# MCQs in Modulation Part XVII

Compiled MCQs in Modulation Part 17 of the series as one topic in Electronic System and Technologies (Communications Engineering) in the ECE Board Exam.

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:

Modulation MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI
PART 7: MCQs from Number 301 – 350                 Answer key: PART VII
PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII
PART 9: MCQs from Number 401 – 450                 Answer key: PART IX
PART 17: MCQs from Number 801 – 850                 Answer key: PART XVII

### 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?

• b. TV video
• c. mobile communications

823. Under what condition would a 1 kHz AF signal produce a single pair of FM sidebands?

• a. wideband
• 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

833. In a stagger-tuned discriminator, the AF output voltage is _________.

• a. varying DC
• b. varying AC

834. In a ratio detector, the AF output voltage is

• b. varying AC
• d. varying DC

835. In a gated-beam detector, the AF output voltage is _________.

• b. varying AC
• c. varying DC

836. Which of the following discriminator circuits require limiters ahead of them?

• 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
• d. stagger-tuned detector

838. Which of the following discriminator circuits has its diodes in series?

• a. ratio
• 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

• 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
• d. simplicity

842. With what FM detectors would AGC be an advantage?

• a. foster-seeley detector
• b. ratio 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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