MCQs in Modulation Part IV

(Last Updated On: December 8, 2017)

MCQs in Modulation - Part IV

This is the Multiples Choice Questions Part 4 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:

Modulation MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI
PART 7: MCQs from Number 301 – 350                 Answer key: PART VII
PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII
PART 9: MCQs from Number 401 – 450                 Answer key: PART IX
PART 10: MCQs from Number 451 – 500                 Answer key: PART X

Continue Practice Exam Test Questions Part IV of the Series

151. An effect in which, the modulation of an unwanted signal is transferred to the desired carrier.

  • A. Crossmodulation
  • B. Intermodulation
  • C. Modulation mixing
  • D. Image-channel interference

152. Leads should be kept as short as possible in radio circuit so that

  • A. Skin effect is reduced
  • B. There is less hysteresis effect
  • C. There is less dielectric loss
  • D. Stray coupling is minimized

153. The number of voice transmissions that can be packed into a given frequency band for amplitude-compandored single-sideband systems over conventional FM-phone systems.

  • A. 2
  • B. 18
  • C. 16
  • D. 4

154. Neutralization of an RF amplifier stage can be necessary in order to

  • A. Increase the amplifier’s gain
  • B. Prevent the generation of spurious oscillations
  • C. Reduce the amplifier’s gain
  • D. Reduce the level of the output harmonics

155. The ability of a communications receiver to perform well in the presence of strong signals outside the band of interest is indicated by what parameter?

  • A. Blocking dynamic range
  • B. Noise figure
  • C. Signal-to-noise ratio
  • D. Audio output

156. Stages that are common to both AM and FM receivers

  • A. Tuner, local oscillator, detector, AF amplifier
  • B. RF amplifier, mixer, IF amplifier, AF amplifier
  • C. Local oscillator, RF amplifier, frequency discriminator, detector
  • D. Tuner, IF amplifier, detector, AF amp

157. Occurs during CW reception if too narrow a filter bandwidth is used in the IF stage of a receiver

  • A. Filter ringing
  • B. Undesired signals will reach the audio stage
  • C. Output-offset overshoot
  • D. Cross-modulation distortion

158. What stage mainly determines a communication receiver’s sensitivity?

  • A. IF amplifier
  • B. Mixer stage
  • C. Detector stage
  • D. RF amplifier

159. What is the main advantage of FM over AM?

  • A. Better signal-to-noise-ratio
  • B. Narrower bandwidth
  • C. Greater propagation range
  • D. Total freedom from adjacent-channel interference

160. An amplitude modulation created in an amplifier before the final RF stage.

  • A. Low-level modulation
  • B. High-level modulation
  • C. Direct modulation
  • D. Indirect modulation

161. Receiver desensitizing can be reduced by

  • A. Increasing the transmitter audio gain
  • B. Decreasing the receiver squelch gain
  • C. Increasing the receiver bandwidth
  • D. Ensuring good RF shielding between the transmitter

162. In a narrow-band FM system, the deviation ratio is commonly one and the highest audio frequency is generally limited to

  • A. 300 Hz
  • B. 10,000 Hz
  • C. 3,000 Hz
  • D. 7,500 Hz

163. A type of emission is produced when an amplitude modulated transmitter is modulated by a facsimile signal

  • A. A3F
  • B. F3F
  • C. A3C
  • D. F3C

164. Where is the noise generated which primarily determines the signal to noise ratio in a VHF (150 MHz) marine band receiver?

  • A. In the detector
  • B. In the atmosphere
  • C. In the ionosphere
  • D. In the receiver front end

165. Cross-modulation in a receiver can be reduced by

  • A. Installing a filter at the receiver
  • B. Using a filter at the receiver
  • C. Increasing the receiver’s RF gain while decreasing the AF
  • D. Adjusting the pass-band tuning

166. What is the emission designation for FM telephony?

  • A. F3E
  • B. G3E
  • C. J3E
  • D. H3E

167. What is the cause of receiver desensitizing?

  • A. The presence of a strong signal on a nearby frequency
  • B. Audio gain adjusted too low
  • C. Squelch gain adjusted too high
  • D. Squelch gain adjusted too low

168. In a phase-modulated signal (indirect FM), the frequency deviation is directly proportional to the

  • A. Carrier amplitude only
  • B. Amplitude of the modulating tone and frequency of the carrier
  • C. Carrier frequency only
  • D. Modulating signal amplitude only

169. An RF stage precedes the mixer stage in a superheterodyne receiver. One advantage of including this RF stage is

  • A. Better selectivity
  • B. Better rejection ratio
  • C. Greater sensitivity
  • D. Improved signal-to-noise-ratio

170. Two factors that determine the sensitivity of a receiver.

  • A. Dynamic range and third-order intercept
  • B. Cost and availability
  • C. Bandwidth and noise figure
  • D. Intermodulation distortion and dynamic range

171. What is an undesirable effect of using too-wide a filter bandwidth in the IF section of a receiver?

  • A. Undesired signals will reach the audio stage
  • B. Output-offset overshoot
  • C. Thermal-noise distortion
  • D. Filter ringing

172. A system containing a limiter stage, a discriminator, and a de-emphasis circuit?

  • A. Direct FM transmitter
  • B. Indirect FM transmitter
  • C. Single sideband AM receiver
  • D. FM receiver

173. The limiter stage of an FM receiver

  • A. Prevents any amplitude modulation of the IF signal
  • B. Limits the amount of frequency deviation in the IF signal
  • C. Limits the overall bandwidth of the IF stages
  • D. Corrects any deviation in carrier frequency

