SSTV.org.uk

FAX mode

FAX480

FAX family analog SSTV operation and compatibility reference.

Supported in app

Mode sample

BBC-style colour test card and app-generated audio

The image is generated locally for this mode's raster. For supported modes, the audio sample is encoded from that image with the SSTV Signal Desk transmitter code, then published as lossless FLAC for static playback.

FLAC, 48 kHz, 16-bit mono, 139.235 s.

FAX480 SSTV BBC-style colour test card
FAX480 test card, 512 x 500

Mode spec

Short nameFAX480
Support statusSupported in app
Spec statusSupported in app; public VIS and timing summary are separated from the app raw timing fields.
Duration138 s public catalog; app table 133.633 s without the 5-second FAX header
Frame512 x 480 image (+20 phasing lines)
Data lines480 image lines + 20 phasing lines
Public VISNo Robot VIS in Dayton FAX480 timing; OK2MNM catalog lists VIS 85
Standard VIS codeNot applicable or not published in checked sources
Extended/N-VISNo
Color modelBW
Component sequenceY
Line rate224.495 lpm
Public timing profilePublic FAX480 timing: monochrome 512 x 480 radiofacsimile-style frame, 5-second FAX tone header, 20-line phasing interval, then 5.12 ms sync plus 512-pixel scan lines.
App duration133.633 s
App frame512 x 500
App raw VIS0x00 (0)
App timing profileApp RX line fields: sync 5.12 ms; front porch 0 ms; back porch 0 ms; separator/blank 0 ms; video tones 1500-2300 Hz around 1900 Hz.
App RX sync5.12 ms
App RX front porch0 ms
App RX back porch0 ms
App RX separator/blank0 ms
App subcarrier1900 Hz
App deviation400 Hz
App tone range1500-2300 Hz

Strengths

  • FAX480 is a standard-length high-detail FAX mode: 138 s public catalog; app table 133.633 s without the 5-second FAX header, 512 x 480 image (+20 phasing lines), BW.
  • FAX480 uses monochrome Y FAX-style scanning; the catalogue caveat is recorded as: No Robot VIS in Dayton FAX480 timing; OK2MNM catalog lists VIS 85. Timing and VIS identity stay separate.
  • FAX480 has explicit app timing fields: 5.12 ms sync, 0 ms front porch, 0 ms back porch, 0 ms separator/blank, and 1500-2300 Hz around 1900 Hz video tones.
  • FAX480 has a checked public timing summary plus app timing fields, so the public spec and implementation timing can be compared line by line.

Tradeoffs

  • FAX480's duration caveat matters: 138 s public catalog; app table 133.633 s without the 5-second FAX header. Keep that distinction visible when checking the full 512 x 480 image (+20 phasing lines) scan.
  • FAX480 has this VIS caveat: No Robot VIS in Dayton FAX480 timing; OK2MNM catalog lists VIS 85; receivers that require a normal Robot VIS announcement may need manual FAX-style setup.

Source notes

Public VIS/timing labels are normalized from checked SSTV references where available. App raw VIS 0x00 and app timing fields are generated from sstv/sstv/sstv/sstvparam.swift during the website build.