| 76. |
FM transmitting and receiving equipment as compared to AM equipment is |
| A. | costly |
| B. | cheaper |
| C. | almost equally costly |
| D. | none of the above |
| Answer» A. costly | |
| 77. |
An audio signal (say from 50 Hz to 10000 Hz) is frequency translated by a carrier having a frequency of 106 Hz. The values of initial (without frequency translation) and final (after frequency translation) fractional change in frequency from one band edge to the other are |
| A. | 200 and 1.01 |
| B. | 200 and 10.01 |
| C. | 200 and 100.1 |
| D. | 200 and 200 |
| Answer» A. 200 and 1.01 | |
| 78. |
If in a broadcasting studio, a 1000 kHz carrier is modulated by an audio signal of frequency range 100-5000 kHz, the width of channel is __________ kHz. |
| A. | 5 |
| B. | 4.9 |
| C. | 995 |
| D. | 10 |
| Answer» D. 10 | |
| 79. |
Which one of the following is analog? |
| A. | pcm |
| B. | pwm |
| C. | delta modulation |
| D. | differential pcm |
| Answer» B. pwm | |
| 80. |
The disadvantage of FM over AM is that |
| A. | high output power is needed |
| B. | high modulating power is needed |
| C. | noise is very high for high frequency |
| D. | large bandwidth is required |
| Answer» D. large bandwidth is required | |
| 81. |
Which of the following is a digital modulation technique? |
| A. | pcm |
| B. | psk |
| C. | dm |
| D. | all |
| Answer» B. psk | |
| 82. |
Which of the following is used to generate PDM? |
| A. | free running multi-vibrator |
| B. | monostable multi-vibrator |
| C. | jk flip-flop |
| D. | schmitt trigger |
| Answer» B. monostable multi-vibrator | |
| 83. |
SSB can be generated by |
| A. | filter method |
| B. | phase cancellation method |
| C. | good attenuation characteristics |
| D. | all of the above |
| Answer» D. all of the above | |
| 84. |
A zero mean white Gaussian noise is passed through an ideal low pass filter of bandwidth 10 kHz. The output of the samples so obtained would be |
| A. | correlated |
| B. | statistically independent |
| C. | uncorrelated |
| D. | orthogonal |
| Answer» B. statistically independent | |
| 85. |
What is the purpose of peak clipper circuits in radio transmitters? |
| A. | to prevent overmodulation |
| B. | to reduce bandwidth |
| C. | to increase bandwidth |
| D. | to regulate oscillator i/p voltage |
| Answer» A. to prevent overmodulation | |
| 86. |
In case of low level amplitude modulation system, the amplifiers following the modulated stage must be |
| A. | class c amplifiers |
| B. | linear devices |
| C. | non-linear devices |
| D. | harmonic devices |
| Answer» B. linear devices | |
| 87. |
Under ordinary circumstances, impulse noise can be reduced in |
| A. | fm only |
| B. | am only |
| C. | both am and fm |
| D. | none of the above |
| Answer» A. fm only | |
| 88. |
In case of frequency modulation, modulating voltage remains constant if the modulating frequency is lowered, then |
| A. | amplitude of distant sidebands decreases |
| B. | amplitude of distant sidebands increases |
| C. | amplitude of distant sidebands remains constant |
| D. | amplitude of distant sidebands first increases, then decreases |
| Answer» B. amplitude of distant sidebands increases | |
| 89. |
If sampling is done at the rate of 10 kHz. The bandwidth required is |
| A. | 35 khz |
| B. | 70 khz |
| C. | 10 khz |
| D. | 1280 khz |
| Answer» A. 35 khz | |
| 90. |
It is found that a ship to ship communication suffers from fading. This can be avoided by using |
| A. | space diversity |
| B. | frequency diversity |
| C. | broad band antenna |
| D. | directional antenna |
| Answer» B. frequency diversity | |
| 91. |
In practical commercial FM system, channel bandwidth is |
| A. | 150 khz |
| B. | 100 khz |
| C. | 88 mhz |
| D. | 108 mhz |
| Answer» A. 150 khz | |
| 92. |
In EM waves, polarization |
| A. | is always vertical in an isotropic medium |
| B. | is caused by reflection |
| C. | is due to transverse nature of waves |
| D. | results from longitudinal nature of waves |
| Answer» C. is due to transverse nature of waves | |
| 93. |
The maximum power output of a standard A earth station over the total band allocated to satellite communication is about |
| A. | 0.5 kw |
| B. | 8 kw |
| C. | 20 kw |
| D. | 50 kw |
| Answer» A. 0.5 kw | |
| 94. |
PAM stands for |
| A. | pulse analogue modulation |
| B. | phase analogue modulation |
| C. | pulse amplitude modulation |
| D. | phase amplitude modulation |
| Answer» C. pulse amplitude modulation | |
| 95. |
The characteristic impedance of a twin wire feeder used for TV signals is about |
| A. | 1000 ohm |
| B. | 500 ohm |
| C. | 300 ohm |
| D. | 100 ohm |
| Answer» C. 300 ohm | |
| 96. |
In a FM receiver, amplitude limiter |
| A. | amplifiers low frequency signals |
| B. | reduces the amplitude of signals |
| C. | eliminates any change in amplitude of received fm signals |
| D. | none of the above |
| Answer» C. eliminates any change in amplitude of received fm signals | |
| 97. |
A buffer amplifier is |
| A. | a double-tuned amplifier |
| B. | a high gain d.c. amplifier |
| C. | a cathode follower stage |
| D. | none of the above |
| Answer» B. a high gain d.c. amplifier | |
| 98. |
Leak type bias is used in plate modulated class C amplifier to |
| A. | increase the bandwidth |
| B. | prevent over modulation |
| C. | prevent excessive grid current |
| D. | prevent tuned circuit damping |
| Answer» C. prevent excessive grid current | |
| 99. |
The direction of rotation of a CD is |
| A. | clockwise |
| B. | anticlockwise |
| C. | clockwise or anticlockwise depending on frequency of data stored |
| D. | mostly anticlockwise but some times clockwise |
| Answer» B. anticlockwise | |
| 100. |
One of the advantages of base modulation over collector modulation of a transistor class C amplifier is |
| A. | improved efficiency |
| B. | better linearity |
| C. | high power output per transistor |
| D. | the lower modulating power requirement |
| Answer» D. the lower modulating power requirement | |
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