PhosphorTEX
NAVTEX Decoder
Only for iPhone
$0.99 · Designed for iPhone. Not verified for macOS.
iPhone
Live NAVTEX on your iPhone. Gale warnings, storm fronts, nav hazards. The sea's own teleprinter, rendered in a phosphor glow.
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 for national language broadcasts, or 4209.5 kHz for tropical HF. Most entry-level general-coverage receivers work. WebSDR audio played through a speaker works too.
PhosphorTEX is part of the Phosphor suite of retro-CRT radio tools: PhosphorRTTY (RTTY), PhosphorCW (Morse), PhosphorFeld (Hellschreiber), PhosphorSSTV (slow-scan TV), and more. Look out for bundles as new apps become available.
Built in Swift with Apple's native frameworks only. No external dependencies. Runs entirely on-device.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
The developer, Stuart Woolley, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Stuart Woolley
- Size
- 2.9 MB
- Category
- Utilities
- Compatibility
Requires iOS 26.4 or later.
- iPhone
Requires iOS 26.4 or later. - Mac
Requires macOS 26.4 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.4 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Stuart Woolley
