{
  "terms": [
    {
      "code": "AM",
      "category": "Betriebsart",
      "meaning": "Amplitudenmodulation — amplitude modulation.",
      "exam": true,
      "explanation": "The carrier amplitude follows the audio signal. Both sidebands and the carrier are transmitted, so AM needs more bandwidth and power than SSB."
    },
    {
      "code": "FM",
      "category": "Betriebsart",
      "meaning": "Frequenzmodulation — frequency modulation.",
      "exam": true,
      "explanation": "The carrier frequency follows the audio signal at constant amplitude. Robust against amplitude noise; the usual mode for VHF/UHF (UKW) voice and repeaters."
    },
    {
      "code": "PM",
      "category": "Betriebsart",
      "meaning": "Phasenmodulation — phase modulation.",
      "exam": true,
      "explanation": "The carrier phase follows the signal; closely related to FM and often used to generate it."
    },
    {
      "code": "DSB",
      "category": "Betriebsart",
      "meaning": "Doppelseitenbandmodulation — double-sideband modulation.",
      "exam": true,
      "explanation": "Both sidebands are transmitted; with the carrier suppressed it is DSB-SC, the starting point for generating SSB."
    },
    {
      "code": "SSB",
      "category": "Betriebsart",
      "meaning": "Einseitenbandmodulation — single sideband.",
      "exam": true,
      "explanation": "Only one sideband is sent and the carrier is suppressed, making it the most bandwidth- and power-efficient analogue voice mode on HF."
    },
    {
      "code": "USB",
      "category": "Betriebsart",
      "meaning": "oberes Seitenband — upper sideband.",
      "exam": true,
      "explanation": "SSB using the sideband above the suppressed carrier. Convention on HF above 10 MHz and on VHF/UHF."
    },
    {
      "code": "LSB",
      "category": "Betriebsart",
      "meaning": "unteres Seitenband — lower sideband.",
      "exam": true,
      "explanation": "SSB using the sideband below the suppressed carrier. Convention on the HF bands below 10 MHz (160/80/40 m)."
    },
    {
      "code": "CW",
      "category": "Betriebsart",
      "meaning": "Continuous Wave — Morsetelegrafie (A1A).",
      "exam": true,
      "explanation": "On/off keying of an unmodulated carrier. Very narrow bandwidth and excellent weak-signal readability."
    },
    {
      "code": "FSK",
      "category": "Betriebsart",
      "meaning": "Frequency Shift Keying — Frequenzumtastung.",
      "exam": true,
      "explanation": "Digital keying that shifts the carrier between discrete frequencies; the basis of RTTY."
    },
    {
      "code": "PSK",
      "category": "Betriebsart",
      "meaning": "Phase Shift Keying — Phasenumtastung.",
      "exam": true,
      "explanation": "Digital keying that encodes data in carrier phase shifts."
    },
    {
      "code": "ASK",
      "category": "Betriebsart",
      "meaning": "Amplitude Shift Keying — Amplitudenumtastung.",
      "exam": true
    },
    {
      "code": "QAM",
      "category": "Betriebsart",
      "meaning": "Quadraturamplitudenmodulation — quadrature amplitude modulation.",
      "exam": true,
      "explanation": "Combines amplitude and phase modulation on two quadrature carriers to carry several bits per symbol."
    },
    {
      "code": "RTTY",
      "category": "Betriebsart",
      "meaning": "Radioteletype — Funkfernschreiben.",
      "exam": true,
      "explanation": "Classic FSK teleprinter mode using the 5-bit Baudot code."
    },
    {
      "code": "PSK31",
      "category": "Betriebsart",
      "meaning": "Phase-Shift Keying, 31 Baud — narrowband keyboard digital mode.",
      "exam": true
    },
    {
      "code": "FT8",
      "category": "Betriebsart",
      "meaning": "digitale Schwachsignal-Betriebsart (WSJT-X) — weak-signal digital mode.",
      "exam": true,
      "explanation": "Highly sensitive mode with fixed 15-second transmit slots; decodes signals well below the noise floor."
    },
    {
      "code": "WSPR",
      "category": "Betriebsart",
      "meaning": "Weak Signal Propagation Reporter — Bakenbetrieb zur Ausbreitungsforschung.",
      "exam": true,
      "explanation": "Very low-power beacon mode whose reception reports are pooled to map propagation."
    },
    {
      "code": "SSTV",
      "category": "Betriebsart",
      "meaning": "Slow Scan Television — Schmalband-Bildübertragung.",
      "exam": true,
      "explanation": "Sends still pictures slowly enough to fit a voice-bandwidth channel."
    },
    {
      "code": "ATV",
      "category": "Betriebsart",
      "meaning": "Amateurfernsehen — (fast-scan) amateur television.",
      "exam": true,
      "explanation": "Real-time video, typically on the higher bands because of its wide bandwidth."
    },
    {
      "code": "NBFM",
      "category": "Betriebsart",
      "meaning": "Schmalband-FM — narrowband FM.",
      "exam": true,
      "explanation": "FM with reduced deviation (e.g. a 12.5 kHz channel), the usual form for amateur FM voice."
    },

