{"id": "card_n_c39a51a03b6f", "kind": "note", "title": "Oscillator — LC resonance, the bench's own Schumann", "body": "Energy sloshing between a coil and a capacitor rings at f = 1/(2π√(LC)); sealed:\n100 µH with 100 pF gives 1.591 MHz — the middle of the AM broadcast band: https://narrowhighway.com/s/1ee0d3ed486453eee0967146a531984888709198b39fb16a7b2c2a5f58ef1b73 . This is\nthe crystal radio's tuner and every radio's local oscillator. Honest boundary: the ideal LC\nis lossless; a real oscillator must replace what its finite Q dissipates (an amplifier\nsatisfying Barkhausen's condition) — the gain stage is engineering, measured not derived.", "source": {"label": "Concordance assay — 2026-07-09", "url": "https://narrowhighway.com/s/1ee0d3ed486453eee0967146a531984888709198b39fb16a7b2c2a5f58ef1b73", "ref": "electronics_dig", "authority_tier": "engine_derived"}, "shelf": "science", "box": "electronics", "bands": ["oscillator", "lc resonance", "tuned circuit", "electronics", "am band", "frequency"], "connections": [], "author": "engine", "created_at": "2026-07-10T00:59:49.508624+00:00", "updated_at": "2026-07-10T00:59:49.508624+00:00", "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "surface": "secular", "metrics": {"paperclips_count": 0, "helpful_count": 0, "not_helpful_count": 0, "cite_count": 0, "walks_through_count": 0, "flagged_count": 0}, "source_hash": "796ba78753cee4d0224a85538ea60fc4fd0142db95857b8151c736a3fc6f8002"}