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IIT JEE Principles Of Communication set-1

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1. A radiowave signal propagating from one point to other following the surface of Earth is called




2. In a true WBFM all the energy is associated with None of these




3. Out of the following which type of sampling is preferred ?




4. If carrier frequency is 100 kH and modulating frequency is 5kH then band width of AM transmission is




5. he digital transmission is done mostly via None of these




6. Base band pulses travels




7. The transmission band width in WBFM is




8. If the ratio of wavelength emitted from two different sources is 1 : 2 then ratio of their velocities will be None of these




9. The disadvantage of FM over AM is




10. The circuits that produces PDM requires




11. Purpose of modulator is




12. In FM if frequency deviation is doubled




13. The threshold in FM depends upon




14. Waves used for long distance broadcast are




15. Out of the following which is not a correct statement for FM ?




16. In amplitude modulated wave power content of the carrier is maximum when A17m is




17. Out of the following which is not a correct statement for FM ?




18. Demodulation




19. Select the incorrect statement




20. Dibits in PM are




21. If the frequency of EM radiations is halved then the energy of EM radiation will become




22. The sampling rate lies between




23. Optical fibres made of glass or plastic are




24. If 100% modulation is produced in AM then




25. If AM having 100% modulation of the total transmitted power each side band carries




26. In an AM system full information can be conveyed by transmitting only




27. In an AM transmission band width is equal to




28. Audio signal can t be directly transmitted into the space because




29. A glass coating surrounding the glass core in an optical fibre is called




30. The region that contains free electrons and negative ions and positive ions and positive ions is




31. In AM if modulation index is more than 100% then




32. Voice communication is done by using




33. Wavelength of the waves having frequency 3000 MHz is




34. Broadcast band in which FM lies is




35. The DSB-SC signal are detected by




36. Satellite used for only reflecting back the signal to earth stations is called




37. Modulation index in FM depends upon




38. The carrier suppression is done son as to




39. The frequency used in TV and radar system lies in




40. Which of the following waves gets affected by solar cycle ?




41. The total channel band width allotted to FM is




42. Intelsat satellite is used in




43. Out of following which wave disappears because of tilting ?




44. In AM transmission which modulator is being used ?




45. Tropospheric scatter happens in




46. The product demodulator is also known as




47. Select the wrong statement in case of EM waves.




48. Crystal oscillator is used to generate carrier waves because of




49. Space waves normally propagated in




50. The modulation index in case of FM is defined for




51. Balance modulator is used to produce




52. The product modulator basically is a




53. The satellite that seems stationary w r t Earth is




54. The fading process applies to




55. The modulation index of an ores-modulated wave is




56. 7.Ring modulator is used to produce




57. The waves that are related to telecommunication are




58. Intelsat satellite works as a




59. Data communicated by optical fibres system is generally




60. In AM wave the modulation index is 100% If the carrier is suppressed the percentage saving in power will be




61. Absorption of radiowaves by atmosphere depends upon




62. A 500 W carrier is amplitude modulated with modulation index of 60%. What will be total power of modulated wave




63. In optical fibre propagation angle of light must be less than or equal to




64. The number of AM broadcast stations that can be accommodated in a 300 kHz band w+A65idth for the highest modulating frequency 15 kHz will be




65. A 400 W carrier AM modulated to a depth of 75%. The total power of the system is




66. Lasers are used in alignment of pipes because




67. Out of the following subsystems which is used for satellite or+A68bit position and altitude




68. The antenna current of an AM transmission is 8A when only carrier is sent but is increases to 893 A when the carrier is modulate The modulation of the wave is




69. The layer that absorbs largest proportion of UV rays is




70. Bit rate is given by




71. Lasers are used as an endoscope in which field ?




72. The total power contact of an AM wave is 1200 W. What will be modulation index if each side band contains 150 W of power




73. The process in which the wave follows the Earth s curvature is called as




74. Optical fibra communication have an advantage over general communication because




75. The loop gain in case of two wire repeater is must be