 # Communications Engineering Mastery Test 3: ECE Pre-Board

(Last Updated On: January 8, 2018) This is 100 items set of Practice Examination 3 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 3

Choose the letter of the best answer in each questions.

1. ECE Board Exam April 1997

What is the impedance of a balance 4-wire with a diameter of 0.25 cm and spaced 2.5 cm apart using an insulator with a dielectric constant of 2.56?

• A. 100 Ω
• B. 65 Ω
• C. 75 Ω
• D. 50 Ω

2. ECE Board Exam April 1997

What is the impedance in ohms of a transformer marked for 25V, 4W, when the secondary is correctly loaded?

• A. 150 Ω
• B. 156 Ω
• C. 160 Ω
• D. 165 Ω

3. ECE Board Exam April 1997

A single conductor running from the transmitter to the antenna.

• A. RG-8/U
• B. Single line wire
• D. MIcrostrip

4. ECE Board Exam April 1997

If voltage change equal to twice its original value, what is its corresponding change in dB?

• A. 9 dB
• B. 6 dB
• C. 10 dB
• D. 3 dB

5. ECE Board Exam April 1997

To couple a coaxial line to parallel line, it is better to use a ______.

• A. Slotted line
• B. Quarter-wave transformer
• C. Directional Coupler
• D. Balun

6. ECE Board Exam April 1997

What is the characteristic impedance of a single wire with a diameter d= 0.25 mm placed at the center between grounded parallel planes separated by 1 mm apart. The wire is held by a material with a velocity factor of 0.75.

• A. 85 Ω
• B. 63 Ω
• C. 50 Ω
• D. 75 Ω

7. ECE Board Exam April 1997

If you have available number of power amplifiers with a gain of 100 each, how many such amplifiers do you need to cascade to give an overall gain of 60 dB?

• A. 3
• B. 4
• C. 5
• D. 2

8. ECE Board Exam April 1997

________ sets a limit on the maximum capacity of a channel with a give noise level.

• A. Hartley theorem
• B. Shannon-Hartley theorem
• C. Nyquist theorem
• D. Shannon theorem

9. ECE Board Exam April 1997

Transmission sent in both directions simultaneously.

• A. Full duplex
• B. Duplex
• C. Half duplex
• D. Simplex

10. ECE Board Exam April 1997

Industrial noise frequency is between _________.

• A. 200 to 3000 Mhz
• B. 15 to 160 Mhz
• C. 0 to 10 Khz
• D. 20 Ghz

11. ECE Board Exam April 1997

Reference noise temperature.

• A. 70 deg F
• B. 30 deg C
• C. 290 Kelvin
• D. 25 deg C

12. ECE Board Exam April 1997

What is the reference frequency of CCITT psophometric noise measurement?

• A. 800 Hz
• B. 1500 Hz
• C. 3400 Hz
• D. 1000 Hz

13. ECE Board Exam April 1997

Which does not effect noise in a channel?

• A. None of these
• B. Bandwidth
• C. Temperature
• D. Quantizing level

14. ECE Board Exam April 1997

The random and unpredictable electric signal from natural causes, both internal and external to the system is know as ________.

• A. Distortion
• B. Noise
• C. Attenuation
• D. Interference

15. ECE Board Exam April 1997

The most common unit of noise measurement in white noise testing.

• A. dBw
• B. dBk
• C. dBm
• D. NPR

16. ECE Board Exam April 1997

Unit of noise power of psophometer

• A. dBa
• B. pWp
• C. dBm
• D. dBmO

17. ECE Board Exam April 1997

100% modulation in AM means a corresponding increase in total power by:

• A. 25%
• B. 75%
• C. 100%
• D. 50%

18. ECE Board Exam April 1997

If the modulation index of an AM wave is doubled, the antenna current is also doubled, the AM system being used is

• A. A5C
• B. A3J
• C. A3H
• D. A3

19. ECE Board Exam April 1997

What particular circuit that rids FM of noise?

• A. HPF
• B. Phase shifter
• C. Limiter
• D. LPF

20. ECE Board Exam April 1997

What is the advantage of PTM over PAM?

• A. Simpler to generate
• B. Low sampling rate is required
• C. Much better noise immunity
• D. All of these

21. ECE Board Exam April 1997

At 100% modulation, the sum for the effective voltages in both sidebands is equal to ______% of the unmodulated carrier voltage.

• A. 50
• B. 71
• C. 100
• D. 25

22. ECE Board Exam April 1997

A carrier signal has ______.

• A. Constant peak amplitude
• B. The information
• C. Frequency range 20-20000 Hz
• D. A varying amplitude

23. ECE Board Exam April 1997

Which transmit only one sideband?

