This is the Multiples Choice Questions Part 17 of the Series in Modulation as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.
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 XVII of the Series
801. What is the maximum deviation for monoaural TV sound
- a. 25 kHz
- b. 75 kHz
- c. 50 kHz
- d. 125 kHz
802. What is the maximum deviation for stereo TV sound?
- a. 25 kHz
- b. 75 kHz
- c. 50 kHz
- d. 125 kHz
803. In FM stereo broadcasting, the L + R signal
- a. double-sideband modulates a subcarrier
- b. modulates the FM carrier
- c. frequency modulates a subcarrier
- d. is not transmitted
804. In FM stereo broadcasting, the L – R signal
- a. double-sideband modulates a subcarrier
- b. modulates the FM carrier
- c. frequency modulates a subcarrier
- d. none of these
805. The SCA signal if used in FM broadcasting is transmitted via
- a. a 19 kHz subcarrier
- b. a 38 kHz subcarrier
- c. a 67 kHz subcarrier
- d. the main FM carrier
806. Which of the following is considered as an indirect method of generating FM?
- a. reactance modulator
- b. balanced modulator
- c. varactor diode modulation
- d. armstrong system
807. In an FM system, if the modulation index is doubled by halving the modulating frequency, what will be the effect on the maximum deviation?
- a. remains the same
- b. doubles
- c. decrease by 1/2
- d. increase by 1/4
808. Determine from the following the common use of DSB in broadcast and telecommunication.
- a. satellite communications
- b. FM/TV stereo
- c. two-way communications
- d. telephone systems
809. Phase modulation emission type
- a. F3F
- b. G3E
- c. F3E
- d. F3C
810. The range of frequencies over which a PLL will cause the input of the VCO signals to remain synchronized is known as the _________ range.
- a. capture
- b. lock
- c. acquisition
- d. any of these
811. If the PLL input is zero, the VCO will operate at its ____________ frequency.
- a. free-running
- b. natural
- c. operating
- d. any of these
812. Since a PLL will only respond to signals over a narrow frequency range, it acts likes a ________.
- a. low-pass filter
- b. high-pass filter
- c. bandpass filter
- d. bandstop filter
813. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ___________.
- a. modulating signal
- b. carrier signal
- c. carrier amplitude
- d. VCO output
814. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ________.
