# MCQ in Modulation Part 18 | ECE Board Exam

(Last Updated On: February 24, 2021) This is the Multiples Choice Questions Part 18 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 18 of the Series

851. Having an information signal change some characteristic of a carrier signal is called

a. Multiplexing

b. Modulation

c. Duplexing

d. Linear mixing

View Answer:

Answer: Option B

Solution:

852. Which of the following is not true about AM?

a. The carrier amplitude varies.

b. The carrier frequency remains constant.

c. The carrier frequency changes.

d. The information signal amplitude changes the carrier amplitude.

View Answer:

Answer: Option C

Solution:

853. The opposite of modulation is

a. Reverse modulation

b. Downward modulation

c. Unmodulation

d. Demodulation

View Answer:

Answer: Option D

Solution:

854. The circuit used to produce modulation is called

a. Modulator

b. Demodulator

c. Variable gain amplifier

d. Multiplexer

View Answer:

Answer: Option A

Solution:

855. A modulator circuit performs what mathematical operation on its two inputs?

a. Addition

b. Multiplication

c. Division

d. Square root

View Answer:

Answer: Option B

Solution:

856. The ratio of the peak modulating signal voltage to the peak carrier voltage is referred to as

a. The voltage ratio

b. Decibels

c. The modulation index

d. The mix factor

View Answer:

Answer: Option C

Solution:

857. If m is greater than 1, what happens?

a. Normal operation

b. Carrier drops to zero

c. Carrier frequency shifts

d. Information signal is distorted

View Answer:

Answer: Option D

Solution:

858. For ideal AM, which of the following is true?

a. m = 0

b. m = 1

c. m < 1 d. m > 1

View Answer:

Answer: Option B

Solution:

859. The outline of the peaks of a carrier has the shape of the modulating signal and is called the

a. Trace

b. Waveshape

c. Envelope

d. Carrier variation

View Answer:

Answer: Option C

Solution:

860. Overmodulation occurs when

a. Vm > Vc

b. Vm < Vc c. Vm = Vc d. Vm = Vc = 0 [toggle title="View Answer:"] Answer: Option A

Solution:

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861. The values of Vmax and Vmin as read from an AM wave on oscilloscope are 2.8 and 0.3. the percentage of modulation is

a. 10.7%

b. 41.4%

c. 80.6%

d. 93.3%

View Answer:

Answer: Option C

Solution:

862. The new signals produced by modulation are called

a. Spurious emissions

b. Harmonics

c. Intermodulation products

d. Sidebands

View Answer:

Answer: Option D

Solution:

863. A carrier of 880 kHz is modulated by a 3.5 kHz sine wave. The LSB and USB are, respectively,

a. 873 and 887 kHz

b. 876.5 and 883.5 kHz

c. 883.5 and 876.5 kH

d. 887 and 873 kHz

View Answer:

Answer: Option B

Solution:

864. A display of signal amplitude versus frequency is called the

a. Time domain

b. Frequency Spectrum

c. Amplitude Spectrum

d. Frequency Domain

View Answer:

Answer: Option D

Solution:

865. Most of the power in an AM signal is in the

a. Carrier

b. Upper sideband

c. Lower sideband

d. Modulating signal

View Answer:

Answer: Option A

Solution:

866. An AM signal has a carrier power of 5 W. the percentage of modulation is 80% the total sideband power is

a. 0.8 W

b. 1.6 W

c. 2.5 W

d. 4.0 W

View Answer:

Answer: Option B

Solution:

867. For 100% modulation, what percentage of power is in each sideband?

a. 25%

b. 33.3%

c. 50%

d. 100%

View Answer:

Answer: Option A

Solution:

868. An AM transmitter has a percentage of modulation of 88. The carrier power is 440 W. The power is 440 W. The power in one sideband is

a. 85 W

b. 110 W

c. 170 W

d. 610 W

View Answer:

Answer: Option A

Solution:

869. An AM transmitter antenna current is measured with no modulation and found to be 2.6 amperes. With modulation, the current rises to 2.9 amperes. The percentage of modulation is

a. 35%

b. 70%

c. 42%

d. 89%

View Answer:

Answer: Option B

Solution:

870. What is the carrier power in the problem above if the antenna resistance is 75 ohms?

a. 195 W

b. 631 W

c. 507 W

d. 792 W

View Answer:

Answer: Option C

Solution:

871. In an AM signal, the transmitted information is contained within the

a. Carrier

b. Modulating signal

c. Sidebands

d. Envelope

View Answer:

Answer: Option C

Solution:

872. An AM signal without the carrier is called a(n)

a. SSB

b. Vestigial sideband

c. FM signal

d. DSB

View Answer:

Answer: Option D

Solution:

873. What is the minimum AM signal needed to transmit information?

a. Carrier plus sidebands

b. Carrier only

c. One sideband

d. Both sideband

View Answer:

Answer: Option C

Solution:

874. The main advantage of SSB over standard AM or DSB is

a. Less spectrum space is used

b. Simpler equipment is used

c. Less power is consumed

d. A higher modulation percentage

View Answer:

Answer: Option A

Solution:

875. In SSB, which sideband is the best to use?

a. Upper

b. Lower

c. Neither

d. Depends upon the use

View Answer:

Answer: Option D

Solution:

876. The typical audio modulating frequency range used in radio and telephone communication is

a. 50 Hz to 5 kHz

b. 50 Hz to 15 kHz

c. 100 Hz to 10kHz

d. 300 Hz to 3 kHz

View Answer:

Answer: Option D

Solution:

877. An AM signal with a maximum modulating signal frequency of 4.5 kHz has a total bandwidth of

a. 4.5 kHz

b. 6.75 kHz

c. 9 kHz

d. 18 kHz

View Answer:

Answer: Option C

Solution:

878. The modulation system used for telegraphy is

a. Frequency-shift keying

b. Two-tone modulation

c. Pulse-code modulation

d. Single-tone modulation

View Answer:

Answer: Option A

Solution:

879. The process of translating a signal, with or without modulation, to a higher or lower frequency for processing is called

a. Frequency multiplication

b. Frequency division

c. Frequency shift

d. Frequency conversion

View Answer:

Answer: Option D

Solution:

880. Frequency translation is carried out by a circuit called a

a. Translator

b. Convertor

c. Balanced modulator

d. Local oscillator

View Answer:

Answer: Option B

Solution:

881. An input signal of 1.8 MHz is mixed with a local oscillator of 5 MHz. A filter selects the difference signal. The output is

a. 1.8 MHz

b. 3.2 MHz

c. 5 MHz

d. 6.8 MHz

View Answer:

Answer: Option B

Solution:

882. One type of pulse communications system uses pulse that appear as a group, and which vary in number according to the loudness of the voice. This type of pulse modulation is called

a. Pulse duration modulation

b. Pulse amplitude modulation

c. Pulse code modulation

d. Pulse position modulation

View Answer:

Answer: Option C

Solution:

883. An SSB transmitter produces a 400-V peak to peak signal across a 52-Ω antenna load. The PEP output is

a. 192.2 W

b. 384.5 W

c. 769.2 W

d. 3077 W

View Answer:

Answer: Option C

Solution:

884. The output power of an SSB transmitter is usually expressed in terms of

a. Average power

b. RMS power

c. Peak-to-peak power

d. Peak envelope power

View Answer:

Answer: Option D

Solution:

885. The letter-number designation B8E is a form of modulation also known as

a. Pilot-carrier system

b. Independent sideband emission

c. Lincomlex

d. Vestigial sideband transmission

View Answer:

Answer: Option B

Solution:

886. Amplitude modulation is the same as

a. Linear mixing

b. Analog multiplication

c. Signal summation

d. Inductor

View Answer:

Answer: Option B

Solution:

887. In a diode modulator, the negative half of the AM wave is supplied by a(n)

a. Tuned circuit

b. Transformer

c. Capacitor

d. Inductor

View Answer:

Answer: Option A

Solution:

888. Amplitude modulation can be produced by

a. Having the carrier vary a resistance

b. Having the modulating signal vary a capacitance

c. Varying the carrier frequency

d. Varying the gain of an amplifier

View Answer:

Answer: Option A

Solution:

889. Amplitude modulators that vary the carrier amplitude with the modulating signal by passing it through an attenuator work on the principle of

a. Rectification

b. Resonance

c. Variable resistance

d. Absorption

View Answer:

Answer: Option C

Solution:

890. The component used to produce AM at very high frequencies is a

a. Varactor

b. Thermistor

c. Cavity resonator

d. PIN diode

View Answer:

Answer: Option D

Solution:

891. Amplitude modulation generated at a very low voltage or power amplitude is known as

a. High-level modulation

b. Low-level modulation

c. Collector modulation

d. Minimum modulation

View Answer:

Answer: Option B

Solution:

892. A collector modulator has a supply voltage of 48 V. The peak-to-peak amplitude of the modulating signal for 100 percent modulation is

a. 24 V

b. 48 V

c. 96 V

d. 120 V

View Answer:

Answer: Option C

Solution:

893. A collector modulated transmitter has a supply voltage of 24 V and collector current of 0.5 A. The modulator power for 100 percent modulation is

a. 6 W

b. 12 W

c. 18 W

d. 24 W

View Answer:

Answer: Option B

Solution:

894. The circuit that recovers the original modulating information from an AM signal is known as a

a. Modulator

b. Demodulator

c. Mixer

d. Crystal set

View Answer:

Answer: Option B

Solution:

895. The most commonly used amplitude demodulator is the

a. Diode mixer

b. Balanced modulator

c. Envelope detector

d. Crystal filter

View Answer:

Answer: Option A

Solution:

896. A circuit that generates the upper and lower sidebands but no carrier is called a(n)

a. Amplitude modulator

b. Diode detector

c. Class C amplifier

d. Balanced modulator

View Answer:

Answer: Option D

Solution:

897. The inputs to a balance modulator are 1 MHz and a carrier of 1.5 MHz. The outputs are

a. 500 kHz

b. 2.5 MHz

c. 1.5 MHz

d. Both a and b

View Answer:

Answer: Option D

Solution:

898. A widely used balanced modulator is called the

a. Diode bridge circuit

b. Full-wave bridge rectifier

c. Lattice Modulator

d. Balanced bridge modulator

View Answer:

Answer: Option C

Solution:

899. In a diode ring modulator, the diodes act like

a. Variable resistors

b. Switches

c. Rectifiers

d. Variable capacitors

View Answer:

Answer: Option B

Solution:

900. The output of a balanced modulator is

a. AM

b. FM

c. SSB

d. DSB

View Answer:

Answer: Option D

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

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

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