• A. A3E
• B. 3AJ
• C. 11BE
• D. H3E

24. ECE Board Exam April 1997

The final amplifier of either FM or AM transmitter operates as

• A. Class B
• B. Class C
• C. Class A
• D. Class D

25. ECE Board Exam April 1997

Modulation means

• A. Varying of information
• B. Utilization of a single transmission channel to carry multiple signals
• C. Varying of some parameters of a carrier such as its amplitude to transmit information
• D. Transmit pulses in DC form on a copper wire

26. ECE Board Exam April 1997

What is the advantage of sidetone?

• A. High transmission efficiency
• B. Results to a strengthened signal
• C. No energy dissipation
• D. Assures that the telephone is working

27. ECE Board Exam April 1997

The standard test tone

• A. 0 dB
• B. 10 dBm
• C. 0 dBm
• D. 10 dB

28. ECE Board Exam April 1997

One (1) Erlang is equal to ________.

• A. 360 CCS
• B. 100 CCS
• C. 36 CCS
• D. 3.6 CCS

29. ECE Board Exam April 1997

Transmission of printed material over telephone lines.

• A. Video text
• B. Facsimile
• C. Encoding
• D. Xerox copy

30. ECE Board Exam April 1997

1-CCS is equal to?

• A. 60
• B. 100
• C. 600
• D. 1

31. ECE Board Exam April 1997

1 Erlang is ______.

• A. 1000 TU
• B. 10 TU
• C. 100 TU
• D. 1 TU

32. ECE Board Exam April 1997

When waves bend away from straight lines of travel, it is called _________.

• A. Refraction
• B. Reflection
• C. Rarefaction
• D. Diffraction

33. ECE Board Exam April 1997

Highest frequency that can be used for skywave HF communications between two given points on earth.

• A. Gyro frequency
• B. Maximum usable frequency
• C. Critical frequency
• D. Virtual frequency

34. ECE Board Exam April 1997

Electromagnetic radiation theory was profounded by ______.

• A. Sir Edward Appleton
• B. Sir Isaac Newton
• C. James Clerk Maxwell

35. ECE Board Exam April 1997

Type of transmission path that permits communication in the frequency range from 30 to 60 MHz and over distances form about 1000 to 2000 km.

• A. Ducting
• B. Ionospheric scatter
• C. Microwave
• D. Troposcatter

36. ECE Board Exam April 1997

What is the thickest layer of the ionosphere?

• A. E
• B. F1
• C. F2
• D. D

37. ECE Board Exam April 1997

Distance traveled by a wave in the time of one cycle.

• A. Hop
• B. Frequency
• C. Wavelength
• D. Crest

38. ECE Board Exam April 1997

Which region of the ionosphere is mainly responsible for long distance night time communication?

• A. A layer
• B. D layer
• C. E layer
• D. F layer

39. ECE Board Exam April 1997

What is the effective earth’s radius when N = 300?

• A. 8500 km
• B. 6370 km
• C. 7270 km
• D. 7950 km

40. ECE Board Exam April 1997

The polarization of a discone antenna is _____.

• A. Horizontal
• B. Vertical
• C. Omni
• D. Directional

41. ECE Board Exam April 1997

_______ is the horizontal pointing angle of an antenna.

• A. Right angle
• B. Angle of elevation
• C. Bandwidth
• D. Azimuth

42. ECE Board Exam April 1997

Which is properly terminated antenna?

• A. Rhombic
• B. Hertz
• C. Marconi
• D. Dipole

43. ECE Board Exam April 1997

______ is a device that detects both vertically and horizontally polarized signals simultaneously.

• A. Crystal
• B. Orthomode transducer
• C. Light transducer
• D. Optoisolator

44. ECE Board Exam April 1997

How much does the radiated power of an antenna increases if its current increased by 3.3 times?

• A. 6.6 times
• B. 3.3 times
• C. 10.89 times
• D. 9.9 times

45. ECE Board Exam April 1997

What do you call the energy that was not radiated into space or completely transmitted?

• A. Incident waves
• B. Captured waves
• C. Standing waves
• D. Modulated waves

46. ECE Board Exam April 1997

What is the estimated medium wind loading in the Philippines for antenna tower design?

• A. 200 kph
• B. 250 kph
• C. 300 kph
• D. 100 kph

47. ECE Board Exam April 1997

The minimum number of turns a helix antenna must have.

• A. 4
• B. 5
• C. 3
• D. 6

48. ECE Board Exam April 1997

When testing transmitter to prevent interfering with other stations, which type of antenna must be used?

• A. Dummy antenna
• B. Hertzian antenna
• C. None of these
• D. Void antenna

49. ECE Board Exam April 1997

• A. Antenna
• B. Transmitter
• C. Transmission line
• D. Transceiver

50. ECE Board Exam April 1997

The frequency of operation of a dipole antenna cut to length of 3.4 m.

