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MCQs

Communication Systems(12th Grade -Physics)

Total Questions : 167 | Page 16 of 17 pages
Question 151. Which of the following is used to generate PDM?
  1.    Free running multi-vibrator
  2.    Monostable multi-vibrator
  3.    JK flip-flop
  4.    Schmitt trigger
 Discuss Question
Answer: Option B. -> Monostable multi-vibrator
Question 152. When the length of antenna is a whole wavelength
  1.    The radiation at right angles is zero
  2.    The radiation at right angles is maximum
  3.    The radiation is zero in all directions
  4.    The radiation is maximum in all directions
 Discuss Question
Answer: Option A. -> The radiation at right angles is zero
Question 153. For telegraphy the most commonly used modulation system is
  1.    FSK
  2.    Two tone modulation
  3.    PCM
  4.    Single tone modulation
 Discuss Question
Answer: Option A. -> FSK
Question 154. Which of the following is a digital modulation technique?
  1.    PCM
  2.    PSK
  3.    DM
  4.    All
 Discuss Question
Answer: Option B. -> PSK
Question 155. The disadvantage of FM over AM is that
  1.    High output power is needed
  2.    High modulating power is needed
  3.    Noise is very high for high frequency
  4.    Large bandwidth is required
 Discuss Question
Answer: Option D. -> Large bandwidth is required
Question 156. If output power of a radio receiver is doubled, its volume is increased by __________ dB
  1.    2
  2.    3
  3.    1
  4.    -3
 Discuss Question
Answer: Option B. -> 3
Question 157. A telephone channel requires a bandwidth of about
  1.    1 kHz
  2.    3 kHz
  3.    10 kHz
  4.    50 kHz
 Discuss Question
Answer: Option B. -> 3 kHz
Question 158. Which of the following is an indirect way of generating FM?
  1.    Armstrong modulator
  2.    Varactor diode modulator
  3.    Reactance FET modulator
  4.    Reactance bipolar transistor
 Discuss Question
Answer: Option A. -> Armstrong modulator
Question 159. For attenuation of high frequencies we should use
  1.    Shunt capacitance
  2.    Series capacitance
  3.    Inductance
  4.    Resistance
 Discuss Question
Answer: Option A. -> Shunt capacitance
Question 160. One of the advantages of base modulation over collector modulation of a transistor class C amplifier is
  1.    Improved efficiency
  2.    Better linearity
  3.    High power output per transistor
  4.    The lower modulating power requirement
 Discuss Question
Answer: Option D. -> The lower modulating power requirement

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