MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 299 Mcqs, each offering curated multiple-choice questions to sharpen your Communication knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
An AM wave10[1 + 0 6 cos 2 103t] cos 2 106t is to be detected by a linear diode detector, the value of the time constant is |
| A. | 0.17 ms |
| B. | 1.7 ms |
| C. | 0.212 ms |
| D. | None of these |
| Answer» D. None of these | |
| 52. |
The sum of two signals e1 = 3 sin (4 103t) and e1= 5 sin(4 256t) is sampled at 1024 Hz. The sampled signal is passed through a low pass filter with cut off at 2048 Hz. The output of the filter will contain components at |
| A. | 256 Hz and 10 |
| B. | Hz |
| C. | 256 Hz and 1024 Hz |
| D. | 256 Hz Only |
| E. | 1024 Hz Only |
| Answer» D. 256 Hz Only | |
| 53. |
Indicate the false statement. Noting that no carrier is transmitted with J3E, we see that |
| A. | The receiver cannot use a phase comparator for AFC |
| B. | Adjacent-channel rejection is more difficult |
| C. | Production of AGC is a rather complicated process |
| D. | The transmission is not compatible with A3E |
| Answer» C. Production of AGC is a rather complicated process | |
| 54. |
One of the following cannot be used to demodulate SSB |
| A. | Product detector |
| B. | Diode balanced modulator |
| C. | Bipolar transistor balanced modulator |
| D. | Complete phase-shift generator |
| Answer» D. Complete phase-shift generator | |
| 55. |
In an FM stereo multiplex transmission, the |
| A. | Sum signal modulates the 19 kHz subcarrier |
| B. | Difference signal modulates the 19 kHz subcarrier |
| C. | Difference signal modulates the 38 kHz subcarrier |
| D. | Difference signal modulates the 67 kHz subcarrier |
| Answer» D. Difference signal modulates the 67 kHz subcarrier | |
| 56. |
Following is not the purpose of modulation |
| A. | Multiplexing |
| B. | Effective radiation |
| C. | Narrow banding |
| D. | Increase in signal power |
| Answer» E. | |
| 57. |
A signal x (t) = 100 cos (2 10 |
| A. | 12 kHz only |
| B. | 8 kHz only |
| C. | 12 kHz and 9 kHz |
| D. | 12 kHz and 8 kHz |
| Answer» E. | |
| 58. |
A carrier is amplitude modulated to a depth of 40%. The increase in power is |
| A. | 40% |
| B. | 20% |
| C. | 16% |
| D. | 8% |
| Answer» E. | |
| 59. |
A plot of modulation index versus carrier amplitude yields a |
| A. | Horizontal line |
| B. | Vertical line |
| C. | Parabola |
| D. | Hyperbola |
| Answer» E. | |
| 60. |
The received signal frequency at any time of a superheterodyne receiver having IF = 456 kHz, is 1 MHz. The corresponding image signal is |
| A. | Within its medium band |
| B. | Outside the medium band |
| C. | Depends on modulation index |
| D. | Depends on modulating frequency |
| Answer» B. Outside the medium band | |
| 61. |
The resonant frequency of an RF amplifier is 1 MHz and its bandwidth is 10 kHz. The Q-factor will be |
| A. | 10 |
| B. | 100 |
| C. | 0.01 |
| D. | 0.1 |
| Answer» C. 0.01 | |
| 62. |
In a single tone FM discriminator (S |
| A. | Proportional to deviation |
| B. | Proportional to cube of deviation |
| C. | Inversely proportional to deviation |
| D. | Proportional to square of deviation |
| Answer» E. | |
| 63. |
Assuming other parameters unchanged, if the modulating frequency is halved in a modulating systems, the modulation index is doubled. The modulation system is |
| A. | A M |
| B. | F M |
| C. | Phase modulation |
| D. | Angle modulation |
| Answer» C. Phase modulation | |
| 64. |
The basic restriction on the reconstruction of a sampled signal is |
| A. | The sampling must be in the form of impulse train |
| B. | The signal must be passed through low pass filter |
| C. | Both and |
| D. | None of these |
| Answer» D. None of these | |
| 65. |
If a time function contains highest components of whz, then it can be completely determined by specifying its ordinates at a series of points spaced every |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">sec or less</td></tr><tr><td style="text-align: center;">w</td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">sec or less</td></tr><tr><td style="text-align: center;">2w</td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">sec</td></tr><tr><td style="text-align: center;">w</td></tr></table> |
| D. | None of these |
| Answer» C. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">sec</td></tr><tr><td style="text-align: center;">w</td></tr></table> | |
| 66. |
The sampling theory is applicable to bandlimited time functions which are |
| A. | Continuous |
| B. | Single valued |
| C. | Both and |
| D. | None of these |
| Answer» D. None of these | |
