You dont have javascript enabled! Please enable it! Communications Engineering Mastery Test 7: ECE Pre-Board

# Communications Engineering Mastery Test 7: ECE Pre-Board

This is 100 items set of Practice Examination 7 in Communications Engineering (Electronics Systems and Technology) composed of previous Board Exams Questions. Read each question and choice 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 question 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 question.

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

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

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

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

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

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

Solution:

7. What is the typical satellite transponder bandwidth?

A. 24 MHz

B. 500 MHz

C. 36 MHz

D. 48 MHz

Solution:

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

A. 1000 MHz

B. 36 MHz

C. 250 MHz

D. 500 MHz

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

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

Solution:

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

A. C band

B. X band

C. L band

D. P band

Solution:

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

A. L

B. K

C. S

D. J

Solution:

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

A. Ku

B. C band

C. J

D. P

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

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

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

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

Solution:

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

A. Iridium

B. Globalstar

C. ANIK

D. Molniya

Solution:

19. What is the orbit of Motorolaโs Iridium satellite system?

A. Polar

B. Equatorial

C. Inclined elliptical

D. Inclined equatorial

Solution:

20. What band of frequencies do these satellites operate?

A. L band

B. Ka band

C. C band

D. Ku band

Solution:

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

A. 1200

B. 4800

C. 2400

D. 3840

Solution:

22. What satellite system is also known as Navstar?

A. GPS

B. Iridium

C. Globalstar

D. Intelsat

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

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

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

Solution:

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

A. 55ห

B. 65ห

C. 105ห

D. 45ห

Solution:

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

A. PVC

B. Teflon

C. PE

D. Polystyrene

Solution:

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

A. 2.5

B. 3.3

C. 2.27

D. 2.1

Solution:

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

A. polystyrene

B. teflon

C. ceramic

D. bakelite

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 โฆ

B. 250 โฆ

C. 305 โฆ

D. 301 โฆ

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 โฆ

B. 75 โฆ

C. 50 โฆ

D. 150 โฆ

Solution:

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

A. 0.1

B. 0.3

C. 0.2

D. 0.4

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

Solution:

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

A.0.82 m

B. 0.82 ft

C. 0.82 in

D. 0.82 cm

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

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

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

Solution:

38. Which coaxial connector is a more complex and expensive but does 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

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

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

Solution:

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

A. 0.9

B. 0.8

C. 0.5

D. 0.7

Solution:

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

A. Shielded pair

B. Flexible coaxial

D. Open-wire line

Solution:

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

A. 0.58

B. 0.68

C. 0.98

D. 0.81

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

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

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

Solution:

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

A. 108.5ห

B. 106.5ห

C. 115.5ห

D. 166.5ห

Solution:

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

A. 93 โฆ

B. 75 โฆ

C. 50 โฆ

D. 300 โฆ

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

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. 24.59โฆ

B. Either A or C

C. 228.75โฆ

D. Neither A nor C

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

Solution:

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

A. Tempo

B. Attack

C. Rhythm

D. Timbre

Solution:

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

A. Sound

B. Speech

C. Music

D. Noise

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

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

Solution:

56. The basic voice band has how many octaves?

A. 10

B. 4

C. 5

D. 3

Solution:

57. The ratio of frequencies is termed.

A. interval

B. octave

C. harmonics

D. factor

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

Solution:

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

A. 100

B. 90

C. 106

D. 96

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

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

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

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

Solution:

64. What do you call the perceptible sound repetition?

A. Reverberation

B. Echo

C. Reflection

Solution:

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

A. Sound Attenuation

B. Transmission loss

C. Sound absorption

D. Barrier loss

Solution:

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

A. 76 kHz

B. 76 Hz

C. 76 MHz

D. 76 mHz

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

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

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

Solution:

70. The sound intensity received from the nearby jet plane is 12.6 ยตW/m^2 and that from another jet plane some distance away is 0.45 ยตW/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

Solution:

71. The noise from an airplane engine 100 ft from an observer is found to have an intensity of 45 dB. 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

Solution:

72. What is the apparent loudness of 80 dB?

A. Moderate

B. Very loud

C. Loud

D. Deafening

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

Solution:

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

A. 114 dB

B. 11.4 dB

C. 94 dB

D. 57 dB

Solution:

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

A. 330

B. 3600

C. 3300

D. 5800

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

Solution:

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

A. 3.1

B. 2.8

C. 7.1

D. 4.2

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

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

Solution:

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

A. 1250

B. 500

C. 1000

D. 1500

Solution:

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

A. 33

B. 30

C. 40

D. 25

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

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

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

Solution:

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

A. 7.8ยฐ

B. 5.04ยฐ

C. 6.04ยฐ

D. 7.04ยฐ

Solution:

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

A. 4.4 MHz

B. 3.5 MHz

C. 6.5 MHz

D. 1.5 MHz

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

Solution:

88. The electromagnetic radiation theory was profounded by

A. Sir Edward Appleton

B. Guglielmo Marconi

C. Heinrich Hertz

D. James C. Maxwell

Solution:

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

A. Polarization

B. Interference

C. Beamwidth

D. Gain

Solution:

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

A. Space wave

B. Troposcatter

C. Ground wave

D. Direct wave

Solution:

91. What is the orbit inclination of geostationary satellites?

A. 0ยฐ

B. 10ยฐ

C. 20ยฐ

D. 30ยฐ

Solution:

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

A. 100 ฮฉ

B. 212 ฮฉ

C. 300 ฮฉ

D. 112 ฮฉ

Solution:

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

A. Ultrasonic

B. Transonic

C. Subsonic

D. Supersonic

Solution:

94. What frequency is 10 octaves above 30 Hz?

A. 30.72 kHz

B. 30 kHz

C. 300 Hz

D. 307.2 kHz

Solution:

95. A radio signal travels ____ yards per microseconds.

A. 273

B. 328

C. 618

D. 123.6

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

Solution:

97. The range of speech power is ____.

A. 1 โ 10 watts

B. 100 โ 1000 milliwatts

C. 10 โ 100 milliwatts

D. 10 โ 1000 microwatts

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

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

Solution:

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

A. 80

B. 50

C. 30

D. 40

Solution:

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

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