From 4a51997167da3b369c454c6c0823c0948431b5a4 Mon Sep 17 00:00:00 2001
From: Renat Nurgaliyev <renat@rnu.one>
Date: Fri, 22 May 2026 17:42:32 +0200
Subject: [PATCH] Add explanations for N* questions

Automatically generated using Codex and GPT 5.5 in high reasoning mode
and Claude Code with Opus 4.7 in high reasoning mode, models cross
checking each other
---
 explanations.json | 1170 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1170 insertions(+)

diff --git a/explanations.json b/explanations.json
index 11321ba..fdde375 100644
--- a/explanations.json
+++ b/explanations.json
@@ -1031,6 +1031,1176 @@
     "source": "https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Frequenzen/Amateurfunk/Fragenkatalog/BetriebVorschriftFragKlAuEId7830pdf.pdf?__blob=publicationFile",
     "confidence": 8
   },
+  "NA101": {
+    "revision": 2,
+    "explanation": "Cutting at $2/3$ of 20 m gives a $13.33$ m piece; the remaining $1/3$ is $6.67$ m.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA102": {
+    "revision": 1,
+    "explanation": "The maximum count is the whole-number quotient: $250/18.5 = 13.5$, so only 13 complete antennas fit before the remaining wire is too short.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA103": {
+    "revision": 1,
+    "explanation": "Mass scales linearly with length for the same wire: $55/210$ of 100 m is about 26.2 m.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA201": {
+    "revision": 1,
+    "explanation": "Electric potential difference is measured in volts; amperes measure current, ohms resistance, and ampere-hours charge capacity.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA202": {
+    "revision": 1,
+    "explanation": "Electric current is the rate of flow of charge, and the SI unit for current is the ampere.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA203": {
+    "revision": 1,
+    "explanation": "Electrical resistance is measured in ohms, the unit that relates voltage and current through Ohm's law.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA204": {
+    "revision": 1,
+    "explanation": "Electrical power is measured in watts; joule is energy, kilowatt-hour is energy, and ampere-hour is charge capacity.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA205": {
+    "revision": 1,
+    "explanation": "Wavelength is a length, so it is normally expressed in metres rather than hertz or seconds.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA206": {
+    "revision": 1,
+    "explanation": "Frequency is cycles per second, and the named SI unit for that is hertz.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA207": {
+    "revision": 1,
+    "explanation": "One hertz means one cycle per second, so dimensionally $Hz = 1/s$.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA208": {
+    "revision": 1,
+    "explanation": "Milli means $10^{-3}$, so one volt is 1000 millivolts and 4.2 V is 4200 mV.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA209": {
+    "revision": 1,
+    "explanation": "Milli means $10^{-3}$; therefore 42 mA is $42/1000$ A, or 0.042 A.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA210": {
+    "revision": 1,
+    "explanation": "Milli means one thousandth, so one watt contains 1000 milliwatts.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA211": {
+    "revision": 2,
+    "explanation": "$0.010\\,\\mathrm{W} \\cdot 1000\\,\\mathrm{mW/W} = 10\\,\\mathrm{mW}$.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA212": {
+    "revision": 1,
+    "explanation": "Mega means $10^6$; $144000000$ Hz divided by $10^6$ is 144 MHz.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NA213": {
+    "revision": 1,
+    "explanation": "145000000 periods per second is 145000000 Hz, which is 145 MHz after dividing by $10^6$.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NB101": {
+    "revision": 2,
+    "explanation": "Among the listed metals, copper has the lowest resistivity at room temperature, so it has the highest conductivity in that group.",
+    "source": "https://50ohm.de/N_leiter_nichtleiter.html",
+    "confidence": 7
+  },
+  "NB102": {
+    "revision": 2,
+    "explanation": "Silver has even lower resistivity than copper, gold or tin at room temperature, so it is the best conductor in this list.",
+    "source": "https://50ohm.de/N_leiter_nichtleiter.html",
+    "confidence": 7
+  },
+  "NB103": {
+    "revision": 2,
+    "explanation": "Tin has higher resistivity than copper, gold and aluminium, so it is the poorest conductor among the listed metals.",
+    "source": "https://50ohm.de/N_leiter_nichtleiter.html",
+    "confidence": 7
+  },
+  "NB104": {
+    "revision": 2,
+    "explanation": "Porcelain and the plastics PE and PS are insulating materials; the other options include metals such as tungsten, brass or bronze.",
+    "source": "https://50ohm.de/N_leiter_nichtleiter.html",
+    "confidence": 7
+  },
+  "NB201": {
+    "revision": 1,
+    "explanation": "The alternating long and short parallel plates are the conventional schematic symbol for a battery or cell stack.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NB202": {
+    "revision": 1,
+    "explanation": "The shown reference symbol marks circuit ground or chassis reference, not an active source or switch.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NB203": {
+    "revision": 1,
+    "explanation": "In a battery symbol the longer plate denotes the positive terminal and the shorter plate denotes the negative terminal.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NB204": {
+    "revision": 2,
+    "explanation": "Series-connected cells add their voltages; six 1.5 V cells give $6 \\cdot 1.5 V = 9 V$.",
+    "source": "https://50ohm.de/N_batterien_und_akkus.html",
+    "confidence": 8
+  },
+  "NB205": {
+    "revision": 2,
+    "explanation": "The voltmeter is connected across two 1.5 V cells in series, so it reads their sum: 3 V.",
