MCQs in Modulation Part IX

(Last Updated On: September 10, 2019)

MCQs in Modulation - Part IX

This is the Multiples Choice Questions Part 9 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 IX of the Series

401. What is receiver desensitizing?

  • a. A burst of noise when the squelch is set to low
  • b. A burst of noise when the squelch is set to high
  • c. A reduction in receiver sensitivity because of a strong signal on a nearby frequency
  • d. A reduction in receiver sensitivity is turned down

402. What is the term used to refer to the reduction of receiver gain caused by the signals of a nearby station transmitting in the same frequency band?

  • a. Desensitizing
  • b. Quieting
  • c. Cross-modulation interference
  • d. Squelch gain roll back

403. What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?

  • a. Intermodulation distortion
  • b. Quieting
  • c. Desensitizing
  • d. Overloading

404. How can receiver desensitizing be reduced?

  • a. Ensure good RF shielding between the transmitter and receiver
  • b. Increase the transmitter audio gain
  • c. Decrease the receiver squelch gain
  • d. Increase the receiver bandwidth

405. What is cross-modulation interference?

  • a. Interference between two transmitters of different modulation types
  • b. Interference caused by audio rectification in the receiver preamp
  • c. Decrease the receiver squelch gain
  • d. Modulation from an unwanted signal is heard in addition to the desired signal

406. What is the term used to refer to the condition where the signals from a very strong station are super imposed on the other signals being received?

  • a. Intermodulation distortion
  • b. Cross-modulation interference
  • c. Receiver quieting
  • d. Capture effect

407. How can cross-modulation in a receiver be reduced?

  • a. By installing a filter at the receiver
  • b. By using a better antenna
  • c. By increasing the receiver’s RF gain while decreasing the AF gain
  • d. By adjusting the passband tuning

408. What is the result of cross-modulation?

  • a. Decrease in modulation level of transmitted signals
  • b. Receiver quieting
  • c. The modulation of an unwanted signal is heard on the desired signal
  • d. Inverted sidebands in the final stage of the amplifier

409. What is the capture effect?

  • a. All signals on a frequency are demodulated by an FM receiver
  • b. All signals on a frequency are demodulated by an AM receiver
  • c. The loudest signal received is the only demodulated signal
  • d. The weakest signal received is the only demodulated signal

410. What is a product detector?

  • a. A detector that provides local oscillator for input to the mixer
  • b. A detector that amplifies and narrows the bandpass frequencies
  • c. A detector that uses mixing process with a locally generated carrier
  • d. A detector used to detect cross-modulation products

411. What is the term used to refer to the reception blockage of one FM-phone signal?

  • a. Desensitization
  • b. Cross-modulation interference
  • c. Capture effect
  • d. Frequency discrimination

412. What is the process of detection?

  • a. The process of masking out the intelligence on a received carrier to make an S-meter operational
  • b. The recovery of intelligence from the modulated RF signal
  • c. The modulation of a carrier
  • d. The mixing of noise with the received signal

413. What is the principle of detection in a diode detector?

  • a. Rectification and filtering of RF
  • b. Breakdown of the Zener voltage
  • c. Mixing with the noise in the transition region of the diode
  • d. The change of reactance in the diode with respect to frequency

414. How are FM phone signals detected?

  • a. By a balanced modulator
  • b. By a frequency discriminator
  • c. By a product detector
  • d. By a phase splitter

415. What is the mixing process?

  • a. The elimination of noise in a wideband receiver by phase comparison
  • b. The elimination of noise in a wideband receiver by phase differentiation
  • c. Distortion caused by aural propagation
  • d. The combination of the two signals to produce sum and difference frequencies

416. What is a frequency discriminator?

  • a. A circuit for detecting FM signals
  • b. A circuit for filtering two closely adjacent signals
  • c. An automatic band switching circuit
  • d. An FM generator

417. What are the principal frequencies which appear at the output of a mixer circuit?

  • a. Two and four times the original frequency
  • b. The sum, difference and square root of the input frequencies
  • c. The original frequencies and the sum and difference frequencies
  • d. 1.414 and 0.707 times the frequency

