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General · Element 3 · Signals & Emissions

General G8A: Modulation types

These are the 14 official questions in group G8A of the 2023–2027 General question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.

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  1. G8A01Question 1

    How is direct binary FSK modulation generated?

    • ABy keying an FM transmitter with a sub-audible tone
    • BBy changing an oscillator’s frequency directly with a digital control signal Correct
    • CBy using a transceiver’s computer data interface protocol to change frequencies
    • DBy reconfiguring the CW keying input to act as a tone generator

    Why: Direct binary FSK changes an oscillator's frequency with a digital control signal.

  2. G8A02Question 2

    What is the name of the process that changes the phase angle of an RF signal to convey information?

    • APhase convolution
    • BPhase modulation Correct
    • CPhase transformation
    • DPhase inversion

    Why: Changing the phase angle to carry information is phase modulation.

  3. G8A03Question 3

    What is the name of the process that changes the instantaneous frequency of an RF wave to convey information?

    • AFrequency convolution
    • BFrequency transformation
    • CFrequency conversion
    • DFrequency modulation Correct

    Why: Changing the instantaneous frequency is frequency modulation.

  4. G8A04Question 4

    What emission is produced by a reactance modulator connected to a transmitter RF amplifier stage?

    • AMultiplex modulation
    • BPhase modulation Correct
    • CAmplitude modulation
    • DPulse modulation

    Why: A reactance modulator on an RF amplifier stage produces phase modulation.

  5. G8A05Question 5

    What type of modulation varies the instantaneous power level of the RF signal?

    • APower modulation
    • BPhase modulation
    • CFrequency modulation
    • DAmplitude modulation Correct

    Why: Varying the instantaneous power level is amplitude modulation.

  6. G8A06Question 6

    Which of the following is characteristic of QPSK31?

    • AIt is sideband sensitive
    • BIts encoding provides error correction
    • CIts bandwidth is approximately the same as BPSK31
    • DAll these choices are correct Correct

    Why: All the listed traits of QPSK31 are true.

  7. G8A07Question 7

    Which of the following phone emissions uses the narrowest bandwidth?

    • ASingle sideband Correct
    • BVestigial sideband
    • CPhase modulation
    • DFrequency modulation

    Why: SSB uses the narrowest bandwidth of the phone modes.

  8. G8A08Question 8

    Which of the following is an effect of overmodulation?

    • AInsufficient audio
    • BInsufficient bandwidth
    • CFrequency drift
    • DExcessive bandwidth Correct

    Why: Overmodulation makes the signal take up too much bandwidth.

  9. G8A09Question 9

    What type of modulation is used by FT8?

    • A8-tone frequency shift keying Correct
    • BVestigial sideband
    • CAmplitude compressed AM
    • D8-bit direct sequence spread spectrum

    Why: FT8 uses 8-tone frequency shift keying.

  10. G8A10Question 10

    What is meant by the term “flat-topping,” when referring to an amplitude-modulated phone signal?

    • ASignal distortion caused by insufficient collector current
    • BThe transmitter’s automatic level control (ALC) is properly adjusted
    • CSignal distortion caused by excessive drive or speech levels Correct
    • DThe transmitter’s carrier is properly suppressed

    Why: Flat-topping is AM distortion caused by too much drive or speech level.

  11. G8A11Question 11

    What is the modulation envelope of an AM signal?

    • AThe waveform created by connecting the peak values of the modulated signal Correct
    • BThe carrier frequency that contains the signal
    • CSpurious signals that envelop nearby frequencies
    • DThe bandwidth of the modulated signal

    Why: The AM envelope is the waveform you get by connecting the signal's peaks.

  12. G8A12Question 12

    What is QPSK modulation?

    • AModulation using quasi-parallel to serial conversion to reduce bandwidth
    • BModulation using quadra-pole sideband keying to generate spread spectrum signals
    • CModulation using Fast Fourier Transforms to generate frequencies at the first, second, third, and fourth harmonics of the carrier frequency to improve noise immunity
    • DModulation in which digital data is transmitted using 0-, 90-, 180- and 270-degrees phase shift to represent pairs of bits Correct

    Why: QPSK sends pairs of bits as phase shifts of 0, 90, 180 and 270 degrees.

  13. G8A13Question 13

    What is a link budget?

    • AThe financial costs associated with operating a radio link
    • BThe sum of antenna gains minus system losses
    • CThe sum of transmit power and antenna gains minus system losses as seen at the receiver Correct
    • DThe difference between transmit power and receiver sensitivity

    Why: A link budget is transmit power plus antenna gains minus system losses at the receiver.

  14. G8A14Question 14

    What is link margin?

    • AThe opposite of fade margin
    • BThe difference between received power level and minimum required signal level at the input to the receiver Correct
    • CTransmit power minus receiver sensitivity
    • DReceiver sensitivity plus 3 dB

    Why: Link margin is how far the received level is above the minimum required.

Learn G8A step by stepThe General course teaches this group in a short guided lesson, then drills you on the questions you miss. Start with the free lessons to see how it works.
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