+    "source": "https://50ohm.de/N_spannungsmessung.html",
+    "confidence": 7
+  },
+  "NB206": {
+    "revision": 2,
+    "explanation": "Both meter leads are on points with the same potential in the shown circuit, so the potential difference is 0 V.",
+    "source": "https://50ohm.de/N_spannungsmessung.html",
+    "confidence": 7
+  },
+  "NB207": {
+    "revision": 2,
+    "explanation": "Current needs a complete closed loop through a source and load; the shown connection alone does not close a usable circuit.",
+    "source": "https://50ohm.de/N_slide_n_bauteile_und_schaltkreise.html",
+    "confidence": 7
+  },
+  "NB301": {
+    "revision": 1,
+    "explanation": "Electromagnetic waves in free space travel at the speed of light, about $3 \\cdot 10^8$ m/s or 300000 km/s.",
+    "source": "https://www.bipm.org/en/publications/si-brochure",
+    "confidence": 8
+  },
+  "NB302": {
+    "revision": 2,
+    "explanation": "Use $f = c/\\lambda$: $300000000 / 2.08$ is about 144 MHz.",
+    "source": "https://50ohm.de/N_wellenlaenge.html",
+    "confidence": 8
+  },
+  "NB303": {
+    "revision": 2,
+    "explanation": "Use $\\lambda = c/f$: $300000000 / 433500000$ is about 0.69 m.",
+    "source": "https://50ohm.de/N_wellenlaenge.html",
+    "confidence": 8
+  },
+  "NB304": {
+    "revision": 2,
+    "explanation": "Radio waves are transverse, so the receiving antenna should match the electric-field orientation; mismatched polarisation causes avoidable loss.",
+    "source": "https://50ohm.de/NEA_polarisation.html",
+    "confidence": 7
+  },
+  "NB401": {
+    "revision": 2,
+    "explanation": "A sinusoidal AC waveform is the smooth periodic curve with equal positive and negative half cycles shown in the correct figure.",
+    "source": "https://50ohm.de/N_sinusschwingung.html",
+    "confidence": 7
+  },
+  "NB402": {
+    "revision": 2,
+    "explanation": "Amplitude is the maximum displacement from the centre line; marker 1 points to that vertical height.",
+    "source": "https://50ohm.de/N_wellenlaenge.html",
+    "confidence": 7
+  },
+  "NB403": {
+    "revision": 2,
+    "explanation": "Wavelength is the spatial distance for one complete cycle, which is what marker 2 spans in the wave snapshot.",
+    "source": "https://50ohm.de/N_wellenlaenge.html",
+    "confidence": 7
+  },
+  "NB404": {
+    "revision": 2,
+    "explanation": "On an oscilloscope trace, amplitude is the vertical distance from the reference level to a peak; marker 1 indicates that height.",
+    "source": "https://50ohm.de/N_sinusschwingung.html",
+    "confidence": 7
+  },
+  "NB405": {
+    "revision": 2,
+    "explanation": "Period is the time for one complete cycle, so the horizontal interval marked 2 is one period.",
+    "source": "https://50ohm.de/N_sinusschwingung.html",
+    "confidence": 7
+  },
+  "NB501": {
+    "revision": 1,
+    "explanation": "Ohm's law relates voltage, current and resistance as $U = R \\cdot I$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB502": {
+    "revision": 1,
+    "explanation": "Rearranging Ohm's law gives current as voltage divided by resistance: $I = U/R$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB503": {
+    "revision": 1,
+    "explanation": "Rearranging $U = R \\cdot I$ for resistance gives $R = U/I$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB504": {
+    "revision": 1,
+    "explanation": "Using Ohm's law with the shown resistance, $U = R \\cdot I$ gives 9.000 V for 90 mA.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB505": {
+    "revision": 1,
+    "explanation": "Resistance is found from $R = U/I$; applying the voltage and current shown in the figure gives 40 ohm.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 7
+  },
+  "NB601": {
+    "revision": 1,
+    "explanation": "DC input power is $P = U \\cdot I$, so $13.8 V \\cdot 1.5 A = 20.7 W$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB602": {
+    "revision": 1,
+    "explanation": "Power converted to heat is $P = U \\cdot I$; 50 V times 0.050 A gives 2.5 W.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB603": {
+    "revision": 1,
+    "explanation": "20 mA is 0.020 A, and $3.2 V \\cdot 0.020 A = 0.064 W = 64.0 mW$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB604": {
+    "revision": 1,
+    "explanation": "From $P = U \\cdot I$, current is $I = P/U = 100 W / 12 V = 8.33 A$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB605": {
+    "revision": 1,
+    "explanation": "A 3 W load at 12 V draws $I = P/U = 3/12 = 0.25 A$, which is 250 mA.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB606": {
+    "revision": 1,
+    "explanation": "A 48 W load at 12 V draws $I = P/U = 48/12 = 4 A$.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 8
+  },
+  "NB701": {
+    "revision": 1,
+    "explanation": "The open contact in the shown schematic is the conventional symbol for a switch.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NB702": {
+    "revision": 1,
+    "explanation": "Technical current direction is defined from the positive terminal through the external circuit toward the negative terminal.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 7
+  },
+  "NB703": {
+    "revision": 2,
+    "explanation": "An LED lights only when the circuit is closed and the diode is forward-biased with current flowing through it.",
+    "source": "https://50ohm.de/N_slide_n_bauteile_und_schaltkreise.html",
+    "confidence": 7
+  },
+  "NC101": {
+    "revision": 1,
+    "explanation": "The zig-zag or rectangular two-terminal schematic element is the conventional resistor symbol.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC102": {
+    "revision": 1,
+    "explanation": "In the resistor colour code, green as the multiplier band means $10^5$, or 100000.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC103": {
+    "revision": 1,