418. What occurs in a receiver when an excessive amount of signal energy reaches the mixer circuit?

  • a. Spurious mixer products are generated
  • b. Mixer blanking occurs
  • c. Automatic limiting occurs
  • d. A beat frequency is generated

419. How much gain should be used in the RF amplifier stage of a receiver?

  • a. As much as possible short of self oscillation
  • b. Sufficient gain to allow weak signals to overcome noise generated in the first mixer
  • c. Sufficient gain to keep weak signals below the noise of the first mixer stage
  • d. It depends on the amplification factor of the first IF stage

420. Why should the RF amplifier stage of a receiver only have sufficient gain to allow weak signals to overcome noise generated in the first mixer stage?

  • a. To prevent the sum and difference frequencies from being generated
  • b. To prevent bleed-through of the desired signal
  • c. To prevent generation of spurious mixer products
  • d. To prevent bleed-trough of the local oscillator

421. What is the primary purpose of an RF amplifier in a receiver?

  • a. To provide most of the receiver gain
  • b. To vary the receiver image rejection by utilizing the AGC
  • c. To improve the receiver’s noise figure
  • d. To develop the AGC voltage

422. What is an IF amplifier stage?

  • a. A fixed-tuned passband amplifier
  • b. A receiver demodulator
  • c. A receiver filter
  • d. A buffer oscillator

423. What factors should be considered when selecting an intermediate frequency?

  • a. A cross-modulation distortion and interference
  • b. Interference to other services
  • c. Image rejection and selectivity
  • d. Noise figure and distortion

424. What is the primary purpose of the first IF amplifier stage in a receiver?

  • a. A noise figure performance
  • b. Tune out cross-modulation distortion
  • c. Dynamic response
  • d. Selectivity

425. What is the primary purpose of the final IF amplifier stage in a receiver?

  • a. Dynamic response
  • b. Gain
  • c. Noise figure performance
  • d. Bypass undesired signals

426. Which stage of a receiver primarily establishes its noise figure?

  • a. The audio stage
  • b. The IF stage
  • c. The RF stage
  • d. The local oscillator

427. What is meant by the term noise figure in a communications receiver?

  • a. The level of noise entering the receiver from the antenna
  • b. The relative strength of a strength of a received signal 3 kHz removed from the carrier frequency
  • c. The level of noise generated in the front end and succeeding stages of a receiver
  • d. The ability of a receiver to reject unwanted signals at frequencies close to the desired one

428. 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. Noise figure
  • b. Blocking dynamic range
  • c. Signal-to-noise ratio
  • d. Audio output

429. What type problems are caused by poor dynamic range in a communications receiver?

  • a. Cross-modulation of the desired signal and desensitization from strong adjacent signals
  • b. Oscillator instability requiring frequent returning, and loss of ability to recover the opposite sideband should it be transmitted
  • c. Cross-modulation of the desired signal and insufficient audio power to operate the speaker
  • d. Oscillator instability and severe audio distortion of all but the strongest signal received signals

430. What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?

  • a. Intermodulation distortion
  • b. Noise floor
  • c. Noise figure
  • d. Dynamic range

431. What occurs during CW reception if too narrow a filter bandwidth is used in the IF stage of a receiver?

  • a. Undesired signals will reach the audio stage
  • b. Output-offset overshoot
  • c. Cross-modulation distortion
  • d. Filter ringing

432. How can selectivity be achieved in the front and circuitry of a communications receiver?

  • a. By using an audio filter
  • b. By using a pre-selector
  • c. By using an additional RF amplifier stage
  • d. By using an additional IF amplifier stage

433. How should the filter bandwidth of a receiver IF section compare with the bandwidth of a received signal?

  • a. Filter bandwidth should be slightly greater than the received signal bandwidth
  • b. Filter bandwidth should be approximately half the received signal bandwidth
  • c. Filter bandwidth should be approximately two times the received signal bandwidth
  • d. Filter bandwidth should be approximately four times the received signal bandwidth

