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📻 IU8LMC — Martino Merola
🏢 ARI Caserta — Santa Maria Capua Vetere, CE
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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
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