SSTV modes explained: Martin, Scottie, Robot & PD
Every SSTV mode trades airtime against resolution and robustness. This is the full set Open Signal transmits and receives — with the resolution, airtime and colour format of each — plus which family to reach for and when.
SSTV mode reference table
| Mode | Family | Resolution | Airtime | Colour | When to use |
|---|---|---|---|---|---|
| Robot 36 | Robot | 320×240 | 36 s | YCrCb | Fastest colour mode — the ISS SSTV events use it. |
| Robot 72 | Robot | 320×240 | 1m 12s | YCrCb | More detail than Robot 36 for double the airtime. |
| Martin M1 | Martin | 320×256 | 1m 54s | RGB | The European colour standard; 16 px of banner room. |
| Martin M2 | Martin | 320×256 | 58 s | RGB | Half the airtime of M1 for lighter conditions. |
| Martin M3 | Martin | 320×128 | 57 s | RGB | Half-height M1 — 128 lines at full line rate; rarely heard today. |
| Martin M4 | Martin | 320×128 | 29 s | RGB | The fastest Martin — half-height at M2's line rate. |
| Scottie S1 | Scottie | 320×256 | 1m 50s | RGB | The classic North-American colour mode. |
| Scottie S2 | Scottie | 320×256 | 1m 11s | RGB | Faster Scottie for busier bands. |
| Scottie DX | Scottie | 320×256 | 4m 29s | RGB | Long, robust mode for weak DX paths. |
| Wraase SC2-180 | Wraase | 320×256 | 3m | RGB | High-quality colour, popular for pictorial work. |
| PD50 | PD | 320×256 | 50 s | YCrCb | Fast PD mode — two lines per sweep, shared chroma. |
| PD90 | PD | 320×256 | 1m 30s | YCrCb | The most-used PD mode; a good detail/time balance. |
| PD120 | PD | 640×496 | 2m 6s | YCrCb | High resolution at a moderate airtime. |
| PD160 | PD | 512×400 | 2m 41s | YCrCb | Wide-frame high resolution. |
| PD180 | PD | 640×496 | 3m 7s | YCrCb | Full-resolution PD for good conditions. |
| PD240 | PD | 640×496 | 4m 8s | YCrCb | Maximum-detail PD; long airtime. |
| PD290 | PD | 800×616 | 4m 49s | YCrCb | The largest SSTV frame Open Signal sends. |
Airtimes are each mode's published-spec transmission time — the value Open Signal shows on every mode chip before you press Transmit. The table lists the most-used modes; Open Signal also carries the remaining Scottie, Robot colour/B/W, Wraase and MP/MR variants — six families in all.
The six SSTV families
Robot
The oldest colour family and still the fastest. Robot 36 sends a colour picture in 36 seconds and is the mode the ISS uses for its SSTV events, so it is the one beginners decode first.
Martin
Developed by Martin Emmerson (G3OQD) and the European colour standard. Martin M1 is the reference; the 256-line frame leaves 16 pixels of banner room for a callsign.
Scottie
Developed by Eddie Murphy (GM3BSC) and popular in North America. Scottie S1 is the classic; Scottie DX is a long, robust mode built for weak DX paths.
Wraase
Wraase SC2-180 is a high-quality colour mode favoured for pictorial work where the extra airtime buys visibly cleaner images.
PD
The high-resolution family. PD modes carry two lines per sweep with pair-averaged chroma, reaching up to 800×616 (PD290). PD120 is a favourite balance of detail and airtime.
MP / MR
MMSSTV's native narrow modes — MP73–175 and MR73–175. Open Signal transmits and receives them like any other family, so you can work MMSSTV operators in their home modes.
Which SSTV mode should I use?
A quick rule of thumb: match the mode to the band and the goal. On a busy or noisy band, a faster mode (Robot 36, Scottie S2, PD50) gets the picture through before conditions change. For a showcase image on a good path, a high-resolution mode (PD180, PD290, Wraase SC2-180) rewards the extra airtime. For weak DX, Scottie DX is built to survive the trip.
And when the other station also runs Open Signal, you can skip analog SSTV entirely: the Open Signal digital picture mode is error-corrected and arrives pixel-exact, and the photo-file mode delivers the real image byte-for-byte.
For the hands-on side — picking a family tab, the transmit countdown, and what receiving looks like — see using SSTV modes in Open Signal in the docs.
SSTV modes — questions
What is the fastest SSTV mode?
Robot 36 is the fastest common colour SSTV mode, sending a 320×240 picture in about 36 seconds. It is the mode used for the ISS SSTV events, which is why it is so widely decoded.
Which SSTV mode gives the best quality?
For analog SSTV, the high-resolution PD modes (up to PD290 at 800×616) and Wraase SC2-180 give the most detail, at the cost of longer airtime. For the best quality per second overall, Open Signal's own error-corrected digital picture mode beats analog SSTV — a 320×240 colour picture in under a minute, arriving pixel-exact.
How does Open Signal know which SSTV mode is arriving?
Every SSTV transmission begins with a VIS (Vertical Interval Signalling) header that identifies the mode. Open Signal reads it, announces the mode, switches to it if needed, and decodes the picture — no manual selection required.
More about Open Signal
Put any of these modes on the air
Open Signal transmits and receives every mode in the table above, and detects the incoming one automatically. Enter your callsign and pick a chip.