MCQOPTIONS
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MCQOPTIONS
This section includes 147 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
If the intermediate frequency is very high (indicate false statement) |
| A. | Image frequency rejection is very good |
| B. | The local oscillator need not be extremely stable |
| C. | The selectivity will be poor |
| D. | Tracking will be improved |
| Answer» E. | |
| 52. |
Indicate which of the following circuits could not demodulate SSB: |
| A. | Balance modulator |
| B. | Product modulator |
| C. | BFO |
| D. | Phase discriminator |
| Answer» E. | |
| 53. |
A low ratio of the ac to the dc load impedance of a diode detector results in |
| A. | Diagonal clipping |
| B. | Poor AGC operation |
| C. | Negative-peak clipping |
| D. | Poor AF response |
| Answer» D. Poor AF response | |
| 54. |
The passband of the tuned circuits of a radio receiver should be equal to |
| A. | 20 kHz |
| B. | 455 kHz |
| C. | 1455 kHz |
| D. | more than 455 kHz |
| Answer» B. 455 kHz | |
| 55. |
Vividh Bharati programme is transmitted in |
| A. | short wave |
| B. | medium frequency |
| C. | very high frequency |
| D. | all of the above |
| Answer» C. very high frequency | |
| 56. |
An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The efficiency of detection is |
| A. | 0.34 |
| B. | 0.555 |
| C. | 0.688 |
| D. | 0.847 |
| Answer» E. | |
| 57. |
The typical squelch circuit |
| A. | cuts off an IF amplifier when the AGC is maximum |
| B. | cuts off an IF amplifier when the AGC is minimum |
| C. | cuts off an audio amplifier when the carrier is absent |
| D. | eliminates the RF interference when the signal is weak |
| Answer» D. eliminates the RF interference when the signal is weak | |
| 58. |
When a superheterodyne receiver is tuned to 455 kHz, its local oscillator provides a mixer with the input at 1010 kHz. The image frequency is |
| A. | 555 kHz |
| B. | 1010 kHz |
| C. | 1465 kHz |
| D. | 1920 kHz |
| Answer» D. 1920 kHz | |
| 59. |
Power spectral density of white noise |
| A. | increases with frequency |
| B. | decreases with frequency |
| C. | none |
| D. | four times the modulating frequency |
| Answer» B. decreases with frequency | |
| 60. |
The purpose of incorporating a pre-selector stage in a receiver is to |
| A. | provide higher selectivity |
| B. | provide higher fidelity |
| C. | improve linearity |
| D. | larger passband |
| Answer» B. provide higher fidelity | |
| 61. |
In a radio receiver, the local oscillator is always tuned to a frequency higher than the incoming frequency to |
| A. | facilitate tracking |
| B. | allow permit adequate frequency coverage without switching |
| C. | facilitate image frequency rejection |
| D. | all of the above |
| Answer» C. facilitate image frequency rejection | |
| 62. |
A FM signal with modulation index Mf is passed through a frequency doubler. The wave in the output of the doubler will have modulation index of |
| A. | Mf |
| B. | Mf/2 |
| C. | 2Mf |
| D. | UMf |
| Answer» D. UMf | |
| 63. |
The problem associated with tuned-radio frequency receiver is |
| A. | instability |
| B. | insufficient adjacent frequency rejection |
| C. | bandwidth variation |
| D. | all of the above |
| Answer» E. | |
| 64. |
An arbitrary signal m (t) has zero average value and it is bandlimited to 3.2 kHz. It is sampled at the rate of 8 K samples/S. The samples are passed through an ideal bandpass filter with centre frequency of 32 kHz and bandwidth of 6.4 kHz. The output of band pass filter is |
| A. | AM-DSB signal with suppressed carrier |
| B. | AM-DSB signal with carrier |
| C. | AM-SSB signal with carrier |
| D. | a sequence of exponentially decaying sine waves |
| Answer» C. AM-SSB signal with carrier | |
| 65. |
Which of the following statement about the advantage of phase discriminator over the slope detector is false? |
| A. | Fewer tuned circuits |
| B. | Better linearity |
| C. | Greater limiting |
| D. | Much easier alignment |
| Answer» D. Much easier alignment | |
| 66. |
The household radio receiver uses |
| A. | synchronous |
| B. | envelope detector |
