SimpleSSTV vs PhosphorTEX

SimpleSSTV is a native iOS app for encoding, decoding, and live-transmitting slow-scan television (SSTV) signals — the method ham radio operators use to share images over audio frequencies. Slow-scan television converts images to audio tones. Each pixel's brightness becomes a specific frequency between 1500-2300 Hz. Sync pulses at 1200 Hz mark line boundaries. The result is an audio signal you can transmit over any voice-capable radio, or record for later playback. SSTV has been used by amateur radio operators since the 1950s. It's still actively used today on HF bands, VHF repeaters, and for receiving images from the International Space Station. ENCODING (Image → Audio) • Load any image from your photo library, camera, or Files • Automatic resize and crop to SSTV resolution • 21 supported modes covering all major SSTV formats • Real-time encoding with progress visualization • Play audio directly through speakers for VOX-triggered transmission • Export to WAV or M4A for later use • Optional FSK ID and CW ID (Morse code) callsign transmission • Test pattern generator for signal testing LIVE CAMERA MODE • Real-time camera feed with front/back camera switching • Three trigger modes: Continuous, Motion-triggered, or Periodic interval • Adjustable motion sensitivity with adaptive background model • Captures and encodes directly from camera to audio • Keep the app in the foreground while listening or transmitting DECODING (Audio → Image) • Load WAV, M4A, or MP3 audio files containing SSTV signals • Live microphone capture for real-time SSTV reception • Automatic mode detection via VIS code identification • Capture a transmission, then process it to see the decoded image • FSK callsign detection from received signals • Precision audio trimming with dual-view waveform editor • Re-decode saved images with different mode, sync offset, or slant correction • Handles real-world signal imperfections: timing drift, noise, sample rate variations • Decode watermark with an automatic stamp or custom Pro text • Waterfall spectrogram display shows signal frequency over time SUPPORTED MODES (21 total) • Martin M1, M2, M3, M4 • Scottie S1, S2, S3, S4, DX, DX2 • Robot 36, Robot 72, Robot BW8 • PD50, PD90, PD120, PD160, PD180, PD240, PD290 • Wraase SC2-180 ISS SSTV EVENTS • Get notified when the International Space Station transmits SSTV images • Automatic alerts before and during events, with frequency, mode, and callsign info • Info card on the decode tab with event details and countdown FAQ & SETUP TIPS • Practical advice on audio setup and USB adapters • Decode quality troubleshooting • Quick reference for all 21 SSTV modes IMAGE LIBRARY • Automatic saving of encoded and decoded images • Grid view with full preview, metadata, and sharing • Re-decode any saved image with different settings • Filter by encoded or decoded 10 LANGUAGES Available in Arabic, Chinese (Simplified), Dutch, English, French, German, Polish, Portuguese (BR), Spanish, and Turkish — with full right-to-left support. PRIVACY No accounts, no analytics, no tracking. Your images and audio stay on your device. Free to encode and decode. Optional one-time Pro purchase unlocks watermark customization and Listening Station Mode. We do not use, sell or share your data for advertising or marketing purposes. Be aware: Encoded images are audio signals — anyone receiving the audio can decode them! REQUIREMENTS • iOS 17.6 or later • Camera access for live mode • Microphone access for live decode Built by a ham radio operator for ham radio operators. 73!

PhosphorTEX decodes NAVTEX maritime safety broadcasts in real time on your iPhone or iPad. Tune a receiver to 518 kHz, 490 kHz or 4209.5 kHz, hold your device near the speaker, and watch navigational warnings, gale warnings, ice reports and search-and-rescue notices arrive on an authentic phosphor CRT display. No internet connection required. No account. Nothing leaves the device. WHAT NAVTEX IS NAVTEX (Navigational Telex) is the worldwide maritime safety broadcast of the IMO's Global Maritime Distress and Safety System (GMDSS). Coast stations send storm warnings, navigational hazards, search-and-rescue notices and weather forecasts to ships at sea, each station in its own ten-minute slot. PhosphorTEX puts that live feed on your screen. SIGNAL PROCESSING PhosphorTEX decodes CCIR 476 SITOR-B entirely on the device, with signal processing written for the app: Synchronous 7-bit decoding with phase-locked clock recovery Automatic character alignment that finds the character boundary on its own Automatic polarity detection, so maritime receivers and SDR tuning both work with no toggles Automatic frequency control that finds and tracks the 170 Hz tone pair anywhere from 800 to 2500 Hz Every character checked against the NAVTEX error code, with errors shown rather than guessed Error statistics for every message, measured against the second copy NAVTEX sends of each character Live 512-point FFT spectrum and scrolling waterfall FIVE TABS DECODE: every message as a colour-coded card, with the station letter, subject, serial number, UTC time, a signal quality badge and the full text. Switch to TAPE for the raw teleprinter stream. SIGNAL: FFT spectrum with mark and space cursors, a scrolling waterfall, mark and space tone bars, and an FEC HEALTH panel showing how cleanly each character arrived. SCHEDULE: a built-in database of 43 NAVTEX coast stations across thirteen NAVAREAs, from Cullercoats, Niton and Malin Head to Reykjavik, Las Palmas, Singapore and Valparaíso. A live grid shows which stations transmit in the current ten-minute slot against a running UTC clock. LOG: every decoded message kept on the device, with its header, time, full text and error statistics. Copy, share or delete a message, or export them all as text. CONFIG: amber or green phosphor, three text sizes, automatic or manual tuning, mark and space inversion, alert colours for search-and-rescue and vital messages, and a mute list for subjects you do not want on the cards. Search-and-rescue messages can never be muted. IPHONE AND IPAD On iPad PhosphorTEX runs natively in every orientation, with larger type and the cards, spectrum, waterfall and station schedule opened out across the full width of the screen. PRIVACY PhosphorTEX makes no network requests. No account, no cloud, no analytics, no tracking, no third-party code. Audio is processed in memory as it arrives and is never recorded, stored or sent anywhere. The microphone is used only while decoding. WHERE TO FIND NAVTEX 518 kHz carries the international service in English, 490 kHz carries national services in local languages, and 4209.5 kHz carries the tropical HF service. Any receiver that covers these frequencies with SSB will do, and so will WebSDR audio played through a speaker. REQUIREMENTS iPhone or iPad with a microphone iOS or iPadOS 26.4 or later A receiver tuned to a NAVTEX frequency, or WebSDR audio played through a speaker No in-app purchases. No subscriptions. No tracking. No network access. PhosphorTEX is part of the Phosphor range of retro-CRT radio tools, alongside PhosphorRTTY, PhosphorCW, PhosphorFeld and PhosphorSSTV.