# Communications Engineering Mastery Test 9: ECE Pre-Board

(Last Updated On: March 25, 2020) This is 100 items set of Practice Examination 9 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 9

Choose the letter of the best answer in each questions.

1. What significant element of sound refers to its characteristic tonal quality?

A. Pitch

B. Tempo

C. Rhythm

D. Timbre

Solution:

2. What is the velocity of sound in wood?

A. 5800 m/s

B. 5000 m/s

C. 3300 m/s

D. 3700 m/s

Solution:

3. What is the typical loudness level of a watch ticking?

A. 0 phon

B. 40 phons

C. 20 phons

D. 60 phons

Solution:

4. The typical length of the rhombic antenna is ____.

A. 2λ to 8λ

B. 10λ to 20λ

C. 1λ to 3λ

D. 5λ to 10λ

Solution:

5. What is the carrier frequency of supergroup 10?

A. 2724 kHz

B. 2356 kHz

C. 2108 kHz

D. 3100 kHz

Solution:

6. In SPADE system, how many PCM-encoded voice band channels are there?

A. 800

B. 600

C. 300

D. 240

Solution:

7. The product of the radiated RF power of a transmitter and the gain of the antenna system in a given direction relative to an isotropic radiator is called ____.

B. Effective Isotropic Radiated Power (EIRP)

D. Transmit Power

Solution:

8. The product of antenna input power and the antenna power gain expressed in kW is called __.

B. Effective Isotropic Radiated Power (EIRP)

D. Transmit Power

Solution:

9. What satellite system parameter represents the quality of a satellite or an earth station receiver?

A. Gain-to-Equivalent Noise Temperature Ratio (G/Te)

B. Energy of Bit-to-Noise Density Ratio (Eb/No)

C. Carrier-to-Noise Density Ratio (C/No)

D. Bit energy

Solution:

10. What noise is observable at frequencies in the range from about 8 MHz to somewhat 1.5 GHz?

A. Industrial noise

B. Atmospheric noise

C. Space noise

D. Shot noise

Solution:

11. A special horn antenna consisting of a parabolic cylinder joined to a pyramidal horn.

A. Hoghorn

B. Cass-horn

C. Pyramidal horn

D. Conical horn

Solution:

12. How many telegraph channels are there in the basic voice band channels?

A. 24

B. 96

C. 48

D. 672

Solution:

13. Which of the following is oldest multiplexing scheme?

A. Frequency Division Multiplexing (FDM)

B. Time Division Multiplexing (TDM)

C. Code Division Multiplexing (CDM)

D. Space Division Multiplexing (SDM)

Solution:

14. What carrier system multiplexes 96 voice band channels into a single 6.312 Mbps data signal?

A. T1 carrier system

B. T2 carrier system

C. T1C carrier system

D. T3 carrier system

Solution:

15. What is the metric subdivision of VHF band?

A. Metric

B. Millimetric

C. Decimetric

D. Centimetric

Solution:

16. In satellite communications, what means of attitude control is using the angular momentum of the spinning body to provide the roll and yaw stabilization?

A. Spin stabilization

C. Three-axis stabilization

D. Station keeping

Solution:

17. Which of the following is NOT a porous absorber?

A. Prefabricated tiles

B. Plasters and spray on materials

C. Acoustic blankets

D. Membrane absorber

Solution:

18. What historical satellite broadcasted live the 1964 Olympic games from Tokyo, Japan for the first time?

A. Syncom I

B. Syncom III

C. Syncom II

D. Syncom IV

Solution:

19. In transmission line, which of the following is the first step in the procedure of using stub matching?

A. Calculate stub susceptance.

D. Transform conductance to resistance

Solution:

20. What type of balun (balanced-to-unbalanced) is used in high frequency applications?

A. Transformer type balun

B. A specially configured coaxial transmission line

C. A specially configured parallel-wire line

D. A λ/2 transformer balun

Solution:

21. ____ is defined as any radiation of energy by means of electromagnetic wave.

A. Emission

Solution:

22. In what year did Hertz discover radio waves?

A. 1844

B. 1873

C. 1887

D. 1895

Solution:

23. Which of the following phenomena is possible is free space medium?

Solution:

24. What is the reactance property at the input of a shorted quarter wavelength line?

A. A parallel LC circuit

B. A pure inductive reactance

C. A series LC circuit

D. A pure capacitive reactance

Solution:

25. An early satellite owned by US Department of Defense that lasted only for 17 days

A. Courier

B. Echo

C. Score

D. Westar 1

Solution:

26. Which of the following is the consolidation of H. No. 5224 and S. No. 2683?

A. RA 9292

B. RA 5734

C. RA 7925

D. RA 6849

Solution:

27. Who will appoint the chairman and 2 members of the board of Electronics Engineering?

A. The Senate President

B. The President

C. The Supreme Court

D. The Commission on Appointment

Solution:

28. How many nominees per position of the Electronics Engineering Board are nominated by IECEP to PRC?

A. 3

B. 5

C. 4

D. 6

Solution:

29. According to RA 9292, how many days after the board exam the results will be released?

A. Within 5 days

B. Within 15 days

C. Within 20 days

D. Within 3 days

Solution:

30. How many removal examination (s) will be given to an examinee who obtains a passing rating in the majority of the subjects but obtains a rating in the other subject (s) below seventy percent (70%) but not lower than sixty percent (60%)?

A. 1

B. 3

C. 2

D. Unlimited

Solution:

31. Which of the following determines the acoustic behavior of gases?

A. Density

B. Pressure

C. Temperature

D. All of the choices

Solution:

32. In what medium sound travels the faster?

A. Vacuum

B. Solid

C. Liquid

D. Gas

Solution:

33. For a loudness level between 110 and 120 dB, the maximum daily exposure limit is ____ minute (s).

A. 1

B. 60

C. 20

D. 45

Solution:

34. A porous material is far more efficient at high than low frequency absorption. How to improve sound absorption at lower frequencies using this absorber?

A. Increase the thickness

B. Decrease the thickness

C. Mount with and airspace behind

D. Both A and C above

Solution:

35. Which of the following describes a TDM frame?

A. A 250-μs frame

B. A 125-μs frame

C. A 500-μs frame

D. A 60-μs frame

Solution:

36. ____ system transmits frequency-division-multiplexed voice band signals over a coaxial cable for distances up to 4000 miles.

A. T carrier

B. X carrier

C. L carrier

D. F carrier

Solution:

37. What is the spectrum range of U600 mastergroup?

A. 60 – 108 kHz

B. 564 – 3084 kHz

C. 312 – 552 kHz

D. 60 -2788 kHz

Solution:

38. Which frequency reuse method is less effective because of Faraday’s effect?

A. Dual polarization

B. Reducing antenna beamwidth

C. Zonal rotation

D. Spin stabilization

Solution:

39. Three telephone circuits, each having an S/N ratio of 44 dB, are connected in tandem. What is the overall S/N ratio?

A. 44 dB

B. 39.2 dB

C. 41 dB

D. 43.52 dB

Solution:

40. What is the noise factor if the equivalent noise temperature is 25 K?

A. 1.09

B. 0.09

C. 0.36 dBm

D. 0.36

Solution:

41. A ground station is operating to a geostationary satellite at a 5° angle of elevation. Calculate the round-trip time between ground station and satellite.

A. 275 s

B. 275 ms

C. 137.5 s

D. 137.5 ms

Solution:

42. Calculate the reverberation time of a living room 8 ft high, 13 ft wide and 20 ft long. The total absorption of the building structure inside the room is 180.7 sabines with four persons present in the room.

A. 0.5 ms

B. 0.05 s

C. 0.5 s

D. 5 ms

Solution:

43. What is the number of levels required in a PCM system with S/N ratio of 40 dB?

A. 64

B. 128

C. 256

D. 512

Solution:

44. A radio communications link is to be established via the ionosphere. The maximum virtual height of the layer is 100 km at the midpoint of the path and the critical frequency is 2 MHz. The distance between stations is 600 km. determine the optimum working frequency?

A. 6.32 MHz

B. 2.1 MHz

C. 5.4 MHz

D. 1.8 MHz

Solution:

45. Part of a microwave link can be approximated by free space conditions. The antenna gain are each 40 dB, the frequency is 10 GHz, and the path length is 80 km. Calculate the receive power for a transmitted power of 10 W?

A. 0.871 μW

B. 871 μW

C. 0.871 mW

D. 871 nW

Solution:

46. What is the approximate critical frequency of the E layer?

A. 4 MHz

B. 5 MHz

C. 6 MHz

D. 3 MHz

Solution:

47. What is the approximate single-hop nighttime range of F2 layer?

A. 3840 km

B. 3000 km

C. 4130 km

D. 2350 km

Solution:

48. What ionospheric layer has a daytime approximate critical frequency of 8 MHz?

A. F2 layer

B. F1 layer

C. E layer

D. D layer

Solution:

49. Determine the additional absorption (sabines) contributed by 10 persons in a room.

A. 47

B. 4.7

C. 0.47

D. 470

Solution:

50. A frequency of 3000 Hz has how many octaves above 1000 Hz?

A. 1.6 octaves

B. 2.1 octaves

C. 1 octave

D. 3 octaves

Solution:

51. The loudness level increased from 40 to 56 phons. What is the increase in loudness sensation?

A. 3 times

B. 4.5 times

C. 2 times

D. 4 times

Solution:

52. In the North American TDM system, what is the transmission rate in Mbps of T3 carrier system?

A. 44.736

B. 6.312

C. 3.152

D. 274.176

Solution:

53. What is the data rate in Mbps of a single satellite transponder considering an S/N of 30 dB?

A. 35.8

B. 3.58

C. 358

D. 3580

Solution:

54. What condition occur when the refractive index of the air decreases with height much more rapidly the normal?

A. Refraction

B. Superrefraction

C. Subrefraction

D. Diffraction

Solution:

55. What do you call the increase of temperature with height?

A. Temperature inversion

B. Normal inversion

C. Ducting

D. Superrefraction

Solution:

56. ____ is a term given to the region where superrefraction occurs.

A. Strata

B. Duct

C. Isothermal region

D. Tropospheric region

Solution:

57. Which of the following wavelengths where absorption of electromagnetic waves becomes peak due to vibrational resonances in the water vapor molecule?

A. 1.35 cm and 1.7 mm

B. 1.5 mm and 5 mm

C. 1.35 dm and 1.7 cm

D. 1.5 cm and 5mm

Solution:

58. Oxygen molecule absorption peaks to electromagnetic wave are at what wavelengths?

A. 1.35 cm and 1.7 mm

B. 5 mm and 2.5 mm

C. 5 cm and 2.5 cm

D. 1.35 mm and 1.7 μm

Solution:

59. What instrument normally measures the virtual height of ionosphere?

A. Ionosonde

B. Altimeter

C. Field meter

Solution:

60. The angle of elevation of the antenna beam is 20°. Calculate the transmission-path distance for an ionospheric transmission that utilizes a layer of virtual height 200 km. Use flat-earth approximation.

A. 966 km

B. 2100 km

C. 1100 km

D. 405 km

Solution:

61. If temperature change is 19°C, what amount of change to sound velocity is possible?

A. 11.53 ft/s

B. 11.53 m/s

C. 19.304 ft/s

D. 19.304 m/s

Solution:

62. In the above problem, what is the new velocity of sound assuming dry air medium?

A. 343 ft/s

B. 3430 m/s

C. 343 m/s

D. 342 m/s

Solution:

63. In acoustics, if the volume of the room is 200 m3 then at what frequency the coefficient of absorption is measured?

A. 120 kHz

B. 120 Hz

C. 100 Hz

D. 150 Hz

Solution:

64. What is the approximate bandwidth of an FM system with 10 kHz of modulating frequency and a 150 kHz of frequency deviation?

A. 300 kHz

B. 320 kHz

C. 150 kHz

D. 200 kHz

Solution:

65. Which of the following layers of the ionosphere has no effect on sky wave propagation during daytime?

A. D

B. E

C. F1

D. F2

Solution:

66. What phenomenon causes the radio-path horizon distance to exceed the geometric horizon?

A. Diffraction

B. Ducting

C. Reflection

D. Refraction

Solution:

67. How to maximize the skip distance?

A. Using the smallest possible radiation angle and highest possible frequency

B. Using the smallest possible radiation angle and lowest possible frequency

C. Using the biggest possible radiation angle and highest possible frequency

D. Using the biggest possible radiation angle and lowest possible frequency

Solution:

68. For a space wave transmission, the radio horizon distance of a receiving antenna with a height of 64 meters is approximately

A. 8 km

B. 32 km

C. 64 km

D. 256 km

Solution:

69. What bandwidth is needed to support a capacity of 128 kbps when the signal power to noise power ratio in decibels is 100?

A. 19224 Hz

B. 3853 Hz

C. 19244 Hz

D. 3583 Hz

Solution:

70. Which of the following systems uses frequency band 870-885 MHz as a transmit band of its base station?

A. TACS

B. NTT

C. NMT

D. AMPS

Solution:

71. A transmitted signal 5 meters in wavelength is received by an antenna coil having a 50-Ω resistance and a 0.01 H inductance. What is the capacitance of the tuner shunting the antenna coil at this point?

A. 0.704 fF

B. 0.704 μF

C. 0.704 nF

D. 0.704 mF

Solution:

72. Which of the following is the basic component of a communications satellite receiver?

A. On-board computer

B. Reflector

C. Telemetry

D. Transponder

Solution:

73. The reverberation time of a 184.2 cubic meters broadcast studio is 0.84 sec. Find the absorption effect of the materials used in metric sabines.

