This is 100 items set of Practice Examination 1 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 1
Choose the letter of the best answer in each questions.
1. ECE Board Exam March 1996
That dielectric material of an optical fiber surrounding the core
- A. Cladding
- B. Armor
- C. Shield
- D. Cover
2. ECE Board Exam March 1996
An antenna that is circularly polarized is the ____________.
- A. parabolic reflector
- B. helical
- C. Yagi-uda
- D. small circular loop
3. ECE Board Exam March 1996
A word in telegraphy consist of __________ characters plus a word space.
- A. 11
- B. 7 and ½
- C. 8
- D. 5
4. ECE Board Exam March 1996
The number of voice band channels in master group per CCITT standard is __________.
- A. 300
- B. 480
- C. 600
- D. 120
5. ECE Board Exam March 1996
The power of standard test tone is normally ____________.
- A. 1 dB
- B. 0 mW
- C. 1 mW
- D. 1 W
6. ECE Board Exam March 1996
LORAN is a navigational system used primarily for _____________.
- A. blind landing
- B. obtaining your fixes location over large distances
- C. automatic collision warning
- D. approach control
7. ECE Board Exam March 1996
The expander in a companding device provides ___________.
- A. greater amplification for low signal levels
- B. less amplification for low signal levels
- C. greater amplification for high signal levels
- D. lesser pressure for transmission cables
8. ECE Board Exam March 1996
LORAN is a navigation system used primarily for
- A. approach control
- B. obtaining fixes over large distances
- C. blind landing
- D. automatic collision warning
9. ECE Board Exam March 1996
At what power level does a 1 kHz tone cause zero interference (144 weighted) ?
- A. -90 dB
- B. -90 dBm
- C. 90 dBm
- D. 90 dB
10. ECE Board Exam March 1996
One character or a sequence of characters forming a part, or the whole of a message with a specific meaning
- A. Signs
- B. Call sign
- C. Code
- D. Identifier
11. ECE Board Exam March 1996
The K-factor under normal atmospheric conditions in a microwave radio data profile calculation is equal to ___________.
- A. 2/3
- B. 0
- C. 4/3
- D. Infinity
12. ECE Board Exam March 1996
What is the IBM’s asynchronous data link protocol designation?
- A. 83 B
- B. 8A1 / 8B1
- C. 93 B
- D. 9A1/ 9B1
13. ECE Board Exam March 1996
EIRP stands for _______________.
- A. effective isotropic refracted power
- B. effective and ideal radiated power
- C. effective isotropic reflected power
- D. effective isotropic radiated power
14. ECE Board Exam March 1996
The modulation system used for telegraphy is
- A. frequency-shift keying
- B. two-tone modulation
- C. pulse-code modulation
- D. single-tone modulation
15. ECE Board Exam March 1996
The standard that specifies a balanced interface cable that will operate bit rates up to 10 Mbps with in a span distances up to 1200 m.
- A. RS-423A
- B. RS-422A
- C. RS-550A
- D. RS-449A
16. ECE Board Exam March 1996
An antenna which is not resonant at a particular frequencies and so can be used over a wide band of frequencies and so can be used over a wide band of frequencies is called
- A. aperiodic
- B. boresight
- C. cassegrain
- D. top-loaded
17. ECE Board Exam March 1996
A receiver connected to an antenna whose resistance is 50 ohms has an equivalent noise resistance of 30 ohms. What is the receiver’s noise temperature?
- A. 754 K
- B. 464 K
- C. 174 K
- D. 293 K
18. ECE Board Exam March 1996
___________ occurs when the microwave beam is at point of grazing over an obstacle.
- A. Diffraction
- B. Refraction
- C. Absorption
- D. Reflection
19. ECE Board Exam March 1996
Atmospheric condition is controlled by
- A. humidity
- B. pressure
- C. temperature
- D. all of these
20. ECE Board Exam March 1996
The characteristics impedance of a transmission line does not depend upon its ________.