| C. | radio detector |
| D. | none of the above |
| Answer» C. radio detector | |
| 67. |
The IF stage of a receiver employs |
| A. | capacitive coupling |
| B. | impedance coupling |
| C. | double-tuned transformer coupling |
| D. | single-tuned transformer coupling |
| Answer» D. single-tuned transformer coupling | |
| 68. |
Most of the amplification of the received signal is obtained in a superheterodyne receiver from the |
| A. | IF stage |
| B. | RF stage |
| C. | power amplification stage |
| D. | none of the above |
| Answer» B. RF stage | |
| 69. |
Three point tracking can be achieved with |
| A. | gang condenser |
| B. | variable selectivity |
| C. | paddar capacitor |
| D. | any of the above |
| Answer» C. paddar capacitor | |
| 70. |
A receiver having poor IF selectivity will also have poor |
| A. | sensitivity |
| B. | double spotting |
| C. | blocking |
| D. | all of the above |
| Answer» D. all of the above | |
| 71. |
A padder is basically a/an |
| A. | insulator |
| B. | variable resistor |
| C. | capacitor |
| D. | inductor |
| Answer» E. | |
| 72. |
High IF in a superheat receiver |
| A. | improves selectivity |
| B. | increases tracking problems |
| C. | decreases tracking problems |
| D. | reduces adjacent channel rejection |
| Answer» C. decreases tracking problems | |
| 73. |
In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. The image frequency at 1000 kHz will be |
| A. | 1010 kHz |
| B. | 1455 kHz |
| C. | 1910 kHz |
| D. | 545 kHz |
| Answer» D. 545 kHz | |
| 74. |
In radio receiver, the maximum contribution to noise is from |
| A. | mixer stage |
| B. | power supply |
| C. | power amplifier |
| D. | equally from above three |
| Answer» D. equally from above three | |
| 75. |
A communication channel with additive white Gaussian noise, has a bandwidth of 4 kHz and an SNR of 15. Its channel capacity is |
| A. | 1.6 kbps |
| B. | 16 kbps |
| C. | 32 kbps |
| D. | 256 kbps |
| Answer» C. 32 kbps | |
| 76. |
In a FM waveform, the side bands are spaced at intervals equal to |
| A. | four times the modulating frequency |
| B. | twice the modulating frequency |
| C. | half the modulating frequency |
| D. | modulating frequency |
| Answer» D. modulating frequency | |
| 77. |
Which of the following circuit cannot be used to demodulate SSB? |
| A. | Phase discriminator |
| B. | Produce detector |
| C. | Balanced modulator |
| D. | Beat frequency oscillator |
| Answer» B. Produce detector | |
| 78. |
In an FM signal, the power |
| A. | increases as the modulation index increases |
| B. | reduces as the modulation index increase |
| C. | increases as the modulation index decreases |
| D. | remains constant when the modulation index increases |
| Answer» E. | |
| 79. |
Fidelity of a receiver represents |
| A. | the sensitivity expressed in terms of voltage that must be applied to the receiver input to give a standard output |
| B. | the extent to which the receiver is capable of distinguishing between the desired signal and other frequencies |
| C. | the variation of the output with the modulation frequency when the output impedance is a resistance |
| D. | none of the above |
| Answer» D. none of the above | |
| 80. |
Which of the following produces upper and lower side frequencies? |
| A. | Microphone |
| B. | Demodulator in a superheterodyne receiver |
| C. | Modulator in a. radio transmitter |
| D. | Oscillator in a receiver |
| Answer» B. Demodulator in a superheterodyne receiver | |
| 81. |
Which of the following noise becomes of great importance at high frequencies? |
| A. | Transit-time noise |
| B. | Shot noise |
| C. | Flicker noise |
| D. | Agitation noise |
| Answer» B. Shot noise | |
| 82. |
Superheterodyne receiver can be used in |
| A. | AM |
| B. | FM |
| C. | SSB |
| D. | All of the above |
| Answer» E. | |
| 83. |
Statement 1Diode is the most common device used for demodulation.Statement 2A discriminator is a FM detector. |
| A. | Statement 1 is true but statement 2 is false |
| B. | Statement 1 is false but statement 2 is true |
| C. | Both the statements are true |
| D. | Both the statements are false |
