# Communications Engineering Mastery Test 7: ECE Pre-Board

(Last Updated On: March 25, 2020) This is 100 items set of Practice Examination 7 in Communications Engineering (Electronics Systems and Technology) composed of previous Board Exams Questions. Read each questions and choices carefully! Choose the best answer. In the actual board, you have to answer 100 items in Communications Engineering within 5 hours. You have to get at least 70% to pass the subject. Communications Engineering is 30% of the total 100% Board Rating along with Mathematics (20%), General Engineering and Applied Sciences (20%) and Electronics Engineering (30%). Familiarize each and every questions to increase the chance of passing the ECE Board Examination.

#### Start the Test Yourself Exam 7

Choose the letter of the best answer in each questions.

1. How far away is the radio horizon of an antenna 100 ft high?

A. 14.14 mi

B. 40 km

C. 14.14 km

D. 40 mi

View Answer:

Answer: Option A

Solution:

2. What is the maximum line-of-sight distance between a paging antenna 250 ft high and a pager receiver 3.5 ft of the ground?

A. 25 km

B. 25 mi

C. 70.73 km

D. 70.73 mi

View Answer:

Answer: Option B

Solution:

3. What is the path attenuation between transmitter and receiver at a frequency of 1.2 Ghz and a distance of 11,000 mi?

A. 119 dB

B. 115 dB

C. 179 dB

D. 174 dB

View Answer:

Answer: Option C

Solution:

4. What is the uplink receiver frequency if the downlink transmitter is on channel 4 (3.84 Ghz)?

A. 6.065 GHz

B. 6.84 GHz

C. 6.65 GHz

D. 6.05 GHz

View Answer:

Answer: Option A

Solution:

5. What is the maximum theoretical data rate of the above problem if one transponder is used for binary transmission?

A. 36 Mbps

B. 72 Mbps

C. 18 Mbps

D. 144 Mbps

View Answer:

Answer: Option B

Solution:

6. What is the guardband between transponder channels in the commercial C-band for satellite communications?

A. 6 MHz

B. 36 MHz

C. 4 MHz

D. 2 MHz

View Answer:

Answer: Option C

Solution:

7. What is the typical satellite transponder bandwidth?

A. 24 MHz

B. 500 MHz

C. 36 MHz

D. 48 MHz

View Answer:

Answer: Option C

Solution:

8. What is the bandwidth available in the commercial C-band?

A. 1000 MHz

B. 36 MHz

C. 250 MHz

D. 500 MHz

View Answer:

Answer: Option D

Solution:

9. Which of the following is the uplink frequency in C-band?

A. 5.925 GHz

B. 4.2 GHz

C. 7.425 GHz

D. 3.7 GHz

View Answer:

Answer: Option A

Solution:

10. How many transponder channels are realized in the commercial C-band without frequency re-use?

A. 24

B. 12

C. 36

D. 48

View Answer:

Answer: Option B

Solution:

11. Which band of frequencies used by military for its satellites and radar?

A. C band

B. X band

C. L band

D. P band

View Answer:

Answer: Option B

Solution:

12. For navigation as well as marine and aeronautical communications and radar, ____ band is used.

A. L

B. K

C. S

D. J

View Answer:

Answer: Option A

Solution:

13. What is the current frequency band given most attenuation for satellite communications?

A. Ku

B. C band

C. J

D. P

View Answer:

Answer: Option A

Solution:

14. What satellite subsystem monitors onboard conditions such as temperature and battery voltage and transmits this data back to a ground station for analysis?

A. Communications subsystem

B. AKM

C. TTC

D. Transponder

View Answer:

Answer: Option C

Solution:

15. Which of the following satellite subsystem provides stabilization in orbit and senses changes in orientation?

A. Attitude control subsystem

B. TTC

C. AKM

D. Transponder

View Answer:

Answer: Option A

Solution:

16. What is the typical center frequency spacing between adjacent channels (transponders) in satellites?

A. 36 MHz

B. 40 MHz

C. 500 MHz

D. 4 MHz

View Answer:

Answer: Option B

Solution:

17. Which of the following are uplinks in the Ku band?

A. 14 to 14.5 GHz

B. 11.7 to 12.2 GHz

C. 14 to 15.5 GHz

D. 11 to 11.5 GHz

View Answer:

Answer: Option A

Solution:

18. What is considered as the most advanced satellite system developed for cellular telephones?

A. Iridium

B. Globalstar

C. ANIK

D. Molniya

View Answer:

Answer: Option A

Solution:

19. What is the orbit of Motorola’s Iridium satellite system?

A. Polar

B. Equatorial

C. Inclined elliptical

D. Inclined equatorial

View Answer:

Answer: Option A

Solution:

20. What band of frequencies do these satellites operate?

A. L band

B. Ka band

C. C band

D. Ku band

View Answer:

Answer: Option A

Solution:

21. Iridium satellites can provide data communications of up ____ bps data rate.

A. 1200

B. 4800

C. 2400

D. 3840

View Answer:

Answer: Option C

Solution:

22. What satellite system is also known as Navstar?

A. GPS

B. Iridium

C. Globalstar

D. Intelsat

View Answer:

Answer: Option A

Solution:

23. What is the orbit height of a GPS satellite?

A. 10,898 nmi

B. 10,898 mi

C. 10,898 km

D. 10, 898 m

View Answer:

Answer: Option A

Solution:

24. What is the orbital period of each satellite in the GPS constellation?

A. 6 h

B. 12 h

C. 5 h

D. 15 h

View Answer:

Answer: Option B

Solution:

25. What term is normally associated with specifying the location of a celestial body in space?

A. Constellation

B. Galaxy

C. Satellite

D. Ephemeris

View Answer:

Answer: Option D

Solution:

26. What is the angle of inclination of GPS system?

A. 55˚

B. 65˚

C. 105˚

D. 45˚

View Answer:

Answer: Option A

Solution:

27. What material is most often used for the outer covering of coaxial cables?

A. PVC

B. Teflon

C. PE

D. Polystyrene

View Answer:

Answer: Option A

Solution:

28. What is the dielectric constant of polyethylene (PE) insulator?

A. 2.5

B. 3.3

C. 2.27

D. 2.1

View Answer:

Answer: Option C

Solution:

29. Polytetrafluoroethylene (PTFE) is also widely used insulator and is known as.

A. polystyrene

B. teflon

C. ceramic

D. bakelite

View Answer:

Answer: Option B

Solution:

30. What is the characteristic impedance of a two-wire line with the following data: diameter = 0.023 in., spacing =0.5 in., insulation = PE.?

A. 300 Ω

B. 250 Ω

C. 305 Ω

D. 301 Ω

View Answer:

Answer: Option D

Solution:

31. What is the characteristic impedance of a coaxial line with the following data: inner diameter = 0.2 in., center conductor diameter = 0.06 in., insulation = Teflon.

A. 200 Ω

B. 75 Ω

C. 50 Ω

D. 150 Ω

View Answer:

Answer: Option C

Solution:

32. A pair of current-carrying conductors is not considered a transmission line unless it is at least ___ λ long at the signal frequency.

A. 0.1

B. 0.3

C. 0.2

D. 0.4

View Answer:

Answer: Option A

Solution:

33. If the operating frequency is 450 MHz what length of a pair of conductors is considered to be a transmission line?

A. 2.19 ft

B. 2.19 m

C. 0.219 ft

D. 0.219 m

View Answer:

Answer: Option C

Solution:

34. What is the physical length of the above transmission line at 3/8λ long?

A.0.82 m

B. 0.82 ft

C. 0.82 in

D. 0.82 cm

View Answer:

Answer: Option B

Solution:

35. Which of the following coaxial cable connectors is called the UHF connector?

A. PL-259

B. BNC

C. N-type connector

D. F connector

View Answer:

Answer: Option A

Solution:

36. What connector is popular in attaching test instruments like oscilloscopes, frequency counters, spectrum analyzers, etc?

A. UHF connector

B. PL-259

C. BNC

D. SMA

View Answer:

Answer: Option C

Solution:

37. Which coaxial cable connector is least expensive and is widely used for TV sets,VCRs and cable TV?

A. N-type connector

B. F-type connector

C. BNC

D. PL-259

View Answer:

Answer: Option B

Solution:

38. Which coaxial connector is a more complex and expensive but do a better job in maintaining the electrical characteristics of the cable through the interconnections?

