MCQ in Modulation Part 5 | ECE Board Exam

This is the Multiples Choice Questions Part 5 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 5 of the Series

201. What is emission F3F?

A. AM

B. Facsimile

C. Television

D. RTTY

202. What type of emission is produced when a frequency modulated transmitter is modulated by a facsimile signal?

A. F3C

B. A3C

C. F3F

D. A3F

203. Two AM transmitting antennas are close together. As a result the two modulated signals are mixed in the final RF stage of both transmitters. What is the resultant effect on other station?

A. Harmonic interference

B. Intermodulation interference

C. Spurious interference

D. Crossmodulation interference

204. The term used to refer to the reduction of receiver gain caused by the signal of a nearby station transmitter in the same frequency band?

A. Quieting

B. Cross-modulation interference

C. Squelch gain rollback

D. Desensitizing

205. What is the bandwidth occupied by the carrier, both sidebands and harmonics?

A. Authorized bandwidth

B. Bandwidth of emission and occupied bandwidth

C. Operating bandwidth

D. All of these

206. A class-C RF amplifier is collector amplitude modulated and its average dc level collector current does not change. This means

A. A normal condition

B. Excessive drive to the base

C. Insufficient drive to the base

D. Insufficient audio modulation

207. What determines the percentage modulation of an FM transmitter?

A. Amplitude of the carrier

B. Modulating frequency

C. Carrier frequency

D. Amplitude of the modulating signal

208. 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

209. The main purpose of the beat frequency oscillator (BFO) is to generate

A. A 1 kHz not for Morse reception

B. Aid in the reception of weak voice-modulated signals

C. An output, whose frequency differs from the IF by 1 kHz

D. A signal, whose frequency is the same as intermediate frequency

210. Normally, a linear class BRF power amplifier operates with a bias approximately equal to

A. Twice cut-off

B. Ten times cut-off value

C. 50% of cut-off value

D. Projected cut-off

211. The purpose why an RF amplifier is operated under linear class-B conditions (as opposed to class-C) is to

A. Generate only even harmonics

B. Generate only odd harmonics

C. Increase the efficiency

D. Amplify of an AM signal

212. The term used to refer to the condition where the signal from a very strong station are superimposed on other signal being received.

A. Cross-modulation interference

B. Intermodulation distortion

C. Receiver quieting

D. Capture effect

213. _________ is the amplitude of the maximum negative excursion of a signal as viewed on an oscilloscope.

A. Peak-to-peak voltage

B. Inverse peak positive voltage

C. RMS voltage

D. Peak negative voltage

214. The type of emission that suffer most from selective fading.

A. CW and SSB

B. SSB and TV

C. FM and double sideband AM

D. SSTV and CW

215. In an FM-phone signal, ________ is the ratio between the actual frequency deviation to the maximum frequency deviation.

A. FM compressibility

B. Modulating index

C. Percentage of modulation

D. Quieting index

216. _______ is used to refer to the reception blockage of one FM-phone signal by another FM-phone signal.

A. Capture effect

B. Desensitization

C. Cross-modulation interference

D. Frequency discrimination

217. A receiver selectivity of 10 kHz in the IF circuitry is optimum for what type of signals?

A. SSB voice

B. Facsimile

C. FM

D. Double-sideband AM

218. If the envelope of modulation is constant in amplitude this means

A. Zero beat

B. Under-modulation

C. Zero-modulation

D. Over-modulation

219. What is the approximate bandwidth of an FM with a modulation factor of 12.5 and a modulating frequency of 10 kHz?

A. 20 kHz

B. 270 kHz

C. 250 kHz

D. 45 kHz

220. Amplitude modulation is the same as

A. Linear mixing

B. Analog multiplication

C. Signal summation

D. Multiplexing

221. The negative half of the AM wave is supplied by a/an _______ on a diode modulator.

A. The tuned circuit

B. Transformer

C. Capacitor

D. Inductor

222. One of the following can produce AM.

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

223. Amplitude modulators that vary the carrier amplitude with the modulating signal by passing it through an attenuator network is the principle of