+    "explanation": "For 1.2 kOhm, the first two digits are 1 and 2, brown and red, and the multiplier is $10^2$, red.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC104": {
+    "revision": 1,
+    "explanation": "Red and violet give the digits 2 and 7; a red multiplier is $10^2$, so the value is $27 \\cdot 100 = 2700$ ohm, or 2.7 kOhm.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC105": {
+    "revision": 1,
+    "explanation": "Yellow and violet give 4 and 7; a red multiplier is $10^2$, so the value is 4700 ohm or 4.7 kOhm.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC106": {
+    "revision": 1,
+    "explanation": "Red and violet give 27; an orange multiplier is $10^3$, so the value is 27000 ohm or 27 kOhm.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC107": {
+    "revision": 1,
+    "explanation": "Yellow and violet give 47; an orange multiplier is $10^3$, so the value is 47000 ohm or 47 kOhm.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC108": {
+    "revision": 1,
+    "explanation": "In the resistor tolerance colour code, silver denotes a tolerance of plus or minus 10 percent.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC109": {
+    "revision": 1,
+    "explanation": "In the resistor tolerance colour code, gold denotes a tolerance of plus or minus 5 percent.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC110": {
+    "revision": 1,
+    "explanation": "In the resistor tolerance colour code, brown denotes a tolerance of plus or minus 1 percent.",
+    "source": "IEC 60062 marking codes for resistors and capacitors",
+    "confidence": 8
+  },
+  "NC201": {
+    "revision": 1,
+    "explanation": "Two separated plates in the schematic symbol represent a capacitor, because a capacitor stores charge between two conductors.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC301": {
+    "revision": 1,
+    "explanation": "The looped or coiled schematic element is the conventional symbol for an inductor or coil.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC401": {
+    "revision": 1,
+    "explanation": "A diode symbol shows a one-way junction; current flows conventionally from anode toward cathode when forward-biased.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC402": {
+    "revision": 1,
+    "explanation": "A light-emitting diode is drawn as a diode with arrows showing emitted light.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC403": {
+    "revision": 1,
+    "explanation": "The diode terminal at the triangle side is the anode, and the terminal at the bar side is the cathode.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NC404": {
+    "revision": 2,
+    "explanation": "Current flows through a diode circuit only when the diode is forward-biased and the loop is closed.",
+    "source": "https://50ohm.de/N_slide_n_bauteile_und_schaltkreise.html",
+    "confidence": 7
+  },
+  "NC501": {
+    "revision": 1,
+    "explanation": "A transistor symbol has three terminals for controlling current through the device, unlike two-terminal passive components.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "ND101": {
+    "revision": 2,
+    "explanation": "A mains power supply converts 230 V AC from the wall outlet into the DC voltage a mobile transceiver needs.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND102": {
+    "revision": 3,
+    "explanation": "Mobile amateur transceivers are normally designed for vehicle electrical systems, so an external supply is usually around 13.8 V DC.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND103": {
+    "revision": 2,
+    "explanation": "A complete DC circuit needs an outgoing and a return conductor, so current leaves through one lead and returns through the other.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND104": {
+    "revision": 2,
+    "explanation": "The two conductors complete the current path through the transceiver; without the return lead the circuit is open.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND105": {
+    "revision": 3,
+    "explanation": "DC equipment conventionally marks the positive lead red and the negative lead black to reduce polarity mistakes.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND106": {
+    "revision": 3,
+    "explanation": "Transceivers are polarity-sensitive DC loads, so reversing plus and minus can put voltage on the wrong internal circuitry.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND107": {
+    "revision": 3,
+    "explanation": "Reverse polarity can drive current through protection parts or semiconductor junctions in the wrong direction and damage the radio.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND108": {
+    "revision": 3,
+    "explanation": "Current limiting protects against short circuits, and thermal shutdown protects the supply when internal heating becomes excessive.",
+    "source": "https://50ohm.de/N_netzgeraet_1.html",
+    "confidence": 7
+  },
+  "ND109": {
+    "revision": 2,
+    "explanation": "The protective contact connects exposed conductive parts to the protective-earth conductor so fault current can be carried safely away.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "ND110": {
+    "revision": 2,
+    "explanation": "A short circuit can make batteries or accumulators deliver very high current, causing heat, fire risk or cell damage.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 7
+  },
+  "ND201": {
+    "revision": 1,
+    "explanation": "An oscillator is a circuit that generates a periodic electrical signal without needing an external signal of that frequency.",
+    "source": "IEC 60050 International Electrotechnical Vocabulary",
+    "confidence": 7
+  },
+  "NE101": {
+    "revision": 2,
+    "explanation": "Modulation varies a carrier in a controlled way so information can be transported by the radio-frequency signal.",
+    "source": "https://50ohm.de/N_rauch_und_morsezeichen.html",
+    "confidence": 7
+  },
+  "NE102": {
+    "revision": 2,
+    "explanation": "SSB, FM and AM are all modulation methods; the distractors mix in bands, equipment names or operating procedures.",
+    "source": "https://50ohm.de/NE_trxmodulation.html",
+    "confidence": 7
+  },
+  "NE201": {
+    "revision": 2,
+    "explanation": "CW conveys information by keying a continuous RF carrier on and off, which forms the Morse elements.",
+    "source": "https://50ohm.de/N_rauch_und_morsezeichen.html",
+    "confidence": 7
+  },
+  "NE202": {
+    "revision": 2,
+    "explanation": "In amplitude modulation, the carrier amplitude follows the information signal while the carrier frequency ideally stays fixed.",
+    "source": "https://50ohm.de/NE_am.html",
+    "confidence": 7
+  },
+  "NE203": {
+    "revision": 2,
+    "explanation": "Ordinary AM transmits a carrier plus both sidebands; SSB suppresses the carrier and one sideband to save bandwidth and power.",
+    "source": "https://50ohm.de/NE_ssb.html",
+    "confidence": 7
+  },
+  "NE204": {
+    "revision": 2,
+    "explanation": "LSB and USB are the lower and upper sideband versions of SSB; both suppress the carrier but keep opposite sides of the spectrum.",
+    "source": "https://50ohm.de/NE_ssb.html",
+    "confidence": 7
+  },
+  "NE205": {
+    "revision": 2,
+    "explanation": "In an AM spectrum, the lower sideband lies below the carrier and the upper sideband lies above it.",
+    "source": "https://50ohm.de/NE_ssb.html",
+    "confidence": 7
+  },
+  "NE206": {
+    "revision": 2,
+    "explanation": "AM produces two mirror sidebands around the carrier, so the correct spectrum contains both LSB and USB for the audio content.",
+    "source": "https://50ohm.de/NE_am.html",
+    "confidence": 7
+  },
+  "NE207": {
+    "revision": 2,
+    "explanation": "USB keeps the sideband above the carrier, with audio-frequency components translated upward in frequency.",
+    "source": "https://50ohm.de/NE_ssb.html",
+    "confidence": 7
+  },
+  "NE208": {
+    "revision": 2,
+    "explanation": "LSB keeps the sideband below the carrier, so the audio spectrum appears on the lower-frequency side.",
+    "source": "https://50ohm.de/NE_ssb.html",
+    "confidence": 7
+  },
+  "NE209": {
+    "revision": 2,
+    "explanation": "USB is the upper-sideband mode of SSB, meaning the receiver demodulates only the sideband above the suppressed carrier frequency.",
+    "source": "https://50ohm.de/NE_trxmodulation.html",
+    "confidence": 7
+  },
+  "NE210": {
+    "revision": 2,
+    "explanation": "The 2 m amateur SSB convention uses upper sideband, so the transceiver mode must be USB.",
+    "source": "https://50ohm.de/NE_trxmodulation.html",
+    "confidence": 7
+  },
+  "NE211": {
+    "revision": 2,
+    "explanation": "On 80 m, amateur SSB voice conventionally uses lower sideband, so the receiver mode is LSB.",
+    "source": "https://50ohm.de/NE_trxmodulation.html",
+    "confidence": 7
+  },
+  "NE212": {
+    "revision": 2,
+    "explanation": "SSB speech depends on the correct sideband and precise tuning; checking sideband mode and tuning the VFO addresses both causes.",
+    "source": "https://50ohm.de/NE_trxmodulation.html",
+    "confidence": 7
+  },
+  "NE301": {
+    "revision": 2,
+    "explanation": "In frequency modulation, the information signal varies the carrier frequency while the carrier amplitude ideally remains constant.",
+    "source": "https://50ohm.de/NEA_fm.html",
+    "confidence": 7
+  },
+  "NE302": {
+    "revision": 2,
+    "explanation": "FM is defined by varying a carrier's frequency according to the signal being transmitted.",
+    "source": "https://50ohm.de/NEA_fm.html",
+    "confidence": 7
+  },
+  "NE303": {
+    "revision": 2,
+    "explanation": "FM information is carried by frequency deviation, so the RF amplitude is ideally unaffected by microphone audio.",
+    "source": "https://50ohm.de/NEA_fm.html",
+    "confidence": 7
+  },
+  "NE304": {
+    "revision": 2,
+    "explanation": "In ideal FM the transmitter output power is essentially constant; speaking louder changes deviation, not the set RF power.",
+    "source": "https://50ohm.de/NEA_fm.html",
+    "confidence": 7
+  },
+  "NE305": {
+    "revision": 2,
+    "explanation": "A 15 kHz-wide emission extends about half its bandwidth on each side of the centre frequency, so it needs at least 7.5 kHz clearance.",
+    "source": "https://50ohm.de/NE_bandbreite.html",
+    "confidence": 7
+  },
+  "NE306": {
+    "revision": 2,
+    "explanation": "Too much FM deviation usually comes from excessive audio level, so speaking more quietly reduces the modulation hub.",
+    "source": "https://50ohm.de/NEA_fm.html",
+    "confidence": 7
+  },
+  "NE307": {
+    "revision": 2,
+    "explanation": "Handheld VHF/UHF amateur radios commonly support analogue FM and digital voice systems such as DMR and D-STAR.",
+    "source": "https://50ohm.de/N_digital_voice.html",
+    "confidence": 7
+  },
+  "NE308": {
+    "revision": 2,
+    "explanation": "Voice repeaters on VHF/UHF commonly carry analogue FM and digital voice modes such as DMR and D-STAR.",
+    "source": "https://50ohm.de/N_relaisfunkstellen.html",
+    "confidence": 7
+  },
+  "NE309": {
+    "revision": 2,
+    "explanation": "Analogue amateur voice repeaters on VHF/UHF conventionally use FM because it is robust for local line-of-sight voice links.",
+    "source": "https://50ohm.de/N_relaisfunkstellen.html",
+    "confidence": 7
+  },
+  "NE310": {
+    "revision": 2,
+    "explanation": "An FM receiver cannot cleanly demodulate two equal-strength co-channel signals at once, so simultaneous relay input signals interfere badly.",
+    "source": "https://50ohm.de/N_relaisfunkstellen.html",
+    "confidence": 7
+  },
+  "NE401": {
+    "revision": 2,
+    "explanation": "Digital text modes only interoperate when both stations use the same waveform and parameters such as speed, tone spacing or protocol settings.",
+    "source": "https://50ohm.de/N_funkfernschreiben.html",
+    "confidence": 7
+  },
+  "NE402": {
+    "revision": 2,
+    "explanation": "Digital voice repeater networks need more than frequency and mode; routing parameters such as reflector, time slot or colour code select the intended network path.",
+    "source": "https://50ohm.de/N_digital_voice.html",
+    "confidence": 7
+  },
+  "NE403": {
+    "revision": 2,
+    "explanation": "Time-division systems carry separate conversations in alternating time slots, allowing more than one channel on the same RF frequency.",
+    "source": "https://50ohm.de/N_digital_voice.html",
+    "confidence": 7
+  },
+  "NE404": {
+    "revision": 2,
+    "explanation": "DMR, D-STAR, C4FM, M17 and FreeDV are amateur digital voice systems, unlike analogue-only or non-voice modes.",
+    "source": "https://50ohm.de/N_digital_voice.html",
+    "confidence": 7
+  },
+  "NE405": {
+    "revision": 2,
+    "explanation": "Link paths are fixed radio links used as infrastructure, for example to connect repeaters with each other or to HAMNET nodes.",
+    "source": "https://50ohm.de/N_slide_n_amateurfunkstationen.html",
+    "confidence": 7
+  },
+  "NF101": {
+    "revision": 2,
+    "explanation": "SWR indication reports the antenna matching condition during transmit, so display item 1 is the SWR meter.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NF102": {
+    "revision": 2,
+    "explanation": "In transmit mode, a power meter display shows the RF output power being delivered by the transceiver.",
+    "source": "https://50ohm.de/N_ausgangsleistung.html",
+    "confidence": 7
+  },
+  "NF103": {
+    "revision": 2,
+    "explanation": "An S-meter indicates received signal strength, so it is the relevant receive-level display.",
+    "source": "https://50ohm.de/N_slide_n_erste_schritte.html",
+    "confidence": 7
+  },
+  "NF104": {
+    "revision": 2,
+    "explanation": "An amplitude spectrum shows signal strength versus frequency, which matches display item 3.",
+    "source": "https://50ohm.de/N_wasserfall.html",
+    "confidence": 7
+  },
+  "NF105": {
+    "revision": 2,
+    "explanation": "A waterfall diagram adds time to the spectrum display, with newer signal traces appearing as coloured or bright lines.",
+    "source": "https://50ohm.de/N_wasserfall.html",
+    "confidence": 7
+  },
+  "NF106": {
+    "revision": 2,
+    "explanation": "A waterfall plot uses one axis for frequency, one for time, and colour or brightness for received signal strength.",
+    "source": "https://50ohm.de/N_wasserfall.html",
+    "confidence": 7
+  },
+  "NF107": {
+    "revision": 2,
+    "explanation": "A mismatched or missing load reflects RF power back toward the transmitter, which can overheat or damage the final amplifier.",
+    "source": "https://50ohm.de/N_dummy_load_1.html",
+    "confidence": 7
+  },
+  "NF108": {
+    "revision": 2,
+    "explanation": "PTT means push-to-talk: pressing the microphone switch keys the transmitter.",
+    "source": "https://50ohm.de/N_erste_schritte.html",
+    "confidence": 7
+  },
+  "NF109": {
+    "revision": 2,
+    "explanation": "VOX is voice-operated transmit control, where microphone audio automatically keys the transmitter.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF110": {
+    "revision": 2,
+    "explanation": "If VOX is enabled, room noise or microphone audio can key the transmitter without pressing PTT.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF111": {
+    "revision": 2,
+    "explanation": "RIT changes only the receive frequency, letting you clarify the other station without moving your transmit frequency.",
+    "source": "https://50ohm.de/NE_rit.html",
+    "confidence": 7
+  },
+  "NF112": {
+    "revision": 2,
+    "explanation": "With RIT active, receive and transmit can be offset; the operator may tune reception while transmitting on a slightly different frequency.",
+    "source": "https://50ohm.de/NE_rit.html",
+    "confidence": 7
+  },
+  "NF113": {
+    "revision": 2,
+    "explanation": "Using different uplink and downlink bands makes filtering easier because the satellite can separate its receiver and transmitter signals more effectively.",
+    "source": "https://50ohm.de/N_slide_n_amateurfunkstationen.html",
+    "confidence": 7
+  },
+  "NF114": {
+    "revision": 2,
+    "explanation": "Digital modes need baseband audio or data between computer and radio, either by an audio/USB interface or by a modem that performs that conversion.",
+    "source": "https://50ohm.de/NE_computersteuerung.html",
+    "confidence": 7
+  },
+  "NF115": {
+    "revision": 2,
+    "explanation": "A data connector bypasses audio shaping intended for speech, giving digital signals a cleaner path into or out of the FM transceiver.",
+    "source": "https://50ohm.de/NE_computersteuerung.html",
+    "confidence": 7
+  },
+  "NF116": {
+    "revision": 2,
+    "explanation": "CAT control is a serial command interface used to read and set radio functions such as frequency, power and PTT from a computer.",
+    "source": "https://50ohm.de/NE_computersteuerung.html",
+    "confidence": 7
+  },
+  "NF117": {
+    "revision": 2,
+    "explanation": "Computer control can assert PTT or change settings unexpectedly, so it can create unintended transmissions or safety hazards if not supervised.",
+    "source": "https://50ohm.de/NE_computersteuerung.html",
+    "confidence": 7
+  },
+  "NF118": {
+    "revision": 2,
+    "explanation": "A digipeater is a digital relay: it receives packet data and retransmits it, possibly after updating fields such as routing information.",
+    "source": "https://50ohm.de/N_slide_n_amateurfunkstationen.html",
+    "confidence": 7
+  },
+  "NF201": {
+    "revision": 2,