A. N-type connector

B. F-type connector

C.BNC

D. PL-259

View Answer:

Answer: Option A

Solution:

39. The velocity factor in transmission lines vary from ___ to ___.

A. 0.6 to 0.8

B. 0.3 to 0.5

C. 0.5 to 0.9

D. 0.8 to 0.9

View Answer:

Answer: Option C

Solution:

40. What is the typical velocity factor of coaxial cables?

A. 0.6 to 0.8

B. 0.3 to 0.5

C. 0.5 to 0.9

D. 0.4 to 0.6

View Answer:

Answer: Option A

Solution:

41. What is the typical velocity factor of open-wire line?

A. 0.9

B. 0.8

C. 0.5

D. 0.7

View Answer:

Answer: Option A

Solution:

42. What line has a typical velocity factor of about 0.8?

A. Shielded pair

B. Flexible coaxial

C. Twin-lead

D. Open-wire line

View Answer:

Answer: Option C

Solution:

43. What is the velocity factor of coaxial cable with a characteristic impedance of 50 Ω and capacitance of 30 pF/ft and inductance of 75 nH/ft?

A. 0.58

B. 0.68

C. 0.98

D. 0.81

View Answer:

Answer: Option B

Solution:

44. What is transit time (time delay) of a 50-ft length transmission line of the above problem?

A. 50 ns

B. 100 ns

C. 75 ns

D. 65 ns

View Answer:

Answer: Option C

Solution:

45. What do you call a transmission line used specifically for the purpose of achieving delay?

A. Delay line

B. Flat line

C. Resonant line

D. Non-resonant line

View Answer:

Answer: Option A

Solution:

46. What is the time delay introduced by a 75-ft coaxial cable with a dielectric constant of 2.3?

A. 1.54 ns

B. 11.5 ns

C. 115.6 ns

D. 1156 ns

View Answer:

Answer: Option C

Solution:

47. Assume a frequency of 4 MHz, determine the phase shift offered by the line in the above problem.

A. 108.5˚

B. 106.5˚

C. 115.5˚

D. 166.5˚

View Answer:

Answer: Option D

Solution:

48. Find the load impedance that must be used to terminate RG-62A/U to avoid reflections?

A. 93 Ω

B. 75 Ω

C. 50 Ω

D. 300 Ω

View Answer:

Answer: Option A

Solution:

49. Find the equivalent inductance per foot of the above cable?

A. 13.5 nF/ft

B. 13.5 pF/ft

C. 116.8 nH/ft

D. 116.8 pF/ft

View Answer:

Answer: Option C

Solution:

50. An RG-11/U foam coaxial cable has a maximum voltage standing wave of 52 V and a minimum voltage of 17 V. Find the value of the resistive load.

A. 24.59Ω

B. Either A or C

C. 228.75Ω

D. Neither A nor C

View Answer:

Answer: Option B

Solution:

51. Sound provides all sorts of information. What information is related to mental processes of knowledge, reasoning, memory, judgement and perception?

A. Cognitive

B. Affective

C. Digital

D. Analog

View Answer:

Answer: Option A

Solution:

52. What sound characteristic relates to a sonic time pattern?

A. Tempo

B. Attack

C. Rhythm

D. Timbre

View Answer:

Answer: Option C

Solution:

53. What is considered the most obvious conveyor of information?

A. Sound

B. Speech

C. Music

D. Noise

View Answer:

Answer: Option B

Solution:

54. Attack is a sound characteristic that refers to the way a sound begins. Which of the following is NOT an attack of sound?

A. Hard

B. Soft

C. Crisp

D. Simple

View Answer:

Answer: Option D

Solution:

55. At what loudness level do pitch (in mels) and frequency (in Hz) are numerically equal?

A. 0 dB

B. 20 dB

C. 60 dB

D. 40 dB

View Answer:

Answer: Option D

Solution:

56. The basic voice band has how many octaves?

A. 10

B. 4

C. 5

D. 3

View Answer:

Answer: Option B

Solution:

57. The ratio of frequencies is termed.

A. interval

B. octave

C. harmonics

D. factor

View Answer:

Answer: Option A

Solution:

58. What is the tonal ratio of an octave?

A. 1 to 2

B. 1 to 3

C. 2 to 1

D. 3 to 1

View Answer:

Answer: Option C

Solution:

59. If the loudness level is 100 phons, what is this in sone unit?

A. 100

B. 90

C. 106

D. 96

View Answer:

Answer: Option C

Solution:

60. What octave bands are there in the midrange?

A. 1st and 2nd

B. 5th, 6th and 7th

C. 3rd and 4th

D. 8th and 9th

View Answer:

Answer: Option B

Solution:

61. How much louder is 80 phons over 60 phons?

A. 1000 times

B. 4 times louder

C. 100 times

D. Twice as loud

View Answer:

Answer: Option B

Solution:

62. What increase in sound level is commonly perceived by most people?

A. 6 to 10 dB

B. 1 to 3 dB

C. 3 to 6 dB

D. 10 to 20dB

View Answer:

Answer: Option A

Solution:

63. What is typical loudness level of an acoustic guitar 1 foot away?

A. 60 dB

B. 100 dB

C. 80 dB

D. 40 dB

View Answer:

Answer: Option C

Solution:

64. What do you call the perceptible sound repetition?

A. Reverberation

B. Echo

C. Reflection

D. Masking

View Answer:

Answer: Option B

Solution:

65. What is the amount of sound reduction provided by a barrier – wall, floor, or ceiling called?

A. Sound Attenuation

B. Transmission loss

C. Sound absorption

D. Barrier loss

View Answer:

Answer: Option B

Solution:

66. What is the frequency of a 2-cm sound wave in sea water at 25˚C?

A. 76 kHz

B. 76 Hz

C. 76 MHz

D. 76 mHz

View Answer:

Answer: Option A

Solution:

67. A choir consisting of 36 individuals all of whom can sing with the same intensity. A soloist sings a certain passage and then is joined by the remainder of the choir members for a repeat of the passage. What is the difference in the sound intensity level in the two cases?

A. 3 dB

B. 6 dB

C. 36 dB

D. 15.6 dB

View Answer:

Answer: Option D

Solution:

68. For the safety and comfort of factory workers, the sound-intensity level in a certain factory must remain below 85 dB. What is the maximum sound intensity allowed in this factory?

A. 3.2 x 10^-4 W/m^2

B. 3.2 x 10^-6 W/m^2

C. 3.2 x 10^-10 W/m^2

D. 3.2 x 10^-3 W/m^2

View Answer:

Answer: Option A

Solution:

69. What sound intensity corresponds to a sound-intensity level of 50 dB?

A. 1 x 10^-6 W/m^2

B. 1 x 10^-7 W/m^2

C. 1 x 10^-8 W/m^2

D.1 x 10^-5 W/m^2

View Answer:

Answer: Option B

Solution:

70. The sound intensity received from the nearby jet plane is 12.6 µW/m^2 and that from another jet plane some distance away is 0.45 µW/m^2. Find the relative loudness of the two.

A. 14.0 dB

B. 13.5 dB

C. 12.5 dB

D. 14.5 dB

View Answer:

Answer: Option D

Solution:

71. The noise from an airplane engine 100 ft from an observer is found to have an intensity of 45dB. What will be the intensity when the plane flies overhead at an altitude of 1 mi?

A. 10.5 dB

B. 34.5 dB

C. 35 dB

D. 20.5 dB

View Answer:

Answer: Option A

Solution:

72. What is the apparent loudness of 80 dB?

A. Moderate

B. Very loud

C. Loud

D. Deafening

View Answer:

Answer: Option B

Solution:

73. What loudness level in which permanent damage to hearing is possible?

A. 120 dB

B. 140 dB

C. 130 dB

D. 150 dB

View Answer:

Answer: Option D

Solution:

74. What is sound pressure level if the RMS sound pressure is 100 μbars?

A. 114 dB

B. 11.4 dB

C. 94 dB

D. 57 dB

View Answer:

Answer: Option A

Solution:

75. What is the velocity of sound in wood (m/s)?

A. 330

B. 3600

C. 3300

D. 5800

View Answer:

Answer: Option C

Solution:

76. What is the optimum reverberation time at 500 to 1000 Hz of an auditorium?

A. 0.9 to 1.1 s

B. 1.4 to 1.6 s

C. 1.5 to 1.6 s

D. 1.6 to 1.8 s

View Answer:

Answer: Option D

Solution:

77. For a cinema, the optimum volume per person required is

A. 3.1

B. 2.8

C. 7.1

D. 4.2

View Answer:

Answer: Option A

Solution:

78. Which of the following is NOT an acoustical defect to be avoided in acoustical designs?

A. Reverberation

B. Flutter echo

C. Distortion

D. Sound concentration

View Answer:

Answer: Option A

Solution:

79. What absorber in which efficient absorption is only possible over a very narrow band approaching 1.0 (total absorption)?

