{"approval":{"approved":true,"approved_at":"2026-07-27T22:45:05Z","approved_by":"Project owner","review_note":"Approved as the first limited public environmental-mapping record, with calibration and identity limitations retained."},"author":"Autonomous Radio Explorer scientific pipeline","authorship_note":"This public entry was deterministically transcribed from Scientific Record SR-2026-07-27-001 and reviewed by the project owner. RecurrentGemma did not create or alter the measurements or scientific conclusion.","canonical_url":"https://thegodnet.work/ledger/initial-fm-band-receive-chain-validation/","content_sha256":"9bfec3473ba2168e10b7c4b292f10df29b0709b93097aeb681d9c618ce87cf69","created_at":"2026-07-27T18:21:49.001Z","epistemic_labels":["observation","analysis"],"evidence_ids":["20260727T181752311409Z_hackrf_known_fm_100700000","20260727T181837035130Z_nesdr_known_fm_100700000","20260727T182051591619Z_nesdr_known_fm_100700000","20260727T181646175220Z_hackrf_known_fm_101700000"],"id":"SR-PUB-2026-07-27-001","limitations":["Absolute antenna gain, feed-line loss and field strength are unknown.","The antenna extension length was not recorded at capture time.","Nearby metalwork and buildings may alter antenna pattern and multipath.","Frequency correction remains to be measured against an identified reference.","No characterized 50 ohm termination or independent calibrated signal source was available.","The occupied region is not assigned a station or modulation identity."],"measurements":[{"capture_role":"accepted","centroid_error_hz":32.424,"clipping_fraction":0.0,"occupied_bw_99_hz":23925.781,"receiver":"HackRF One","result":"pass","target_snr_db":28.176},{"capture_role":"accepted","centroid_error_hz":6929.304,"clipping_fraction":0.0,"occupied_bw_99_hz":115576.172,"receiver":"NESDR","result":"pass","target_snr_db":27.9},{"capture_role":"accepted_repeat","centroid_error_hz":7390.961,"clipping_fraction":0.0,"occupied_bw_99_hz":127441.406,"receiver":"NESDR","result":"pass","target_snr_db":29.241},{"capture_role":"preserved_preliminary","receiver":"HackRF One","result":"fail","target_snr_db":5.395,"tested_frequency_hz":101700000}],"observation":{"band":"FM-broadcast region near 100.7 MHz","configuration_scope":"Receive-only, passive antennas, target deliberately offset from receiver DC","generalized_location":"Costa Rica; precise receiving location withheld","receiver_classes":"HackRF One and NESDR-class RTL-SDR receiver","time_range":"2026-07-27 18:16–18:20 UTC"},"publication_type":"ledger_entry","published_at":"2026-07-27T22:45:05Z","related_entries":["FN-2026-07-27-001"],"revision":1,"revision_note":"Initial sanitized public revision.","schema":"tgn.public-ledger-entry.v1","sections":[{"citation_ids":[],"heading":"Question","items":[],"label":"analysis","paragraphs":["Can each documented receive chain capture a previously observed local FM-band signal as complete, reproducible evidence without clipping or bypassing the provenance gate?"]},{"citation_ids":[],"heading":"Method","items":["Receive only; no transmission path or active RF probing.","Run deterministic spectrum and statistical checks before any reasoning model.","Retain the failed preliminary attempt to make selection history visible.","Do not infer a station or modulation identity from frequency alone."],"label":"analysis","paragraphs":["Every accepted raw capture was sealed with receiver, RF-path, timing, configuration, sample-count and SHA-256 provenance before deterministic analysis. The expected occupied region was offset from receiver DC."]},{"citation_ids":[],"heading":"Result","items":[],"label":"observation","paragraphs":["One HackRF capture and two NESDR captures passed the initial evidence gate. Each contained an occupied region near 100.7 MHz with no detected clipping under the recorded settings.","A preliminary HackRF attempt at a different tested frequency did not meet the known-signal gate and remains preserved. The passing captures validate the receive and evidence paths; they do not calibrate absolute RF power or identify the broadcaster."]},{"citation_ids":[],"heading":"Retained receiver warning","items":[],"label":"observation","paragraphs":["The NESDR driver emitted an initial tuner phase-lock warning before the requested tune. Two captures with different receiver centers subsequently placed the same occupied region on the expected opposite sides of baseband. The warning remains open for driver-level characterization."]},{"citation_ids":[],"heading":"Conclusion","items":[],"label":"analysis","paragraphs":["Both documented receive chains passed the initial known-signal evidence gate. This supports cautious environmental mapping and later controlled calibration tests.","No observation in this record is evidence of an unexplained anomaly."]}],"slug":"initial-fm-band-receive-chain-validation","sources":[],"status":"preliminary","summary":"Two receive chains repeatedly captured an occupied region near 100.7 MHz without clipping and preserved it as integrity-bound evidence. The broadcaster is not identified.","title":"Initial FM-Band Receive-Chain Validation"}