Tempo v0.2.0 — IR-HARQ + DX1 full-band (beta)

Tempo v0.2.0 — a beta release. This adds the two flagship modem capabilities and lands the
session's app work. It is simulation- and Windows-cross-build-validated, but not yet on-air
validated — see Status below.

✨ What's new

IR-HARQ — adaptive retransmission combining (now live, on by default)

FT1's signature feature, previously dormant, is finished end-to-end. A frame that fails to decode
on its own (RV0) is recovered by joint-turbo-combining its retransmissions (RV0→RV1→RV2 — each
with distinct Costas sync + punctured LDPC parity). The QSO sequencer drives it automatically
(escalate on implicit NAK, reset on implicit ACK).

• Measured: combiner +1.3 dB (AWGN, 3-TX) / +3.2 dB (1 Hz/1 ms fading); through the full
  live pipeline, ≈ +2.5 dB threshold shift and ~2× QSO completion in the −11…−13 dB zone.
• Reliable RV detection (coherent CPM-Costas discriminator): >99% accurate, <1% false to −11 dB.
• UI: HARQ·RVn decode badge, a HARQ on/off toggle (default on, for A/B), and a session rescue counter.

DX1 full-passband acquisition

The DX1 robust tier now decodes every signal across 200–2900 Hz in one slot (like FT1's Costas
search) instead of only the carrier under the green marker. rx_offset_hz becomes a waterfall
marker / TX-pairing hint. Internally a three-stage scan — coarse chirp-correlation carrier sweep
(12.5 Hz grid, pre-folded replicas) → median-threshold peak-pick → full CRC-gated decode per
survivor — running ~3–4 s/slot (vs ~19 min for a naive sweep on Windows; the design's
trig-free hot loop is what makes it tractable on the target).

Also in this release

• Coordinated QSY (announced, Part-97-legal channel moves), passive-launch fix, composer level
  meter, FT8/FT4 tier honesty (the unfinished tier no longer mis-advertises), FT1 docs.
• .wav replay path — turn a captured slot into a deterministic regression fixture.

✅ Validation

• FT1 AWGN 50% ≈ −15 dB; DX1 AWGN 50% ≈ −18.6 dB with a ~3.7 dB fading penalty.
• Live IR-HARQ: +2.5 dB / ~2× completion in the marginal zone.
• Cross-built and smoke-tested on Windows — all 5 modem exes pass (FT1 −15 dB, DX1 −18 dB,
  the 3-signal full-band scan, FT1 acquisition + IR-HARQ rv through the C-ABI), plus tempo.exe
  and the installer build clean.
• The full headless Rust suite is green; clippy clean; UI builds clean.

⚠️ Status — this is a beta

Everything above is proven in simulation + on the Windows cross-build. The open gate is real
RF: on-air decode-rate-vs-SNR has not been measured. If you run it on the air, please share
reports in Discussions — that's the feedback the
project most needs.

📦 Install (Windows x64)

1. Download Tempo_0.2.0_x64-setup.exe and run it. The installer bundles the offline WebView2
   runtime + Hamlib (rigctld), so CAT works with no separate install.
2. Optional: win_smoke.exe — a fully-static modem self-test (FT1 + DX1 round-trip; runs
   anywhere, no install). dx1_band_test_standalone.exe demonstrates the new full-band scan
   (3 signals decoded in one slot).

Tempo v0.1.0 (beta)

Tempo is a modern, chat-first HF/VHF/UHF text-messaging app for the off-grid /
preparedness ham community — fast conversational two-way text, fading-resilient
reach, presence, store-and-forward, a one-click ARRL Field Day exchange, and
WSJT-X-familiar operating controls + a logbook.

⚠️ Beta — read this. Initial pre-release, updated in place as the build
improves. The FT1 and DX1 waveforms are validated by simulation (AWGN +
fading), not yet on the air. The Windows binary is cross-compiled and
pending real-world validation. Operate within your license privileges.

Try it without installing

▶ Live demo — kd9taw.github.io/tempo runs the
real UI in your browser on simulated data (no radio, no install). Click through
Chat / QSO / Field Day, flip the Fast/Robust tier and the themes.

Download

Tempo_0.1.0_x64-setup.exe — Windows x64 installer (~199 MB).

• Installs per-user (no admin prompt).
• Bundles the WebView2 runtime offline → clean install on an air-gapped PC.
• Bundles Hamlib (rigctld) → CAT rig control with zero extra installs (a verified 56-rig dropdown).

SHA-256: d7d951a4404ac080c888a5ba333b3c399e318d84e66b45ada7945094271abc5f

Get-FileHash .\Tempo_0.1.0_x64-setup.exe -Algorithm SHA256   # verify after download

First run

1. Run the installer, then launch Tempo.
2. Settings → callsign/grid; rig (CAT model + COM port, or VOX/serial);
   pick your audio input/output device and set the Tx power so the RX
   meter sits mid-scale (not clipping). Pick a band or type a frequency.
3. It starts passive (hunt-and-pounce) — it listens; it does not auto-call CQ.

Full walkthrough: Getting Started.

What's in this build

• Two weak-signal tiers: FT1 (fast, coherent) and DX1 (robust,
  non-coherent, fading-resilient) — operator-visible toggle.
• Tempo frequency plan (HF + VHF/UHF): US-General-legal, CW-clear calling
  frequencies off the FT8/FT4/JS8 watering holes; one-tap band selector + manual
  entry. See docs/FREQUENCIES.md.
• WSJT-X-familiar operating controls: RX level meter, Tx power,
  audio-device selection; Tune / Monitor / Stop-TX; time-sync
  health + a Tx watchdog.
• Work a station + ADIF logbook: click a heard station (or decode) to start a
  directed QSO; a persistent logbook auto-logs contacts and shows worked-before
  (B4); inbound WSJT-X Reply (GridTracker/JTAlert double-click) drives Tempo.
• Live decode feed + alerts: color-coded decode list (CQ / calling-you /
  worked / new) and audio+visual alerts on your call / CQ / new station.
• Comforts: UTC clock, great-circle bearing, editable quick-reply macros,
  three field themes, a prominent waterfall.
• Chat / QSO / Field Day modes; store-and-forward; open broadcast; ADIF/Cabrillo
  export; WSJT-X-compatible UDP API + PSK Reporter.

Documentation

• Operator manual — the complete guide
  (Getting Started, Operating Guide, Rig & Audio Setup, Frequency Plan, Tiers,
  Building, FAQ, Troubleshooting).
• README · Discussions for on-air reports.

Known limitations

• On-air decode-rate-vs-SNR validation is pending (the next gate).
• The FT8/FT4 tier is Phase 2 (internals exist in libft1; decode not wired).
• DX1 receive currently decodes at the calling carrier (no full-band search yet).
• Frequencies are proposed, editable defaults — override any dial manually;
  VHF/UHF FM channels are band-plan segments, confirm with your local coordinator.
• The installer is unsigned (cross-compiled on Linux); SmartScreen may warn —
  More info → Run anyway.

GPL-3.0-or-later · Seth McCallister (KD9TAW) · kd9taw@protonmail.com