| Answer» D. Both the statements are false | |
| 84. |
The source of which of the following noise is different from that of the remaining? |
| A. | Solar noise |
| B. | Cosmic noise |
| C. | Galactic noise |
| D. | Atmospheric noise |
| Answer» E. | |
| 85. |
Selectivity varies with receiving frequency, frequency is raised. |
| A. | Somewhat better when the receiving frequency is raised |
| B. | Somewhat better at intermediate frequency |
| C. | Somewhat worse when the receiving frequency is lowered |
| D. | Somewhat worse when the receiving frequency is raised |
| Answer» E. | |
| 86. |
Double spotting in a receiver is due to |
| A. | poor sensitivity of RF amplifier |
| B. | high gain of IF amplifier |
| C. | inadequate image frequency rejection |
| D. | all of the above |
| Answer» D. all of the above | |
| 87. |
In a radio receiver with simple AGC |
| A. | the highest AGC voltage is produced between stations |
| B. | the faster the AGC time constant, the more accurate the output |
| C. | an increase in signal strength produces more AGC |
| D. | the audio stage gain is normally controlled by AGC |
| Answer» D. the audio stage gain is normally controlled by AGC | |
| 88. |
Which of the following is used to provide tracking between RF amplifier and local oscillator stages of receiver? |
| A. | Variable tuning inductor |
| B. | Ganged tuning inductor |
| C. | Variable capacitor |
| D. | Variable preset |
| Answer» C. Variable capacitor | |
| 89. |
A notch filter is sometimes used in communication receivers to |
| A. | reduce receiver gain at some specific frequency |
| B. | increase receiver gain at some specific frequency |
| C. | made selectivity more precise |
| D. | spread the bandwidth |
| Answer» B. increase receiver gain at some specific frequency | |
| 90. |
The output of a diode detector contains |
| A. | D.C. voltage |
| B. | modulating signal |
| C. | RF ripple |
| D. | all of the above |
| Answer» E. | |
| 91. |
In a superheterodyne receiver, the IF stage has better selectivity than RF stage because |
| A. | of higher frequency |
| B. | of lower frequency |
| C. | of high L/C ratio |
| D. | of constant passband |
| Answer» E. | |
| 92. |
In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. The rejection ratio at 25 MHz will be |
| A. | 1.116 |
| B. | 1.386 |
| C. | 2.116 |
| D. | 2.386 |
| Answer» B. 1.386 | |
| 93. |
Transistor are free from which type of noise? |
| A. | Resistance noise |
| B. | Partition noise |
| C. | Flicker noise |
| D. | Shot noise |
| Answer» C. Flicker noise | |
| 94. |
Which of the following noise does not occur in transistors? |
| A. | Partition noise |
| B. | Shot noise |
| C. | Flicker noise |
| D. | Resistance noise |
| Answer» B. Shot noise | |
| 95. |
In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. In receivers operating upto the limit of shortwave broadcasting the local oscillator often used is |
| A. | Armstrong oscillator |
| B. | Colpitts oscillator |
| C. | Clapp oscillator |
| D. | Ultra Audio oscillator |
| Answer» B. Colpitts oscillator | |
| 96. |
A heterodyne frequency changer is called a |
| A. | Modulator |
| B. | Mixer |
| C. | Demodulator |
| D. | Frequency translator |
| Answer» C. Demodulator | |
| 97. |
Which of the following oscillator is generally not used at VHF? |
| A. | Colpitts oscillator |
| B. | Clapp oscillator |
| C. | Armstrong oscillator |
| D. | Ultra Audio oscillator |
| Answer» D. Ultra Audio oscillator | |
| 98. |
Which curve represents the fidelity curve of a standard receiver? |
| A. | Curve A |
| B. | Curve B |
| C. | Curve C |
| D. | Curve D |
| Answer» D. Curve D | |
| 99. |
In a receiver, at higher frequencies |
| A. | tracking will be improved |
| B. | tracking will be poor |
| C. | selectivity will be poor |
| D. | image frequency rejection will be poor |
| Answer» B. tracking will be poor | |
| 100. |
In a communication system, noise is most likely to affect the signal |
| A. | at the transmitter |
| B. | in the channel |
| C. | in the information source |
| D. | at the destination |
| Answer» C. in the information source | |