+    "explanation": "The block diagram is a receiver because the signal path runs from antenna input through receiving stages toward audio or data output.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF301": {
+    "revision": 2,
+    "explanation": "The S-meter gives the operator a relative indication of received signal level.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF302": {
+    "revision": 2,
+    "explanation": "Squelch mutes the receiver audio until a signal exceeds the set threshold, hiding FM noise when no useful signal is present.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF303": {
+    "revision": 2,
+    "explanation": "Receiver sensitivity describes how weak a signal the receiver can still detect or demodulate usefully.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF401": {
+    "revision": 2,
+    "explanation": "The block diagram is a transmitter because the signal path builds an RF signal and delivers it toward the antenna output.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF402": {
+    "revision": 2,
+    "explanation": "A simple transmitter generates RF, combines it with modulation, filters unwanted products, and amplifies the wanted signal.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF403": {
+    "revision": 2,
+    "explanation": "The stages follow the usual transmitter chain: audio amplification, mixing with an RF oscillator, filtering, RF amplification, and final filtering.",
+    "source": "https://50ohm.de/N_slide_n_transceiver.html",
+    "confidence": 7
+  },
+  "NF404": {
+    "revision": 2,
+    "explanation": "A transmitter output filter should pass the wanted VHF band while attenuating unwanted frequencies outside it.",
+    "source": "https://50ohm.de/NE_slide_ne_sender.html",
+    "confidence": 7
+  },
+  "NG101": {
+    "revision": 1,
+    "explanation": "The shown schematic symbol represents an antenna connection, the point where RF energy is radiated or received.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NG102": {
+    "revision": 1,
+    "explanation": "The ground symbol marks an earth connection or earth reference in the antenna diagram.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NG103": {
+    "revision": 2,
+    "explanation": "A dipole has two arms fed near the centre, which is the configuration shown.",
+    "source": "https://50ohm.de/N_dipol.html",
+    "confidence": 7
+  },
+  "NG104": {
+    "revision": 2,
+    "explanation": "A Marconi antenna is a quarter-wave vertical worked against earth or a counterpoise, so it is a $\\lambda/4$ vertical antenna.",
+    "source": "https://50ohm.de/N_rundstrahler.html",
+    "confidence": 7
+  },
+  "NG105": {
+    "revision": 2,
+    "explanation": "A ground-plane antenna is a vertical radiator with radial conductors forming the counterpoise, matching the shown structure.",
+    "source": "https://50ohm.de/N_rundstrahler.html",
+    "confidence": 7
+  },
+  "NG106": {
+    "revision": 2,
+    "explanation": "The conductors that provide the counterpoise for a ground-plane antenna are called radials.",
+    "source": "https://50ohm.de/N_rundstrahler.html",
+    "confidence": 7
+  },
+  "NG107": {
+    "revision": 2,
+    "explanation": "An end-fed antenna is fed at one end rather than at the centre, which matches the depicted arrangement.",
+    "source": "https://50ohm.de/N_endgespeiste_antennen.html",
+    "confidence": 7
+  },
+  "NG108": {
+    "revision": 2,
+    "explanation": "A Yagi-Uda antenna uses a driven element with parasitic reflector and director elements on a boom, matching the shown directional antenna.",
+    "source": "https://50ohm.de/N_yagi_uda_1.html",
+    "confidence": 7
+  },
+  "NG109": {
+    "revision": 2,
+    "explanation": "Long-wire antennas are practical mainly on HF; at VHF/UHF their physical size and radiation behaviour make other antenna types usual.",
+    "source": "https://50ohm.de/N_endgespeiste_antennen.html",
+    "confidence": 7
+  },
+  "NG110": {
+    "revision": 2,
+    "explanation": "For a local round with stations in several directions, an omnidirectional antenna avoids aiming a directional beam at each station.",
+    "source": "https://50ohm.de/N_rundstrahler.html",
+    "confidence": 7
+  },
+  "NG111": {
+    "revision": 2,
+    "explanation": "Repeaters around the station may lie in many directions, so a roof-mounted omnidirectional antenna gives broad azimuth coverage and height.",
+    "source": "https://50ohm.de/N_rundstrahler.html",
+    "confidence": 7
+  },
+  "NG201": {
+    "revision": 2,
+    "explanation": "Common coaxial cable impedances include 50 ohm for transmitting systems and 75 ohm for receiving or video systems; 60 ohm also exists historically.",
+    "source": "https://50ohm.de/N_uebertragungsleitungen.html",
+    "confidence": 7
+  },
+  "NG202": {
+    "revision": 2,
+    "explanation": "The connector shown has the form used by the PL or UHF connector family.",
+    "source": "IEC 61169 radio-frequency connector series",
+    "confidence": 6
+  },
+  "NG203": {
+    "revision": 2,
+    "explanation": "The bayonet-lock form shown is characteristic of a BNC connector.",
+    "source": "IEC 61169 radio-frequency connector series",
+    "confidence": 6
+  },
+  "NG204": {
+    "revision": 2,
+    "explanation": "The threaded RF connector shown is the N connector, widely used at VHF/UHF for lower loss and better impedance control.",
+    "source": "IEC 61169 radio-frequency connector series",
+    "confidence": 6
+  },
+  "NG205": {
+    "revision": 2,
+    "explanation": "The small threaded connector shown is SMA, a compact RF connector commonly used on handhelds and microwave gear.",
+    "source": "IEC 61169 radio-frequency connector series",
+    "confidence": 6
+  },
+  "NG206": {
+    "revision": 2,
+    "explanation": "N and SMA connectors maintain better RF performance above 300 MHz than older connector systems such as PL.",
+    "source": "IEC 61169 radio-frequency connector series",