    {
      "code": "MF",
      "category": "Band",
      "meaning": "Mittelwelle — medium frequency, 300 kHz to 3 MHz.",
      "exam": true
    },
    {
      "code": "KW",
      "category": "Band",
      "meaning": "Kurzwelle — shortwave / HF, 3 to 30 MHz.",
      "exam": true,
      "explanation": "The classic long-distance amateur range; relies on ionospheric (skywave) propagation."
    },
    {
      "code": "UKW",
      "category": "Band",
      "meaning": "Ultrakurzwelle — VHF, 30 to 300 MHz.",
      "exam": true,
      "explanation": "Mostly line-of-sight propagation; home of FM voice and repeaters. In the BNetzA band names UKW is exactly VHF; 300 MHz to 3 GHz is UHF / Dezimeterwelle. Colloquially 'UKW' is sometimes stretched to mean VHF and up, but that is not the exam definition."
    },
    {
      "code": "VHF",
      "category": "Band",
      "meaning": "Very High Frequency — 30 to 300 MHz (UKW).",
      "exam": true
    },
    {
      "code": "UHF",
      "category": "Band",
      "meaning": "Ultra High Frequency — 300 MHz to 3 GHz.",
      "exam": true
    },
    {
      "code": "SHF",
      "category": "Band",
      "meaning": "Super High Frequency — 3 to 30 GHz (Mikrowellen).",
      "exam": true
    },
    {
      "code": "EHF",
      "category": "Band",
      "meaning": "Extremely High Frequency — 30 to 300 GHz.",
      "exam": false
    },

    {
      "code": "NF",
      "category": "Signal & Frequenz",
      "meaning": "Niederfrequenz — audio frequency (about 16 Hz to 20 kHz).",
      "exam": true,
      "explanation": "The baseband audio signal before modulation or after demodulation."
    },
    {
      "code": "HF",
      "category": "Signal & Frequenz",
      "meaning": "Hochfrequenz — radio frequency (RF), above the audio range.",
      "exam": true,
      "explanation": "In German usage HF denotes RF signals in general, not specifically the 3 to 30 MHz band (that band is called KW / Kurzwelle)."
    },
    {
      "code": "ZF",
      "category": "Signal & Frequenz",
      "meaning": "Zwischenfrequenz — intermediate frequency (IF).",
      "exam": true,
      "explanation": "The fixed frequency a superheterodyne receiver mixes the signal to, where most selective amplification and filtering happens."
    },
    {
      "code": "IF",
      "category": "Signal & Frequenz",
      "meaning": "Intermediate Frequency — englische Bezeichnung für die Zwischenfrequenz (ZF).",
      "exam": false
    },
    {
      "code": "RF",
      "category": "Signal & Frequenz",
      "meaning": "Radio Frequency — englische Bezeichnung für Hochfrequenz (HF).",
      "exam": false
    },

