100mcq

1. The first geostationary satellite launched in 1965 was called

A. ANIK

B. EARLY BIRD (Intelsat-I)

C. WESTAR

D. MOLNIYA

ANSWER B

2. Rotation of a geosynchronous satellite means its

A. drift from stationary position

B. wobbling

C. three-axis stabilization

D. three-dimensional stabilization

ANSWER B

3. The present total cost per watt of power generation in geosynchronous orbit is nearly Rs.

A. 20 B. 50

C. 100 D. 5

ANSWER A

4. Noise temperature of Sun is more than __________ °K.

A. 1000 B. 5000

C. 100000 D. 500

ANSWER C

5. A 20 m antenna gives a certain uplink gain at frequencies of 4/6 GHz. For getting same gain in the 20/30 GHz band, antenna size required is meter.

A. 100 B. 4

C. 1 D. 10

ANSWER B

6. The discussing sharing of a communication satellite by many geographically dispersed Earth station, DAMA means

A. Demand-Assigned Multiple Access

B. Decibel Attenuated Microwave Access

C. Digital Analog Master Antenna

D. Dynamically-Assigned Multiple Access

ANSWER A

7. The angle subtended by earth at geostationary communication satellite is

A. 17.34° B. 51.4°

C. 120° D. 60°

ANSWER A

8. The INTELSAT-IV satellite launched in 1974 had two earth coverage antenna and two narrower-angle antennas subtending 4.5°. The signal from narrow-angle antenna was stronger than that from earth- coverage antenna by a factor of

A. 17.34/4.5

B. 17.34 x 4.5

C. (17.34/4.5)2

D. (17.34/4.5)4

ANSWER C

9. A transponder is a satellite equipment which

A. receives a signal from Earth station and amplifies

B. changes the frequency of the received signal

C. retransmits the received signal

D. does all of the above-mentioned functions

ANSWER D

10. A geosynchronous satellite

A. has the same period that of the Earth

B. has a circular orbit

C. rotates in the equatorial plane

D. has all of the above

ANSWER B

11. To make antenna more directional, either its size must be increased or

A. the number of its feed horns must be increased

B. the frequency of its transmission must be increased

C. its effective isotropic radiated power (EIRP) must be increased

D. its footprint must be increased

ANSWER B

12. India's first domestic geostationary satellite 1NSAT-IA was launched on 10th April 1982 from

A. USSR B. USA

C. UK D. UP

ANSWER B

13. Satellite launch sites are invariably located on Eastern seaboards to ensure that

A. launch takes place eastward

B. expenditure of propulsion fuel is reduced during plane changing

C. the satellite achieves circular orbit quickly

D. spent rocket motor and other launcher debris falls into the sea

ANSWER D

14. The owner of a communication satellite is usually required to keep the spacecraft on station at its assigned place in the geosynchronous orbit with an accuracy of __________ degree.

A. 0.1 B. 1.0

C. 2.0 D. 0.5

ANSWER A

15. The number of days when Earth's shadow falls on a geosynchronous satellite is

A. 88 B. 277

C. 5 D. 10

ANSWER A

16. Of the four INSAT-I satellites planned by India so far, only __________ has proved to be successful.

A. INSAT-IA B. INSAT-IB

C. INSAT-IC D. INSAT-ID

ANSWER B

17. Radio broadcasting is a familiar example of

A. space multiplexing

B. time multiplexing

C. frequency multiplexing

D. none of the above

ANSWER C

18. As compared to 17.34° antenna, the total increase in the signal relayed by 4.5° antenna of INTELSAT-IV is

A. 14.85 B. 220

C. 78 D. 3.85

ANSWER B

19. Which one of the following statements regarding DSI is wrong?

A. It is a digital form of TASI

B. Though it is more efficient than TASI, it is much slower

C. A speaker has to wait (it at all) for only a few milliseconds for reallocation of channel

D. It has increased the capacity of satellite channels by a factor of 2.2 or more without degrading speech quality

ANSWER B

20. Which one of the following statements regarding compandor is FALSE?

A. It compresses the higher-amplitude parts of a signal before modulation and expands them back to normal again after demodulation.

