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# MCQ in Modulation Part 11 | ECE Board Exam

This is the Multiples Choice Questions Part 11 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 11 of the Series

501. The predominant cause of phase distortion.

a. overmodulation

b. buffering

c. filtering

d. clipping

Solution:

502. It is the total phase shift encountered by a signal and can generally be tolerated as long as all frequencies undergo the same amount of phase delay.

a. differential phase shift

b. absolute phase shift

c. relative phase shift

d. integrated phase shift

Solution:

503. ________ occurs when different frequencies undergo different phase shifts and may have a detrimental effect on the complex waveform.

a. differential phase shift

b. absolute phase shift

c. relative phase shift

d. integrated phase shift

Solution:

504. What is the minimum AM signal needed to transmit information

a. carrier plus sidebands

b. carrier only

c. one sideband

d. both sidebands

Solution:

505. 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

Solution:

506. __________ occurs when the amplitude-versus-frequency characteristics of a signal at the output of a receiver cover from those in the original information signal.

a. frequency distortion

b. digital distortion

c. phase distortion

d. amplitude distortion

Solution:

507. The circuit used to produced modulations called

a. modulator

b. demodulator

c. variable gain amplifier

d. multiplexer

Solution:

508. It is the result of non-uniform gain in amplifiers and filters.

a. harmonic distortion

b. amplitude distortion

c. frequency distortion

d. phase distortion

Solution:

509. It is a result of harmonic and intermodulation distortion and is caused by non-linear amplification.

a. amplitude distortion

b. phase distortion

c. harmonic distortion

d. frequency distortion

Solution:

510. The most commonly used amplitude demodulator is the

a. diode mixer

b. balanced modulator

c. envelope detector

d. crystal filter

Solution:

511. It is a special case of intermodulation distortion and a predominant cause of frequency distortion.

a. second-order intercept distortion

b. phase distortion

c. third-order intercept distortion

d. first-order intercept distortion

Solution:

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

a. time domain

b. frequency spectrum

c. amplitude modulation

d. frequency domain

Solution:

513. It is a parameter associated with frequencies that fall within the passband of the filter.

a. coupling loss

b. diffusion loss

c. insertion loss

d. filter loss

Solution:

514. A circuit that generates the upper and lower sidebands but no carrier is called

a. amplitude modulator

b. diode detector

c. class C amplifier

d. balanced modulator

Solution:

515. Vestigial sideband modulation (C3F) is normally used for

a. HF point-to-point communications

Solution:

516. It is generally defined as the ratio of the power transferred to a load with a filter in the circuit to the power transferred to a load without a filter.

a. distortion loss

b. insertion loss

c. filter loss

d. harmonic loss

Solution:

517. The modulation index of an AM wave is changed from 0 to 1. The transmitted power is

a. unchanged

b. halved

c. doubled

d. increased by 50 percent

Solution:

518. The inputs to a balanced modulator are 1MHz and a carrier of 1.5 MHz. The outputs are

a. 500 kHz and 1.5 MHz

b. 2.5 MHz and 1.5 MHz

c. 1.5 MHz and 500 kHz

d. 500 kHz and 2.5 MHz

Solution:

519. It is an indication of the reduction the signal-to-noise ration as a signal propagates through the receiver.

a. noise figure

b. equivalent noise temperature

c. noise factor

d. signal-to-noise ratio

Solution:

520. Types of receivers where the frequencies generated in the receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter.

a. coherent

b. asynchronous

c. non-coherent

d. none of these

Solution:

521. Types of receiver where either no frequencies are generated in the receiver of the frequencies used for demodulation are completely independent form the transmitter’s carrier frequency.

a. synchronous

b. coherent

c. asynchronous

d. any of these

Solution:

522. A widely used balanced modulator is called the ________.

a. diode bridge circuit

b. full-wave bridge rectifier

c. lattice modulator

d. balanced bridge modulator

Solution:

523. Non-coherent detection is also known as ________.

a. frequency detection

b. noise detection

c. phase detection

d. envelope detection

Solution:

524. It is one of the earliest type of AM receiver

a. TRF

b. transistorized

c. superhet

d. Armstrong

Solution:

525. Which of the following is not true about the disadvantages of tuned radio frequency receiver?

a. their bandwidth is inconsistent and varies with center frequency when tuned over a wide range of input frequencies

b. it is unstable due to the large number of RF amplifiers all tuned to the same center frequency

c. their gains are not uniform over a very wide frequency range

d. it is very complex to construct

Solution:

526. In a diode ring modulator, the diode acts like

a. variable resistors

b. switches

c. rectifiers

d. variable capacitors

Solution:

527. It means to mix two frequencies together in a non-linear device or to translate on frequency to another using non-linear mixing.

a. oscillation

b. heterodyne

c. modulation

d. amplification

Solution:

528. 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 modulation is

a. 35%

b. 70%

c. 42%

d. 89%

Solution:

529. Its primary purpose is to provide enough initial bandlimiting to prevent a specific unwanted radio frequency from entering the receiver.

a. detector

b. predetector

c. preselector

d. mixer

Solution:

530. It function is to reduce the noise bandwidth of the receiver and provides initial step toward reducing the overall receiver bandwidth to the minimum bandwidth required to pass the information signals.

a. preselector

b. detector

c. mixer

d. predetector

Solution:

531. The output of a balanced modulator is

a. AM

b. FM

c. SSB

d. DSB

Solution:

532. What is the first active device encountered by the received signal in the receiver?

a. mixer

b. RF amplifier

c. local oscillator

d. detector

Solution:

533. The IF section is also known as

a. bandpass filters

b. IF strip

c. IF filter

d. intermediate filters

Solution:

534. The detector in an AM receiver is known as

a. audio detector

b. power detector

c. first detector

d. amplitude limiter

Solution:

535. A carrier of 880kHz 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 kHz

d. 887 and 873 kHz

Solution:

536. The most commonly used filter in SSB generators uses

a. LC networks

b. mechanical resonators

c. crystals

d. RC networks and op-amps

Solution:

537. Its purpose of the detector section is to convert the IF signals back to the original source information.

a. mixer

b. audio amplifier

c. converter

d. detector

Solution:

538. It means that the two adjustments are mechanically tied together so that a single adjustment will change the center frequency of the preselector, at the same time, change the oscillator frequency.

a. high-side injecting

b. low-side injecting

c. gang tuning

d. local oscillator tracking

Solution:

539. In a low-level AM system, amplifiers following the modulated stage must be

a. linear devices

b. harmonic devices

c. class C amplifiers

d. nonlinear devices

Solution:

540. When the local oscillator is tuned above the radio frequency, it is called

a. local oscillator tracking

b. low-side injection

c. gang tuning

d. high-side injection

Solution:

541. The equivalent circuit of a quartz us a

a. series resonant circuit

b. parallel resonant circuit

c. none of these

d. series and parallel resonant circuit

Solution:

542. It is the ability of the local oscillator in a receiver to oscillate either above or below the selected radio frequency carrier by an amount equal to the intermediate frequency throughout the entire radio frequency brand.

a. tracking

b. mixing

c. heterodyning

d. tuning

Solution:

543. The difference between the actual local oscillator frequency and the desired frequency is called ________.

a. mixing error

b. gang error

c. tracking error

d. quantizing error

Solution:

544. What technique is used to prevent tracking error?

a. using RLC circuit

b. using tuned circuit

c. using three-point tracking

d. using ganged capacitors

Solution:

545. a crystal lattice filter has a crystal frequencies pf 27.5 and 27.502MHz. The bandwidth is approximately

a. 2 kHz

b. 3 kHz

c. 27.501 MHz

d. 55.502 MHz

Solution:

546. ___________ is any frequency other than selected radio frequency carrier that, if allowed to enter a receiver and mix it with local oscillator, will produce a cross-product frequency that is equal to the intermediate frequency

a. image frequency

b. intermediate frequency

c. aliasing frequency

d. ghost

Solution:

547. It is a equivalent to a second radio frequency that will produce an IF that will interfere with the IF from the desired radio frequency.

a. aliasing frequency

b. image frequency

c. interference

d. intermediate frequency

Solution:

548. An SSB generator has a sideband filter centered at 3.0 MHz. The modulating signal is 3 kHz. To produce both upper and lower sidebands, the following carrier frequencies must be produced:

a. 2.7 and 3.3 MHz

b. 3.3 and 3.6 MHz

c. 2997 and 3003 kHz

d. 3000 and 3003 kHz

Solution:

549. It is a numerical measure of the ability of the preselector to reject the image frequency.

a. image frequency rejection ratio

b. noise figure

c. numerical aperture

d. signal-to-noise ratio

Solution:

550. _________ occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial.

a. spurious pointing

b. under coupling

c. double spotting

d. optimal coupling

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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