Ryan Malloy
5867c54de3
Ported from zleffke/gr-sarsat (2018, GNU Radio 3.7): - Updated Python 2 → Python 3 - Converted XML block definitions to YAML - Added pyproject.toml for modern packaging - Preserved original MIT license Blocks: - biphase_l_decode_bb: Manchester decoder (decim_block) - pds_frame_sync: Frame synchronizer with PDU output - sarp_msg_extract: SARP message splitter/validator
65 lines
1.4 KiB
Markdown
65 lines
1.4 KiB
Markdown
# gr-sarsat-modern
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GNU Radio 3.10+ compatible Cospas-Sarsat 406 MHz beacon decoder.
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Ported from [zleffke/gr-sarsat](https://github.com/zleffke/gr-sarsat) (2018, GNU Radio 3.7).
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## Blocks
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| Block | Description |
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|-------|-------------|
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| **Biphase-L Decoder** | Decodes Manchester/Biphase-L encoded bit stream |
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| **PDS Frame Sync** | Synchronizes and extracts 72-byte PDS frames |
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| **SARP Message Extractor** | Splits PDS frames into 24-byte SARP messages |
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## Installation
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```bash
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# Install Python package
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cd gr-sarsat-modern
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pip install -e .
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# Copy GRC blocks to GNU Radio
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cp grc/*.yml ~/.local/share/gnuradio/grc/blocks/
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```
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## Signal Chain
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```
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RF Input (406 MHz)
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v
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[FM Demod] -> [Clock Recovery] -> [Slicer]
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v
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[Correlate Access Code - Tag] (Frame sync: 0x7FF, tag: "pds_sync")
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v
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[Biphase-L Decoder]
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v
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[PDS Frame Sync]
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v
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[SARP Message Extractor]
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+---> valid (sync word OK)
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+---> invalid (sync word mismatch)
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```
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## Protocol Background
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Cospas-Sarsat is the international satellite-based search and rescue system:
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- **Frequency**: 406.025 MHz
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- **Modulation**: Phase-modulated carrier, Biphase-L encoded
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- **Bit rate**: 400 bps
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- **Frame structure**:
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- 15-bit frame sync (0x7FF)
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- 576-bit PDS frame (3 × 24-byte SARP messages)
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- Each SARP message starts with 0xD60 sync word
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## License
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MIT License - Original work (c) 2018 zleffke
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