MCQOPTIONS
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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.
| 101. |
The Hartley law states that |
| A. | The maximum rate of information transmission depends on the channel bandwidth |
| B. | The maximum rate of information transmission depends on the depth of modulation |
| C. | Redundancy is essential |
| D. | Only binary codes may be used |
| Answer» B. The maximum rate of information transmission depends on the depth of modulation | |
| 102. |
A signalling system in which each letter of the alphabet is represented by a different symbol is not used because |
| A. | It would be too difficult for an operator to memorize |
| B. | It is redundant |
| C. | Noise would introduce too many errors |
| D. | Too many pulses per letter are required |
| Answer» D. Too many pulses per letter are required | |
| 103. |
Which of the following pulse systems is preferred for communication in the presence of noise? |
| A. | PAM |
| B. | PDM |
| C. | PPM |
| D. | None of these |
| Answer» D. None of these | |
| 104. |
Amplitude limiter essentially is a |
| A. | Squaring circuit |
| B. | Clamping circuit |
| C. | Clipping circuit |
| D. | None of these |
| Answer» D. None of these | |
| 105. |
Tracking is not much problem in FM receivers because tuning frequency range is |
| A. | Much more than in AM broadcasting |
| B. | Much less than in AM broadcasting |
| C. | Any in AM broadcasting |
| D. | None of these |
| Answer» C. Any in AM broadcasting | |
| 106. |
Aperative effect in the reconstructed signal from samples is due to loss of |
| A. | High frequency components |
| B. | Mid range frequency components |
| C. | Low frequency components |
| D. | None of these |
| Answer» B. Mid range frequency components | |
| 107. |
Which of the following pulse systems requires higher bandwidth? |
| A. | PAM |
| B. | PDM |
| C. | PPM |
| D. | None of these |
| Answer» D. None of these | |
| 108. |
If the synchronization between transmitter and receiver fails, which of the following pulse systems would be affected |
| A. | PAM |
| B. | PDM |
| C. | PPM |
| D. | None of these |
| Answer» D. None of these | |
| 109. |
In indirect method of FM generation generally |
| A. | Narrow-band FM is produced |
| B. | Wideband FM is produced |
| C. | Both of these |
| D. | None of these |
| Answer» B. Wideband FM is produced | |
| 110. |
A supergroup pilot is |
| A. | Applied at each multiplexing bay |
| B. | Used to regulate the gain of individual repeaters |
| C. | Applied at each adjustable equalizer |
| D. | Fed in at a GTE |
| Answer» E. | |
| 111. |
Time-division multiplex |
| A. | Can be used with PCM only |
| B. | Combines five groups into a supergroup |
| C. | Stacks 24 channels in adjacent frequency slots |
| D. | Interleaves pulses belonging to different transmissions |
| Answer» E. | |
| 112. |
The number of repeaters along a coaxial cable link depends on |
| A. | Whether separate tubes are used for the two directions of transmission |
| B. | The bandwidth of the system |
| C. | The number of coaxial cables in the tube |
| D. | The separation of the equalizers |
| Answer» C. The number of coaxial cables in the tube | |
| 113. |
As compared to collector modulation of a transistor, base modulation has |
| A. | Higher efficiency |
| B. | Higher linearity |
| C. | Lower modulating power requirements |
| D. | Both and |
| Answer» D. Both and | |
| 114. |
Ring modulator is used to produce |
| A. | DSB-SC |
| B. | SSB |
| C. | USB |
| D. | VSB |
| Answer» B. SSB | |
| 115. |
The type of modulator amplifier used in AM transmitter is |
| A. | Class A |
| B. | Class B |
| C. | Class C with negative feedback |
| D. | None of these |
| Answer» D. None of these | |
| 116. |
If modulation index in an AM system is low, it means the system is |
| A. | Less efficient |
| B. | More efficient |
| C. | More reliable |
| D. | Both and |
| Answer» B. More efficient | |
| 117. |
An FM signal with a modulation index mf is passed through a frequency tripler. The wave in the output of the tripler will have a modulation index of |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>m<sub>f</sub></center></td></tr><tr><td style="text-align: center;">3</td></tr></table> |
| B. | |
| C. | mf |
