SSTV.org.uk

Wraase mode

Wraase SC2 120

Wraase 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, 124.052 s.

SC2-120 SSTV BBC-style colour test card
SC2-120 test card, 320 x 256

Mode spec

Short nameSC2-120
Support statusSupported in app
Spec statusSupported in app; public line-level timing was not found in checked sources, so app timing fields are labeled separately.
Duration121.743 s
Frame320 x 256
Data lines256
Public VISVIS 63 (0x3F)
Standard VIS code0x3F (63)
Extended/N-VISNo
Color modelRGB
Component sequenceR-G-B
Line rate126.168 lpm
Public timing profileNo implementation-grade public line timing was found in checked sources; app implementation fields are listed separately.
App duration121.743 s
App frame320 x 256
App raw VIS0x3F (63)
App timing profileApp RX line fields: sync 5 ms; front porch 1 ms; back porch 1 ms; separator/blank 1 ms; video tones 1500-2300 Hz around 1900 Hz.
App RX sync5 ms
App RX front porch1 ms
App RX back porch1 ms
App RX separator/blank1 ms
App subcarrier1900 Hz
App deviation400 Hz
App tone range1500-2300 Hz

Strengths

  • SC2-120 is a standard-length standard colour Wraase mode: 121.743 s, 320 x 256, RGB.
  • SC2-120 uses R-G-B RGB component order and VIS 63 (0x3F), giving receivers enough mode identity to separate it from neighbouring Wraase rows.
  • SC2-120 has explicit app timing fields: 5 ms sync, 1 ms front porch, 1 ms back porch, 1 ms separator/blank, and 1500-2300 Hz around 1900 Hz video tones.
  • SC2-120 is documented from the app timing row; the line fields are explicit even where checked public sources do not publish every porch value.

Tradeoffs

  • SC2-120's 121.743 s frame is a balanced choice, but it still needs a stable path for the full 320 x 256 scan.
  • SC2-120 sends colour sequentially in RGB; sync drift can appear as colour fringing before the whole frame becomes unreadable.

Source notes

Public VIS/timing labels are normalized from checked SSTV references where available. App raw VIS 0x3F and app timing fields are generated from sstv/sstv/sstv/sstvparam.swift during the website build.