A. 35.3

B. 10.96

C. 379.8

D. 109.6

Solution:

74. What is the highest frequency that can be sent straight upward and be returned to earth?

A. MUF

B. Gyro frequency

C. Skip frequency

D. Critical frequency

Solution:

75. What is the most important specification of loudspeakers and microphones?

A. Frequency response

B. Power density

C. Field Strength

D. Gain

Solution:

76. Atmospheric attenuation is an attenuation which is due to

A. mist and fog

B. gasses in the atmosphere

C. water vapor and oxygen

D. rain

Solution:

77. Satellite orbits around the earth are ____ orbits.

A. circular

B. either elliptical or circular

C. elliptical

D. circular only

Solution:

78. How does spatial isolation technique in satellite communications avoid interference?

A. Use of different polarity antennas

B. Use of different types of antennas

C. Employment of highly directional spot-beam antennas

D. Use of low gain antennas

Solution:

79. An area on earth covered by a satellite radio beam is called ____.

A. SSP

B. Region

C. footprint

D. primary area

Solution:

80. The American concert pitch A is equivalent to which if the following frequencies?

A. 440 Hz

B. 435 Hz

C. 260 Hz

D. 255 Hz

Solution:

81. The international pitch A is equivalent to ___ Hz.

A. 435

B. 440

C. 260

D. 255

Solution:

82. The speed of the satellite increases as its height in orbit gets

A. lower

B. higher

C. closer to the moon

D. closer to the sun

Solution:

83. What is the effective radiated power of a repeater with 50 watts transmitter power output , 4 dB feedline loss, 3 dB duplexer and circulator loss, and 6 dB antenna gain?

A. 158 W

B. 39.7 W

C. 251 W

D. 69.9 W

Solution:

84. A cellular standard known as the cdmaOne.

A. IS-95

B. IS-136

C. IS-54

D. IS-100

Solution:

85. What is the effective radiated power of a repeater with 50 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 7 dB antenna gain?

A. 300 W

B. 315 W

C. 31.5 W

D. 69.9 W

Solution:

86. Which Ethernet system is restricted only to 100 m?

A. 10 Base T

B. 20 Base 2

C. 10 Base 5

D. 10 Base 1

Solution:

87. What is the effective radiated power of a repeater with 75 watts transmitter power output, 4 dB feedline loss, 3 dB duplexer and circulator loss, and 10 dB antenna gain?

A. 600 W

B. 75 W

C. 18.75 W

D. 150 W

Solution:

88. Which of the following regulates the ownership and operation of radio and television stations in the country?

A. PD 576-A

B. PD 756

C. PD 657

D. PD 677

Solution:

89. What is the effective radiated power of a repeater with 75 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 6 dB antenna gain?

A. 37.6 W

B. 237 W

C. 150 W

D. 23.7 W

Solution:

90. In GSM cellular system, the speech coding rate is ____.

A. 13 kbps

B. 8 kbps

C. 15 kbps

D. 20 kbps

Solution:

91. What is the effective radiated power of a repeater with 100 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 10 dB antenna gain?

A. 800 W

B. 126 W

C. 12.5 W

D. 1260 W

Solution:

92. Which NTC memorandum circular governs the rules and regulations about the manufacture, acquisition, sale and service of radio communication equipment?

A. MC No. 2-05-88

B. MC No. 2-04-88

C. MC No. 2-07-88

D. MC No. 2-09-88

Solution:

93. What is the effective radiated power of a repeater with 120 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 6 dB antenna gain?

A. 601 W

B. 240 W

C. 60 W

D. 379 W

Solution:

94. What do you call a short bit sequence sent typically 128 bits in digital signatures?

A. Hash

B. Public key

C. Private key

Solution:

95. What medium is used by IBM token ring network that operates at either 4 Mbps or 16 Mbps?

A. Twisted pair

B. Coaxial cable

C. Fiber-optic

D. Parallel-wire line

Solution:

96. What is known as the final stage in the evolution of the GSM standard?

A. WAP

B. GPRS

C. EDGE

D. Bluetooth

Solution:

97. According to KBP revised radio code which airtime below is classified class D for AM stations?

A. 6:00 AM to 12:00 NN

B. 12:00 NN to 6:00 PM

C. 9:00 PM to 12 Midnight

D. 12:00 Midnight to 5:00 AM

Solution:

98. Encryption of data is important to ensure its privacy. It is most commonly achieved by using a ____.

A. public-key encryption

B. private-key encryption

D. character set encryption

Solution:

99. The speech coding rate in D-AMPS is ____.

A. 8 kbps

B. 13 kbps

C. 15 kbps

D. 20 kbps

Solution:

100. Which of the following principal musical intervals is considered dissonant?

A. 7:8

B. 1:2

C. 5:8

D. 3:5

Solution: