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Digital image receive

DRM digital SSTV receiving: confirm the signal before the image.

Analog SSTV turns audio tones directly into image lines. DRM-derived digital SSTV is different: the first job is to lock the digital signal, then reconstruct the advertised file or image object.

Open the DRM A-E tablesRead the algorithm notes

Station checklist

  1. Record the audio first: keep a clean WAV or IQ capture before changing decoder settings. A marginal DRM receive can improve on replay when frequency offset and levels are corrected.
  2. Identify the exact profile: write down whether the signal is broadcast DRM30/DRM+, HamDRM, EasyPal, or another DRM-derived digital SSTV profile. Similar names do not guarantee compatible settings.
  3. Log the DRM signal: robustness mode, bandwidth or spectrum occupancy, FAC lock, SDC decode, MSC constellation, and protection level are part of the picture evidence.
  4. Reassemble the application: for slideshow or file-style payloads, watch object names, segment repeats, missing data units, and whether a later carousel pass fills the gaps.
  5. Archive the image with the route: save the final image next to the recording, decoder log, mode settings, UTC time, frequency, and station notes.

What to write in the log

RF facts

Frequency, sideband, audio bandwidth, SNR, drift, receiver, antenna, and whether you used direct audio, microphone audio, or SDR replay.

DRM facts

Mode A/B/C/D/E where known, spectrum occupancy, FAC stability, SDC success, MSC constellation, and reported decoder corrections or failures.

Image facts

Application type, file name, object count, repeats completed, final image dimensions, corruption pattern, and whether another listener can merge missing parts.

Why the order matters

With DRM, a poor image may be caused by lost OFDM sync, a failed FAC, an unreadable SDC, bad MSC coding recovery, an incomplete file carousel, or a normal image decoder problem. Calling every failure an "image problem" hides the clue that would fix the next receive.

The practical rule is simple: confirm the DRM signal before judging the picture. A partial file with a strong FAC history is a very different result from a recording that never found the COFDM grid.