| 67. |
Indicate which one of the following is not an advantage of FM over AM? |
| A. | Better noise immunity is provided |
| B. | Lower bandwidth is required |
| C. | The transmitted power is more useful |
| D. | Less modulating power is required |
| Answer» C. The transmitted power is more useful | |
| 68. |
When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is |
| A. | Amplitude modulation |
| B. | Phase modulation |
| C. | Frequency modulation |
| D. | Any one of the three |
| Answer» D. Any one of the three | |
| 69. |
Since noise phase-modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude |
| A. | Remains constant |
| B. | Is decreased |
| C. | Is increased |
| D. | Is equalized |
| Answer» C. Is increased | |
| 70. |
An FM signal with a deviation is passed through a mixer, and has its frequency reduced fivefold. The deviation in the output of the mixer is |
| A. | 5 |
| B. | Indeterminate |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"> </td></tr><tr><td style="text-align: center;">5</td></tr></table> |
| D. | |
| Answer» E. | |
| 71. |
Show which of the following statements about the amplitude limiter is untrue? |
| A. | The circuit is always biased in class C, by virtue of the leak-type bias |
| B. | When the input increases past the threshold of limiting, the gain decreases to keep the output constant |
| C. | The output must be tuned |
| D. | Leak-type bias must be used |
| Answer» B. When the input increases past the threshold of limiting, the gain decreases to keep the output constant | |
| 72. |
Indicate which of the following statements about the advantages of the phase discriminator over the slope detector is false? |
| A. | Much easier alignment |
| B. | Better linearity |
| C. | Greater limiting |
| D. | Fewer tuned circuits |
| Answer» D. Fewer tuned circuits | |
| 73. |
One of the following is an indirect way of generating FM. This is the |
| A. | Reactance FET modulator |
| B. | Varactor diode modulator |
| C. | Armstrong modulator |
| D. | Reactance bipolar transistor modulator |
| Answer» D. Reactance bipolar transistor modulator | |
| 74. |
Indicate the false statement in connection with communications receivers |
| A. | The noise limiter cuts off the receiver s output during a noise pulse. |
| B. | A product demodulator could be used for the reception of Morse code |
| C. | Double conversion is used to improve image rejection |
| D. | Variable sensitivity is used to eliminate selective fading |
| Answer» E. | |
| 75. |
To prevent overloading of the last IF amplifier in a receiver, one should use |
| A. | Squelch |
| B. | Variable sensitivity |
| C. | Variable selectivity |
| D. | Double conversion |
| Answer» C. Variable selectivity | |
| 76. |
If an FET is used as the first AF amplifier in a transistor receiver, this will have the effect of |
| A. | Improving the effectiveness of the AGC |
| B. | Reducing the effect of negative-peak clipping |
| C. | Reducing the effect of noise at low modulation depths |
| D. | Improving the selectivity of the receiver |
| Answer» C. Reducing the effect of noise at low modulation depths | |
| 77. |
Indicate which of the following circuits could not demodulate SSB? |
| A. | Balanced modulator |
| B. | Product detector |
| C. | BFO |
| D. | Phase discriminator |
| Answer» E. | |
| 78. |
The controlled oscillator synthesizer is sometimes preferred to the direct one because |
| A. | It is a simpler piece of equipment |
| B. | Its frequency stability is better |
| C. | It does not require crystal oscillators |
| D. | It is relatively free of spurious frequencies |
| Answer» E. | |
| 79. |
The information capacity of narrow-pulse systems is |
| A. | Low |
| B. | Of medium range |
| C. | High |
| D. | None of these |
| Answer» D. None of these | |
| 80. |
Narrow pulse systems require |
| A. | Zero bandwidth |
| B. | Smaller bandwidth |
| C. | Greater bandwidth |
| D. | None of these |
| Answer» D. None of these | |
| 81. |
When a receiver has a good blocking performance, this means that |
| A. | It does not suffer from double-spotting |
| B. | Its image frequency rejection is poor |
| C. | It is unaffected by AGC derived from nearby transmissions |
| D. | Its detector suffers from burnout |
| Answer» D. Its detector suffers from burnout | |
| 82. |
It is necessary to transmit a series of synchronous pulses in |
| A. | PAM |
| B. | PDM |
| C. | PPM |
| D. | None of these |
| Answer» D. None of these | |
| 83. |
A communication receiver can be used for |
| A. | Signal strength measurement |
| B. | Detection and display of individual components of a high frequency wave |
