Solved papers for JEE Main & Advanced Physics Communication System / संचार तंत्र JEE PYQ-Communication System

done JEE PYQ-Communication System Total Questions - 37

• question_answer1) 

  This question has Statement-1 and Statement-2.

  Of the four choices given after the statements, choose the one that best describes the two statements.

  Statement-1: Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.

  Statement-2: The state of ionosphere varies from hour to hour, day to day and season to season. [AIEEE 2011]

  A)
  Statement-1 is false, Statement-2 is true
  done clear
  B)
  Statement-1 is true, Statement-2 is false
  done clear
  C)
  Statement-1 is true, Statement-2 is true and Statement-2 is the correct explanation of Statement-1
  done clear
  D)
  Statement-1 is true, Statement-2 is true and Statement-2 is not the correct explanation of Statement-1
  done clear
  View Answer play_arrow

• question_answer2) 

  Which of the following four alternatives is not correct?

  We need modulation:        [AIEEE 11-05-2011]

  A)
  to reduce the time lag between transmission and reception of the information signal
  done clear
  B)
  to reduce the size of antenna
  done clear
  C)
  to reduce the e fractional band width, that is the ratio of the signal band width to the centre frequency
  done clear
  D)
  to increase the selectivity.
  done clear
  View Answer play_arrow

• question_answer3) A radar has a power of 1kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth ) is:                     [AIEEE 2012]
  A)
  80 km
  done clear
  B)
  16 km
  done clear
  C)
  40 km
  done clear
  D)
  64 km
  done clear
  View Answer play_arrow

• question_answer4) Broadcasting antennas are generally                                        [JEE ONLINE 07-05-2012]
  A)
  vertical type
  done clear
  B)
  both vertical and horizontal type
  done clear
  C)
  omni directional type
  done clear
  D)
  horizontal type
  done clear
  View Answer play_arrow

• question_answer5) 

  Given the electric field of a complete amplitude modulated wave as

  Where the subscript c stands for the carrier wave and m for the modulating signal. The frequencies present in the modulated wave are                            [JEE ONLINE 19-05-2012]

  A)
  and
  done clear
  B)
   and
  done clear
  C)
  and                    
  done clear
  D)
  and
  done clear
  View Answer play_arrow

• question_answer6) A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.                                 [JEE MAIN 2013]
  A)
  10.62 MHz
  done clear
  B)
  10.62 kHz
  done clear
  C)
  5.31 MHz
  done clear
  D)
  5.31 kHz
  done clear
  View Answer play_arrow

• question_answer7) If a carrier wave  is amplitude modulated by a modulator single then the equation of modulated signal and its modulation index are respectively  [JEE ONLINE 09-04-2013]
  A)
  and 2       
  done clear
  B)
              and 1       
  done clear
  C)
              and 1
  done clear
  D)
              and 2
  done clear
  View Answer play_arrow

• question_answer8) Which of the following statement is not correct?                        [JEE ONLINE 23-04-2013]
  A)
              Ground wave signals are more stable than the sky wave signals.
  done clear
  B)
              The critical frequency of an ionosphere layer is the highest frequency that will be reflected back by the layer when it is vertically incident.
  done clear
  C)
              Electromagnetic waves of frequencies higher than about 30 MHz cannot penetrate the ionosphere.
  done clear
  D)
              Sky wave singles in the broadcast frequency range are stronger at night than in the day time.
  done clear
  View Answer play_arrow

• question_answer9) Which of the following modulated signal has the best noise-tolerance?   [JEE ONLINE 25-04-2013]
  A)
              long-wave
  done clear
  B)
  Short - wave
  done clear
  C)
              medium-wave  
  done clear
  D)
              amplitude-modulated
  done clear
  View Answer play_arrow

• question_answer10) A transmitting antenna at the top of a tower has height 32 m and height of the receiving antenna is 50 m. What is the maximum distance between them for satisfactory communication in line of sight (LOS) mode?         [JEE ONLINE 09-04-2014]
  A)
  55.4 km
  done clear
  B)
  45.5 km
  done clear
  C)
  54.5 km
  done clear
  D)
  455 km
  done clear
  View Answer play_arrow

