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Communications Engineering Mastery Test 17: ECE Pre-Board

(Last Updated On: April 2, 2021)

Communications Engineering Mastery Test 17: ECE Pre-Board

This is 100 items Practice Examinations set 17 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 17

Choose the letter of the best answer in each questions.

1. A method of comparing two audio systems by switching inputs so the same recording is heard in rapid succession over one system and then the other.

a. AB test

b. trade test

c. system test

d. end test

View Answer:

Answer: Option A

Solution:

2. An AM receiver is tuned to broadcast station at 600 kHz. Calculate the image rejection in dB assuming that the input filter consists of one tuned circuit with a Q of 40.

a. 19.28 dB

b. 39.65 dB

c. 38.57 dB

d. 19.83 dB

View Answer:

Answer: Option C

Solution:

3. A sonic frequency lying above audio frequencies, ranging usually above 20 kHz.

a. voice frequency

b. mid-range frequency

c. ultrasonic frequency

d. light frequency

View Answer:

Answer: Option C

Solution:

4. What principle is used by a carbon type microphone?

a. variable capacitance

b. variable resistance

c. variable inductance

d. piezoelectric effect

View Answer:

Answer: Option C

Solution:

5. The ratio in decibels of the incident power to the reflected power on a transmission line.

a. return loss

b. reflection loss

c. buffer loss

d. clutter loss

View Answer:

Answer: Option A

Solution:

6. A ray that propagates through a fiber by total internal reflection and passing through the optical axis of the fiber.

a. light ray

b. visual ray

c. reflected ray

d. meridional ray

View Answer:

Answer: Option D

Solution:

7. Electromagnetic frequencies in the range of 33-40 GHz (0.909 to 0.750 centimeter wavelengths).

a. Ku band

b. Ka band

c. L band

d. S band

View Answer:

Answer: Option B

Solution:

8. An organization consisting of representatives from national standards bodies from different countries, responsible for development standards to facilitate international trade and services.

a. ISO

b. ANSI

c. OSI

d. ITU

View Answer:

Answer: Option A

Solution:

9. Also known as IEEE 1394, a scalable, flexible, and low-cost serial digital interlace that connects consumer electronic devices such as video cameras, digital camera, etc. with personal computers.

a. Fire hazard

b. Fire wire

c. Fire wall

d. Fixed wire

View Answer:

Answer: Option B

Solution:

10. A computer hardware and/or software that acts as a buffer between an internal network and the Internet to provide security against unauthorized access

a. casing

b. buffer

c. security code

d. firewall

View Answer:

Answer: Option D

Solution:

11. A unit of luminance. It is equal to the uniform luminance of an emitting or reflecting light at a rate of one lumen per square centimeter.

a. lambert

b. lux

c. lumens

d. phons

View Answer:

Answer: Option A

Solution:

12. The protocol used for transmitting e-mail on the Internet

a. SIMM

b. SMTP

c. SPX

d. RJ-II

View Answer:

Answer: Option B

Solution:

13. A figure of merit used to measure the dependence of the signal output of a photo detector on the input radiant power

a. Responsitivity

b. resolution

c. quality factor

d. precision

View Answer:

Answer: Option A

Solution:

14. The GSM cellular radio system uses GMSK in a 200-kHz channel, with a channel data rate of 270.833 kb/s. Calculate the bandwidth efficiency of the scheme.

a. 5.4167 bits/cycle

b. 1.35 bits/cycle

c. 5.4167 x 1010 bits/cycle

d. 270.833 kbits/cycle

View Answer:

Answer: Option B

Solution:

15. In radio wave propagation, what is the lowest layer of the ionosphere whose intensity is greatest at noon, when maximum solar radiation is absorbed by the upper atmosphere.

a. ozone layer

b. stratosphere

c. troposphere

d. D layer

View Answer:

Answer: Option D

Solution:

16. Frequency of operation of a low-power wireless technology (Bluetooth) that provides a connectivity standard for network devices.

a. 2.4 GHz

b. 4.2 GHz

c. 3.4 GHz

d. 4.3 GHz

View Answer:

Answer: Option A

Solution:

17. A fiber has an index of refraction of 1.6 for the core and 1.4 for the cladding. Calculate the critical angle.

a.  29°

b. 30°

c. 60°

d. 61°

View Answer:

Answer: Option D

Solution:

18. What is the effective earth’s radius when Ns = 300?

a. 8500 km

b. 9320 km

c. 5600 km

d. 4850 km

View Answer:

Answer: Option A

Solution:

19. It refers to IEEE 802.11 network

a. Wi-Fi

b. WWW

c. WAN

d. LAN

View Answer:

Answer: Option A

Solution:

20. In electronic navigation, the Omega system uses time sharing so that all stations can use the same frequencies. It can cover the whole world, has a lesser bandwidth, and has a small widening of lanes giving good hyperbolic Lines. What is the frequency band used by Omega?

a. 100 kHz

b. 10 to 13 kHz

c. 70 to 130 kHz

d. 2 MHz

View Answer:

Answer: Option B

Solution:

21. A component that samples the microwave signal traveling in one direction down a transmission line.

a. directional coupler

b. combiner

c. isolator

d. circulator

View Answer:

Answer: Option A

Solution:

22. What is the major disadvantage of a klystron?

a. low efficiency

b. narrow bandwidth

c. low gain

d. high noise

View Answer:

Answer: Option B

Solution:

23. A phase-locked loop has a VCO with a free-running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHz and comes out of lock again at 18 MHz. Calculate the lock range.

a. 4 MHz

b. 2 MHz

c. 12 MHz

d. 8 MHz

View Answer:

Answer: Option D

Solution:

24. A single telephone signal is fitted into a frequency band from 0 Hz to __________.

a. 3,400 Hz

b. 4000 Hz

c. 3000 Hz

d. 4,100 Hz

View Answer:

Answer: Option B

Solution:

25. What carrier-to-noise ratio is required for microwave relay systems?

a. 5-10 dB

b. 10-15 dB

c. 20-25 dB

d. 10-20 dB

View Answer:

Answer: Option D

Solution:

26. If the incident voltage wave to an open-ended transmission line is 40 V and the reflected voltage wave is 25 V, what is the percentage of power reflected?

a. 62.5%

b. 37.5%

c. 39.1%

d. 60.9%

View Answer:

Answer: Option C

Solution:

27. Which of the following is the most difficult for a radar to measure accurately?

a. angle

b. velocity

c. range

d. b and c

View Answer:

Answer: Option A

Solution:

28. A metal foil launched from a target to create false radar target.

a. decoy

b. chaff

c. missile

d. stealth

View Answer:

Answer: Option B

Solution:

29. What is the frequency range of cellular telephone?

a. 860-949 MHz

b. 806-949 MHz

c. 608-948 MHz

d. 860-849 MHz

View Answer:

Answer: Option B

Solution:

30. A deceptive jamming technique where the jamming signal is given a false Doppler shift so that the radar thinks the target velocity is different than it really is.

a. Home-on jammer

b. Velocity-gate pull-off

c. Inverse-gate pull-off

d. Range-gate pull-in

View Answer:

Answer: Option B

Solution:

31. It pertains to sound which also corresponds to color in light.

a. hue

b. pitch

c. intensity

d. chrominance

View Answer:

Answer: Option B

Solution:

32. This is the ability of sound to inhibit the perception of another sound.

a. overlapping

b. interruption

c. masking

d. interference

View Answer:

Answer: Option C

Solution:

33. An standard protocol used to connect after packet switching network

a. x.75

b. x.25

c. x.76

d. x.74

View Answer:

Answer: Option A

Solution:

34. In a single gun color CRT, what electron beam travels straight through the tube?

a. red

b. blue

c. black

d. green

View Answer:

Answer: Option D

Solution:

35. A microwave system has a reliability of 99.99%, compute for the amount of outage in minutes.

a. 53 min.

b. 58 min.

c. 68 min.

d. 98 min.