- A. conductor spacing
- B. conductor diameter
- C. length
- D. conductor radius
21. ECE Board Exam March 1996
What is the purpose of a beat frequency oscillator (BFO)?
- A. Aid in the reception of weak voice-modulated signals
- B. Generates a signal, whose frequency is the same as that of the intermediate frequency
- C. Generates a 1kHz note for Morse code reception
- D. Generates an output, whose frequency differs from that of the intermediate frequency by 1 kHz
22. ECE Board Exam March 1996
The point on the satellite orbit, closest to the earth is
- A. prograde
- B. perigee
- C. zenith
- D. apogee
23. ECE Board Exam March 1996
The potential difference between any exposed structured to ground in any electrical installation should not exceed _________ volts RMS.
- A. 10
- B. 45
- C. 0
- D. 30
24. ECE Board Exam March 1996
The capture area of an antenna is directly proportional to the
- A. frequency of the received signal
- B. distance between transmitter and receiver
- C. gain of the antenna
- D. power density of the signal
25. ECE Board Exam March 1996
Modems are required to connect computer to telephone lines because ___________.
- A. telephone company rules required them
- B. the telephone network bandwidth is too high
- C. none of the above
- D. the telephone network will pass direct current
26. ECE Board Exam March 1996
The standard reference antenna for the directive gain is ___________.
- A. elementary doublet
- B. isotropic antenna
- C. half-wave dipole
- D. infinitesimal dipole
27. ECE Board Exam March 1996
One hundred twenty µbars of pressure variation is equal to
- A. 120 dBSPL
- B. 115.56 dBSPL
- C. 41.58 dBSPL
- D. 57.78 dBSPL
28. ECE Board Exam March 1996
It is a spacecraft placed in orbit around the earth carrying onboard microwave receiver and transmitting equipment.
- A. Fiber optic equipment
- B. Communications satellite
- C. Wireless radio system
- D. Coaxial cable system
29. ECE Board Exam March 1996
One type of pulse communications system uses pulse that appear as a group, and which vary in number according to the loudness of the voice. This type of pulse modulation is called
- A. pulse duration modulation
- B. pulse amplitude modulation
- C. pulse code modulation
- D. pulse position modulation
30. ECE Board Exam March 1996
A device to be connected across the headset in telephone receivers to reduce the effects of acoustic shock.
- A. Ground
- B. Two rectifiers in parallel with opposite polarities
- C. Protector
- D. Fuse
31. ECE Board Exam March 1996
Judgment on the case against an ECE shall become final and executory after
- A. 10 days
- B. 60 days
- C. 30 days
- D. 15 days
32. ECE Board Exam March 1996
The equivalent noise temperature of the amplifier is 25 K. What is the noise figure?
- A. 1.86
- B. 0.1086
- C. 1.086
- D. 10.86
33. ECE Board Exam March 1996
The letter-number designation B8E is a form of modulation also known as ___________.
- A. pilot carrier system
- B. independent sideband emission
- C. lincomplex
- D. vestigial sideband transmission
34. ECE Board Exam March 1996
When the transmitting and receiving antennas are in line-of-sight of each other, the mode of propagation is ________ wave.
- A. space or direct
- B. ground
- C. surface
- D. sky
35. ECE Board Exam March 1996
Crosstalk coupling is ___________.
- A. dBm (disturbing pair) minus dBm (disturbed pair)
- B. the difference between readings on a cable pair with a tone and a cable pair without tone read at the far end of a cable
- C. signals from one circuit that get into another circuit
- D. All of these are true
36. ECE Board Exam March 1996
According to the Nyquist theorem, the sampling rate that can be used in a PCM system is ________ the highest audio frequency.
- A. once
- B. eight times
- C. twice
- D. thrice
37. ECE Board Exam March 1996
Passive crossover components cause some frequencies to be delayed with respect to the other frequencies at the crossover point.