    {
      "code": "VFO",
      "category": "Baugruppe",
      "meaning": "variabler Oszillator — variable frequency oscillator.",
      "exam": true,
      "explanation": "The tunable oscillator that sets the operating frequency of a transmitter or receiver."
    },
    {
      "code": "VCO",
      "category": "Baugruppe",
      "meaning": "spannungsgesteuerter Oszillator — voltage-controlled oscillator.",
      "exam": true,
      "explanation": "An oscillator whose frequency follows a control voltage; the tunable element inside a PLL."
    },
    {
      "code": "PLL",
      "category": "Baugruppe",
      "meaning": "Phasenregelschleife — phase-locked loop.",
      "exam": true,
      "explanation": "Locks a VCO to a stable reference by comparing phase, forming the basis of modern frequency synthesizers."
    },
    {
      "code": "DDS",
      "category": "Baugruppe",
      "meaning": "direkte digitale Synthese — direct digital synthesis.",
      "exam": true,
      "explanation": "Generates a signal numerically from a clock and a phase accumulator, giving fine, fast frequency steps."
    },
    {
      "code": "BFO",
      "category": "Baugruppe",
      "meaning": "Schwebungsoszillator — beat frequency oscillator.",
      "exam": true,
      "explanation": "Reinjects a carrier at the product detector so CW and SSB become audible."
    },
    {
      "code": "LO",
      "category": "Baugruppe",
      "meaning": "Lokaloszillator — local (mixing) oscillator.",
      "exam": false
    },
    {
      "code": "AGC",
      "category": "Baugruppe",
      "meaning": "automatische Verstärkungsregelung — automatic gain control.",
      "exam": true,
      "explanation": "Holds the receiver output roughly constant across strong and weak signals."
    },
    {
      "code": "ALC",
      "category": "Baugruppe",
      "meaning": "automatische Pegelregelung — automatic level control.",
      "exam": true,
      "explanation": "Limits transmitter drive to prevent overdrive and splatter."
    },
    {
      "code": "PA",
      "category": "Baugruppe",
      "meaning": "Endstufe / Leistungsverstärker — power amplifier.",
      "exam": true
    },
    {
      "code": "LNA",
      "category": "Baugruppe",
      "meaning": "rauscharmer Vorverstärker — low-noise amplifier.",
      "exam": true,
      "explanation": "A low-noise preamplifier, often at the antenna, to improve weak-signal reception on VHF and up."
    },
    {
      "code": "ATU",
      "category": "Baugruppe",
      "meaning": "Antennenanpassgerät — antenna tuning unit.",
      "exam": false,
      "explanation": "Matches the feed line to the transmitter so the PA sees a low SWR; it does not 'tune' the antenna itself."
    },
    {
      "code": "TRX",
      "category": "Baugruppe",
      "meaning": "Transceiver — combined transmitter and receiver.",
      "exam": true
    },
    {
      "code": "Balun",
      "category": "Baugruppe",
      "meaning": "Symmetrierglied — balanced-to-unbalanced transformer.",
      "exam": true,
      "explanation": "Couples a balanced antenna (e.g. a dipole) to an unbalanced coax feed, suppressing currents on the outside of the shield."
    },

    {
      "code": "Diode",
      "category": "Bauteil",
      "meaning": "Diode — conducts current in one direction only.",
      "exam": true
    },
    {
      "code": "LED",
      "category": "Bauteil",
      "meaning": "Leuchtdiode — light-emitting diode.",
      "exam": true
    },
    {
      "code": "FET",
      "category": "Bauteil",
      "meaning": "Feldeffekttransistor — field-effect transistor.",
      "exam": true,
      "explanation": "A voltage-controlled transistor with very high input impedance."
    },
    {
      "code": "MOSFET",
      "category": "Bauteil",
      "meaning": "Metall-Oxid-Halbleiter-FET — metal-oxide-semiconductor FET.",
      "exam": true,
      "explanation": "An insulated-gate FET; common in switching and RF power stages."
    },
    {
      "code": "BJT",
      "category": "Bauteil",
      "meaning": "Bipolartransistor — bipolar junction transistor.",
      "exam": false
    },
    {
      "code": "IC",
      "category": "Bauteil",
      "meaning": "integrierter Schaltkreis — integrated circuit.",
      "exam": false
    },
    {
      "code": "NTC",
      "category": "Bauteil",
      "meaning": "Heißleiter — NTC thermistor (negative temperature coefficient).",
      "exam": true,
      "explanation": "Its resistance falls as temperature rises; used for temperature sensing and inrush limiting."
    },
    {
      "code": "PTC",
      "category": "Bauteil",
      "meaning": "Kaltleiter — PTC thermistor (positive temperature coefficient).",
      "exam": true,
      "explanation": "Its resistance rises as temperature rises; used as a resettable fuse and for protection."
    },
    {
      "code": "LDR",
      "category": "Bauteil",
      "meaning": "Fotowiderstand — light-dependent resistor.",
      "exam": true
    },
    {
      "code": "VDR",
      "category": "Bauteil",
      "meaning": "spannungsabhängiger Widerstand (Varistor) — voltage-dependent resistor.",
      "exam": true,
      "explanation": "Resistance drops sharply above a threshold voltage; clamps surges and protects against overvoltage."
    },