B. It gives preferential treatment to the weaker parts of the signal

C. For weaker signals it gives a poor ratio of signal strength to quantizing error

D. Weaker signals, traverse more quantum steps than they would do otherwise and so quantizing error is reduced.

ANSWER C

21. The quality of a space-link is measured in terms of the __________ ratio.

A. C/N B. S/N

C. G/T D. EIRP

ANSWER A

22. The useful operational life of INSAT-IB (launched in 1983) is expected to end by

A. 1992-93 B. 1991-92

C. 1989-90 D. 1993-94

ANSWER C

23. At present, the radio-frequency band mainly used by most satellites is

A. EHF B. UHF

C. VHF D. SHF

ANSWER D

24. Orbital disturbances of a geosynchronous satellite are caused by the

A. moon

B. sun

C. earth

D. all of the above

ANSWER D

25. Which one of the following statement is correct?

A. Satellite spacing is not affected by the bandwidth of the transmitting earth station

B. Beam width is independent of antenna size and frequency band used

C. The width of a beam in space is inversely proportional to the width of the transmitting antenna

D. Use of high-frequency bands permits less number of satellites to share the orbit

ANSWER C

26. In a stop-and-wait ARQ system, the transmitting terminal

A. waits for positive or negative acknowledgement from the receiving terminal after sending a block

B. sends another block if positive acknowledge is received through ACK character

C. resends the previous block if negative acknowledgement is received through a NAK character

D. does not wait for acknowledgement after sending a block

ANSWER D

27. A geostationary satellite is one which

A. hangs motionless in space about 36000 km about Earth

B. travels around the Earth in 24 hours

C. remains stationary above the Earth

D. appears stationary to everybody on Earth

ANSWER D

28. The geostationary communication satellite APPLE is parked in the equatorial orbit at

A. 102° E longitude over Sumatra

B. 90° E longitude over Bangladesh

C. 74° E longitude over India

D. 67° E longitude over Pakistan

ANSWER A

29. Power received from Sun per m2 surface area of a geosynchronous satellite in nearly __________ watt.

A. 100 B. 500

C. 2000 D. 1000

ANSWER D

30. A certain sound has 10000 times more energy than another sound. The number of times it would sound stronger to a listener is

A. 40 B. 10000

C. 100 D. 10

ANSWER A

31. While keeping the down-link frequency constant, the diameter of a satellite antenna is reduced by half. To offer the same EIRP over the increased coverage area, the RF output power has to be increases by a factor of

A. 2 B. 4

C. 8 D. 16

ANSWER B

32. A communication satellite is a repeater between

A. a transmitting station and a receiving station

B. a transmitting station and many receiving station

C. many transmitting station and many receiving station

D. none

ANSWER C

33. The ending part of the popular tele-serial Mahabharata will be beamed to the viewers

A. WESTAT B. INSAT-IC

C. ARABSAT D. INSAT-ID

ANSWER C

34. The most effective anti-jamming technique is

A. frequency hopping

B. spread-spectrum modulation

C. key leverage

D. once-only key

ANSWER B

35. For satellite communication, standard Earth stations have antenna diameters in the range of __________ meter.

A. 27.5 to 30

B. 10 to 15

C. 30 to 50

D. 5 to 10

ANSWER A

36. The Sun blots out the transmission of a geosynchronous satellite twice a year when satellite passes directly in front of it. This outage lasts for about

A. 10 minutes on 5 consecutive days

B. 5 minutes on 10 consecutive days

C. 30 minutes for 5 consecutive days

D. one hour for 5 consecutive days

ANSWER A

37. In satellite communication, frequency modulation is used because satellite channel has

A. small bandwidth and negligible noise

B. large bandwidth and severe noise

C. maximum bandwidth and minimum noise

D. high modulation index

ANSWER B

38. In the case of a 70-MHz IF carrier for a transponder bandwidth of 36 MHz, energy must lie between MHz.

A. 34 and 106

B. 52 and 88

C. 106 and 142

D. 34 and 142

ANSWER B

39. Which of the following factor does NOT contribute to the drift of a geostationary satellite from its stationary position in space?

