrazyScan-compatible TBS tuner cards for LNB power and hardware DVB reception.

Meanwhile, the original DecSAT remains satellite-focused. Since our last post it has added support for Fobos SDR, Airspy and network IQ input (including rtl_tcp), and has merged some of VMA's early RTL-SDR, PlutoSDR, B210 and analog TV code.

VMA Radio Lab is GPLv3 and available as a Windows 64-bit build and source zip on the website. We note that TETRA audio needs a separate ACELP codec DLL that isn't included for legal licensing reasons, and the bundled development notes describe several of the newer decoders, such as AIS and ACARS, as experimental. 

Decscat-VMA Screenshot
Decscat-VMA Screenshot

AI Disclaimer: The original DecSAT lists Claude as a contributor. While VMA does not disclose it, the development notes included with the VMA Radio Lab source suggest that its extensions were also written with the help of AI.

RS41 and M20 Android Decoder: A Standalone Radiosonde Decoder Android App for RTL-SDR

Back in June 2025, we posted about a radiosonde decoder and tracker program for Windows written by Mario Ančić (9A4AM). Mario has now written in again to share a new radiosonde decoder for Android, which works with an RTL-SDR dongle connected via a USB OTG adapter. As far as Mario is aware, it is the first standalone Android app dedicated to radiosonde decoding, as other solutions only offer it as an add-on within a larger SDR program.

The app decodes the common RS1729 radiosonde protocol and supports Vaisala RS41 and Meteomodem M20 sondes, with the type detected automatically, so you only need to enter the frequency and start decoding. As it is designed for radiosonde hunters, it skips PTU (pressure, temperature and humidity) data and focuses on position, altitude, speed, climb rate and heading. A 'Geo App' button passes the sonde's coordinates to your map app as a marker.

The decoder runs via the 'SDR driver' app by Signalware and was tested with our RTL-SDR Blog V3 and V4. The code is open source under the GPL-3.0 licence and available on GitHub, with the APK in the Releases section. Since the app runs as a background service, Android's battery optimization settings may need adjusting for it.

RS41 and M20 Android Decoder Screenshot
RS41 and M20 Android Decoder Screenshot

AI Disclaimer: The project README notes that parts of the code were written with the help of an AI assistant and reviewed by the author.

Backtrail Pro: An Open-Source App for Discontinued goTenna Mesh Radios and Meshtastic

Thank you to Patrick Gartner for writing in and sharing Backtrail Pro, a new iOS and Android app that brings discontinued goTenna Mesh radios back into use and also supports Meshtastic. The goTenna Mesh is a pocket-sized 1 W radio for the 902 - 928 MHz ISM band that pairs with a phone over Bluetooth for mesh texting without cell service.

The company behind goTenna Mesh has since shifted focus to military and public safety customers with its goTenna Pro line. In 2024, the security researchers who disclosed a series of goTenna vulnerabilities noted that goTenna discontinued support for the goTenna v1 and Mesh and exited the civilian market, around the same time CISA published its advisories on the Pro line. The consumer app has since disappeared, and goTenna was acquired by defense autonomy company Forterra in October 2025, leaving many owners with working radios and no app. With no vendor support, it's also unlikely that the Mesh's disclosed vulnerabilities, such as spoofed message injection with an SDR, will ever be patched.

Backtrail Pro talks to the goTenna Mesh through an independent implementation of its Bluetooth protocol, building on earlier community reverse engineering work. It supports group and direct messages, delivery receipts, location sharing, and optional AES-256 encryption. For Meshtastic radios, it lists every node heard and can change basic radio settings. The goTenna Mesh uses FSK rather than LoRa, so the two radio types can't talk to each other directly. However, with one of each connected to the phone, an optional relay can re-send group messages between the goTenna group and the Meshtastic mesh. The app costs US$0.99 on the Google Play Store and Apple App Store with no account or servers, and the code is open-source under GPL-3.0 and available on GitHub.

Backtrail Pro App for GoTenna Mesh Radios
Backtrail Pro App for GoTenna Mesh Radios

AI Disclaimer: The Backtrail commit on GitHub lists Claude as a co-author.

Frugal Radio: Testing the Discovery Dish on Inmarsat AERO with JAERO and InmarScope

Over on YouTube, Rob from the 'Frugal Radio' channel has uploaded part one of a review of our Discovery Dish, which we sent over for testing. Rob used the Inmarsat L-band feed with an RTL-SDR Blog V4, SDR++ and JAERO to receive AERO signals from the 98W satellite, which sits at about 27 degrees elevation from Rob's location in central Alberta.

Rob notes that the 10500 bps channels, which carry most aviation traffic and are usually the hardest to decode, held a steady Eb/No (a signal-to-noise measure for digital signals) of 14-16 over several days of testing. For comparison, Rob's previous best of 10 came from a grid dish designed for 1.7 GHz GOES reception, while our RTL-SDR Blog L-band patch antenna peaked at 8. Rob also shows the dish assembly, which took about 30 minutes.

Later in the video, Rob briefly tries out InmarScope, the multichannel Inmarsat decoder from Sarah Rose that we posted about previously. It decoded every 600, 1200 and 10500 bps AERO channel at once and automatically followed a voice call when one was assigned. Part two will cover maritime EGC, GOES reception, or more InmarScope, depending on viewer feedback.

Discovery Dish Review Pt 1 : High Gain Inmarsat AERO reception with SDR++, JAERO & Inmarscope