- A. Phase shift
- B. Phase correction
- C. Phase-error correction
- D. Time alignment
38. ECE Board Exam March 1996
A car horn outdoors produces a sound intensity level of 90 dB at 10 ft away. At this distance, what is the sound power in watt?
- A. 12 W
- B. 0.12 W
- C. 0.012 W
- D. 1.2 W
39. ECE Board Exam March 1996
What is the one principal difference between synchronous and asynchronous transmission?
- A. the pulse height are different
- B. the clocking is derived from the data in synchronous transmission
- C. the clocking is mixed with the data in asynchronous
- D. the bandwidth required is different
40. ECE Board Exam March 1996
The lowest layer in the ionosphere
- A. D
- B. F2
- C. E
- D. F1
41. ECE Board Exam March 1996
What is the number of pins in the RS-232C interface?
- A. 25
- B. 15
- C. 20
- D. 20
42. ECE Board Exam March 1996
SSB transmission requires only ______ of the bandwidth for a DSBFC transmission.
- A. ¼
- B. 2/3
- C. ½
- D. ¾
43. ECE Board Exam March 1996
The method of generating FM used by broadcasting station is
- A. direct
- B. all of these
- C. indirect
- D. insertion
44. ECE Board Exam March 1996
What is the transmission rate of a system for transmitting the output of a microcomputer to a line printer operating at a speed of 30 lines/minute? Assume that the line printer has 8 bits of data per character and prints out 80 characters/line.
- A. 800 bps
- B. 400 bps
- C. 320 bps
- D. 640 bps
45. ECE Board Exam March 1996
Communications code is ____________.
- A. eight bits per character
- B. agreed upon in advance between sender and receiver
- C. the same in all modern computers
- D. either seven or eight bits per character
46. ECE Board Exam March 1996
What is the reference tone level for dBm?
- A. -82 dBm
- B. -85 dBm
- C. -67 dBm
- D. -90 dBm
47. ECE Board Exam March 1996
A type of an underground antenna is a/an __________ antenna.
- A. Hertz
- B. isotropic
- C. parabolic
- D. Marconi
48. ECE Board Exam March 1996
Which of the following pulse modulation systems is analog?
- A. Delta
- B. Differential PCM
- C. PWM
- D. PCM
49. ECE Board Exam March 1996
What is the purpose of the receiver’s squelch circuit?
- A. To overcome fluctuations in the level the RF signal arriving at the receiver antenna
- B. To prevent fluctuations in the AGC bias level
- C. To reduce the receiver’s sensitivity to all incoming signals
- D. To prevent amplified noise from reaching the loudspeaker during the absence of an incoming signal
50. ECE Board Exam March 1996
TACAN is a navigational aid providing ___________.
- A. bearing and distance indication
- B. speed and height indication
- C. bearing and weather information
- D. instrument-landing glide paths
51. ECE Board Exam March 1996
In __________ transmission, a unique SYNC character is transmitted at the beginning of each message.
- A. asynchronous
- B. synchronous
- C. digital
- D. analogue
52. ECE Board Exam March 1996
If the terminating impedance is exactly equal to the characteristic impedance of the transmission line the return loss is ___________.
- A. zero
- B. one
- C. infinite
- D. None of these
53. ECE Board Exam March 1996
What is the main purpose of a communications system?
- A. None of these
- B. To have a frequency assignment
- C. For modulation
- D. To provide an acceptable replica of the information at the destination
54. ECE Board Exam March 1996
What is meant by antenna gain?
- A. The final amplifier gain minus the transmission line losses (including any phasing lines present)
- B. The ratio of the amount of power produced by the antenna compared to the output power of the transmitter
- C. The ratio of the signal in the backward direction
- D. The numeric ratio relating the radiated signal strength of an antenna to that of another antenna
55. ECE Board Exam March 1996
Binary communications systems are better because
- A. they can interface directly with the analog telephone network
- B. the components are simpler, less costly, and more reliable
- C. people think better in binary
- D. interstate calls are less costly
56. ECE Board Exam March 1996
In the phase shift method, How many circuits must be balanced?