174. High selectivity occurs when the degree of coupling between a receiver’s RF stages is

  • A. Tight
  • B. Loose
  • C. Critical
  • D. Adjusted for maximum power transfer

175. A carrier is phase modulated by a test tone. If the amplitude and the frequency of the tone are both doubled, the amount of the deviation is

  • A. Doubled
  • B. Unchanged
  • C. Halved
  • D. Multiplied by four

176. The degree of selectivity desirable in the IF circuitry of a single-sideband receiver.

  • A. 1 kHz
  • B. 2.4 kHz
  • C. 4.2 kHz
  • D. 4.8 kHz

177. The component most apt to break down in the radio circuit is the

  • A. Crystal
  • B. Resistor
  • C. Transformer
  • D. Diode

178. The base in an RF amplifier is grounded in order to

  • A. Avoid the requirement of neutralizing the stage
  • B. Raise the input impedance
  • C. Lower the output impedance
  • D. Obtain maximum power output

179. The AM detector performs two basic functions in the receiver.

  • A. Rectifies and filters
  • B. Amplifiers and filters
  • C. Buffer and amplifier
  • D. Buffer and detector

180. A varactor diode can be used in a/an

  • A. Direct FM modulator circuit
  • B. AFC circuit in a direct FM transmitter
  • C. Phase-modulator circuit
  • D. All of these

181. Receiver interference is not reduced by including a/an

  • A. Crystal filter
  • B. Insulating enclosures around the receiver
  • C. Wave trap
  • D. RF stage

182. What is the emission C3F?

  • A. RTTY
  • B. SSB
  • C. Television
  • D. Modulated CW

183. What is the approximate dc input power to a class AB RF power amplifier stage in an unmodulated carrier transmitter when the PEP output is 500 W?

  • A. Approximately 1000 W
  • B. Approximately 800 W
  • C. Approximately 250 W
  • D. Approximately 600 W

184. Which of the following stages in an FM receiver is responsible for drastically reducing the effect of static noise during the reception of a signal

  • A. De-emphasis circuit
  • B. Mixer stage
  • C. Squelch circuit
  • D. Limiter stage

185. The letters “SSSC” stands for

  • A. Single sideband, single carrier
  • B. Suppressed sideband, single channel
  • C. Suppressed sideband, single carrier
  • D. Single sideband, suppressed carrier

186. For many types of voices, what is the ratio of PEP-to-average power during a modulation peak in a single-sideband phone signal?

  • A. Approximately 1.0 to 1
  • B. Approximately 25 to 1
  • C. Approximately 100 to 1
  • D. Approximately 2.5 to 1

187. In most mixers, the oscillator frequency is ______ than the carrier frequency of the input signal.

  • A. Higher
  • B. Lower
  • C. The same
  • D. 10 kHz above

188. Features of a transmitter’s buffer stage include

  • A. High stage
  • B. Harmonic generation
  • C. Improvement in frequency stability of the oscillator
  • D. Low input impedance

189. Type of emission produced when an amplitude modulated transmitter is modulated by a television signal

  • A. F3F
  • B. A3C
  • C. F3C
  • D. A3F

190. A network is

  • A. A network consisting entirely of four inductors or four capacitors
  • B. A power incidence network
  • C. An antenna matching network that is isolated from ground
  • D. A network consisting of one inductor and two capacitors

191. How is G3E FM-phone signals produced?

  • A. A network consisting modulator on the audio amplifier
  • B. With a reactance modulator on the final amplifier
  • C. With a reactance modulator on the oscillator
  • D. With a balanced modulator on the oscillator

192. A way of eliminating auto interference to radio reception

  • A. Installing resistive spark plugs
  • B. Installing capacitive spark plugs
  • C. Installing resistors in series with the spark plugs
  • D. Installing two copper-braid ground strips

193. The carrier in an AM transmitter is the

  • A. Transmitter’s output signal when the modulation is present
  • B. Transmitter’s output signal when the modulation is zero
  • C. Output signal from the crystal oscillator
  • D. RMS value of the AM signal

194. What stage feeds the discriminator of an FM receiver?

  • A. Local oscillator
  • B. Mixer stage
  • C. Final IF amplifier, which also acts as a limiter stage
  • D. Buffer

195. In an FM receiver, the stage that has the IF signal is input and the audio signal output.

  • A. Limiter
  • B. Audio amplifier
  • C. IF amplifier
  • D. Discriminator

196. What is capture effect?

  • A. All signals on a frequency are demodulated by an FM receiver
  • B. The loudest signal received is the only demodulated signal
  • C. All signals on a frequency are demodulated by an AM receiver
  • D. The weakest signal received is the only demodulated signal

197. A double-sideband phone signal can be generated by

  • A. Feeding a phase-modulated signal into a low-pass filter
  • B. Modulating the plate voltage of a class-C amplifier
  • C. Using a balanced modulator followed by a filter
  • D. Detuning a Hartley oscillator

198. Pre-emphasis is used in FM transmitters to improve the signal-to-noise ratio of

  • A. High modulating frequencies
  • B. Low modulating frequencies
  • C. All modulating frequencies
  • D. Frequencies carrier

199. The result of cross-modulation is that

  • A. The modulation of an unwanted signal is heard on the desired signal
  • B. A decrease in modulation level of transmitted signals
  • C. Of receiver quieting
  • D. Of inverting sidebands in the final stage of the amplifier

200. Which of the following contains de-emphasis circuit?

  • A. FM transmitter
  • B. FM receiver
  • C. VHF transmitter
  • D. VHF receiver

Complete List of MCQs in Communications Engineering per topic

MCQs in Modulation Part IV
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