• A. 42.9 MHz
• B. 61.3 MHz
• C. 38.5 MHz
• D. 53.5 MHz

51. ECE Board Exam April 1997

Full duplex transmission means

• A. One way transmission
• B. 24-hour transmission
• D. Two-way simultaneous transmission

52. ECE Board Exam April 1997

Transmission system for a multidrop network

• A. Taken passing
• B. Polling
• C. Switching
• D. CSMA/CD

53. ECE Board Exam April 1997

Synchronous modems cost more than asynchronous modem because _______.

• A. They have larger bandwidth
• B. They are larger
• C. The production volume is larger
• D. They have clock recovery circuits

54. ECE Board Exam April 1997

What equation defines the composition of an ISDN basic access line?

• A. B+2D
• B. B+D
• C. 2B+2D
• D. 2B+D

55. ECE Board Exam April 1997

Modem is referred to as ______.

• A. Universal asynchronous Rx/Tx
• B. Data communication equipment
• C. Universal synchronous Rx/Tx
• D. Data terminal equipment

56. ECE Board Exam April 1997

_______ character signifies the start of the test for Bisync.

• A. STX
• B. ETX
• C. SOH
• D. BCC

57. ECE Board Exam April 1997

What is the reason why companding is employed in PCM systems?

• A. To overcome impulse noise in PCM receivers
• B. To allow amplitude limiting in the receivers
• C. To solve quantizing noise problem
• D. To protect small signals in PCM from quantizing distortion

58. ECE Board Exam April 1997

What is framing?

• A. Is concerned of synchronous system
• B. Refers to parallel transmission
• C. Is concerned with the boundaries between characters
• D. Is concerned with individual bits

59. ECE Board Exam April 1997

The method of determining the bandwidth of any processing system is ______.

• A. Bandwidth analysis
• B. Frequency spectrum
• C. Spectral analysis
• D. Frequency analysis

60. ECE Board Exam April 1997

It is a protocol used to connect the other packet witching network.

• A. X.25
• B. X.50
• C. X.10
• D. X.75

61. ECE Board Exam April 1997

Slowest communications hardware product.

• A. Synchronous
• B. Asynchronous
• C. Ethernet
• D. Internet

62. ECE Board Exam April 1997

Highest theoretical frequency that can be processed at a sampling rate without aliasing.

• A. Folding frequency
• B. Resonant frequency
• C. Natural frequency
• D. Critical frequency

63. ECE Board Exam April 1997

Data is directly on the transmission cable.

• A. Asynchronous
• B. Synchronous
• C. Baseband

64. ECE Board Exam April 1997

A source code whose average word length approaches the fundamental limit set by the entropy of a discrete memory less source.

• A. Prefix code
• B. Huffman code
• C. Entropy code
• D. Source code

65. ECE Board Exam April 1997

______ sets the limit on the maximum capacity of a channel with a given noise level.

• A. Hartley theorem
• B. Shannon-hartley theorem
• C. Nyquist theorem
• D. Shannon theorem

66. ECE Board Exam April 1997

Gateway can interconnect LANs that have ____ protocols and formats.

• A. The same
• B. Different or the same
• C. Totally different
• D. None of these

67. ECE Board Exam April 1997

Steps to follow to produce PCM signal.

• A. Quantizing, sampling, and coding
• B. Sampling, quantizing, and coding
• C. Sampling, coding and quantizing
• D. Coding, quantizing and coding

68. ECE Board Exam April 1997

Transmission sent in both directions simultaneously.

• A. Full duplex
• B. Duplex
• C. Half duplex
• D. Simplex

69. ECE Board Exam April 1997

_______ detects the satellite signal relayed from the feed and converts it to an electric current, amplifies and lower its frequency.

• A. Feedhorn
• B. Satellite dish
• D. LNB

70. ECE Board Exam April 1997

What kind of battery panels are used in some advance satellites?

• A. Gallium Arsenide solar panel
• B. Germanium based panels
• C. Silicon based panels
• D. Gallium Phosphate solar panel

71. ECE Board Exam April 1997

Footprint refers to coverage area in the globe

• D. Satellite coverage

72. ECE Board Exam April 1997

Asia Sat I covers how many countries in Asia?

• A. 38
• B. 40
• C. 44
• D. 42

73. ECE Board Exam April 1997

Insertion loss of connector-type splices for a single-mode fiber cable.

• A. 0.2 dB
• B. 0.3 dB
• C. 0.09 dB
• D. 0.38 dB

74. ECE Board Exam April 1997

A non-coherent light source for optical communications system.

• A. PIN Diode
• B. ILD
• C. APD
• D. LED

75. ECE Board Exam April 1997

Type of fiber that has the highest modal dispersion

• A. Step-index multimode
• B. Step-index single mode

76. ECE Board Exam April 1997

Fiber optic cable operates near _______ frequencies.

