Do not guess from the image alone
The visible result hides the transport. A beautiful picture can arrive through a fragile path, and a broken picture may still contain good diagnostic evidence.
Mode comparison
DRM, SSDV, and analog SSTV: three ways to move pictures by radio.
The names often meet in the same station log, but they solve different problems. Analog SSTV paints lines. SSDV packetises JPEG scan data. DRM provides a COFDM digital radio signal layer that can carry audio and data.
Comparison table
| Question | Analog SSTV | SSDV | DRM / HamDRM-style digital SSTV |
|---|---|---|---|
| What is being sent? | Timed audio tones for sync, luminance, and colour components. | Fixed-size packets carrying abbreviated JPEG scan data and metadata. | A DRM-derived digital signal carrying service data, files, or slideshow-style objects. |
| Main technical contract | VIS, line timing, component order, tone frequencies, and frame raster. | Packet type, callsign, image ID, packet ID, MCU offsets, CRC32, and optional Reed-Solomon FEC. | Robustness mode A-E, bandwidth, FAC/SDC/MSC, constellation, code rate, interleaving, and application data. |
| Typical failure | Slant, sync tearing, wrong colour order, noise lines, or mode mis-detection. | Bad CRC, uncorrectable FEC, missing packet IDs, incomplete MCU blocks. | No FAC lock, missing SDC, MSC decode failure, incomplete carousel or file object. |
| What should be archived? | Audio WAV, decoded image, mode, slant correction, UTC, frequency, station setup. | Raw audio/IQ, packet file, decode log, correction counts, JPEG output. | Audio/IQ, DRM decoder log, robustness mode, service description, object files, final image. |
| Why it belongs here | This is the core SSTV reference library. | SSDV appears in satellite and balloon image experiments beside SSTV practice. | DRM-derived tools such as EasyPal are part of digital SSTV operating culture, especially for file-based image exchange. |
Station notes
Use the right first question
Analog SSTV asks "which line timing?" SSDV asks "which packets?" DRM asks "did the DRM signal and service decode?"
Keep the boundaries explicit
Putting all three on one site helps receiving practice, but the mode tables should not pretend that packet or COFDM systems are analog SSTV modes.