    {
      "code": "dB",
      "category": "Messgröße & Leistung",
      "meaning": "Dezibel — logarithmic ratio of two powers (10·log₁₀).",
      "exam": true,
      "explanation": "+3 dB is roughly double the power, +10 dB ten times. As a power ratio it is relative, not an absolute level."
    },
    {
      "code": "dBi",
      "category": "Messgröße & Leistung",
      "meaning": "Gewinn über Isotropstrahler — gain relative to an isotropic radiator.",
      "exam": true
    },
    {
      "code": "dBd",
      "category": "Messgröße & Leistung",
      "meaning": "Gewinn über Dipol — gain relative to a half-wave dipole.",
      "exam": true,
      "explanation": "0 dBd = 2.15 dBi; the dipole already has 2.15 dBi of gain over isotropic."
    },
    {
      "code": "dBm",
      "category": "Messgröße & Leistung",
      "meaning": "Pegel bezogen auf 1 mW — power level referenced to 1 milliwatt.",
      "exam": true,
      "explanation": "An absolute level: 0 dBm = 1 mW, 30 dBm = 1 W."
    },
    {
      "code": "dBW",
      "category": "Messgröße & Leistung",
      "meaning": "Pegel bezogen auf 1 W — power level referenced to 1 watt.",
      "exam": true
    },
    {
      "code": "SWR",
      "category": "Messgröße & Leistung",
      "meaning": "Stehwellenverhältnis — standing wave ratio.",
      "exam": true,
      "explanation": "Ratio of the standing wave's maximum to minimum on the feed line; 1:1 is a perfect match, higher values mean more reflected power."
    },
    {
      "code": "VSWR",
      "category": "Messgröße & Leistung",
      "meaning": "Spannungs-Stehwellenverhältnis — voltage standing wave ratio.",
      "exam": false
    },
    {
      "code": "ERP",
      "category": "Messgröße & Leistung",
      "meaning": "effektive Strahlungsleistung — effective radiated power.",
      "exam": true,
      "explanation": "Power referenced to a half-wave dipole: transmitter power minus losses, times the antenna gain in dBd."
    },
    {
      "code": "EIRP",
      "category": "Messgröße & Leistung",
      "meaning": "äquivalente isotrope Strahlungsleistung — equivalent isotropically radiated power.",
      "exam": true,
      "explanation": "Like ERP but referenced to an isotropic radiator; EIRP = ERP + 2.15 dB."
    },
    {
      "code": "PEP",
      "category": "Messgröße & Leistung",
      "meaning": "Spitzenleistung — peak envelope power.",
      "exam": true,
      "explanation": "The average power over one RF cycle at the peak of the modulation envelope; the standard rating for SSB transmitters."
    },
    {
      "code": "RMS",
      "category": "Messgröße & Leistung",
      "meaning": "Effektivwert — root mean square.",
      "exam": true,
      "explanation": "The equivalent DC value that produces the same heating; for a sine wave it is the peak divided by √2."
    },
    {
      "code": "Q",
      "category": "Messgröße & Leistung",
      "meaning": "Güte — quality factor of a resonant circuit.",
      "exam": true,
      "explanation": "Ratio of stored to dissipated energy; a higher Q means a narrower, sharper resonance."
    },
    {
      "code": "SNR",
      "category": "Messgröße & Leistung",
      "meaning": "Signal-Rausch-Verhältnis — signal-to-noise ratio.",
      "exam": true
    },

    {
      "code": "AC",
      "category": "Strom & Spannung",
      "meaning": "Wechselstrom / Wechselspannung — alternating current.",
      "exam": true
    },
    {
      "code": "DC",
      "category": "Strom & Spannung",
      "meaning": "Gleichstrom / Gleichspannung — direct current.",
      "exam": true
    },

    {
      "code": "MUF",
      "category": "Ausbreitung",
      "meaning": "höchste brauchbare Frequenz — maximum usable frequency.",
      "exam": true,
      "explanation": "The highest frequency the ionosphere still reflects back for a given path; above it the signal escapes into space."
    },
    {
      "code": "LUF",
      "category": "Ausbreitung",
      "meaning": "niedrigste brauchbare Frequenz — lowest usable frequency.",
      "exam": true,
      "explanation": "Below it absorption (mainly in the D layer) makes the path unusable."
    },
    {
      "code": "NVIS",
      "category": "Ausbreitung",
      "meaning": "Steilstrahlung — near-vertical incidence skywave.",
      "exam": true,
      "explanation": "Near-vertical HF radiation that comes back down over a wide area, giving gap-free regional coverage out to a few hundred km."
    },