• A. 800 THz
• B. 20 MHz
• C. 200 MHz
• D. 2 GHz

77. ECE Board Exam April 1997

• A. 150,000 h
• B. 100,000 h
• C. 50,000 h
• D. 200,000 h

78. ECE Board Exam April 1997

The sound energy per unit area at right angles to the propagation direction per unit time.

• A. Sound intensity
• B. Loudness
• C. Coherence
• D. Sound stress

79. ECE Board Exam April 1997

_______ is the transmission of sound from one room to an adjacent room thru common walls, floors or ceilings.

• A. Reverberation
• B. Refraction
• C. Flanking transmission
• D. Reflection

80. ECE Board Exam April 1997

The sound power level of a jet plane flying at a height of 1 km is 160 dB. What is the maximum sound pressure level on the ground directly below the plane assuming that the aircraft radiates sound equally in all directions?

• A. 59.1 dB
• B. 69.1 dB
• C. 79.1 dB
• D. 89.1 dB

81. ECE Board Exam April 1997

Lowest frequency produced by a musical instrument.

• A. Fundamental
• B. Midrange
• C. Period
• D. Harmonic

82. ECE Board Exam April 1997

Sound intensity level is ________.

• A. 10 log I/I(ref)
• B. 10 log I(ref)/I
• C. 30 log I/I(ref)
• D. 20 log I/I(ref)

83. ECE Board Exam April 1997

Tendency of sound energy to spread.

• A. Reflection
• B. Diffraction
• C. Rarefaction
• D. Refraction

84. ECE Board Exam April 1997

______ used to measure speech volume

• A. Volume meter
• B. Audio frequency meter
• C. Volume unit meter
• D. Speech meter

85. ECE Board Exam April 1997

What is the local oscillator frequency range commercial AM broadcast if it is equal to 455 KHz.

• A. 540 to 1600 KHz
• B. 0 to 1600 KHz
• C. 995 to 2055 KHz
• D. 0 to 455 KHz

86. ECE Board Exam April 1997

TV channels 2, 4 and 5 are known as ________.

• A. Mid band UHF
• B. Low band UHF
• C. High band VHF
• D. Low band VHF

87. ECE Board Exam April 1997

______ is the first component of any MATV system to received broadcast signals.

• B. Antenna
• C. Filter
• D. Transmitter

88. ECE Board Exam April 1997

Mechanism or device which enables the TV camera to move in internal and tilting motion.

• A. Tilting
• B. Scanner
• C. Pan/tilt device
• D. Panning device

89. ECE Board Exam April 1997

The allowable deviation ratio of commercial FM broadcast.

• A. 25
• B. 15
• C. 5
• D. 75

90. ECE Board Exam April 1997

______ is the time duration for one horizontal trace.

• A. 48µs
• B. 52 µs
• C. 62 µs
• D. 50 µs

91. ECE Board Exam April 1997

Which is atmospheric attenuation?

• A. Attenuation due to rain
• B. Attenuation due to other gasses
• C. Attenuation due to mist and fog
• D. Due to water vapor and oxygen

92. ECE Board Exam April 1997

A microwave system that requires the use of repeater.

• A. Intervening terrain is favorable
• B. Distances involved are greater
• C. The required reliability is met
• D. All of these

93. ECE Board Exam April 1997

What frequency does oxygen causes excessive attenuation

• A. 119 GHz
• B. 183 GHz
• C. 310 GHz
• D. 60 GHz

94. ECE Board Exam April 1997

• A. Radio detection and rating
• B. Radio detection and ranging
• C. Radio distance and ranging
• D. Radio delay and ranging

95. ECE Board Exam April 1997

A microwave link between the earth station and the down-town terminal.

• A. STL

96. ECE Board Exam April 1997

The advantage of periscope antenna in microwave

• A. Minimize interference to and from other neighboring stations
• C. Reduce tower height
• D. All of these

97. ECE Board Exam April 1997

Professional Regulations Commission was created under ______.

• A. PD 323
• B. PD 223
• C. PD 232
• D. RA 223

98. ECE Board Exam April 1997

The institutionalization of the continuing Professional Education (CPE) Program of the various regulated profession under the supervision of the Professional Regulation Commission.

• A. E.O. No. 266
• B. E.O. No. 626
• C. E.O. No. 662
• D. P.D. 381

99. ECE Board Exam April 1997

The basic law providing for the regulation of radio station, communications in the Philippines and other purposes.

• A. Act. No.`3846
• B. D.O. No. 11
• C. D.O. No. 88
• D. D.O. No. 5

100. ECE Board Exam April 1997

Listing of the date and time events, programs , equipment, test, malfunctions and corrections in communication system.

• A. File
• B. Documentation
• C. Reporting
• D. Log

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