434. How can receiver selectivity be achieved in the IF circuitry of a communications receiver?

  • a. Incorporate a means of varying the supply voltage to the local oscillator circuitry
  • b. Replace the standard JFET mixer with a bipolar transistor followed by a capacitor of the proper value
  • c. Remove AGC action from the IF stage and confine it to the audio stage only
  • d. Incorporate a high-Q filter

435. A receiver has a sensitivity of 0.6 microvolts and a blocking dynamic range of 60 dB. What is the strongest signal that can be present along with a 0.6 microvolt signal without blocking taking place

  • a. 600 millivolts
  • b. 600 microvolts
  • c. 300 millivolts
  • d. 300 mircovolts

436. An AM receiver is tuned to broadcast station at 600 kHz. Calculate the image rejection in dB assuming that the input filter consists of one tuned circuit with a Q of 40?

  • a. 19.28 dB
  • b. 39.65 dB
  • c. 38.57 dB
  • d. 19.83 dB

437. A receiver has two uncoupled tuned circuits before the mixer, each with a Q of 75. The signal frequency is 100.1 MHz. The IF is 10.7 Mhz. The local oscillator uses high-side injection. Calculate the image rejection ratio.

  • a. 23.69 dB
  • b. 58.66 dB
  • c. 29.33 dB
  • d. 11.84 dB

438. What oscillator frequency is needed to heterodyne 626 kHz up to 3.58 MHz?

  • a. 2.954 MHz
  • b. 4.832 MHz
  • c. 4.210 MHz
  • d. 2.328 MHz

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

  • a. Output-offset overshoot
  • b. Undesired signals will reach the audio stage
  • c. Thermal noise distortion
  • d. Filter ringing

440. What is the limiting condition for sensitivity in a communications receiver?

  • a. the noise floor of the receiver
  • b. the power supply output ripple
  • c. the two-tone intermodulation distorting
  • d. the input impedance to the detector

441. What parameter must be selected when designing an audio filter using an op-amp?

  • a. Bandwidth characteristics
  • b. Desired current gain
  • c. Temperature coefficient
  • d. Output-offset overshoot

442. What two factors determine the sensitivity of a receiver?

  • a. Dynamic range and third-order intercept
  • b. Cost and availability
  • c. Intermodulation distortion and dynamic range
  • d. Bandwidth and noise figure

443. How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?

  • a. Restrict both gain and Q
  • b. Restrict gain, but increase Q
  • c. Restrict Q but increase gain
  • d. Increase both gain and Q

444. What is meant by the dynamic range of a communications receiver?

  • a. The number of kHz between the lowest and the highest frequency to which the receiver can be tuned
  • b. The maximum possible undistorted audio output of the receiver referenced to one milliwatt
  • c. The ratio between the minimum discernible signal and the largest tolerable signal without causing audible distortion products
  • d. The difference between the lowest frequency signal detectable without moving the tuning knob

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

  • a. In the receiver front end
  • b. Man-made noise
  • c. In the atmosphere
  • d. In the ionosphere

446. An AM receiver uses a diode detector for demodulation. This enables it satisfactorily to receive

  • a. Single-sideband, suppressed carrier (J3E)
  • b. Single-sideband, reduced carrier (R3E)
  • c. ISB(B8E)
  • d. Single-sideband, full carrier (H3E)

447. Three-point tracking is achieved with

  • a. Variable selectivity
  • b. The padder capacitor
  • c. Double spotting
  • d. Double conversion

448. A receiver has poor IF selectivity. It will therefore also have poor

  • a. Blocking
  • b. Double-spotting
  • c. Diversity reception
  • d. Sensitivity

449. If a FET is used as the first AF amplifier in a transistor receiver, this will have the effect of

  • a. Gain variation over the frequency coverage range
  • b. Insufficient gain and selectivity
  • c. Inadequate selectivity at high frequencies
  • d. Instability

450. The image frequency of a superheterodyne receiver

  • a. Is created within the receiver itself
  • b. Is due to insufficient adjacent channel rejection
  • c. Is not rejected by the IF tuned circuits
  • d. Is independent of the frequency to which receiver is tuned

Complete List of MCQs in Communications Engineering per topic

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