A. Porous material

B. Helmholtz resonator

C. Panel Absorber

D. Membrane absorber

View Answer:

Answer: Option B

Solution:

80. How many voice signals (4 kHz max.) would fit into a 5 MHz spectrum?

A. 1250

B. 500

C. 1000

D. 1500

View Answer:

Answer: Option A

Solution:

81. How many FM stations would be accommodated I an ordinary TV channel?

A. 33

B. 30

C. 40

D. 25

View Answer:

Answer: Option B

Solution:

82. What is the actual length in feet of a one-quarter wavelength of a coax with a velocity factor of 0.695 at 45 MHz?

A. 17.82

B. 19.26

C. 16.28

D. 16.97

View Answer:

Answer: Option C

Solution:

83. Determine the terrain sensitivity loss for a 4-GHz carrier that is propagating over a very dry, mountainous area.

A. -1.25 dB

B. -3.05 dB

C. -2.01 dB

D. -5.01 dB

View Answer:

Answer: Option A

Solution:

84. A satellite transmitter operates at 4GHz with an antenna gain of 4dBi. The receiver 40000 km away has an antenna gain of 50 dBi. If the transmitter has a power of 8 W, find (ignoring feedline losses and mismatch) the EIRP in dBW.

A. 50

B. 69

C. 49

D. 30

View Answer:

Answer: Option C

Solution:

85. A radio signal moves from air to glass. The angle of incidence is 20°. Calculate the angle of refraction. The relative permittivity of the glass is 7.8.

A. 7.8°

B. 5.04°

C. 6.04°

D. 7.04°

View Answer:

Answer: Option D

Solution:

86. At a certain time, the MUF for transmission at an angle of incidence of 75° is 17 MHz. What is the critical frequency?

A. 4.4 MHz

B. 3.5 MHz

C. 6.5 MHz

D. 1.5 MHz

View Answer:

Answer: Option A

Solution:

87. A properly matched transmission line has a loss of 1.5 dB/100m. if 10 W is supplied to one end of the line, how many watts reach the load, 27 m away?

A. 10 W

B. 7.2 W

C. 9.9 W

D. 9.1 W

View Answer:

Answer: Option D

Solution:

88. The electromagnetic radiation theory was profounded by

A. Sir Edward Appleton

B. Guglielmo Marconi

C. Heinrich Hertz

D. James C. Maxwell

View Answer:

Answer: Option D

Solution:

89. What is caused by the transverse nature of electromagnetic waves?

A. Polarization

B. Interference

C. Beamwidth

D. Gain

View Answer:

Answer: Option A

Solution:

90. Which propagation method is known as special case of skywave?

A. Space wave

B. Troposcatter

C. Ground wave

D. Direct wave

View Answer:

Answer: Option B

Solution:

91. What is the orbit inclination of geostationary satellites?

A. 0°

B. 10°

C. 20°

D. 30°

View Answer:

Answer: Option A

Solution:

92. A transmission line of unknown impedance is terminated with two different resistances, and an SWR is measured each time. With a 75 Ω termination, the SWR measures 1.5. With a 300 Ω termination, it measures 2.67. What is the impedance of the line?

A. 100 Ω

B. 212 Ω

C. 300 Ω

D. 112 Ω

View Answer:

Answer: Option D

Solution:

93. What is the high frequency sound that cannot be heard by the human ear?

A. Ultrasonic

B. Transonic

C. Subsonic

D. Supersonic

View Answer:

Answer: Option A

Solution:

94. What frequency is 10 octaves above 30 Hz?

A. 30.72 kHz

B. 30 kHz

C. 300 Hz

D. 307.2 kHz

View Answer:

Answer: Option A

Solution:

95. A radio signal travels ____ yards per microseconds.

A. 273

B. 328

C. 618

D. 123.6

View Answer:

Answer: Option C

Solution:

96. What is the actual length in feet of a one-half wavelength of a coax with a velocity factor of 0.63 at 28 MHz?

A. 44.28

B. 43.46

C. 11.07

D. 46.27

View Answer:

Answer: Option C

Solution:

97. The range of speech power is ____.

A. 1 – 10 watts

B. 100 – 1000 milliwatts

C. 10 – 100 milliwatts

D. 10 – 1000 microwatts

View Answer:

Answer: Option D

Solution:

98. What is the actual length in feet of a one-quarter wavelength of a coax with a velocity factor of 0.68 to 30 MHz?

A. 19.26

B. 5.6

C. 17.82

D. 16.97

View Answer:

Answer: Option B

Solution:

99. What is actual length in feet of a one-half wavelength of a coax with a velocity factor of 0.59 at 26 MHz?

A. 11.16

B. 40.29

C. 42.46

D. 46.28

View Answer:

Answer: Option A

Solution:

100. The agreed standard for measuring loudness is the loudness sensation produced by a 1000 Hz sine wave _____ dB above the listener’s threshold of hearing.

A. 80

B. 50

C. 30

D. 40

View Answer:

Answer: Option D

Solution:

### Complete List of Communications Engineering Exams: ECE Pre-Board

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