View Answer:

Answer: Option A

Solution:

36. It pertains to the change of the crystal oscillator frequency by loading.

a. pushing

b. swaying

c. drifting

d. pulling

View Answer:

Answer: Option D

Solution:

37. Audio frequency response is confined to

a. 300-3400 Hz

b. 300-3000 Hz

c. 300-4000 Hz

d. either a or b

View Answer:

Answer: Option B

Solution:

38. Determine the cut-off wavelength of a fiber with a 5 micrometer diameter core. The core and the cladding indices of refraction are 1.6 and 1.4 respectively.

a. 5.059 mm

b. 6.059 mm

c. 3.059 mm

d. 4.059 mm

View Answer:

Answer: Option A

Solution:

39. The transmitter power output in single sideband operation is expressed in terms of

a. watts

b. dBm

c. dB

d. PEP

View Answer:

Answer: Option D

Solution:

40. Flicker noise in radio communications is also referred to as ________ noise.

a. pink noise

b. white noise

c. thermal noise

d. agitation noise

View Answer:

Answer: Option A

Solution:

41. Suppose that the transmitter and receiver towers have equal height. How high would they have to be to communicate over a distance of 34 km?

a. 23.5 m

b. 28.47 m

c. 17 m

d. 8.47 m

View Answer:

Answer: Option C

Solution:

42. What is the peak power of a radar pulse if the width is 1.0 microsecond, PRR is 900 and the average plate power input is 45 watts?

a. 50 kW

b. 60 kW

c. 45 kW

d. 62.5 kW

View Answer:

Answer: Option A

Solution:

43. Gain of a folded dipole above an isotropic antenna

a. 1.74 dB

b. 1.64 dB

c. 2.14 dB

d. 3.64 dB

View Answer:

Answer: Option B

Solution:

44. In a fiber optic system, the core of PCS fiber is ________.

a. mica

b. paper

c. plastic

d. glass

View Answer:

Answer: Option D

Solution:

45. Determine the dB gain of a receiving antenna which delivers a microvolt signal to a transmission line over that of an antenna that delivers a 2 microvolt signal under identical circumstances.

a. -6

b. -3

c. 6

d. 3

View Answer:

Answer: Option A

Solution:

46.The 1.55 µm “window” is not yet in use with fiber optic systems because

a. the attenuation is higher than at 0.85 µm

b. the attenuation is higher than at 1.3 µm

c. suitable laser devices have not yet been developed

d. it does not lend itself to wavelength multiplexing

View Answer:

Answer: Option C

Solution:

47. A ferrite is

a. a nonconductor with magnetic properties

b. an intermetallic compound with particularly good conductivity

c. an insulator which heavily attenuates magnetic fields

d. a microwave semiconductor invented by Faraday

View Answer:

Answer: Option A

Solution:

48. IEEE standard for local area networks (LAN) covering OSI layers 3 to 7.

a. 802.3

b. 802.4

c. 802.2

d. 802.1

View Answer:

Answer: Option D

Solution:

49. A particular amplifier is designed to be a frequency doubler. If the input signal frequency is 15.4 MHz, a circuit in the output will be tuned to

a. 7.7 MHz

b. 15.4 MHz

c. 30.8 MHz

d. 61.6 MHz

View Answer:

Answer: Option C

Solution:

50. R3E modulation is sometimes used to

a. allow the receiver to have a frequency synthesizer

b. simplify the frequency stability problem in reception

c. reduce the power that must be transmitted

d. reduce the bandwidth required for transmission

View Answer:

Answer: Option B

Solution:

51. How many degrees is the phase difference between the I and Q color signal carrier in colored TV sets?

a. 180

b. 270

c. 90

d. 45

View Answer:

Answer: Option C

Solution:

52. What are the typical transmitter- receiver spacing for microwave relay?

a. 10-20 miles

b. 10-30 miles

c. 5-50 miles

d. 10-50 miles

View Answer:

Answer: Option D

Solution:

53. Indicate which of the following statements about the advantages of the phase discriminator over the slope detector is false:

a. Much easier alignment

b. Better linearity

c. Greater limiting

d. Fewer tuned circuits

View Answer:

Answer: Option C

Solution:

54. What limits the transmitter-receiver spacing for a microwave relay?

a. gain of antenna

b. curvature of the earth

c. frequency assigned

d. antenna sites

View Answer:

Answer: Option B

Solution:

55. A GPS satellite has how many orbit period in hours?

a. 24

b. 12

c. 18

d. 36

View Answer:

Answer: Option B

Solution:

56. An AM transmitter supplies a 10 kW of carrier power to a 50 ohm load. It operates at a carrier frequency of 1.2 MHz and is 85% modulated by a 3 MHz sine wave. Calculate the RMS voltage of the signal.

a. 825 W

b. 262.61 V

c. 1166.7 V

d. 825 V

View Answer:

Answer: Option D

Solution:

57. The hue of the color sync burst phase

a. red

b. blue

c. magenta

d. yellow-green

View Answer:

Answer: Option D

Solution:

58. It is known as the unit of pitch.

a. sone

b. phon

c. mel

d. dB

View Answer:

Answer: Option C

Solution:

59. What is the typical value of vidicon dark current?

a. 3 mA

b. 0.2 μA

c. 2 μA

d. 0.5 μA

View Answer:

Answer: Option B

Solution:

60. For a transmission line with incident voltage equal to 8 volts and reflected voltage equal to 1 volt, calculate the standing wave ratio.

a. 0.36

b. 1.115

c. 1.29

d. 1.544

View Answer:

Answer: Option C

Solution:

61. How many voice channels are there in a DS-2 Digital Signal Hierarchy for TDM signals?

a. 69

b. 105

c. 45

d. 96

View Answer:

Answer: Option D

Solution:

62. In measuring the intensity of acoustical signals, the logarithmic unit decibel (dB) is used. The threshold of hearing in dB-SPL is ________.

a. one

b. 10

c. zero

d. 100

View Answer:

Answer: Option C

Solution:

63. In an OSI model, BISYNC protocol belongs to what layer?

a. data link layer

b. physical layer

c.       network layer

d. transport layer

View Answer:

Answer: Option A

Solution:

64. According to the Philippine Electronics Code, what is the maximum permissible accumulated dose of a 68-year old person?

a. 200 rems

b. 230 rems

c. 250 rems

d. 277 rems

View Answer:

Answer: Option C

Solution:

65. A component containing ferrite materials that allows microwave signals to pass in one direction through the component, but absorbs microwave signals passing in the other directions.

a. combiner

b. isolator

c. coupler

d. puller

View Answer:

Answer: Option B

Solution:

66. In electronic radio navigation, the ADF is a navigational aid that is used for automatic determination of relative bearing to a transmitting radio station or Non-Directional Beacon (NDB). It is also used for reception of weather information and other broadcast programs. The frequency of operation of the Automatic Direction Finder is

a. 1030 to 1090 MHz

b. 108 to 112 MHz

c. 16 to 24 kHz, 2 MHz, 75 MHz

d. 190 to 1860 kHz

View Answer:

Answer: Option D

Solution:

67. The frequency change of an electronically tuned oscillator at a specified time after it has reached its desired frequency.

a. freq. deviation

b. post-tuning drift

c. freq. pulling

d. freq. pushing

View Answer:

Answer: Option B

Solution:

68. For reasonably efficient operation of a transistor amplifier, what should be the load resistance be with 12 volts at the collector and 5 watts power output?

