Online Questions and Answers Topic Outline
- MCQs in Amplitude Modulation
- MCQs in Phase Modulation
- MCQs in Sound Pressure Level
- MCQs in Frequency Modulation
- MCQs in Pulse Modulation
MCQs in Modulation Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part XIV of the Series
651. He developed the first successful FM radio system
- a. B.E.Alpine
- b. N.S. Kapany
- c. E.H. Armstrong
- d. A.C.S. Van Heel
652. Results whenever the phase angle of sinusoidal wave is varied with respect to time
- a. angle modulation
- b. digital modulation
- c. amplitude modulation
- d. pulse modulation
653. In the spectrum of a frequency -modulated wave
- a. the carrier frequency disappears with a large modulation index
- b. the amplitude of any sideband depends on the modulation index
- c. the total number of sidebands depends on the modulation index
- d. the carrier frequency cannot disappear
654.What is the frequency swing of an FM broadcast transmitter when modulated 60%
- a. 60 kHz
- b. 45 kHz
- c. 30 kHz
- d. 25 kHz
655. Varying the frequency of a constant -amplitude carrier directly proportional to the amplitude to the modulating signal at a rate equal to the frequency of the modulating signal
- a. amplitude modulation
- b. angle modulation
- c. phase modulation
- d. frequency modulation
656. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the frequency signal?
- a. amplitude
- b. frequency
- c. phase
- d. shape
657. It is a modulation where the angle of a wave carrier is varied from its reference value
- a. amplitude modulation
- b. angle modulation
- c. analog modulation
- d. digital modulation
658. Both FM and PM are types of what kind of modulation?
- a. amplitude
- b. phase
- c. angle
- d. duty cycle
659. Varying the phase of a constant amplitude carrier displacement proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal.
- a. amplitude modulation
- b. angle modulation
- c. phase modulation
- d. frequency modulation
660. The difference between phase and frequency modulation
- a. is purely theoretical because they are the same in practice
- b. is too great to make the two systems compatible
- c. lies in the poorer audio responses of phase modulation
- d. lies in the different definitions of the modulation index
661. The relative angular displacement of the carrier phase in radians with respect to the reference phase is called __________.
- a. phase deviation
- b. carrier deviation
- c. frequency deviation
- d. information deviation
662. If the amplitude of the modulating signal decreases, the carrier deviation
- a. increases
- b. decreases
- c. remains constant
- d. goes to zero
663. On an FM signal, maximum deviation occurs at what point on the modulating signal?
- a. zero-crossing points
- b. peak positive amplitudes
- c. peak negative amplitude
- d. both peak positive and negative amplitudes
664. The amount of oscillator frequency increase and decrease around the carrier frequency is called _________.
- a. frequency deviation
- b. phase shift
- c. intelligence frequency
- d. baseband
665. The relative displacement of the carrier frequency in hertz in respect to its unmodulated value is called _____________.
- a. frequency deviation
- b. phase deviation
- c. information deviation
- d. carrier deviation
666. A pre-emphasis circuit provides extra noise immunity by
- a. boosting the bass frequencies
- b. amplifying the higher audio frequencies
- c. pre-amplifying the whole audio band
- d. converting the phase modulation to FM
667. It is the instantaneous change in phase of the carrier at a given instant of time and indicates how much phase of the carrier is changing with respect to its reference phase.
- a. instantaneous frequency
- b. instantaneous frequency deviation
- c. instantaneous phase
- d. instantaneous phase deviation
668. Calculate the amount of frequency deviation caused by a limited noise spike that still cause an undesired phase shift of 35 degrees when the input frequency is 5 kHz.
- a. 2.40 kHz
- b. 3.05 kHz
- c. 1.29 kHz
- d. 4.45 kHz
669. Which of the following determines the rate of carrier deviation?
- a. intelligence frequency
- b. frequency deviation
- c. carrier frequency
- d. broadband frequency
670. It is the precise phase of the carrier at a given instant of time
- a. instantaneous phase deviation
- b. instantaneous phase
- c. instantaneous frequency deviation
- d. instantaneous frequency
671. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?