A. Rectification

B. Amplification

C. Variable resistance

D. Absorption

224. Which component is used to produce AM at very high frequencies?

A. Varactor diode

B. Thermistor

C. Cavity resonator

D. PIN diode

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

A. 24 V

B. 48 V

C. 96 V

D. 120 V

226. What circuit recovers the original modulating information from an AM signal?

A. Modulator

B. Demodulator

C. Mixer

D. Crystal set

227. What is the most commonly used amplitude demodulator?

A. Envelope detector

B. Balanced modulator

C. Mixer

D. Crystal set

228. What circuit generates the upper and lower sidebands and suppresses the carrier?

A. Amplitude modulator

B. Diode detector

C. Class C amplifier

D. Balanced modulator

229. _________ is a widely used balanced modulator.

A. Diode bridge circuit

B. Full-wave bridge rectifier

C. Lattice modulator

D. Balanced bridge modulator

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

A. Variable resistors

B. Switches

C. Rectifiers

D. Variable capacitors

231. The output of a balanced modulator is

A. AM

B. FM

C. SSB

D. DSB

232. The principal circuit in the popular 1496/1596 IC balanced modulator is a

A. Differential amplifier

B. Rectifier

C. Bridge

D. Constant current source

233. The most commonly used filter in SSB generators uses

A. LC networks

B. Mechanical resonators

C. Crystals

D. RC networks and op amps

234. In the phasing method of SSB generation, one sideband is canceled out due to

A. Phase shifting

B. Sharp selectivity

C. Carrier suppression

D. Phase inversion

235. A balanced modulator used to demodulate a SSB signal is call a/an

A. Transponder

B. Product detector

C. Converter

D. Remodulator

236. Frequency translation is done with a circuit called a

A. Summer

B. Multiplier

C. Divider

D. Mixer

237. Mixing for frequency conversion is the same as

A. Rectification

B. AM

C. Linear summing

D. Filtering

238. Which of the following is not a major advantage of FM over AM?

A. Greater efficiency

B. Noise immunity

C. Capture effect

D. Lower complexity and cost

239. The primary disadvantage of FM is its

A. Higher cost and complexity

B. Excessive use of spectrum space

C. Noise susceptibility

D. Lower efficiency

240. Noise is primarily

A. High-frequency spikes

B. Lowe-frequency variations

C. Random level shifts

D. Random frequency variations

241. The receiver circuit that rids FM of noise is the

A. Modulator

B. Demodulator

C. Limiter

D. Low-pass filter

242. The AM signals generated at a low level may only be amplified by what type of amplifier?

A. Class A

B. Class B

C. Class C

D. All of the above

243. SSB means

A. Single sideband with suppressed carrier

B. Single sideband with carrier

C. Double sideband with no carrier

D. Single sideband with reduced carrier

244. A circuit used to select the desired output from a mixer

A. Transformer

B. Resonant circuit

C. Filter

D. Phase-shift circuit

245. What is the output of a balanced modulator?

A. AM

B. DSB

C. SSB

D. ISB

246. The acronym SSSC refer to

A. Suppressed sideband, single carrier

B. Suppressed sideband, suppressed carrier

C. Single sideband, suppressed carrier

D. Single sideband, single carrier

247. Which process occurs in the receiver?

A. Demodulation

B. Reception

C. Modulation

D. Recreation

248. What is usually used to demodulate SSB or CW signal?

A. PLL

B. BFO

C. Ratio detector

D. All of these

249. Which of the following is the most widely used amplitude modulator

A. Diode detector

B. PLL circuit

C. VCO

D. All of these

250. Which of the following is the most widely used balanced modulator

A. Full-wave bridge circuit

B. Balanced bridge modulator

C. Lattice modulator

D. None of these

Questions and Answers in Modulation Series

Following is the list of multiple choice questions in this brand new series:

Complete List of MCQ in Communications Engineering per topic