DRM Mode B
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 B
Time- and frequency-selective channels with longer delay spread.
General HF/MF robustness mode when fading and moderate multipath are expected.
OFDM timing
| Parameter | Value |
|---|---|
| Useful symbol duration Tu | 21.3333 ms |
| Guard duration Tg | 5.3333 ms |
| Total symbol duration Ts | 26.6667 ms |
| Guard ratio Tg/Tu | 1/4 |
| Carrier spacing | 46.88 Hz |
| Transmission frame | 15 symbols / 400 ms |
| Nominal channel widths | 4.5, 5, 9, 10, 18, 20 kHz |
Longer guard interval than A improves delay-spread tolerance, with lower service capacity.
Carrier ranges
| Occupancy | Bandwidth | Kmin | Kmax | Unused indices | Occupied positions |
|---|---|---|---|---|---|
| 0 | 4.5 kHz | 1 | 91 | none | 91 |
| 1 | 5 kHz | 1 | 103 | none | 103 |
| 2 | 9 kHz | -91 | 91 | 0 | 182 |
| 3 | 10 kHz | -103 | 103 | 0 | 206 |
| 4 | 18 kHz | -87 | 279 | 0 | 366 |
| 5 | 20 kHz | -99 | 311 | 0 | 410 |
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.