{"query": "FM broadcast (VHF) — three-meter waves, line of sight", "count": 17, "results": [{"id": "card_n_a7ae37960cae", "title": "FM broadcast (VHF) — three-meter waves, line of sight", "shelf": "science", "surface": "secular", "snippet": "88–108 MHz; sealed: the 100 MHz wave is 2.99 m, and its quarter-wave whip is 74 cm —\nthe length of a car antenna, derived: https://narrowhighway.com/s/d6211f4efb2518c6de145decf57f27b131a01c24ce7841853", "authority_tier": "engine_derived", "source": "Concordance assay — 2026-07-09", "generated": false}, {"id": "card_c_9610a78874eb", "title": "The radio horizon — why towers are tall ↔ FM broadcast (VHF) — three-meter waves, line", "shelf": "connections", "surface": null, "snippet": "Every VHF/FM/TV coverage map is this square root wearing terrain.  — a concord the card itself states; mined + verified.", "authority_tier": "engine_derived", "source": "Concordance miner — 2026-07-11", "generated": false}, {"id": "card_c_3eab92dc34f4", "title": "The radio spectrum — one law from the cavity ↔ FM broadcast (VHF) — three-meter waves, line", "shelf": "connections", "surface": null, "snippet": "FM's 2.99 m wave and its 74 cm quarter-wave whip  — a concord the card itself states; mined + verified.", "authority_tier": "engine_derived", "source": "Concordance miner — 2026-07-11", "generated": false}, {"id": "card_c_9e441e079649", "title": "FM broadcast (VHF) — three-meter waves, line ↔ AM broadcast (medium wave) — where the dial ", "shelf": "connections", "surface": null, "snippet": "Frequency modulation carries the signal in the wave's TIMING rather than its height, which is why amplitude noise (lightning, ignition) mostly washes out — the static-resistance is structural, not mag", "authority_tier": "engine_derived", "source": "Concordance miner — 2026-07-11", "generated": false}, {"id": "card_c_feb938352b59", "title": "FM broadcast (VHF) — three-meter waves, line ↔ The radio spectrum — one law from the cavity", "shelf": "connections", "surface": null, "snippet": "88–108 MHz; sealed: the 100 MHz wave is 2.99 m, and its quarter-wave whip is 74 cm — the length of a car antenna, derived: https://narrowhighway.com/s/d6211f4efb2518c6de145decf57f27b131a01c24ce7841853", "authority_tier": "engine_derived", "source": "Concordance miner — 2026-07-11", "generated": false}, {"id": "card_comms_antenna_basics", "title": "Antennas — the cheapest way to double your range", "shelf": "communications", "surface": "secular", "snippet": "A better antenna beats more power almost every time. Key ideas: HEIGHT wins for VHF/UHF — they go line-of-sight, so raising the antenna a few metres can double reach. Length matters: a common field an", "authority_tier": "reference", "source": "U.S. Army field antenna & signaling references (public domain)", "generated": false}, {"id": "card_n_9ab6ee5e792c", "title": "The radio horizon — why towers are tall", "shelf": "science", "surface": "secular", "snippet": "Pure geometry, sealed: from height h the horizon lies at √(2hR) — a 100 m tower\nreaches 35,695 m ≈ 35.7 km: https://narrowhighway.com/s/d6211f4efb2518c6de145decf57f27b131a01c24ce7841853f395b7bc986c323", "authority_tier": "engine_derived", "source": "Concordance assay — 2026-07-09", "generated": false}, {"id": "card_comms_murs", "title": "MURS — five license-free VHF channels", "shelf": "communications", "surface": "secular", "snippet": "MURS is five VHF channels (151.820, 151.880, 151.940, 154.570, 154.600 MHz), license-free, up to 2 watts. VHF often reaches farther than FRS/GMRS UHF across open ground and hills. Popular for farms, p", "authority_tier": "reference", "source": "FCC Part 95 — Personal Radio Services: GMRS/FRS/MURS/CB (U.S. regulation, public domain)", "generated": false}, {"id": "card_comms_propagation", "title": "Propagation — why range changes with band and time of day", "shelf": "communications", "surface": "secular", "snippet": "Match the band to the distance: VHF/UHF (2m/70cm, GMRS, MURS) travel LINE-OF-SIGHT — great local, blocked by hills and horizon. HF (80/40/20m) bounces off the ionosphere ('skip') to reach over the hor", "authority_tier": "reference", "source": "U.S. Army field antenna & signaling references (public domain)", "generated": false}, {"id": "card_comms_ham_bands", "title": "The common ham bands — where to find people", "shelf": "communications", "surface": "secular", "snippet": "Key US amateur bands (edges are FCC regulation): HF for distance — 80m 3.5–4.0 MHz (regional, night), 40m 7.0–7.3 MHz (day/night workhorse), 20m 14.0–14.35 MHz (worldwide, daytime). VHF/UHF for local/", "authority_tier": "reference", "source": "FCC Part 97 — Amateur Radio Service (U.S. regulation, public domain)", "generated": false}, {"id": "card_comms_distress_signals", "title": "Calling for help — the signals everyone should know", "shelf": "communications", "surface": "secular", "snippet": "MAYDAY (spoken three times) is the voice distress call for grave, immediate danger; PAN-PAN (x3) is urgent but not life-threatening. On Morse or light: SOS ( ...---... ). The universal 'I need help' p", "authority_tier": "reference", "source": "International distress conventions (ITU / ICAO / IMO, public domain)", "generated": false}, {"id": "card_c_87b8bc166a36", "title": "FM broadcast (VHF) instantiates the spectrum walk", "shelf": "connections", "surface": null, "snippet": "One band of the sealed spectrum walk.", "authority_tier": "engine_derived", "source": "Concordance assay — 2026-07-09", "generated": false}, {"id": "card_src_word_vhf", "title": "vhf", "shelf": "dictionary", "surface": "secular", "snippet": "vhf: (noun) a group of illnesses caused by a viral infection (usually restricted to a specific geographic area); fever and gastrointestinal symptoms are followed by capillary hemorrhage — syn: hemorrh", "authority_tier": "reference", "source": "WordNet 3.0, Princeton University (WordNet License)", "generated": false}, {"id": "card_comms_noaa_weather", "title": "NOAA weather radio — the seven frequencies that warn you", "shelf": "communications", "surface": "secular", "snippet": "NOAA Weather Radio broadcasts continuous forecasts and emergency alerts on seven VHF frequencies: 162.400, 162.425, 162.450, 162.475, 162.500, 162.525, and 162.550 MHz. A cheap weather radio (or any s", "authority_tier": "reference", "source": "NOAA NWS — Weather Radio All Hazards (U.S. government, public domain)", "generated": false}, {"id": "card_comms_ham_license", "title": "Getting a ham license — the key to the long-range bands", "shelf": "communications", "surface": "secular", "snippet": "Amateur ('ham') radio reaches from across town to across the world, and is the backbone of volunteer emergency comms. Three US license classes, each a 35-question multiple-choice exam (no Morse requir", "authority_tier": "reference", "source": "FCC Part 97 — Amateur Radio Service (U.S. regulation, public domain)", "generated": false}, {"id": "card_comms_repeaters", "title": "Repeaters — how a hilltop doubles your range", "shelf": "communications", "surface": "secular", "snippet": "A repeater sits high (hilltop, tower) and re-transmits what it hears, so two low handhelds reach each other across a whole region. Your radio listens on the repeater's OUTPUT and transmits on a fixed ", "authority_tier": "reference", "source": "FCC Part 97 — Amateur Radio Service (U.S. regulation, public domain)", "generated": false}, {"id": "card_comms_emergency_frequencies", "title": "The frequencies to know for an emergency", "shelf": "communications", "surface": "secular", "snippet": "Worth writing on the radio: Marine VHF Ch 16 = 156.800 MHz (international distress/hailing, Coast Guard monitors). Aviation emergency = 121.500 MHz. NOAA weather 162.400–162.550 MHz (receive alerts). ", "authority_tier": "reference", "source": "International distress conventions (ITU / ICAO / IMO, public domain)", "generated": false}]}