{"id": "card_n_072d00893a26", "kind": "note", "title": "Build a Crystal Radio", "body": "A working radio with no batteries — runs on the energy of the radio waves themselves. The first DIY electronics project a generation of American kids built.", "source": {"label": "Popular Science, March 1922 (and many others)", "url": "/maker.html#build-a-crystal-radio", "ref": "Popular Science, March 1922 (and many others)", "authority_tier": "external_aligned"}, "shelf": "maker", "box": "electronics", "bands": ["A galena crystal (or a 1N34A germanium diode as substitute)", "Several yards of insulated copper wire", "A cardboard tube (toilet paper or oatmeal canister)", "Earphones (high-impedance vintage; or use a crystal earpiece)", "Long wire antenna (15+ feet) and a ground connection", "Small variable capacitor or a slider made from foil"], "connections": [{"to_card_id": "card_n_0916717648d8", "relationship": "shelf_anchor", "origin": "nesting_2026_06_12"}], "author": "engine", "created_at": "2026-05-19T00:00:00Z", "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "metrics": {"paperclips_count": 0, "helpful_count": 0, "not_helpful_count": 0, "cite_count": 0, "walks_through_count": 0, "flagged_count": 0, "trust_weighted_score": 0.0}, "updated_at": "2026-05-19T11:52:46.109581+00:00", "source_hash": "97024c7e9559739c5a93acb50427f5d65ee2efbddb3930ca3e014b7c4a50fe99", "witnesses": [{"class": "self", "label": "Popular Science, March 1922 (and many others)", "ref": "Popular Science, March 1922 (and many others)", "url": "/maker.html#build-a-crystal-radio"}], "witness_status": "self_only", "witness_status_reason": "no registry entry matched 'Popular Science, March 1922 (and many others)'; only the source itself attests", "surface": "secular"}