A. Pressure of solar radiations

B. Gravitational changes due to Sun and Moon

C. Oblateness of the Earth

D. Weight of the satellite

ANSWER D

40. In communication satellites, the up-link normally operates at a higher frequency than the down-link because it

A. gives a narrow beam shining into space

B. results in lesser signal attenuation

C. gives better beam-shaping

D. is easier to polarize a high frequency beam

ANSWER A

41. For global communication, the number of satellites needed is

A. 1 B. 3

C. 10 D. 5

ANSWER B

42. System satellites orbit the Earth once in

A. 24 hours

B. 12 hours

C. 1 hours

D. 6 hours

ANSWER A

43. The lowest frequency used in satellite communications is __________ GHz.

A. 0.8 B. 3

C. 18 D. 30

ANSWER A

44. Geosynchronous satellites are always launched in the equatorial plane because it is the only plane which provides

A. 24-hour orbit

B. stationary satellite

C. global communication

D. zero-gravity environs

ANSWER C

45. After the death of INSAT-IB, the mainstay of the entire Indian satellite network for some time to come would be

A. INSTELSAT-V B. INSAT-ID

C. INSAT-2D. ARABSAT

ANSWER D

46. Which statement out of the following statement is wrong?

A. Attenuation of satellite signals by rain and fog varies almost inversely with the angle of elevation

B. At 12/4, GHz link frequencies, signal power loss due to rain and fog is much greater than at 4/6 GHz frequencies

C. The distance between satellite and Earth station varies slightly with angle of elevation

D. At present 4/6 GHz geostationary satellites are being parked in geosynchronous, orbits at least 10° apart

ANSWER D

47. For satellite transmission, analog signals may be converted into digital form with the help of

A. modem B. transponder

C. codec D. compandor

ANSWER C

48. The maximum signal propagation time of a geosynchronous satellite transmission is about __________ millisecond.

A. 540 B. 270

C. 135 D. 1080

ANSWER B

49. The life time of a geosynchronous communication

A. 5 B. 10

C. 20 D. 50

ANSWER B

40. Low-orbit satellites are not used for communications because they

A. produce sonic booms

B. do not provide 24 hour/ day contact to the users on Earth

C. heat up and melt

D. none

ANSWER C

51. The velocity factor of a transmission line depends on

A. temperature

B. skin effect

C. relative permittivity of dielectric

D. none of the above

ANSWER C

52. A loss less line of characteristic impedance Z0 is terminated in pure reactance of -jZ0 value. VSWR is

A. 10 B. 2

C. 1 D. infinity

ANSWER D

53. In a klystron amplifier the input cavity is called

A. buncher

B. catcher

C. Pierce gun

D. collector

ANSWER A

54. In a circular waveguide the dominant mode is

A. TE01 B. TE11

C. TE20 D. TE21

ANSWER B

55. The reflection coefficient on a line is 0.2 ∠45°. The SWR is

A. 0.8 B. 1.1

C. 1.2 D. 1.5

ANSWER D

56. Microwave resonators are used in

A. microwave oscillators

B. microwave narrow band amplifier

C. microwave frequency metres

D. all of the above

ANSWER D

57. Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading.

Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron.

A. Both A and R are correct and R is correct explanation of A

B. Both A and R are correct but R is not correct explanation of A

C. A is correct but R is wrong

D. A is wrong but R is correct

ANSWER A

58. In a TWT the amplitude of resultant wave travelling down the helix

A. increases exponentially

B. increases linearly

C. decreases exponentially

D. is almost constant

ANSWER A

59. Which of the following is not a travelling wave?

A. e = Em sin (βx - ωt)

B. e = Em cos (βx - ωt)

C. e = Em sin (ωt - βx)

D. e = Em sin (βx)

ANSWER D

60. Both Impatt and Trapatt devices use avalanche effect

A. True B. False

ANSWER A

61. In a directional coupler

A. isolation (dB) equals coupling plus directivity

B. coupling (dB) equals isolation plus directivity

C. directivity (dB) equals isolation plus coupling

D. isolation (dB) equals (coupling) (directivity)

ANSWER A

62. As the frequency is increased, the charging MVAR in a cable

A. decreases

B. increases

C. remain the same

D. decreases or remains the scheme

ANSWER B

63. Loss angle of a good quality cable is about

A. 1° B. 30°

C. 70° D. 90°

ANSWER A

64. In a three cavity klystron amplifier, the oscillations are excited in

A. input cavity

B. output cavity

C. intermediate cavity

D. both (a) and (b)

ANSWER C

65. In the given figure reflection coefficient at load is

A. 0.6

B. - 0.6

C. 0.4

D. - 0.4

ANSWER B

66. Which of the following lines is non-radiating?

A. Open two wire

B. Coaxial

C. Both

D. None of the above

ANSWER B

67. Assertion (A): The impedance of a matched load is equal to characteristic impedance of line.

Reason (R): A matched termination absorbs all the power incident on it.





ANSWER A

68. Skin effect is more pronounced at high frequencies.

A. True B. False

ANSWER A

69. Assertion (A): The phenomenon of differential mobility is called transferred electron effect.

Reason (R): GaAs exhibits transferred electron effect.