• question_answer11) For sky wave propagation, the radio waves must have a frequency range in between: [JEE ONLINE 12-04-2014]
  A)
  MHz to 2 MHz
  done clear
  B)
  5 MHz to 25 MHz
  done clear
  C)
  35 MHz to 40 MHz
  done clear
  D)
  45 MHz to 50 MHz
  done clear
  View Answer play_arrow

• question_answer12) Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen the frequency of the radio waves must be in the range: [JEE ONLINE 19-04-2014]
  A)
  80 - 150 MHz
  done clear
  B)
  8 - 25 MHz
  done clear
  C)
  1 - 3 MHz
  done clear
  D)
  None of these
  done clear
  View Answer play_arrow

• question_answer13) A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal is/are:                                     [JEE MAIN 2015]
  A)
  2005 kHz, 2000 kHz and 1995 kHz
  done clear
  B)
  2000 kHz and 1995 kHz
  done clear
  C)
  2 MHz only
  done clear
  D)
  2005 kHz, and 1995 kHz
  done clear
  View Answer play_arrow

• question_answer14) Choose the correct statement:                                                   [JEE MAIN - I 3-4-2016]
  A)
  In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the frequency of the audio signal.
  done clear
  B)
  In amplitude modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
  done clear
  C)
  In amplitude modulation the frequency of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
  done clear
  D)
  In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
  done clear
  View Answer play_arrow

• question_answer15) An audio signal consists of two distinct sound: one a human speech signal in the frequency band of 200 Hz to 2700 Hz, while the other is a high frequency music signal in the frequency band of 10200 Hz to 15200 Hz. The ratio of the AM signal band width required to send both the signals together to the AM signal band width required to send just the human speech is: [JEE ONLINE 09-04-2016]
  A)
  6
  done clear
  B)
  5
  done clear
  C)
  3
  done clear
  D)
  2
  done clear
  View Answer play_arrow

• question_answer16) A modulated signal  has the form The carrier frequency  the modulating frequency (message frequency) , and the modulation index  are respectively given by:                                 [JEE ONLINE 10-04-2016]
  A)
   
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer17) In amplitude modulation, sinusoidal carrier frequency used is denoted by and the signal frequency is denoted byThe bandwidth  of the signal is such thatWhich of the following frequencies is not contained in the modulated wave? [JEE Main 2017]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer18) A signal of frequency 20 kHz and peak voltage of 5 volt is used to modulate a carrier wave of frequency 1.2 MHz and peak voltage 25 volts. Choose the correct statement. [JEE Online 08-04-2017]
  A)
  Modulation index = 5, side frequency bands are at 1400 kHz and 1000 kHz
  done clear
  B)
  Modulation index = 0.8, side frequency bands are at 1180 kHz and 1220 kHz
  done clear
  C)
  Modulation index = 0.2, side frequency bands are at 1200 kHz and 1180 kHz
  done clear
  D)
  Modulation index = 5, side frequency bands are at 21/2 kHz and 18.8 kHz
  done clear
  View Answer play_arrow

• question_answer19) A signal is to be transmitted through a wave of wavelength  using a linear antenna. The length l of the antenna and effective power radiated  will be given respectively as - (K is a constant of proportionality) [JEE Online 09-04-2017]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer20) A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz? [JEE Main Online 08-04-2018]
  A)
  \[2\times {{10}^{5}}\]
  done clear
  B)
  \[2\times {{10}^{6}}\]
  done clear
  C)
  \[2\times {{10}^{3}}\]
  done clear
  D)
  \[2\times {{10}^{4}}\]
  done clear
  View Answer play_arrow

• question_answer21) The number of amplitude modulated broadcast stations that can be accommodated in a \[300kHz\] band width for the highest modulating frequency \[15kHz\] will be: [JEE Online 15-04-2018]
  A)
  20
  done clear
  B)
  10
  done clear
  C)
  8
  done clear
  D)
  15
  done clear
  View Answer play_arrow

• question_answer22) The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance \[49\mu H\] and a capacitance of\[2.5nF\]. It is modulated by an audio signal of\[12kHz\]. The frequency range occupied by the side bands is: [JEE Online 15-04-2018 (II)]
  A)
  \[18kHz-30kHz\]
  done clear
  B)
  \[63kHz-75kHz\]
  done clear
  C)
  \[442kHz-466kHz\]
  done clear
  D)
  \[13482kHz-13494kHz\]
  done clear
  View Answer play_arrow

