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