- a. shape
- b. phase
- c. frequency
- d. amplitude
672. In FM, it is a device that in which amplitude variations are derived in response to frequency or phase variations
- a. detector
- b. discriminator
- c. demodulator
- d. receiver
673. Maximum frequency deviation of a PM signal occurs at
- a. zero-crossing points
- b. peak positive amplitudes
- c. peak negative amplitude
- d. peak positive and negative amplitude
674. Since noise phase-modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude
- a. remains constant
- b. is decreased
- c. is increased
- d. is equalized
675. It is the instantaneous change in frequency of the carrier and is defined as the first time derivative of the phase deviation
- a. instantaneous frequency
- b. instantaneous frequency deviation
- c. instantaneous phase
- d. instantaneous phase deviation
676. Since noise phase- modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude
- a. remains constant
- b. is decreased
- c. is increased
- d. is equalized
677. It is the precise frequency of the carrier at a given instant of time is defined as the first time derivative of the instantaneous phase.
- a. instantaneous frequency
- b. instantaneous frequency deviation
- c. instantaneous phase
- d. instantaneous phase deviation
678. It is the output-versus-input transfer functions for modulators which give the relationship between the output parameter changes in respect to specified changes in the input signal.
- a. frequency deviation
- b. deviation sensitivity
- c. transconductance curve
- d. phase deviation
679. When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is
- a. amplitude modulation
- b. phase modulation
- c. frequency modulation
- d. any of the above
680. In PM, carrier frequency deviation is not proportional to:
- a. modulating signal amplitude
- b. carrier amplitude and frequency
- c. modulating signal frequency
- d. modulator phase shift
681. To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and phase modulator?
- a. low-pass filter
- b. high-pass filter
- c. phase shifter
- d. bandpass filter
682. Indicate which one of the following is not an advantage of PM over AM:
- a. better noise immunity is provided
- b. lower bandwidth is required
- c. the transmitted power is more useful
- d. less modulating power is required
683. With phase modulation, the maximum frequency deviation occurs during what value of the modulating signal?
- a. positive peak value
- b. rms value
- c. negative peak value
- d. zero crossings
684. With frequency modulation, maximum frequency deviation occurs _____ of the modulation signal.
- a. positive peak value
- b. both positive and negative peak value
- c. negative peak value
- d. zero crossings
685. What was the first broadcast FM system called?
- a. Arc transmitter
- b. MOPA
- c. Armstrong
- d. crystal
686. With phase modulation, peak phase deviation is called _________.
- a. modulation index
- b. frequency deviation
- c. phase deviation
- d. instantaneous phase
687. The FM produced by PM is called
- a. FM
- b. PM
- c. indirect FM
- d. indirect PM
688. In a broadcast superheterodyne receiver, the
- a. local oscillator operates below the signal frequency
- b. mixer input must be tuned to the signal frequency
- c. local oscillator frequency is normally double the OF
- d. RF amplifier normally works at 455kHz above the carrier frequency
689. If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be
- a. zero
- b. the carrier frequency
- c. above the carrier frequency
- d. below the carrier frequency
690. To prevent overloading of the last IF amplifier in the receiver, one should use the
- a. squelch
- b. variable sensitivity
- c. variable selectivity
- d. double conversion
691. The peak-to-peak frequency deviation is sometimes called __________.
- a. phase deviation
- b. peak phase deviation
- c. carrier swing
- d. instantaneous frequency
692. A 100MHz carrier is deviated 50 kHz by 4kHz signal. The modulation index is
- a. 5
- b. 8
- c. 12.5
- d. 20
693. With angle modulation, it is defined as the ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form.
- a. modulation index
- b. percent modulation
- c. frequency deviation
- d. phase deviation
694. In a broadcast FM system, the input S/N = 4. Calculate the worst case S/N at the output if the receiver's internal noise effect is negligible.
- a. 19.8:1
- b. 21.6:1
- c. 23:1
- d. 15:1
695. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal.
- a. frequency modulators
- b. amplitude modulators
- c. phase modulators
- d. mixers
696. In a ratio detector
- a. the linearity is worse than in a phase discriminator
- b. stabilization against signal strength variations is provided
- c. the output is twice that obtainable from the similar phase discriminator
- d. the circuit is the same as in a discriminator, except that the diodes are reversed
697. The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. The deviation ratio is
- a. 0.2
- b. 5
- c. 8
- d. 40
698. The unmodulated carrier is a single-frequency sinusoid commonly called _________.
- a. unrest frequency
- b. rest frequency
- c. frequency-modulated frequency
- d. carrier frequency
699. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal
- a. phase modulator
- b. phase deviator
- c. amplitude deviator
- d. frequency modulator
700. The typical squelch circuit
- a. cuts off an audio amplifier when the carrier is absent
- b. eliminates the RF interference when the signal is weak
- c. cuts off an IF amplifier when the AGC is maximum
- d. cuts off an IF amplifier when the AGC is minimum
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