- a. FM input
- b. VCO input
- c. modulating signal
- d. error signal
815. After the IF stages have been aligned, the next state to align in FM receiver is
- a. local oscillator
- b. limiter stage
- c. RF amplifier
- d. mixer stage
816. The modulation system used for telegraphy is
- a. frequency-shift keying
- b. two-tone modulation
- c. purse-code modulation
- d. single-tone modulation
817. What is emission F3F?
- a. Facsimile
- b. RTTY
- c. modulated CW
- d. television
818. What is a frequency discriminator?
- a. a circuit for filtering two closely adjacent signals
- b. a circuit for detecting FM signals
- c. an FM generator
- d. an automatic band switching circuit
819. Type of radio communication transmission utilizing frequency modulation technique
- a. television video
- b. broadcasting in 535-1606 kHz
- c. single sideband HF transmission
- d. television audio
820. Why was FM first developed?
- a. to compete with AM
- b. to overcome noise
- c. to increase listeners
- d. to supplement AM
821. To what feature of the modulating tone is FM deviation proportional?
- a. amplitude
- b. frequency
- c. phase
- d. phase shift
822. Which of the following is not a basic filed of FM?
- a. broadcast
- b. TV video
- c. mobile communications
- d. amateur radio
823. Under what condition would a 1 kHz AF signal produce a single pair of FM sidebands?
- a. wideband
- b. broadcast FM
- c. TV audio FM
- d. narrowband FM
824. What deviation is considered 100% for FM broadcast stations?
- a. 75 kHz
- b. 220 kHz
- c. 270 kHz
- d. 75 kHz or 220 kHz
825. In FM broadcasting, what is the highest required modulating frequency?
- a. 75 kHz
- b. 50 kHz
- c. 25 kHz
- d. 15 kHz
826. In FM broadcasting, what is the lowest required modulating frequency?
- a. 50 Hz
- b. 30 Hz
- c. 10 Hz
- d. 5 Hz
827. What is the disadvantage of slope detection of FM>
- a. no discrimination against noise
- b. less AF distortion
- c. less AF out
- d. no filtering of carrier
828. What is the unction of the dc that comes out of the dc amplifier in a PLL-type FM detector?
- a. carrier signal
- b. filter signal
- c. error signal
- d. phase signal
829. What is the function of the dc that comes out of the dc amplifier in a PLL-type FM detector?
- a. oscillators
- b. AF signal
- c. RF signal
- d. carrier signal
830. Why should discriminators be tuned for a straight characteristic S-curve?
- a. less AF distortion
- b. greater AF out
- c. less RF out
- d. less RF distortion
831. What band for high-Q coils be more desirable for stagger-tuned-type discriminator transformer?
- a. wide
- b. intermediate
- c. interfacing
- d. narrow
832. In a Foster-Seeley circuit, the AF output voltage is ________.
- a. varying DC
- b. varying AC
- c. steady DC
- d. steady AC
833. In a stagger-tuned discriminator, the AF output voltage is _________.
- a. varying DC
- b. varying AC
- c. steady DC
- d. steady AC
834. In a ratio detector, the AF output voltage is
- a. steady AC
- b. varying AC
- c. steady DC
- d. varying DC
835. In a gated-beam detector, the AF output voltage is _________.
- a. steady DC
- b. varying AC
- c. varying DC
- d. steady AC
836. Which of the following discriminator circuits require limiters ahead of them?
- a. quadrature detector
- b. foster-seeley discriminator
- c. slope detector
- d. stagger-tuned
837. Which of the following discriminator circuits provide an automatic gain control voltage?
- a. ratio detector
- b. balanced slope detector
- c. quadrature detector
- d. stagger-tuned detector
838. Which of the following discriminator circuits has its diodes in series?
- a. ratio
- b. quadrature detector
- c. round-travis detector
- d. slope detector
839. To what frequency must the gated-beam quadrature circuit be tuned in a TV receiver?
- a. 10.7 MHz
- b. 455 kHz
- c. 70 MHz
- d. 4.5 MHz
840. To what frequency must the gated-beam quadrature circuit be tuned in an FM broadcast receiver?
- a. 4.3 MHz
- b. 10.7 MHz
- c. 11 MHz
- d. 4.8 MHz
841. What is the advantage of PM?
- a. can use crystal oscillator
- b. uses more multistage
- c. less selective fading
- d. simplicity
842. With what FM detectors would AGC be an advantage?
- a. foster-seeley detector
- b. ratio detector
- c. quadrature detector
- d. phase-locked loop
843. What is the reason for using pre-emphasis?
- a. increase amplitude
- b. reduce carrier shift
- c. amplify RF signal
- d. reduce noise reception
844. What are the two types of stages in an FM receiver that differ from those in an AM receiver?
- a. limiting IF and detectors
- b. oscillators and IF amplifiers
- c. mixers and RF amplifiers
- d. local oscillators and mixers
845. What special circuits are used in a squelch system that can follow changing noise levels?
- a. noise amplifiers
- b. rectifier
- c. dc amplifier
- d. any of these
846. Why might FM be better than AM for mobile ________.
- a. better coverage
- b. not affected by solar cycles
- c. reduce flutter
- d. not absorbed by ionosphere
847. What is the order of circuit alignment in an FM receiver?
- a. discriminator, limiters, IF, mixer and RF
- b. RF, limiters, IF, mixer and discriminator
- c. limiters, mixer, RF, discriminator and IF
- d. RF, mixer, RF, IF, limiters and discriminator
848. What is the another name for the reactance-tube modulator?
- a. Crosby
- b. Foster-Seeley
- c. Round Travis
- d. Messier
849. What effect would be produced if a small inductance were used in place of the 50 pF capacitance in the reactance-tube modulator?
- a. the circuit becomes resistive
- b. reactance modulator looks like an inductive circuit
- c. reactance modulator looks like Xc
- d. any of these
850. The following are significant circuits in the AFC system except:
- a. crystal
- b. mixer
- c. IF
- d. filter
851. Besides the reactance-tube modulator, what is another method of producing direct FM?
- a. armstrong modulator
- b. voltage variable capacitor
- c. impedance modulator
- d. slug indicator
Complete List of MCQs in Communications Engineering per topic
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