The fastest digital mode ever created for amateur radio. 3.8-second cycles, a full QSO in about six seconds, decoding down to −23 dB SNR — now an official ADIF submode.
| UTC | Station | Worked | Band | Country |
|---|
The ADIF Development Group voted to include FT2 as a certified submode in ADIF 3.1.7 — the highest participation in ADIF history.
The multi-decode engine was rewritten in C++ from the ground up. The result: more sensitivity, far lower latency, and a QSO completion rate that jumped from a third to nearly all.
| Aspect | Decodium 3.x | Decodium 4.0 |
|---|---|---|
| Decode passes / period | 5 / 750 ms | ~20 / 187 ms |
| FT2 auto-sequence | broken | 100% working |
| Infinite 73 loops | yes | eliminated |
| TX signal distortion | yes (buffer) | clean |
| Async collisions | frequent | −80% (±25 Hz) |
Shannon proved every noisy channel has a maximum capacity — and that codes approaching it must exist. FT2 gets within a few dB of that boundary for short HF blocks.
Channel limit: Eb/N₀ ≥ −1.59 dB. No code can do better.
Berrou — first practical proof Shannon was reachable. ~0.5 dB gap.
Rediscovered — belief propagation, no error floor, parallelizable.
LDPC(174,91) + scale 3.2 + RMS norm + 5 passes → −23 dB SNR.
FT2 uses the same core as FT8 and FT4 — 77-bit payload, LDPC(174,91), 4-GFSK — but compresses the transmission cycle to 3.8 seconds.
A complete QSO in about six seconds. Theoretical rate near 450 QSO per hour.
77-bit payload, LDPC(174,91), 4-GFSK. The protocol core is identical to FT8/FT4.
Verified 16 February 2026. 2,000+ active operators, 500,000+ QSOs logged.
Official submode SUBMODE=FT2. Unanimous 22:0 vote, 22 March 2026.
| Parameter | FT8 | FT4 | FT2 |
|---|---|---|---|
| T/R cycle | 15 s | 7.5 s | 3.8 s |
| Async TX duration | — | — | 2.47 s |
| Modulation | 8-GFSK | 4-GFSK | 4-GFSK |
| Bandwidth | 50 Hz | 83 Hz | 167 Hz |
| Payload | 77 bit | 77 bit | 77 bit |
| FEC | LDPC(174,91) | LDPC(174,91) | LDPC(174,91) |
| Sensitivity (Raptor) | −21 dB | −16.5 dB | −23 dB |
| Full QSO | ~60 s | ~30 s | ~6 s |
| QSO rate | ~60/h | ~120/h | ~450/h |
| ADIF submode | FT8 | FT4 | FT2 |
Complete C++ rewrite · Raptor Engine −23 dB SNR · ASYMX mode. Cross-platform builds for Windows x64, macOS Apple Silicon and Linux x86_64 (Qt 6.11). Always the latest release, straight from GitHub.
github.com/iu8lmc · latest
github.com/elisir80 · latest
Both mirrors always point to the newest release · Windows x64 installer · macOS Apple Silicon DMG/ZIP · Linux x86_64 AppImage
FT8, FT4 and FT2 decoded right on the phone — the same engine as the desktop Decodium — with real-time waterfall, QSO sequencer, CAT control and PTT. The audio comes from the PC connected to your radio through the free Decolink program: on your home WiFi, or from anywhere via the relay.
The complete FT8/FT4/FT2 decoder runs on the device, not on a server — the same engine as Decodium 4 for the computer.
Real-time waterfall and spectrum, portrait or landscape, QSO sequencer with the real protocol rules, NTP time sync, DX cluster and PSK Reporter.
Decolink on the PC feeds audio and CAT to the phone: over the home WiFi with no account, or through the relay from anywhere — even on mobile data.
No ads, no analytics, no tracking · interface in 15 languages
Decometer is Decodium's RF front panel on the phone: forward and reflected power, SWR, ALC, PEP, S-meter, final-stage telemetry — and a vector antenna analyser that works out resonance, bandwidth and reactance. Everything read from the radio through the PC, and nothing invented.
Part of Decodium Mobile · requires Decodium 4 on the PC
Power, match, drive, signal and the power amplifier: nine readings taken from the radio and eight more derived on board, on the same needle instrument as the desktop.
It gathers frequency and SWR pairs while you operate, or with a sweep that drives the radio, and returns resonance, bandwidth, reactance with its sign and the Smith chart.
When a meter is not available two dashes appear, and at rest the transmit meters stay quiet instead of reading a flattering zero.
The complete feature catalog in PDF — every digital mode, the decode engine, FT2 async, TX & sequencer, panadapter, FT2-Link, CAT, themes, logging and system. Fully localized.
7-page A4 catalog, Ocean Blue design — the fastest way to see everything DECODIUM 4.0 does at a glance.
Download PDF (IT)Official documentation for DECODIUM 4.0 “Shannon” — quick start, full user manual, and advanced reference. Available in PDF, HTML, DOCX and Markdown.
Install, configure and make the first QSO in five minutes. Covers Win/macOS/Linux, CAT setup, audio levels and the CALL feature.
Full operating guide — CAT/audio/PTT setup, FT8 workflow, FT2 protocol with DEEP/ASYMX/Quick QSO, CALL, DX Cluster, PSK Reporter and troubleshooting.
Concept, development and on-air testing. Creator of DECODIUM Fast Track 2.
SANTA MARIA CAPUA VETERE, CESalvatore Raccampo — C++ rewrite, macOS and Linux builds.
macOS / LINUX MAINTAINERFirst FT2 QSO in history — 40 m band, SNR −12 dB.
WORLD FIRST