| D. | 3mf |
| E. | 9mf |
| Answer» D. 3mf | |
| 118. |
Indicate the false statement regarding the Armstrong modulation system |
| A. | The system is basically phase, not frequency modulation |
| B. | AFC is not needed, as a crystal oscillator is used |
| C. | Frequency multiplication must be used |
| D. | Equalization is unnecessary |
| Answer» E. | |
| 119. |
R3E modulation is sometimes used to |
| A. | Allow the receiver to have a frequency synthesizer |
| B. | Simplify the frequency stability problem in reception |
| C. | Reduce the power that must be transmitted |
| D. | Reduce the bandwidth required for transmission |
| Answer» C. Reduce the power that must be transmitted | |
| 120. |
To provide two or more voice circuits with the same carrier, it is necessary to use |
| A. | ISB |
| B. | Carrier re-insertion |
| C. | SSB with pilot carrier |
| D. | Lincompex |
| Answer» B. Carrier re-insertion | |
| 121. |
Vestigial sideband modulation (C3F) is normally used for |
| A. | HF point-to-point communications |
| B. | Monaural broadcasting |
| C. | TV broadcasting |
| D. | Stereo broadcasting |
| Answer» B. Monaural broadcasting | |
| 122. |
In the spectrum of a frequency-modulated wave |
| A. | The carrier frequency disappears when the modulation index is large |
| B. | The amplitude of any sideband depends on the modulation index |
| C. | The total number of sidebands depends on the modulation index |
| D. | The carrier frequency cannot disappear |
| Answer» C. The total number of sidebands depends on the modulation index | |
| 123. |
Indicate the noise whose source is in a category different from that of three |
| A. | Solar noise |
| B. | Cosmic noise |
| C. | Atmospheric noise |
| D. | Noise figure |
| Answer» D. Noise figure | |
| 124. |
Indicate in which one of the following only one sideband is transmitted? |
| A. | H3E |
| B. | A3E |
| C. | B8E |
| D. | C3F |
| Answer» B. A3E | |
| 125. |
The most commonly used filters in SSB generation are |
| A. | Mechanical |
| B. | RC |
| C. | LC |
| D. | Low-pass |
| Answer» B. RC | |
| 126. |
Indicate which one of the following advantages of the phase cancellation method of obtaining SSB over the filter method is false? |
| A. | Switching from one sideband to the other is simpler |
| B. | It is possible to generate SSB at any frequency |
| C. | SSB with lower audio frequencies present can be generated. |
| D. | There are more balanced modulators; therefore the carrier is suppressed better. |
| Answer» E. | |
| 127. |
When the modulation index of an AM wave is doubled, the antenna current is also doubled. The AM system being used a |
| A. | Single-sideband, full carrier (H3E) |
| B. | Vestigial sideband (C3F) |
| C. | Single-sideband, suppressed carrier (J3E) |
| D. | Double sideband, full carrier (A3E) |
| Answer» D. Double sideband, full carrier (A3E) | |
| 128. |
A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4; the total modulation index |
| A. | Is 1 |
| B. | Cannot be calculated unless the phase relations are known |
| C. | Is 0.5 |
| D. | Is 0.7 |
| Answer» D. Is 0.7 | |
| 129. |
The output stage of a television transmitter is most likely to be a |
| A. | Plate-modulated class C amplifier |
| B. | Grid-modulated class C amplifier |
| C. | Screen-modulated class C amplifier |
| D. | Grid-modulated class A amplifier |
| Answer» C. Screen-modulated class C amplifier | |
| 130. |
Leak-type bias is used in a plate-modulated class C amplifier to |
| A. | Prevent tuned circuit damping |
| B. | Prevent excessive grid current |
| C. | Prevent overmodulation |
| D. | Increase the bandwidth |
| Answer» C. Prevent overmodulation | |
| 131. |
In a low-level AM system, amplifiers following the modulated stage must be |
| A. | Linear devices |
| B. | Harmonic devices |
| C. | Class C amplifiers |
| D. | Nonlinear devices |
| Answer» B. Harmonic devices | |
| 132. |
One of the following is not a useful quantity for comparing the noise performance of receivers |
| A. | Input noise voltage |
| B. | Equivalent noise resistance |
| C. | Noise temperature |
| D. | Noise figure |
| Answer» B. Equivalent noise resistance | |
| 133. |
The value of resistor creating thermal noise is doubled, the noise power generated is therefore |
| A. | Halved |
| B. | Quadrupled |
