# MCQ in Modulation Part 10 | ECE Board Exam

(Last Updated On: April 17, 2020) This is the Multiples Choice Questions Part 10 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 10 of the Series

451. The process of impressing a low frequency information signals onto a high-frequency carrier signal is called _____.

a. demodulation

b. oscillation

c. modulation

d. amplification

Solution:

452. A silicon varactor diode exhibits a capacitance of 200 pF at zero bias. If it is in parallel with a 60-pF capacitor and a 200-uH inductor, calculate the range of resonant frequency as the diode varies through a reverse bias of 3 to 15 V.

a. 679 kHz to 2.13 MHz

b. 966 kHz to 1.15 MHz

c. 355 kHz to 3.12 MHz

d. 143 kHz to 4.53 MHz

Solution:

453. A process where the received signal is transformed into its original form.

a. demodulation

b. damping

c. amplification

d. oscillation

Solution:

454. It is the process of changing the amplitude of a relative high frequency carrier signal in proportion with the instantaneous value of the modulating signal.

a. frequency modulation

b. digital modulation

c. phase modulation

d. analog modulation

Solution:

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

a. carrier

b. upper sideband

c. lower sideband

d. modulating signal

Solution:

456. Amplitude modulation is the same as

a. linear mixing

b. analog multiplexing

c. signal summation

d. multiplexing

Solution:

457. The shape of the amplitude-modulated wave is called ______.

a. sidebands

b. modulating signal

c. envelope

d. carrier signal

Solution:

458. In a diode modulator, the negative half of the AM wave is supplied by

a. tuned circuit

b. transformer

c. capacitor

d. inductor

Solution:

459. It is a term used to describe the amount of amplitude change present in an AM waveform.

a. coefficient of modulation

b. modulation index

c. depth of modulation

d. any of these

Solution:

460. When the modulation index in an AM wave is greater than one it will cause _______.

a. buck-shot

b. splatter

c. overmodulation

d. any of these

Solution:

461. The ideal value of modulation index in AM.

a. 1

b. 0

c. 100

d. infinity

Solution:

462. When the amplitude of the information in an AM modulator is equal to zero, what is the value of the modulation index?

a. 1

b. 0

c. 100

d. infinity

Solution:

463. 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 the amplifier

Solution:

464. When the modulation index is equal to zero, the total transmitted power is equal to ________.

a. one of the sidebands

b. carrier

c. double sidebands

d. an AM wave

Solution:

465. When the modulation takes place prior to the output element of the final stage of the transmitter, prior to the collector of the output transistor in a transistorized transmitter, this is called ______.

a. high-level modulation

b. low-level modulation

c. zero-modulation

d. constant modulation

Solution:

466. A circuit that monitors the received signal level and sends a signal back to the RF and IF amplifiers to adjust their gain automatically.

a. automatic phase control

b. automatic gain control

c. automatic frequency control

d. automatic volume control

Solution:

467. When the modulation takes place in the final element of the final stage where the carrier signal is at its maximum amplitude, it is called _____.

a. constant modulation

b. zero-modulation

c. low-level modulation

d. high-level modulation

Solution:

468. If a superheterodyne receiver is tuned to a desired signal at 1000kHz and its conversion (local) oscillator is operating at 1300kHz, what would be the frequency of an incoming signal that would possibly cause image reception?

a. 1600 kHz

b. 2300 kHz

c. 1250 kHz

d. 3420 kHz

Solution:

469. When modulation requires a much higher amplitude modulating signal to achieve a reasonable percent modulation, this is called

a. high-level modulation

b. low-level modulation

c. zero-modulation

d. constant modulation

Solution:

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

a. rectification

b. resonance

c. variable resistance

d. absorption

Solution:

471. A circuit which function is to raise the amplitude of the source signal to a usable level while producing minimum nonlinear distortion adding as little thermal noise as possible.

a. power amplifier

b. non-linear amplifier

c. buffer amplifier

d. preamplifier

Solution:

472. A circuit that has a low-gain, high-input impedance linear amplifier which is used to isolate the oscillator from the high-power amplifiers.

a. power amplifier

b. bandpass filter

c. signal driver

d. buffer amplifier

Solution:

473. With high-level transmitters, which of the following is not a primary function of the modulator circuit?

a. it provides the capacity necessary for modulation to occur

b. it serves as a final amplifier

c. it serves as a frequency up-converter

d. it serves as a mixer

Solution:

