PD160 is a Slow Scan Television (SSTV) mode developed as part of the PD (Paul Turner/Don Rotier) series. It provides a balanced compromise between transmission time and image quality, sitting between PD120 and PD180 in terms of both duration and resolution.
| Property | Value |
|---|---|
| Mode Name | PD 160 |
| VIS Code | 98 |
| Resolution | 512 × 400 pixels |
| Color Encoding | Dual-luminance YUV |
| Transmission Time | ~160 seconds (~2 minutes 40 seconds) |
| Scan Lines | 200 (produces 400 pixel rows) |
| Rows per Scan | 2 rows per scan line |
| Scan Line Duration | ~804.416 ms |
| Pixel Dwell Time | 382 µs per pixel |
Each PD160 scan line contains the following timing structure:
| Component | Duration | Purpose |
|---|---|---|
| Sync Pulse | 20 ms | Line synchronization at 1200 Hz |
| Sync Porch | 2.08 ms | Guard time at 1500 Hz |
| Y-even Channel | 195.584 ms | Luminance for even row |
| V-avg Channel | 195.584 ms | R-Y chroma (shared between rows) |
| U-avg Channel | 195.584 ms | B-Y chroma (shared between rows) |
| Y-odd Channel | 195.584 ms | Luminance for odd row |
| Total | 804.416 ms | Complete scan line |
Total time = 200 scan lines × 804.416 ms/line
≈ 160.88 seconds
≈ 2 minutes 40 seconds
PD160 uses the same dual-luminance YUV color encoding as other PD modes:
- Y-even: Luminance (brightness) for even-numbered pixel row
- V-avg (R-Y): Red difference signal, shared between both rows
- U-avg (B-Y): Blue difference signal, shared between both rows
- Y-odd: Luminance (brightness) for odd-numbered pixel row
- Vertical subsampling: 2:1 (chroma shared between two rows)
- Horizontal subsampling: None (full chroma resolution)
- This provides good color fidelity while reducing transmission time
PD160 uses ITU-R BT.601 color space conversion:
Y_adj = Y - 16
U_adj = U - 128 (B-Y component)
V_adj = V - 128 (R-Y component)
R = ((298 × Y_adj + 409 × V_adj + 128) >> 8)
G = ((298 × Y_adj - 100 × U_adj - 208 × V_adj + 128) >> 8)
B = ((298 × Y_adj + 516 × U_adj + 128) >> 8)
Values are clamped to [0, 255] range.
| Signal Level | Frequency |
|---|---|
| Black | 1500 Hz |
| White | 2300 Hz |
| Sync | 1200 Hz |
The decoder normalizes frequencies to a -1 to +1 scale:
Normalized = (frequency - 1900 Hz) / 400 Hz
Black (1500 Hz) → -1.00
Gray (1900 Hz) → 0.00
White (2300 Hz) → +1.00
Sync (1200 Hz) → -1.75
| Mode | Resolution | Pixel Dwell | Scan Time | Total Time | SNR |
|---|---|---|---|---|---|
| PD120 | 640×496 | 190 µs | 508 ms | 126 s | Baseline |
| PD160 | 512×400 | 382 µs | 804 ms | 161 s | +3.0 dB |
| PD180 | 640×496 | 286 µs | 752 ms | 187 s | +1.8 dB |
Advantages over PD120:
- Better SNR: ~3.0 dB improvement due to 2× longer pixel dwell time
- Better quality: Longer integration time reduces noise
- Cleaner images: More time per pixel allows better filtering
Advantages over PD180:
- Faster: 14% shorter transmission time (161s vs 187s)
- More efficient: Better fit for satellite passes or time-limited operations
- Lower bandwidth: Smaller image size (512×400 vs 640×496)
Trade-offs:
- Lower resolution: 204,800 pixels vs PD120's 317,440 or PD180's 317,440
- Longer than PD120: 28% increase in transmission time
The decoder automatically adapts to the audio sample rate (typically 44.1 kHz or 48 kHz):
// Example for 48 kHz sample rate
scanLineSamples = 804.416 ms × 48000 samples/s = 38,612 samples
channelSamples = 195.584 ms × 48000 samples/s = 9,388 samplesPD160 uses bidirectional exponential moving average (EMA) filtering for horizontal resolution:
// Forward and backward passes
cutoff(horizontalPixels=512, rate=2×channelSamples, passes=2)This provides:
- Smooth pixel transitions
- Noise reduction
- Proper band-limiting to 512 pixels horizontal resolution
Minimum buffer size for one scan line:
At 44.1 kHz: ~35,500 samples
At 48.0 kHz: ~38,612 samples
Recommended buffer: 7 seconds (for safety margin and sync detection)
- Satellite Communications: Good balance for ISS passes (~10 minutes)
- Medium-Quality Images: When PD120 is too noisy but PD180 is too long
- Moderate SNR Conditions: Better noise immunity than PD120
- Time-Constrained Operations: When full PD180 quality isn't needed
- Choose PD120: When time is critical and conditions are good
- Choose PD160: When you want better quality but have time constraints
- Choose PD180: When maximum quality is needed and time permits
- ISS SSTV Events: Occasional use when PD120 is too fast but PD180 won't complete
- Amateur Radio Contests: Good for medium-quality submissions
- DX Stations: Balances quality and transmission time for long-distance contacts
- Weather Satellite Reception: Alternative to standard PD modes
200 scan lines × 804.416 ms = 160.88 seconds
Breakdown:
- Sync pulses: 200 × 20 ms = 4.0 s
- Porch time: 200 × 2.08 ms = 0.416 s
- Data: 200 × 782.336 ms = 156.47 s
- Total: ~161 seconds (2:41)
The PD160 decoder follows the same architecture as PD120 and PD180:
- Sync Detection: 20ms pulse at 1200 Hz
- Line Extraction: Extract 804.416ms of demodulated data
- Channel Separation: Split into 4 channels (Y-even, V, U, Y-odd)
- Filtering: Bidirectional EMA for horizontal resolution
- YUV to RGB: Convert using BT.601 color space
- Output: Two pixel rows per scan line
Image buffer: 512 × 400 × 4 bytes (RGBA) = 819,200 bytes
Line buffer: ~40,000 samples × 4 bytes = 160,000 bytes
Total: ~1 MB per decode session
PD160 is part of the PD mode family developed by Paul Turner (G4IJE) and Don Rotier (K0HEO). The PD modes revolutionized SSTV by introducing:
- Dual-luminance encoding for better efficiency
- Higher resolutions than older modes
- Better use of transmission time
- Improved color fidelity through YUV encoding
PD160 specifically fills the gap between PD120 (fast but lower quality) and PD180 (slow but highest quality), making it useful for scenarios where neither extreme is ideal.
- ITU-R BT.601 Color Space Standard
- Robot36 Android App by Ahmet Inan (xdsopl)
- PD Mode Specifications (Turner/Rotier)
- SSTV Signal Specifications (ARRL)