| C. | Doubled |
| D. | Unchanged |
| Answer» E. | |
| 134. |
Select the wrong statement. The square of the thermal noise voltage generated by a resistor is proportional to |
| A. | Its resistance |
| B. | Its temperature |
| C. | Boltzmann s constant |
| D. | None of these |
| Answer» C. Boltzmann s constant | |
| 135. |
Which of the following types of noise becomes of great importance at high frequencies? It is the |
| A. | Shot noise |
| B. | Random noise |
| C. | Impulse noise |
| D. | Transit-time noise |
| Answer» E. | |
| 136. |
The main advantage of PCM is |
| A. | Less bandwidth |
| B. | Less power |
| C. | Better S/N ratio |
| D. | Possibility of multiplexing |
| Answer» D. Possibility of multiplexing | |
| 137. |
In DM, in order to keep S/N ratio nearly constant, the step size a is kept small but increases as the input signal |
| A. | Increases |
| B. | decreases |
| C. | remains unaffected |
| D. | None of these |
| Answer» B. decreases | |
| 138. |
In DM, slope overload occurs when the modulating signal changes |
| A. | Less rapidly than the encoder can follow |
| B. | More rapidly than the encoder can follow |
| C. | Both of these |
| D. | None of these |
| Answer» C. Both of these | |
| 139. |
An analog signal is quantized and transmitted using a PCM system. The tolerable error in sample amplitude is 0.5% of the peak-to-peak full scale value. The minimum binary digits required to encode a sample is |
| A. | 5 |
| B. | 6 |
| C. | 7 |
| D. | 8 |
| Answer» D. 8 | |
| 140. |
Indicate the wrong statement regarding modulation |
| A. | Separate differing transmissions |
| B. | Allows the use of practical antennas |
| C. | Reduce the bandwidth used |
| D. | Ensure that intelligence may be transmitted over long distances |
| Answer» D. Ensure that intelligence may be transmitted over long distances | |
| 141. |
The main disadvantage of PCM is |
| A. | large bandwidth |
| B. | larger power |
| C. | complex circuitry |
| D. | quantization noise |
| Answer» B. larger power | |
| 142. |
(For the data given in above) The minimum transmission bandwidth is |
| A. | 218.16 kHz |
| B. | 468.32 kHz |
| C. | 136.32 kHz |
| D. | None of the above |
| Answer» B. 468.32 kHz | |
| 143. |
The telemetry signals, each of bandwidth 2 kHz are to be transmitted simultaneously by binary PCM. The maximum tolerable error in sample amplitudes is 0.2% of the peak signal amplitude. The signals must be sampled at least 20% above the Nyquist rate. Framing and synchronizing requires an additional 1% extra bits. The minimum possible data rate must be |
| A. | 273.64 kbits/sec |
| B. | 436.32 kbits/sec |
| C. | 936.64 kbits/sec |
| D. | None of the above |
| Answer» C. 936.64 kbits/sec | |
| 144. |
An analog signal is sampled at 36 kHz and quantized into 256 levels. The time duration of a bit of the binary coded signal is |
| A. | 5.78 s |
| B. | 3.47 s |
| C. | 6.43 ms |
| D. | 7.86 ms |
| Answer» C. 6.43 ms | |
| 145. |
Which of the following modulations is non-linear? |
| A. | A M |
| B. | SSB |
| C. | F M |
| D. | both & |
| Answer» D. both & | |
| 146. |
The most suitable method for detecting a modulated signal (2.5 + 5 cos |
| A. | Envelope detector |
| B. | Synchronous detector |
| C. | Ratio detector |
| D. | Both and |
| Answer» C. Ratio detector | |
| 147. |
The positive RF peaks of an AM voltage rise to a maximum value of 12V and drop to a minimum value of 4V. The modulation index assuming single tone modulation is |
| A. | 3 |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">3</td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">4</td></tr></table> |
| D. | |
| E. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">2</td></tr></table> |
| Answer» E. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">2</td></tr></table> | |
| 148. |
In FM if the modulation index increases, the number of significant sidebands |
| A. | Increases |
| B. | Remain same |
| C. | Decreases |
| D. | None of these |
| Answer» B. Remain same | |
| 149. |
In FM wave expressed in terms of Bessel functions, J |
| A. | The dc component |
| B. | The first pair of sidebands |
| C. | The presence of carrier |
| D. | None of these |
| Answer» D. None of these | |
| 150. |
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 | |