Tempo

Tempo is a modern, chat-first HF text-messaging app for the off-grid and preparedness ham community — off-grid HF text at the speed of conversation. It looks and feels like a messaging app — presence, a live decode feed, a real conversation thread — but it never hides the radio: SNR, offset, dT, band, tier, and T/R timing all stay first-class. A messenger on top, a real radio underneath.

Built in Rust + Tauri for a fast, native app with a tiny footprint, Tempo is free and open source (GPL-3.0), authored by KD9TAW — who also designed the FT1 and DX1 waveforms it runs on.

Why it exists

Weak-signal text got powerful, but it never got fast — or friendly. FT8 is a brilliant beacon, not a conversation. JS8Call brings real keyboard-to-keyboard chat, but rides the same 15-second frame structure, so a single back-and-forth can stretch past half a minute. And almost all of it is wrapped in interfaces that feel like test equipment. Tempo’s bet: weak-signal text should move at the speed of a conversation, and feel like an app you’d actually want to open.

Conversation, not a slideshow

Tempo’s fast tier runs a 4-second over — roughly 4× quicker turnaround than the 15-second cycle behind FT8 and JS8. A keyboard QSO that actually flows back and forth.

FT8 round trip   ~30 s
JS8 Normal         15 s
JS8 Fast           10 s
JS8 Turbo           6 s
Tempo (FT1)         4 s

Two tiers, one conversation

Under the messenger sit two purpose-built weak-signal waveforms and a one-tap toggle:

• FT1 (Fast) — a coherent 4-CPM mode on a 4-second cycle for keyboard QSOs that actually flow back and forth. It borrows cellular-network techniques — turbo equalization and IR-HARQ — to stay competitive at low signal levels.
• DX1 (Robust) — non-coherent 8-FSK on a 15-second cycle that rides through fading which collapses coherent modes (losing only ~3.7 dB under Rayleigh, in simulation).

Both carry the same standard 77-bit, WSJT-X-compatible messages, so Chat, auto-QSO, and Field Day work identically on either. The tier is never switched silently — the operator picks Fast or Robust, and the toggle stays visible.

What’s inside

• Chat-first, ham-aware UI — conversation threads, station presence, a modernized waterfall, and three field themes including a night-vision Amber.
• Live decode feed — color-coded by what matters (directed-to-you, B4, CQ, new) with one-tap Call / Work buttons.
• Three modes — Chat, QSO (Run / Search-&-Pounce auto-sequencer), and Field Day (native exchange, dupe-checked log, ADIF/Cabrillo export).
• Ecosystem interop — ADIF logbook, the WSJT-X UDP API (GridTracker/JTAlert), PSK Reporter spotting, and Hamlib rig control (56-model dropdown, bundled offline).
• Safe by default — starts passive (listen-only); the CQ beacon is opt-in, with a transmit watchdog as backstop.

Where it shines

• EMCOMM / nets — pass real, free-form text across regional and national paths when the grid (and the internet) is gone. Store-and-forward holds traffic for a station until it reappears.
• Ragchew / DX — the fast tier makes weak-signal keyboard QSOs feel like chatting; drop to the robust tier when the path gets ugly, without changing how you work.
• Field Day — a digital two-way that isn’t an FT8 beacon, with a native exchange and dupe-checked log — a natural fit for events (including Winter Field Day) that reward a genuine, confirmed two-way contact.

Status & testers

Tempo is feature-complete and runs on Windows today — a per-user build that bundles WebView2 and Hamlib offline, so there’s no admin rights or internet needed (macOS and Linux are next). The waveforms are validated in simulation, and the project is now recruiting operators with HF stations to put FT1 and DX1 on the air. If you’d like a weak-signal keyboard QSO to move at the speed of an actual conversation, grab the Windows build and help prove it — or read the FT1 protocol deep-dive → to see how it works.