a. 100.3 ohms

b. 14.4 ohms

c. 10.3 ohms

d. 144 ohms

View Answer:

Answer: Option B

Solution:

69. What is the major disadvantage of Traveling Wave Tubes (TWTs)?

a. low efficiency

b. high cost

c. low gain

d. high noise

View Answer:

Answer: Option A

Solution:

70. What is the advantage of cable communication systems compared with a broadcast system?

a. higher gain

b. higher capacity

c. lesser noise

d. low cost

View Answer:

Answer: Option B

Solution:

71. A radar that directs its beam into a given area of space to determine accurately the angular location of a target.

a. search radar

b. tracking radar

c. monopulse radar

d. pulse-compression radar

View Answer:

Answer: Option B

Solution:

72. What position accuracy can be obtained with the GPS?

a. within 5 m

b. within 4 m

c. within 10 m

d. within 2 m

View Answer:

Answer: Option D

Solution:

73. A networking device that allows connection between two dissimilar computer networks.

a. gateway

b. handshaking

c. splitter

d. divider

View Answer:

Answer: Option A

Solution:

74. A type of noise generated by the thermal motion of electrons in a medium at a temperature above absolute zero.

a. Gaussian noise

b. flicker noise

c. pink noise

d. black noise

View Answer:

Answer: Option A

Solution:

75. What is the index of refraction of a certain medium if the velocity of propagation of a radio wave in this medium is 1.527 x 108 m/s?

a. 0.509

b. 0.631

c. 0.713

d. 1.965

View Answer:

Answer: Option A

Solution:

76. The dominant mode of propagation is preferred with rectangular waveguides because (indicate false statement)

a. it leads to the smallest waveguide dimensions

b. the resulting impedance can be matched directly to coaxial lines

c. it is easier to excite than the other modes

d. propagation of it without any spurious geberation can be ensured

View Answer:

Answer: Option B

Solution:

77. Calculate for the color subcarrier frequency for TV channel 9.

a. 196.25 MHz

b. 196.83 MHz

c. 187.25 MHz

d. 190.83 MHz

View Answer:

Answer: Option D

Solution:

78. A condition when an incoming call meets an outgoing call causing a blockage.

a. glitch

b. lock

c. glare

d. crunch

View Answer:

Answer: Option C

Solution:

79. V-numbers less than what value indicate single mode fiber operation.

a. 3.453

b. 2.405

c. 5.426

d. 2.507

View Answer:

Answer: Option B

Solution:

80. If the color oscillator does not operate, the result will be

a. no picture

b. No color

c. incorrect hues

d. No color sync

View Answer:

Answer: Option B

Solution:

81. It minimizes side and blockage radiations from a microwave dish.

a. radome

b. shroud

c. vertex plate

d. dehydrator

View Answer:

Answer: Option B

Solution:

82. If the antenna current increases 3.4 times, the radiated power will increase to _______.

a. 18.5%

b. 15.33%

c. 11.56%

d. 12.825%

View Answer:

Answer: Option C

Solution:

83. The signal to noise ratio for satisfactorily Telephone Communication Service.

a. 40 dB

b. 50 dB

c. 45 dB

d. 35 dB

View Answer:

Answer: Option B

Solution:

84. A protocol for interconnecting digital programmable instruments (DPI).

a. IEEE 488

b. IEEE 802

c. IEEE 394

d. IEEE 801

View Answer:

Answer: Option A

Solution:

85. The probability of a telephone call being blocked and receiving a network busy signal on the telephone circuit.

a. reliability

b. availability

c. grade of service

d. Erlang measurement

View Answer:

Answer: Option C

Solution:

86. A type of RF modulation technique in which the frequency of an analog signal is varied in accordance with the variations in the amplitude of a digital signal.

a. PAM

b. FSK

c. FM

d. PDM

View Answer:

Answer: Option B

Solution:

87. What is the effective radiated power of a repeater with 450 W transmitting power output, 4 dB feedline loss, 6 dB duplexer loss, and 7 dB circulator and feedline loss and antenna gain of 25 dB?

a. 2893.31 W

b. 2523.83 W

c. 2839.31 W

d. 2425.38 W

View Answer:

Answer: Option C

Solution:

88. A rectangular waveguide has a width of 1.2 in and a height of 0.7 in. The waveguide will pass all signals above ___ GHz.

a. 4 GHz

b. 8.44 GHz

c.  10 GHz

d. 4.92 GHZ

View Answer:

Answer: Option D

Solution:

89. In microwave communications systems, for a carrier frequency of 6 GHz and a distance of 40 km, determine the free-space path loss in dB.

a. 80 dB

b. 84.2 dB

c. 140 dB

d. 144.2 dB

View Answer:

Answer: Option C

Solution:

90. In a microwave communications system, if the minimum carrier-to-noise (C/N) requirement for a receiver with a 10 MHz bandwidth is 22 dB, the minimum receive carrier power is

a. -82 dB

b. 76 dBm

c. 84 dB

d. -82 dBm

View Answer:

Answer: Option D

Solution:

91. A rectangular waveguide used for microwave transmission has a width of 1.4 inches and a height of 0.8 inches. All signals above ____ GHz will be passed by the waveguide.

a. 4.3 GHz

b. 2 GHz

c. 4.2 GHz

d. 5 GHz

View Answer:

Answer: Option C

Solution:

92. A pyramidal horn has an aperture (opening) of 58 mm in the E plane and 78 mm in the H plane. It operates at 15 GHz. Calculate the gain in dBi.

a. 19.29

b. 24.14

c. 15.8

d. 19.31

View Answer:

Answer: Option A

Solution:

93. One-hundred twenty microbars of pressure variation is equal to

a. 120 dBSPL

b. 115.56 dBSPL

c. 41.58 dBSPL

d. 57.78 dBSPL

View Answer:

Answer: Option B

Solution:

94. A tuned circuit that dissipates energy taken from another circuit.

a. absorption circuit

b. phantom circuit

c. LC circuit

d. tank circuit

View Answer:

Answer: Option A

Solution:

95. What is the increase in sound pressure level if the pressure is doubled?

a. increases by 6 dB

b. increases by 3 dB

c. decreases by 6 dB

d. decreases by 3 dB

View Answer:

Answer: Option A

Solution:

96.  Find the characteristic impedance of polyethylene, which has a dielectric constant of 2.4.

a. 163.9 ohms

b. 377 ohms

c. 243 ohms

d. 250 ohms

View Answer:

Answer: Option C

Solution:

97. Calculate the electric field intensity in millivolts per meter at 30 kW from a 5 km source.

a. 190 mV/m

b. 95.49 uV/m

c. 0.189 W/m

d. 13.416 V/m

View Answer:

Answer: Option A

Solution:

98. Determine the critical frequency value of an HF signal if its maximum usable frequency is 7050.50 kHz at 35 degrees incidence.

a. 4936.8 kHz

b. 5775 kHz

c. 4044 kHz

d. 4908.75 kHz

View Answer:

Answer: Option B

Solution:

99. A radio wave moves from air (er = 1) to glass (er = 7.8). Its angle of incidence is 20 degrees. What is the angle of refraction?

a. 7 degrees

b. 29 degrees

c. 10.3 degrees

d. 72.79 degrees

View Answer:

Answer: Option A

Solution:

100. Determine the refractive index of an ionospheric layer with 1.567 x 106 free electrons per cu m. The frequency of the radio wave is 32 kHz.

a. 0.999

b. 0.936

c. 0.956

d. 0.987

View Answer:

Answer: Option B

Solution:

Complete List of Communications Engineering Exams: ECE Pre-Board

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