• question_answer23) A carrier wave of peak voltage 14 V is used for transmitting a message signal. The peak voltage of modulating signal given to achieve a modulation index of 80% will be: [JEE Main Online 16-4-2018]
  A)
  11.2 V
  done clear
  B)
  7 V
  done clear
  C)
  22.4 V
  done clear
  D)
  28 V
  done clear
  View Answer play_arrow

• question_answer24) In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accommodated for transmitting TV signals of band width 6 MHz are (Take velocity of light [JEE Main 09-Jan-2019 Evening]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer25) A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be broadcasted from this tower is LOS (Line of Sight) mode? (Given: radius of earth . [JEE Main 10-Jan-2019 Morning]
  A)
  40 km
  done clear
  B)
  65 km
  done clear
  C)
  48 km
  done clear
  D)
  80 km
  done clear
  View Answer play_arrow

• question_answer26) The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot?       [JEE Main 10-Jan-2019 Evening]
  A)
  2900 kHz
  done clear
  B)
  2750 kHz
  done clear
  C)
  2250 kHz
  done clear
  D)
  2000 kz
  done clear
  View Answer play_arrow

• question_answer27) 

  An amplitude modulated signal is given by.

  Here t is in seconds. The side band frequencies [JEE Main 11-Jan-2019 Morning]

  (in kHz) are, [Given ]

  A)
  178.5 and 171.5
  done clear
  B)
  89.25 and 85.75
  done clear
  C)
  1785 and 1715
  done clear
  D)
  892.5 and 857.5
  done clear
  View Answer play_arrow

• question_answer28) 

  An amplitude modulated signal is plotted below [JEE Main 11-Jan-2019 Evening]

  Which one of the following best describes the above signal?

  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer29) A 100 V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index?                                       [JEE Main 12-Jan-2019 Morning]
  A)
  0.4
  done clear
  B)
  0.5
  done clear
  C)
  0.6
  done clear
  D)
  0.3
  done clear
  View Answer play_arrow

• question_answer30) To double the covering range, or' a TV transmission tower, its height should be multiplied by- [JEE Main 12-Jan-2019 Evening]
  A)
   
  done clear
  B)
  2
  done clear
  C)
  4
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer31) The wavelength of the carrier waves in a modern optical fiber communication network is close to :   [JEE Main 8-4-2019 Morning]
  A)
  600 nm
  done clear
  B)
  900 nm
  done clear
  C)
  2400 nm
  done clear
  D)
  1500 nm
  done clear
  View Answer play_arrow

• question_answer32) In an interference experiment the ratio of amplitudes of coherent waves is The ratio of maximum and minimum intensities of fringes will be: [JEE Main 8-4-2019 Morning]
  A)
  4
  done clear
  B)
  2
  done clear
  C)
  9
  done clear
  D)
  18
  done clear
  View Answer play_arrow

• question_answer33) In a line of sight radio communication, a distance of about 50 km is kept between the transmitting and receiving antennas. If the height of the receiving antenna is 70m, then the minimum height of the transmitting antenna should be: (Radius of the Earth ).   [JEE Main 8-4-2019 Afternoon]
  A)
  40 m
  done clear
  B)
  51 m
  done clear
  C)
  32 m
  done clear
  D)
  20 m
  done clear
  View Answer play_arrow

• question_answer34) A signal  is transmitted using  as carrier wave. The correct amplitude modulated (AM) signal is : [JEE Main 9-4-2019 Morning]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer35) The physical sizes of the transmitter and receiver antenna in a communication system are :- [JEE Main 9-4-2019 Afternoon]
  A)
  proportional to carrier frequency
  done clear
  B)
  inversely proportional to modulation frequency
  done clear
  C)
  inversely proportional to carrier frequency
  done clear
  D)
  independent of both carrier and modulation frequency
  done clear
  View Answer play_arrow

• question_answer36) A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side band frequencies are: [JEE Main 10-4-2019 Morning]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow

• question_answer37) 

  Given below in the left column are different modes of communication using the kinds of waves given the right column.

  A. Optical Fibre communication P. Ultrasound B. Radar Q. Infrared Light C. Sonar R. Microwaves D. Mobile Phones S. Radio Waves

  [JEE Main 10-4-2019 Morning]
  A)
  
  done clear
  B)
  
  done clear
  C)
  
  done clear
  D)
  
  done clear
  View Answer play_arrow