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 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
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