| C. | Both of these |
| D. | None of these |
| Answer» D. None of these | |
| 84. |
The function of an amplitude limiter in an FM receiver is |
| A. | To eliminate any change in amplitude of received FM signal |
| B. | To reduce the amplitude of the signal to suit the amplifier |
| C. | To amplify low frequency signals |
| D. | None of these |
| Answer» B. To reduce the amplitude of the signal to suit the amplifier | |
| 85. |
As compared to a phase discriminator, a ratio detector provides |
| A. | Double the output obtainable from a phase discriminator |
| B. | Higher stabilization against signal variations |
| C. | Lower linearity |
| D. | None of these |
| Answer» D. None of these | |
| 86. |
Quantizing noise occurs in |
| A. | Time-division multiplex |
| B. | Frequency-division multiplex |
| C. | Pulse-code modulation |
| D. | Pulse-width modulation |
| Answer» D. Pulse-width modulation | |
| 87. |
Indicate which of the following systems is digital? |
| A. | Pulse-position modulation |
| B. | Pulse-code modulation |
| C. | Pulse-width modulation |
| D. | Pulse-frequency modulation |
| Answer» C. Pulse-width modulation | |
| 88. |
Pulse-width modulation may be generated |
| A. | By differentiating pulse-position modulation |
| B. | With a monostable multivibrator |
| C. | By integrating the signal |
| D. | With a free-running multivibrator |
| Answer» C. By integrating the signal | |
| 89. |
Indicate the false statement. In order to stop noise |
| A. | The channel bandwidth may be increased |
| B. | Redundancy may be used |
| C. | The transmitted power may be increased |
| D. | The signalling rate may be reduced |
| Answer» B. Redundancy may be used | |
| 90. |
The biggest disadvantage of PCM is |
| A. | Its inability to handle analog signals |
| B. | The high error rate which its quantizing noise introduces |
| C. | Its incompatibility with TDM |
| D. | The large bandwidths that are required for it |
| Answer» E. | |
| 91. |
Indicate which of the following pulse modulation systems is analog? |
| A. | PCM |
| B. | Differential PCM |
| C. | PWM |
| D. | Delta |
| Answer» D. Delta | |
| 92. |
The code which provides for parity checks is |
| A. | Baudot |
| B. | ASCII |
| C. | EBCDIC |
| D. | CCITT-2 |
| Answer» C. EBCDIC | |
| 93. |
The modulation system inherently most noise-resistant is |
| A. | SSB, suppressed-carrier |
| B. | Frequency modulation |
| C. | Pulse-position modulation |
| D. | Pulse-code modulation |
| Answer» E. | |
| 94. |
The Hartley-Shannon theorem sets a limit on the |
| A. | Highest frequency that may be sent over a given channel |
| B. | Maximum capacity of a channel with a given noise level |
| C. | Maximum number of coding levels in a channel with a given noise level |
| D. | Maximum number of quantizing levels in a channel of a given bandwidth |
| Answer» C. Maximum number of coding levels in a channel with a given noise level | |
| 95. |
The band rate |
| A. | Is always equal to the bit transfer rate |
| B. | Is equal to twice the bandwidth of an ideal channel |
| C. | Is not equal to the signalling rate |
| D. | Is equal to one-half the bandwidth of an ideal channel |
| Answer» C. Is not equal to the signalling rate | |
| 96. |
The event which marked the start of the modern computer age was |
| A. | Design of ENIAC computer |
| B. | Development of the Hollerith code |
| C. | Development of the transistor |
| D. | Development of disk drives for data storage |
| Answer» D. Development of disk drives for data storage | |
| 97. |
Digital signals |
| A. | Do not provide a continuous set of values |
| B. | Represent values as discrete steps |
| C. | Can utilize decimal or binary systems |
| D. | All of the above |
| Answer» E. | |
| 98. |
Broadband long-distance communications were originally made possible by the advent of |
| A. | Telegraph cables |
| B. | Repeater amplifiers |
| C. | HF radio |
| D. | Geostationary satellites |
| Answer» C. HF radio | |
| 99. |
The RS-232 interface |
| A. | Interconnects data sets and transmission circuits |
| B. | Uses several different connectors |
| C. | Permits custom wiring of signal lines to the |
| D. | connector pins as desired |
| E. | All of the above |
| Answer» B. Uses several different connectors | |
| 100. |
A forward error-correcting code corrects errors by |
| A. | Requiring partial retransmission of the signal |
| B. | Requiring retransmission of the entire signal |
| C. | Requiring no part of the signal to be retransmitted |
| D. | Using parity to correct the errors in all cases |
| Answer» D. Using parity to correct the errors in all cases | |