{"query": "FM broadcast (VHF) — three-meter waves, line of sight", "count": 20, "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", "readable": false, "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)", "readable": false, "generated": false}, {"id": "card_comms_handheld_vhf_uhf", "title": "VHF/UHF FM handhelds (Baofeng-class) — voice and listening, and where the license lines fall", "shelf": "communications", "surface": "secular", "snippet": "A dual-band FM handheld (the $25 Baofeng class) transmits VOICE on 136–174 MHz (2 m) and 400–520 MHz (70 cm), typically 1–5 W: a few km simplex handheld to handheld, far more through a repeater on a h", "authority_tier": "reference", "source": "FCC Part 97 — Amateur Radio Service (U.S. regulation, public domain)", "readable": false, "generated": false}, {"id": "card_comms_packet_over_handheld", "title": "Text over a handheld — packet radio (AX.25 / APRS) with a sound-card TNC", "shelf": "communications", "surface": "secular", "snippet": "A VHF handheld can carry TEXT: packet radio sends short digital frames (AX.25) as 1200-baud audio tones (AFSK) over the ordinary voice channel. The parts: the handheld, a cable to a sound-card interfa", "authority_tier": "reference", "source": "FCC Part 97 — Amateur Radio Service (U.S. regulation, public domain)", "readable": false, "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)", "readable": false, "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)", "readable": false, "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", "readable": false, "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", "readable": false, "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", "readable": false, "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)", "readable": false, "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)", "readable": false, "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", "readable": false, "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)", "readable": false, "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)", "readable": false, "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", "readable": false, "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)", "readable": false, "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)", "readable": false, "generated": false}, {"id": "card_theory_heat_transfer", "title": "Heat transfer (conduction, convection, radiation)", "shelf": "theories", "surface": "secular", "snippet": "Heat transfer (conduction, convection, radiation) — an engine domain that can touch it: thermodynamics. Calibration: seals — Fourier's law, R-values and Stefan–Boltzmann all compute. Heat moves three ", "authority_tier": "reference", "source": "The Theory Assay — calibrated, not judged (docs/THEORY_CATALOG.md)", "readable": false, "generated": false}, {"id": "card_span_cc7fafdda091", "title": "Now work the laps down until the strip is of uniform thickness its entire length", "shelf": "practical", "surface": "secular", "snippet": "Now work the laps down until the strip is of uniform thickness its\r\nentire length, and test it once more; you will find it much weaker than\r\non first trial. That is the smooth skin, sometimes called l", "authority_tier": "primary_pd", "source": "Woodcraft and Camping", "readable": true, "generated": false}, {"id": "card_span_f8adf8b1a4c0", "title": "Bent in position for \\A/e/cfing", "shelf": "sources", "surface": "secular", "snippet": "btraiqht round rod ready for we/d/ng \n\n\n\n1 \n\n\n\nPlate 18 \n\n\n\n56 FARM BLACKSMITHING \n\n4. Bend the scarf over the horn of the anvil to make the slope \nslightly rounding, as shown in Fig. 43. The scarfs m", "authority_tier": "primary_pd", "source": "Farm Blacksmithing (Friese, 1921)", "readable": true, "generated": false}], "house": {"door": "FIND", "kind": "cards", "trail": "results", "seal": null, "next_step": {"do": "open the top card", "door": "FIND", "tool": "card_get", "params": {"id": "card_n_a7ae37960cae"}}, "ends": "a verdict or a card · the trail · a seal · one next step"}}