PhosphorTEX

PhosphorTEX is a real-time NAVTEX maritime-safety decoder for iPhone.

Tune a shortwave receiver to 518 kHz, 490 kHz, or 4209.5 kHz, hold your iPhone near the speaker, and watch navigational warnings, gale warnings, ice reports, and other maritime safety information scroll across an authentic amber phosphor CRT display.

NAVTEX (Navigational Telex) is broadcast worldwide under the IMO Global Maritime Distress and Safety System (GMDSS). Every coast, mariners and ship's radio officers depend on it for up-to-the-minute storm warnings, search-and-rescue notices, navigational hazards, and coastal traffic advisories. PhosphorTEX brings that same live maritime feed to your iPhone — offline, on-device, no account, no network.

SIGNAL PROCESSING

PhosphorTEX implements the full CCIR-476 SITOR-B protocol stack in Swift with purpose-written DSP.

• Synchronous 7-bit framer with DPLL clock recovery
• Time-diversity FEC: alpha / rep pair-merge per CCIR-476 spec
• Shift-until-valid phase search with sentinel-aligned alpha / rep routing — locks to the correct character boundary automatically
• Polarity auto-detection — works with maritime-receiver tuning (mark ~1615 Hz) and SDR tuning (mark ~1085 Hz) equally, no toggles
• Automatic frequency control with sub-bin parabolic peak interpolation and ±3 Hz/frame centre-tracking clamp
• 170 Hz shift locked to spec (±85 Hz around centre)
• Live 512-point FFT spectrum and scrolling waterfall display

DECODE VIEWS

• CARDS — parsed NAVTEX messages as colour-coded cards: station letter, subject badge (SAR/piracy, nav warning, met warning, ice report, met forecast…), serial number, timestamp, FEC quality badge, full body text
• TAPE — raw teleprinter character stream, for purists

NAVAREA SCHEDULE

Built-in database of 42 NAVAREA coast stations across NAVAREA I through XVIII (Cullercoats, Niton, Rogaland, Oostende, Reykjavik, Mondolfo, Las Palmas, Horta, and more). The SCHEDULE tab shows a live 24-slot grid with the current 10-minute broadcast slot highlighted in real time against a ticking UTC clock.

MESSAGE LOG

Every decoded message is logged locally with timestamp, header, body, and FEC statistics. Swipe to delete. Tap for full view. Export the whole log as plain text via iOS share sheet.

CONFIGURATION

• Two phosphor themes: classic amber and green
• Three font sizes for the decoded output
• AFC on/off with manual mark frequency override for unusual receivers
• Invert mark/space for LSB-convention receivers
• Per-subject mute list (urgent D-category SAR/piracy messages always override)
• Alert toggles for SAR/piracy and vital (serial-00) messages

PRIVACY

PhosphorTEX makes zero network requests. No account, no cloud, no analytics, no tracking, no third-party SDKs. Audio is processed entirely in memory — nothing is recorded, stored, or transmitted. Microphone access is used only for live signal decoding.

WHAT YOU NEED

An iPhone and a shortwave receiver tuned to NAVTEX — 518 kHz for international English, 490 kHz f