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.
Online Questions and Answers Topic Outline
- MCQs in Amplitude Modulation
- MCQs in Phase Modulation
- MCQs in Sound Pressure Level
- MCQs in Frequency Modulation
- MCQs in Pulse Modulation
MCQs in Modulation Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part VII of the Series
301. One of the following refers to an output of a balanced modulator
- a. SSB
- b. ISB
- c. AM
- d. DSB
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
303. A third symbol emission which represent data transmission including telemetry, and telecommand
- a. B
- b. D
- c. C
- d. N
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
305. Determine the modulation index of an standard FM broadcast having a hypothetical maximum carrier frequency deviation of ±12 kHz and a maximum modulating frequency pf 4kHz.
- a. 9
- b. 6
- c. 3
- d. 4
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
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
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
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
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
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
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
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
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
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
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
317. Which of the following waveform characteristics determines the wavelength of a sine wave?
- a. Phase
- b. Amplitude
- c. Period
- d. Phase angle
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
319. Which frequency band is the standard AM radio broadcast?
- a. HF
- b. UHF
- c. MF
- d. VHF
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
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
322. 100% modulation in AM means a corresponding increase in total power by ____.
- a. 25%
- b. 75%
- c. 100%
- d. 50%
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
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
325. What is the source of sidebands in frequency modulation?
- a. Oscillator
- b. Baseband frequency
- c. Mixer
- d. Carrier harmonics
326. What is the source of sidebands in frequency modulated voice?
- a. A3F
- b. A3J
- c. F3E
- d. J3E
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
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
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
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
331. The method of generating FM used by broadcasting station is
- a. Direct
- b. All of these
- c. Indirect
- d. Insertion
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
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
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
335. Which circuit in the AM transmitter does the frequency translation?
- a. Synthesizer
- b. Modulator
- c. Mixer
- d. Booster
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
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
338. Diagonal clipping in envelope detection will result in
- a. Distortion
- b. Diagonal clipping
- c. Phase reversal
- d. Amplitude damage
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
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
341. Which among the following is capable of generating frequency conversion?
- a. Balanced modulator
- b. Low-Q LC Circuit
- c. Transmitter
- d. Circulator
342. The most commonly used AM demodulator
- a. Envelope detector
- b. PLL
- c. Mixer
- d. Balanced modulator
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
344. Frequency division is useful in the implementation of a/an
- a. AM demodulator
- b. Frequency synthesizer
- c. AGC circuit
- d. FM demodulator
345. A particular synthesizer which contains only a single crystal is
- a. Direct
- b. Crystal-modulated
- c. Indirect
- d. Exact
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
347. Which major element will not be found in every superheterodyne receiver?
- a. RF amplifier
- b. IF amplifier
- c. LO
- d. Mixer
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
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
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