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# MCQ in Modulation Part 7 | ECE Board Exam

This is the Multiples Choice Questions Part 7 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 7 of the Series

301. One of the following refers to an output of a balanced modulator

a. SSB

b. ISB

c. AM

d. DSB

Solution:

302. Which of the following components is used to produce AM at very high frequencies?

a. Cavity resonator

b. PIN diode

c. Varactor

d. Thermistor

Solution:

303. A third symbol emission which represent data transmission including telemetry, and telecommand

a. B

b. D

c. C

d. N

Solution:

304. In an AM wave, useful power is carried by

a. None of these

b. Sidebands

c. Both the sidebands and the carrier

d. Carrier

Solution:

305. Determine the modulation index of an standard FM broadcast having a hypothetical maximum carrier frequency deviation of ยฑ12 kHz and a maximum modulating frequency of 4kHz.

a. 9

b. 6

c. 3

d. 4

Solution:

306. The process by which the intelligence signals normally at lower frequency are removed from the transmission frequency after it is received in the receiver station.

a. Detection

b. Demodulation

c. Amplification

d. Modulation

Solution:

307. What is meant by the term modulation?

a. The squelching of a signal until a critical signal-to-noise ratio is reached

b. Carrier rejection through phase nulling

c. A linear amplification mode

d. A mixing process whereby information is imposed upon a carrier

Solution:

308. What is a balanced modulator?

a. An FM modulator that produces balance deviation

b. A modulator that produces a DSBSC signal

c. A modulator that produces a SSBSC signal

d. A modulator that produces a full carrier signal

Solution:

309. What is a reactance modulator?

a. A circuit that acts as a variable resistance or capacitance to produce FM signals

b. A circuit that acts as a variable resistance or capacitance to produce AM signals

c. A circuit that acts as a variable inductance or capacitance to produce FM signals

d. A circuit that acts as a variable inductance or capacitance to produce AM signals

Solution:

310. How can an SSB phone signal be generated?

a. By dividing product detector with a DSB signal

b. By using a reactance modulator followed by a mixer

c. By using a loop modulator followed by a mixer

d. By using a balanced modulator followed by a filter

Solution:

311. How can a DSB phone signal be generated?

a. By feeding a phase modulated signal into a low pass filter

b. By using a balanced modulator followed by a filter

c. By detuning a Hartley oscillator

d. By modulating the plate voltage of a class C amplifier

Solution:

312. First symbol in the designation of radio signals emission which refers to use of an unmodulated carrier.

a. J

b. N

c. H

d. A

Solution:

313. One of the following is a communications filter generally used in the transceiver of a single sideband generator.

a. Lowpass filter

b. Crystal filter

c. Bandpass filter

d. Mechanical filter

Solution:

314. What is the modulation index for an AM signal having Vmax and Vmin of 2.6 and 0.29, respectively?

a. 0.799

b. 0.111

c. 0.894

d. 0.639

Solution:

315. What is the bandwidth of an AM signal modulated by a 15-kHz intelligence signal?

a. 7.5 kHz

b. 15 kHz

c. 30 kHz

d. 60 kHz

Solution:

316. If a transmitter supplies 10 kW to the antenna when it is unmodulated, determine the total radiated power when it is modulated at 30%

a. 10.45 watts

b. 10750 watts

c. 11.5 kilowatts

d. 10450 watts

Solution:

317. Which of the following waveform characteristics determines the wavelength of a sine wave?

a. Phase

b. Amplitude

c. Period

d. Phase angle

Solution:

318. In the F3E signal, what is the term for the ratio between the deviation of a frequency modulated signal and the modulating frequency?

a. FM compressibility

b. Quieting index

c. Modulation index

d. Percentage of modulation

Solution:

a. HF

b. UHF

c. MF

d. VHF

Solution:

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

a. Pilot carrier system

b. Independent sideband emission

c. Lincompex

d. Vestigial sideband transmission

Solution:

321. What are the two general categories of methods for generating emission F3E?

a. The only way to produce an emission F3E signal is with reactance modulator on the oscillator

b. The only way to produce an emission F3E signal is with a balanced modulator on the oscillator

c. The only way to produce an emission F3E signal is with a balanced modulator on the audio amplifier

d. The only way to produce an emission F3E signal is with a reactance modulator on the final amplifier

Solution:

322. 100% modulation in AM means a corresponding increase in total power by ____.

a. 25%

b. 75%

c. 100%

d. 50%

Solution:

323. How does the SSB transmitter output power normally expressed?

a. Average power

b. In terms of peak envelope power

c. In terms of peak-to-peak power

d. Peak power

Solution:

324. Determine from the following the common use of DSB in broadcast and telecommunications

a. Satellite communication

b. FM/TV stereo

c. Two-way communications

d. Telephone systems

Solution:

