SimpleSSTV vs PhosphorSSTV

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 • Perfect for portable operation, field day, and unattended stations 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 • Progressive line-by-line image preview during decode • 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 • Optional decode watermark stamps mode, timestamp, and callsign on received images • 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!

PhosphorSSTV decodes Slow Scan Television (SSTV) signals in real time using your iPhone's microphone. SSTV has been the amateur radio image transmission mode since the 1960s. From cold-war era picture transmissions to International Space Station passes, SSTV encodes images as audio tones between 1200–2300Hz. Each scanline is a sweep through frequency space, painting pictures one line at a time across the HF bands. Hold your phone near a shortwave radio tuned to an SSTV signal — or play a recording — and watch the image build scanline by scanline on an authentic phosphor CRT display, just like the original SSTV monitors. No internet connection required. No external hardware. No account. Just your iPhone and a radio. TEN SSTV MODES • Scottie S1, S2, DX — the most widely used SSTV modes on HF worldwide • Martin M1, M2 — popular across European SSTV activity • Robot 36, 72 — YCbCr colour modes, used by the ISS during special events • Robot 8, 12, 24 BW — fast greyscale modes for text, diagrams, and low-bandwidth conditions REAL-TIME DECODING • Progressive scanline rendering — the image builds top to bottom, just like a real SSTV monitor • VIS code detection automatically identifies the transmission mode • Sync-aligned slant correction eliminates timing drift for straight, clean images • Hilbert transform FM discriminator for accurate frequency-to-pixel conversion SIGNAL ANALYSIS • Live FFT spectrum display shows the full 0–4 kHz audio band • Scrolling waterfall reveals the SSTV signal structure in real time • SSTV band markers at 1200 Hz (sync), 1500 Hz (black), and 2300 Hz (white) • Input gain control from 0.1× to 20× IMAGE LOG • Decoded images saved automatically with thumbnails • Full metadata: mode, timestamp, duration, VIS detection status • View full-size, share, or delete • Swipe to delete, tap to view detail AUTHENTIC CRT AESTHETIC • Green and amber phosphor display themes • Scanline overlay, vignette, and glow effects • Monospaced terminal typography throughout • The same retro aesthetic as our PhosphorRTTY and PhosphorCW apps WHERE TO FIND SSTV • 20m band: 14.230 MHz USB — primary worldwide SSTV frequency • 80m band: 3.845 MHz LSB • 40m band: 7.171 MHz LSB • ISS: 145.800 MHz FM during special SSTV events • Or search YouTube/archive.org for SSTV audio recordings to decode PRIVACY PhosphorSSTV makes zero network requests. No accounts, no tracking, no analytics, no ads. Microphone audio is processed entirely on-device and is never recorded or transmitted. See our full privacy policy on our support page. ABOUT SSTV Slow Scan Television was developed in the late 1950s as a way to transmit still images over voice-bandwidth radio channels. Unlike fast-scan television (broadcast TV), SSTV takes seconds to minutes per image, encoding pixel brightness as audio frequency. The 1200 Hz sync pulse marks each line boundary, black is 1500 Hz, and white is 2300 Hz. Every pixel in between is a precise frequency in that range. Amateur radio operators worldwide still use SSTV daily on the HF bands, and the International Space Station periodically transmits commemorative images that can be received with nothing more than a handheld radio.