+    "confidence": 7
+  },
+  "NG207": {
+    "revision": 2,
+    "explanation": "Coaxial-line attenuation accumulates with length and generally rises with frequency, so both matter when choosing VHF/UHF feed line.",
+    "source": "https://50ohm.de/N_uebertragungsleitungen.html",
+    "confidence": 7
+  },
+  "NG208": {
+    "revision": 2,
+    "explanation": "Extra coax adds loss in both forward and reflected waves, so the meter can show a lower SWR even though efficiency has worsened.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NG301": {
+    "revision": 2,
+    "explanation": "An SWR of 1:1 means no reflected power from mismatch, which is the best possible match.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 8
+  },
+  "NG302": {
+    "revision": 2,
+    "explanation": "A high SWR-meter indication means significant reflected power, which points to poor antenna or feed-line matching.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NG303": {
+    "revision": 2,
+    "explanation": "Mismatch or damage changes the line impedance seen by the transmitter, causing RF reflections and therefore a higher SWR.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NG304": {
+    "revision": 2,
+    "explanation": "A dipole that resonates too low is electrically too long; shortening both arms raises its resonant frequency.",
+    "source": "https://50ohm.de/N_slide_n_antennen_und_leitungen.html",
+    "confidence": 8
+  },
+  "NG305": {
+    "revision": 2,
+    "explanation": "A dipole that resonates too high is electrically too short; lengthening both arms lowers its resonant frequency.",
+    "source": "https://50ohm.de/N_slide_n_antennen_und_leitungen.html",
+    "confidence": 8
+  },
+  "NG401": {
+    "revision": 2,
+    "explanation": "ERP is radiated power referenced to a half-wave dipole, not to an isotropic radiator.",
+    "source": "https://life.itu.int/radioclub/rr/art1.pdf",
+    "confidence": 8
+  },
+  "NG402": {
+    "revision": 2,
+    "explanation": "EIRP is radiated power referenced to an ideal isotropic radiator.",
+    "source": "https://life.itu.int/radioclub/rr/art1.pdf",
+    "confidence": 8
+  },
+  "NH101": {
+    "revision": 2,
+    "explanation": "The ionosphere is the ionised upper-atmosphere region that can refract HF radio waves back toward Earth.",
+    "source": "https://50ohm.de/NEA_ionosphaere.html",
+    "confidence": 7
+  },
+  "NH102": {
+    "revision": 2,
+    "explanation": "Free electrons and ions in the ionosphere change the refractive index for radio waves, allowing HF waves to bend rather than travel straight into space.",
+    "source": "https://50ohm.de/NEA_ionosphaere.html",
+    "confidence": 7
+  },
+  "NH201": {
+    "revision": 2,
+    "explanation": "Solar activity controls ionisation density in the ionosphere, and the roughly eleven-year solar cycle therefore strongly affects HF propagation.",
+    "source": "https://50ohm.de/NEA_ionosphaere.html",
+    "confidence": 7
+  },
+  "NH301": {
+    "revision": 2,
+    "explanation": "Standard atmospheric refraction bends VHF paths slightly toward Earth, making the radio horizon about 15 percent beyond the geometric horizon.",
+    "source": "https://50ohm.de/N_funkhorizont.html",
+    "confidence": 7
+  },
+  "NH302": {
+    "revision": 2,
+    "explanation": "VHF coverage is largely line-of-sight; raising the antenna increases the visible radio path over terrain and curvature.",
+    "source": "https://50ohm.de/N_funkhorizont.html",
+    "confidence": 7
+  },
+  "NH303": {
+    "revision": 2,
+    "explanation": "The best VHF path is the station with the clearest quasi-optical path in the terrain profile; in the shown figure that is $\\text{E}_3$.",
+    "source": "https://50ohm.de/N_funkhorizont.html",
+    "confidence": 7
+  },
+  "NH304": {
+    "revision": 2,
+    "explanation": "Tropospheric inversions can form ducts or enhanced refractive layers, allowing VHF signals to travel hundreds of kilometres beyond normal range.",
+    "source": "https://50ohm.de/N_troposphaere.html",
+    "confidence": 7
+  },
+  "NH305": {
+    "revision": 2,
+    "explanation": "Sporadic-E uses dense temporary ionisation patches in the E region, typically around 100 to 110 km altitude.",
+    "source": "https://50ohm.de/NEA_sporadic_e_1.html",
+    "confidence": 7
+  },
+  "NH306": {
+    "revision": 2,
+    "explanation": "On 2 m, Sporadic-E means unusually long VHF paths via refraction in sporadic E-region ionisation, often around 1000 to 2000 km.",
+    "source": "https://50ohm.de/NEA_sporadic_e_1.html",
+    "confidence": 7
+  },
+  "NI101": {
+    "revision": 1,
+    "explanation": "The voltmeter symbol identifies a voltage-measuring instrument, which is connected across the points whose potential difference is measured.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NI102": {
+    "revision": 1,
+    "explanation": "The ammeter symbol identifies a current-measuring instrument, which is inserted in series with the current path.",
+    "source": "IEC 60617 graphical symbols for diagrams",
+    "confidence": 7
+  },
+  "NI103": {
+    "revision": 2,
+    "explanation": "Voltage is measured in parallel with the battery, so the meter must be connected across the battery while the circuit remains operating.",
+    "source": "https://50ohm.de/N_spannungsmessung.html",
+    "confidence": 7
+  },
+  "NI104": {
+    "revision": 2,
+    "explanation": "Current through a component is measured in series, so the meter must be inserted into the path through the resistor and LED.",
+    "source": "https://50ohm.de/N_spannungsmessung.html",
+    "confidence": 7
+  },
+  "NI201": {
+    "revision": 2,
+    "explanation": "A standing-wave meter compares forward and reflected RF power, which is how antenna matching is inferred.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NI202": {
+    "revision": 2,