ANSWER B

70. Which of the following devices uses a helix?

A. Klystron amplifier

B. Klystron oscillator

C. TWT

D. Both (a) and (b)

ANSWER C

71. Which of the following parameters is negligible in transmission lines?

A. R B. L

C. C D. G

ANSWER D

72. The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about

A. 100° B. 50°

C. 5° D. 1°

ANSWER C

73. The diagram to show distance time history of electrons in klystron amplifier is called

A. apple gate diagram

B. asynchronous diagram

C. bunching diagram

D. velocity modulation diagram

ANSWER A

74. Impedance level of Impatt diodes is generally lower than that of Gunn diodes

A. True B. False

ANSWER A

75. A quarter wave line open circuited at far end behaves as

A. inductance

B. L and C in parallel

C. capacitance

D. L and C in series

ANSWER D

76. A line has Z0 = 300 ∠ 0° Ω. If ZL = 150 ∠ 0° Ω, reflection coefficient is

A. 0.5 B. 0.3333

C. -0.3333 D. -0.5

ANSWER C

77. Assertion (A): A backward wave oscillator has an internal positive feedback.

Reason (R): A positive feedback is necessary for sustained oscillations.





ANSWER B

78. In a microstrip transmission the signal can be easily redirected by changing the center strip.

A. True B. False

ANSWER A

79. The frequency of oscillation in a backward wave oscillator can be changed by

A. varying the voltage which controls beam velocity

B. varying the beam current

C. both by varying the beam current and by light varying the voltage which controls beam velocity

D. changing the rate of thermionic emission

ANSWER A

80. A line has a phase constant of 29.8 rad/m. At 1000 MHz the wavelength is

A. 29.8 m

B. 2.98 m

C. 2.1 m

D. 0.21 m

ANSWER D

81. In the given figure the time taken by the wave to make one round trip is

A. 10 ns

B. 20 ns

C. 30 ns

D. 40 ns

ANSWER D

82. For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than

A. 1 μF

B. 1 nF

C. 1 pF

D. 0.1 pF

ANSWER D

83. In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place

A. True B. False

ANSWER A

84. The fabrication of microstrip line is done by

A. photo etching

B. printed circuit technique

C. oxidation

D. cladding

ANSWER B

85. The condition of minimum distortion in a transmission line is

A. RL = 1

B. R = 0

C.

D.

ANSWER D

86. The action of backward wave oscillator is similar to that of

A. klystron amplifier

B. reflex klystron oscillator

C. TWT

D. magnetron

ANSWER C

87. In the given figure the reflection coefficient at source end is

A. 1 B. -1

C. 1/3 D. -1/3

ANSWER C

88. Assertion (A): Artificial transmission lines are frequently used in laboratories.

Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc.





ANSWER A

89. In a backward wave oscillator the wave travelling along the line winds itself back and forth

A. True B. False

ANSWER A

90. A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then

A. there will be no oscillations on line

B. there will be only 1 or 2 oscillations on line

C. there will be a finite number of oscillations on line

D. the oscillations will continue indefinitely

ANSWER D

91. Assertion (A): A coaxial line is a non-radiating line.

Reason (R): In a coaxial line the electric and magnetic fields are confined to the region between the concentric conductors.





ANSWER A

92. Reflex klystron oscillator is essentially a low power device

A. True B. False

ANSWER A

93. A 10 km long line has a characteristic impedance of 400 ohms. If line length is 100 km, the characteristic impedance is

A. 4000 Ω

B. 400 Ω

C. 40 Ω

D. 4 Ω

ANSWER B

94. A matched generator (Zg = Z0) with 1 Ω available. If all ports are matched, the power delivered at ports 1, 2, 3 respectively are

A. 0.5 W, 0.5 W, 0 W

B. 0 W, 0 W, 1 W

C. 0.33 W each

D. 0 W, 0.25 W, 0.25 W

ANSWER A

95. Which TM mode in rectangular waveguide has lowest cutoff frequency?

A. TM11 B. TM01

C. TM10 D. TM21

ANSWER A

96. A resistive microwave load with ZL = 150 Ω is connected to 50 Ω coaxial line. SWR is

A. more than 3

B. less than 3

C. equal to 3

D. either (a) or (c)

ANSWER C

97. Which of the following devices uses a slow wave structure?

A. Klystron two cavity amplifier

B. Klystron multicavity amplifier

C. Reflex klystron oscillator

D. TWT

ANSWER D

98. In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited

A. in phase

B. in phase opposition

C. 90° out of phase with each other

D. 45° out of phase with each other

ANSWER C

99. A waveguide section in a microwave circuit acts as

A. LP filter

B. Bandpass filter

C. HP filter

D. Band stop filter

ANSWER C

100. In a klystron amplifier dc electron velocity is v0 and dc electron charge density is r0 the dc beam current is

A. r0v0

B. r0/v0

C. v0/r0

D. (v0/r0)2

ANSWER A

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100mcq