DRM Mode A
The digital test-card JPEG carried in a DRM MOT image service.
48,000 samples/s · 1 channel · 24.00 s
Generated by the SSTV 2.0 pinned transmitter library; PCM16 WAV verified by its writer.
DRM specification · DRM30
DRM Mode A
Gaussian channels with minor fading.
Best capacity choice when the path is comparatively clean, such as stable local or regional MF/HF coverage.
OFDM timing
| Parameter | Value |
|---|---|
| Useful symbol duration Tu | 24 ms |
| Guard duration Tg | 2.6667 ms |
| Total symbol duration Ts | 26.6667 ms |
| Guard ratio Tg/Tu | 1/9 |
| Carrier spacing | 41.67 Hz |
| Transmission frame | 15 symbols / 400 ms |
| Nominal channel widths | 4.5, 5, 9, 10, 18, 20 kHz |
Small guard interval and narrow carrier spacing maximise useful rate, but give less margin for long multipath and Doppler than B/C/D.
Carrier ranges
| Occupancy | Bandwidth | Kmin | Kmax | Unused indices | Occupied positions |
|---|---|---|---|---|---|
| 0 | 4.5 kHz | 2 | 102 | none | 101 |
| 1 | 5 kHz | 2 | 114 | none | 113 |
| 2 | 9 kHz | -102 | 102 | 0 | 204 |
| 3 | 10 kHz | -114 | 114 | 0 | 228 |
| 4 | 18 kHz | -98 | 314 | 0 | 412 |
| 5 | 20 kHz | -110 | 350 | 0 | 460 |
2.0 input and image service
Select DRM Modes A-D. The reference waveform is 48 kHz mono real IF centred at 12 kHz, with 10 kHz spectrum occupancy. A conventional narrow voice filter can truncate this waveform; use a receiver or SDR path with enough bandwidth.
Synchronization identifies the waveform. FAC describes the multiplex; SDC describes services and stream allocation; MSC carries the application data. The image in this sample is an MOT object. FAC lock alone does not prove image recovery, and an audio-only broadcast may provide no image to display.
Lossless MOT image sample
The sample uses 64-QAM MSC, 4-QAM SDC and short interleaving at occupancy 3. The payload is a JPEG test card, not a recording of a broadcast station.