474. It is a form of amplitude distortion introduced when positive and negative alternations in the AM modulated signal are not equal.

a. phase shift

b. carrier shift

c. amplitude variations

d. frequency shift

Solution:

475. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4, the total modulation index

a. is 1

b. cannot be calculated unless the phase relations are known

c. is 0.5

d. is 0.7

Solution:

476. The component used to produce AM AT very high frequencies is a

a. varactor

b. thermistor

c. cavity resonator

d. PIN diode

Solution:

477. It is also known as upward modulation

a. carrier shift

b. amplitude variations

c. frequency shift

d. phase shift

Solution:

478. Also known as downward modulation

a. carrier shift

b. amplitude variations

c. frequency shift

d. phase shift

Solution:

479. It is a form of amplitude modulation where signals from two separate information sources modulate the same carrier frequency at the same time without interfering with each other.

a. QPSK

b. QUAM

c. PSK

d. FSK

Solution:

480. A receiver has a dynamic range of 81 dB. It has 0.55 nW sensitivity. Determine the maximum allowable input signal.

a. 59 mW

b. 69 mW

c. 79 mW

d. 88 mW

Solution:

481. The information sources modulate the same carrier after it has been separated into two carrier signals are at 90 degrees out of phase with each other.

a. QPSK

b. QUAM

c. PSK

d. FSK

Solution:

482. Demodulating quadrature AM signal requires a carrier recovery circuit to reproduce the original carrier frequency and phase and two balanced modulators to actually demodulate the signals. This is called ________.

a. asynchronous detection

c. synchronous detection

Solution:

483. Quadrature amplitude modulation is also known as ________.

a. phase division multiplexing

b. phase division modulation

c. phase amplitude multiplexing

d. phase angle modulation

Solution:

484. 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

Solution:

485. It is the first stage of the receiver and is therefore often called the receiver front end.

a. mixer

b. RF section

c. local oscillator

d. IF stage

Solution:

486. In an SSB transmitter, one is most likely to find a

a. class C audio amplifier

b. tuned modulator

c. class B RF amplifier

d. class A RF output amplifier

Solution:

487. The section of the receiver than down-converts the received RF frequencies to intermediate frequencies.

a. RF section

b. local oscillator

c. power amplifier

d. mixer

Solution:

488. The circuit that demodulates the AM wave and converts it to the original information signal.

a. power amplifier

b. local oscillator

c. detector

d. IF section

Solution:

489. 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

Solution:

490. What signals might feed into an FM broadcast station audio control console?

a. microphones

b. turntables

c. remote lines

d. any of these

Solution:

491. The noise reduction ratio achieved by reducing the bandwidth is called

a. dynamic range

b. noise figure

c. bandwidth efficiency

d. bandwidth improvement

Solution:

492. It is the minimum RF signal level that can be detected at the input to the receiver and still produce a usable demodulated information signal.

a. selectivity

b. sensitivity

c. Q-factor

d. bandwidth

Solution:

493. For ideal AM, which of the following is true

a. m = 0

b. m = 1

c. m < 1 d. m > 1

Solution:

494. Why are limiters used in FM receivers?

a. provide better noise performance

b. clip noise peaks

c. prevent overdrive of discriminators

d. any of these

Solution:

495. Why are limiters used in FM transmitters?

a. clip noise peaks

b. prevent overdrive of discriminators

c. prevent overdeviation

d. any of these

Solution:

496. It is defined as the difference in decibels between the minimum input level necessary to discern the signal and the input level that will overdrive the receiver and produce distortion.

a. dynamic range

b. noise figure

c. bandwidth efficiency

d. bandwidth improvement

Solution:

497. It is the input power range over which the receiver is useful.

a. dynamic range

b. noise figure

c. bandwidth efficiency

d. bandwidth improvement

Solution:

498. It is defined as the output power when the RF amplifier response is 1-dB less than the ideal linear gain response.

a. 1-dB compression point

b. 1-dB threshold point

c. 1-dB shoot-off point

d. 1-dB pinch-off point

Solution:

499. It is the measure of the ability of a communications system to produce, at the output of the receiver, an exact replica of the original source information.

a. sensitivity

b. threshold

c. selectivity

d. fidelity

Solution:

500. A SSB signal generated around a 200-kHz carrier. Before filtering, the upper and lower sidebands are separated by 200 Hz. Calculate the filter Q required to obtain 40-dB suppression.

a. 1500

b. 1900

c. 2500

d. 2000

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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