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# MCQ in Modulation Part 17 | 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.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Amplitude Modulation
• MCQ in Phase Modulation
• MCQ in Sound Pressure Level
• MCQ in Frequency Modulation
• MCQ in Pulse Modulation

#### Continue Practice Exam Test Questions Part 17 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

Solution:

802. What is the maximum deviation for stereo TV sound?

a. 25 kHz

b. 75 kHz

c. 50 kHz

d. 125 kHz

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

809. Phase modulation emission type

a. F3F

b. G3E

c. F3E

d. F3C

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

816. The modulation system used for telegraphy is

a. frequency-shift keying

b. two-tone modulation

c. purse-code modulation

d. single-tone modulation

Solution:

817. What is emission F3F?

a. Facsimile

b. RTTY

c. modulated CW

d. television

Solution:

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

Solution:

819. Type of radio communication transmission utilizing frequency modulation technique

a. television video

c. single sideband HF transmission

d. television audio

Solution:

820. Why was FM first developed?

a. to compete with AM

b. to overcome noise

c. to increase listeners

d. to supplement AM

Solution:

821. To what feature of the modulating tone is FM deviation proportional?

a. amplitude

b. frequency

c. phase

d. phase shift

Solution:

822. Which of the following is not a basic filed of FM?

b. TV video

c. mobile communications

Solution:

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

Solution:

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

Solution:

825. In FM broadcasting, what is the highest required modulating frequency?

a. 75 kHz

b. 50 kHz

c. 25 kHz

d. 15 kHz

Solution:

826. In FM broadcasting, what is the lowest required modulating frequency?

a. 50 Hz

b. 30 Hz

c. 10 Hz

d. 5 Hz

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

831. What band for high-Q coils be more desirable for stagger-tuned-type discriminator transformer?

a. wide

b. intermediate

c. interfacing

d. narrow

Solution:

832. In a Foster-Seeley circuit, the AF output voltage is ________.

a. varying DC

b. varying AC

Solution:

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

a. varying DC

b. varying AC

Solution:

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

b. varying AC

d. varying DC

Solution:

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

b. varying AC

c. varying DC

Solution:

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

b. foster-seeley discriminator

c. slope detector

d. stagger-tuned

Solution:

837. Which of the following discriminator circuits provide an automatic gain control voltage?

a. ratio detector

b. balanced slope detector

d. stagger-tuned detector

Solution:

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

a. ratio

c. round-travis detector

d. slope detector

Solution:

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

Solution:

a. 4.3 MHz

b. 10.7 MHz

c. 11 MHz

d. 4.8 MHz

Solution:

841. What is the advantage of PM?

a. can use crystal oscillator

b. uses more multistage

d. simplicity

Solution:

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

a. foster-seeley detector

b. ratio detector

d. phase-locked loop

Solution:

843. What is the reason for using pre-emphasis?

a. increase amplitude

b. reduce carrier shift

c. amplify RF signal

d. reduce noise reception

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

848. What is the another name for the reactance-tube modulator?

a. Crosby

b. Foster-Seeley

c. Round Travis

d. Messier

Solution:

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

Solution:

850. The following are significant circuits in the AFC system except:

a. crystal

b. mixer

c. IF

d. filter

Solution:

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

Solution:

#### Questions and Answers in Modulation Series

Following is the list of multiple choice questions in this brand new series:

MCQ in Modulation
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQ from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQ from Number 451 โ 500                 Answer key: PART 10

### Complete List of MCQ in Communications Engineering per topic

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