325. What is the source of sidebands in frequency modulation?

a. Oscillator

b. Baseband frequency

c. Mixer

d. Carrier harmonics

Solution:

326. What is the source of sidebands in frequency modulated voice?

a. A3F

b. A3J

c. F3E

d. J3E

Solution:

327. The third symbol in the designation of radio emission under the ITU refers to

a. Type of modulation of the main carrier

b. Nature of signals

c. Type of information to be transmitted

d. Nature of multiplexing

Solution:

328. An AM transmission of 3 kW is 100% modulated. If it is transmitted as an SSB signal, what would be the total power transmitted?

a. 500 W

b. 1000 W

c. 1500 W

d. 2000 W

Solution:

329. This circuit has the function of demodulating the frequency-modulated signal. It is a

a. Automatic gain control

b. Automatic frequency control

c. Envelope detector

d. Foster-Seeley discriminator

Solution:

330. Calculate the power in one sideband of an AM signal whose carrier power is 50 watts. The unmodulated current is 2 A while the modulated current is 2.4 A.

a. 22 W

b. 33 W

c. 11 W

d. 44 W

Solution:

331. The method of generating FM used by broadcasting station is

a. Direct

b. All of these

c. Indirect

d. Insertion

Solution:

332. Deviation ratio of an FM transmitter is the ratio of the

a. Maximum frequency swing to the highest modulating frequency

b. Operating frequency of the assigned frequency

c. Frequency swing to the modulating frequency

d. Highest modulating frequency to the minimum frequency

Solution:

333. An AM transmitter is modulated by two sine waves at 1.5 kHz and 2.5 kHz with modulations of 20 percent and 80 percent respectively. Calculate the effective modulation index.

a. 0.7776

b. 0.6

c. 0.8246

d. 1.0

Solution:

334. A DSBSC system must suppress the carrier by 50 dB for its original value of 10 W. To what value must the carrier be reduced?

a. 1 milliwatt

b. 10 microwatts

c. 0.10 milliwatts

d. 0.01 microwatts

Solution:

335. Which circuit in the AM transmitter does the frequency translation?

a. Synthesizer

b. Modulator

c. Mixer

d. Booster

Solution:

336. A phase modulator has Kp = 2 rad/V. What RMS voltage of a sine wave would cause a peak phase deviation of 30 degrees?

a. 0.158 V

b. 0.185 V

c. 0.518 V

d. 0.815 V

Solution:

337. In a phase-locked loop, VCO stands for

a. Variable capacitor oscillator

b. Varactor-capacitor oscillator

c. Voltage-controlled oscillator

d. VHF control oscillator

Solution:

338. Diagonal clipping in envelope detection will result in

a. Distortion

b. Diagonal clipping

c. Phase reversal

d. Amplitude damage

Solution:

339. An AM transmitter supplies a 10 kW of carrier power to a 50 ohm load. It operates at a carrier frequency of 1.2 MHz and is 85% modulated by a 3 MHz sine wave. Calculate the RMS voltage of the signal.

a. 825 W

b. 262. 61 V

c. 1166.7 V

d. 825 V

Solution:

340. What will be the total sideband power of the AM transmitting station whose carrier power is 1200W and a modulation of 95%?

a. 270.75 W

b. 900 watts

c. 1.8 kW

d. 542 W

Solution:

341. Which among the following is capable of generating frequency conversion?

a. Balanced modulator

b. Low-Q LC Circuit

c. Transmitter

d. Circulator

Solution:

342. The most commonly used AM demodulator

a. Envelope detector

b. PLL

c. Mixer

d. Balanced modulator

Solution:

343. Which is a disadvantage of direct FM generation?

a. The need for an AFC circuit

b. The need for an AGC circuit

c. Two balanced modulators are used

d. The use of Class A amplifier which is very inefficient

Solution:

344. Frequency division is useful in the implementation of a/an

a. AM demodulator

b. Frequency synthesizer

c. AGC circuit

d. FM demodulator

Solution:

345. A particular synthesizer which contains only a single crystal is

a. Direct

b. Crystal-modulated

c. Indirect

d. Exact

Solution:

346. Type of emission most affected by selective fading

a. FM and DSB AM

b. SSB and TV

c. CCTV and CW

d. CW and SSB

Solution:

347. Which major element will not be found in every superheterodyne receiver?

a. RF amplifier

b. IF amplifier

c. LO

d. Mixer

Solution:

348. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth?

a. 115 kHz

b. 230 kHz

c. 170 kHz

d. 340 kHz

Solution:

349. A quadrature detector requires that

a. The inputs are coherent

b. Four gates are provided

c. The inputs are in phase

d. The inputs are similar

Solution:

350. What is the power in one sideband of an AM signal whose carrier power is 300 W, with 80 percent modulation?

a. 396 W

b. Zero

c. 48 W

d. 96 W

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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