+    "explanation": "To measure reflections in the antenna system, the SWR meter is inserted between the transceiver and antenna, with the transmitter on the other port.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 7
+  },
+  "NI203": {
+    "revision": 2,
+    "explanation": "An ideal match has no reflected wave, so the SWR meter should read 1:1.",
+    "source": "https://50ohm.de/N_swr.html",
+    "confidence": 8
+  },
+  "NI301": {
+    "revision": 2,
+    "explanation": "A frequency counter measures the frequency of an electrical signal directly, so it is the appropriate instrument for transmitter frequency.",
+    "source": "https://50ohm.de/N_frequenz.html",
+    "confidence": 7
+  },
+  "NI401": {
+    "revision": 2,
+    "explanation": "An oscillogram is time-domain display; an amplitude spectrum is frequency-domain display showing the signal components by frequency.",
+    "source": "https://50ohm.de/N_wasserfall.html",
+    "confidence": 8
+  },
+  "NJ101": {
+    "revision": 2,
+    "explanation": "Shielding confines RF currents and fields, reducing unwanted coupling into nearby equipment or wiring.",
+    "source": "https://50ohm.de/NE_elektromagnetische_vertraeglichkeit.html",
+    "confidence": 7
+  },
+  "NJ102": {
+    "revision": 2,
+    "explanation": "Interference complaints should be handled cooperatively; arranging checks can identify whether the cause is the amateur station, the affected device or the installation.",
+    "source": "https://50ohm.de/NE_elektromagnetische_vertraeglichkeit.html",
+    "confidence": 7
+  },
+  "NJ201": {
+    "revision": 2,
+    "explanation": "Unwanted emissions waste spectrum and may interfere with other services, so a transmitter must be adjusted and filtered to avoid them.",
+    "source": "https://50ohm.de/NE_slide_ne_sender.html",
+    "confidence": 7
+  },
+  "NJ202": {
+    "revision": 3,
+    "explanation": "A dummy load provides a non-radiating matched load, letting you align the transmitter without putting test signals on the air.",
+    "source": "https://50ohm.de/N_dummy_load_1.html",
+    "confidence": 7
+  },
+  "NK101": {
+    "revision": 2,
+    "explanation": "Shielding HF stages reduces radiation and susceptibility by keeping RF energy inside the intended circuit region.",
+    "source": "https://50ohm.de/NE_elektromagnetische_vertraeglichkeit.html",
+    "confidence": 7
+  },
+  "NK102": {
+    "revision": 2,
+    "explanation": "A good RF earth gives unwanted RF currents a controlled return path and reduces coupling into equipment, cables and surroundings.",
+    "source": "https://50ohm.de/NE_elektromagnetische_vertraeglichkeit.html",
+    "confidence": 7
+  },
+  "NK201": {
+    "revision": 2,
+    "explanation": "Near antennas, electromagnetic fields can exceed exposure limits; operators need enough knowledge to keep people outside unsafe field strengths.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 7
+  },
+  "NK301": {
+    "revision": 2,
+    "explanation": "Common electrical-safety practice treats contact above 50 V AC or 120 V DC as hazardous under normal dry conditions.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "NK302": {
+    "revision": 2,
+    "explanation": "The main electrical hazards are current through the body, arc faults, and secondary accidents such as falls caused by shock or startle.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "NK303": {
+    "revision": 2,
+    "explanation": "Body current can heat tissue, force muscles to contract, and disturb the heart rhythm, including dangerous fibrillation.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "NK304": {
+    "revision": 2,
+    "explanation": "Heart rhythm disturbances can be delayed after an electric shock, so medical assessment is required even when the person initially feels well.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "NK305": {
+    "revision": 2,
+    "explanation": "A fuse protects only as designed when its current rating and time-current characteristic match the original device.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
+  "NK306": {
+    "revision": 2,
+    "explanation": "Rechargeable batteries can deliver high energy and contain reactive chemicals, so misuse can cause burns, chemical injury or toxic exposure.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 7
+  },
+  "NK307": {
+    "revision": 2,
+    "explanation": "A vehicle battery can supply very high short-circuit current; wrong connection can create arcs and ignite wiring or surrounding material.",
+    "source": "https://50ohm.de/NEA_einbau_kfz.html",
+    "confidence": 7
+  },
+  "NK308": {
+    "revision": 2,
+    "explanation": "Vehicle electronics and approval conditions depend on manufacturer installation limits, so those instructions govern radio installation.",
+    "source": "https://50ohm.de/NEA_einbau_kfz.html",
+    "confidence": 7
+  },
+  "NK309": {
+    "revision": 2,
+    "explanation": "Keeping coax away from vehicle wiring reduces RF coupling into control electronics and avoids parallel runs acting as coupled lines.",
+    "source": "https://50ohm.de/NEA_einbau_kfz.html",
+    "confidence": 7
+  },
+  "NK310": {
+    "revision": 2,
+    "explanation": "The centre of a metal roof gives a VHF mobile antenna a good ground plane and a more even radiation pattern around the car.",
+    "source": "https://50ohm.de/NEA_einbau_kfz.html",
+    "confidence": 7
+  },
+  "NK311": {
+    "revision": 2,
+    "explanation": "Antenna parts must be arranged so that failure cannot bring conductive parts into contact with power lines, where lethal voltages may be present.",
+    "source": "https://publikationen.dguv.de/regelwerk/dguv-informationen/284/sicherheit-bei-arbeiten-an-elektrischen-anlagen",
+    "confidence": 8
+  },
   "VA101": {
     "revision": 1,
     "explanation": "The international definition is in the ITU Radio Regulations, which define radio services globally before national rules implement them.",