    {
      "code": "DMR",
      "category": "Digital & Daten",
      "meaning": "Digital Mobile Radio — digitale Sprach- und Datenbetriebsart.",
      "exam": true,
      "explanation": "TDMA digital voice standard widely used on amateur repeaters and networks."
    },
    {
      "code": "D-STAR",
      "category": "Digital & Daten",
      "meaning": "digitale Sprach- und Datenbetriebsart (ICOM/JARL).",
      "exam": true
    },
    {
      "code": "C4FM",
      "category": "Digital & Daten",
      "meaning": "Continuous 4-level FM — Yaesu System Fusion digital voice.",
      "exam": true
    },
    {
      "code": "APRS",
      "category": "Digital & Daten",
      "meaning": "Automatic Packet Reporting System — Positions- und Telemetriedaten über Packet.",
      "exam": false
    },
    {
      "code": "TNC",
      "category": "Digital & Daten",
      "meaning": "Terminal Node Controller — Packet-Radio-Modem.",
      "exam": false
    },
    {
      "code": "AX.25",
      "category": "Digital & Daten",
      "meaning": "Amateurfunk-Datenprotokoll — amateur packet-radio link protocol.",
      "exam": false
    },
    {
      "code": "CTCSS",
      "category": "Digital & Daten",
      "meaning": "Continuous Tone-Coded Squelch System — subaudible tone squelch.",
      "exam": false,
      "explanation": "A low-frequency tone below the audio that opens a repeater's or receiver's squelch only for stations sending the matching tone."
    },
    {
      "code": "DTMF",
      "category": "Digital & Daten",
      "meaning": "Dual-Tone Multi-Frequency — Mehrfrequenzwahlverfahren.",
      "exam": false
    },
    {
      "code": "DCS",
      "category": "Digital & Daten",
      "meaning": "Digital-Coded Squelch — digitale Rauschsperrencodierung.",
      "exam": false
    },
    {
      "code": "PTT",
      "category": "Digital & Daten",
      "meaning": "Push To Talk — Sendetaste.",
      "exam": true
    },
    {
      "code": "SDR",
      "category": "Digital & Daten",
      "meaning": "Software Defined Radio — softwaredefiniertes Funkgerät.",
      "exam": true
    },
    {
      "code": "RIT",
      "category": "Digital & Daten",
      "meaning": "Receiver Incremental Tuning — Empfänger-Feinverstimmung.",
      "exam": true
    },

    {
      "code": "ITU",
      "category": "Organisation & Vorschrift",
      "meaning": "Internationale Fernmeldeunion — International Telecommunication Union.",
      "exam": true,
      "explanation": "UN agency that allocates spectrum worldwide and defines the three ITU regions."
    },
    {
      "code": "IARU",
      "category": "Organisation & Vorschrift",
      "meaning": "Internationale Amateur-Radio-Union — International Amateur Radio Union.",
      "exam": true,
      "explanation": "Worldwide federation of national amateur-radio societies; coordinates band plans and represents amateurs at the ITU."
    },
    {
      "code": "CEPT",
      "category": "Organisation & Vorschrift",
      "meaning": "Europäische Konferenz der Verwaltungen für Post und Telekommunikation.",
      "exam": true,
      "explanation": "Its recommendations let an amateur licensee operate temporarily in other member countries without applying for a separate licence."
    },
    {
      "code": "BNetzA",
      "category": "Organisation & Vorschrift",
      "meaning": "Bundesnetzagentur — the German telecommunications regulator.",
      "exam": true,
      "explanation": "Issues amateur licences and call signs in Germany and supervises the service."
    },
    {
      "code": "EMV",
      "category": "Organisation & Vorschrift",
      "meaning": "elektromagnetische Verträglichkeit — electromagnetic compatibility (EMC).",
      "exam": true,
      "explanation": "The ability of equipment to operate without causing or suffering undue interference."
    },
    {
      "code": "EMVU",
      "category": "Organisation & Vorschrift",
      "meaning": "elektromagnetische Umweltverträglichkeit — EMF exposure compliance.",
      "exam": true,
      "explanation": "Assessment and limits for human exposure to the electromagnetic fields a station produces."
    },
    {
      "code": "AFu",
      "category": "Organisation & Vorschrift",
      "meaning": "Amateurfunk — amateur radio.",
      "exam": false
    }
  ]
}