- A. None of these
- B. 1
- C. 4
- D. 2
57. ECE Board Exam March 1996
The carrier swing necessary to provide 80% modulation in the FM broadcasting band is __________.
- A. 150 kHz
- B. 120 kHz
- C. 60 kHz
- D. 75 kHz
58. ECE Board Exam March 1996
The correctness and accuracy of the transmitted message content is
- A. verified by the modem
- B. communications system
- C. determined by the sender and receiver
- D. ensured by use of digital technique
59. ECE Board Exam March 1996
The signal in a channel is measured to be 23 dB while noise in the same channel is measured to be 9 dB. The signal to noise ratio therefore is __________.
- A. 9/23
- B. 23/9
- C. 32 dB
- D. 14 dB
60. ECE Board Exam March 1996
Three audio waves with 100,200 and 300 volts amplitude respectively, simultaneously modulate a 450 volts carrier. What is the total percent of modulation of the AM wave?
- A. 69 %
- B. 115.5 %
- C. 50%
- D. 83%
61. ECE Board Exam March 1996
If the percentage modulation of an AM amplifier is 88% and the modulating signal is 1 volt, the carrier has an amplitude of _______________.
- A. 1.14 volts
- B. 0.88 volt
- C. 1.88 volts
- D. 0.12 volt
62. ECE Board Exam March 1996
It consists of a number of dipoles of equal size, equally spaced along a straight line with all dipoles fed in the same phase from the same source.
- A. Log-periodic antenna
- B. Yagi antenna
- C. End-fire array
- D. Broadside array
63. ECE Board Exam March 1996
Data switching systems.
- A. improve the efficiency of data transfer
- B. are limited to small data networks
- C. required additional lines
- D. are not used in data system
64. ECE Board Exam March 1996
A type of array antenna which consists of one half-wave driven dipole, one reflector and one director
- A. Hertzian dipole
- B. Yagi-uda
- C. Broadside collinear
- D. Log periodic dipole array
65. ECE Board Exam March 1996
Power is a _____________ amount of energy used in specific period of time
- A. large
- B. definite
- C. electrical
- D. relative
66. ECE Board Exam March 1996
The midrange frequency range of sound is from
- A. 256 to 2048 Hz
- B. 2048 to 4096 Hz
- C. 512 to 2048 Hz
- D. 16 to 64 Hz
67. ECE Board Exam March 1996
To connect coaxial line to a parallel-wire _________ is the best to use.
- A. directional coupler
- B. quarter-wave transformer
- C. balun
- D. slotted line
68. ECE Board Exam March 1996
In AM, the carrier carries ____________ intelligence.
- A. no
- B. difference
- C. distorted
- D. same
69. ECE Board Exam March 1996
Characteristics impedance of a transmission line is the impedance measured at the ___________ when its length is infinite.
- A. input
- B. shorted end of the line
- C. output
- D. midsection
70. ECE Board Exam March 1996
Cross modulation on a receiver is eliminated at the
- A. RF stage
- B. mixer stage
- C. IF stage
- D. detector stage
71. ECE Board Exam March 1996
A speaker cabinet has an internal volume 84,950 cm3. It has a port area on the baffle of 3,230 cm2 and baffle thickness of 19 mm. What is the Helmholtz resonance hertz of this speaker enclosure?
- A. 260 Hz
- B. 245 Hz
- C. 265 Hz
- D. 250 Hz
72. ECE Board Exam March 1996
What quarterwave transformer will match a 100Ω line to an antenna whose value is 175Ω?
- A. 132.29 Ω
- B. 150 Ω
- C. 16.58 Ω
- D. 137.5 Ω
73. ECE Board Exam March 1996
The local loop of the telephone system is understood to be
- A. a single piece of wire connecting the subscriber’s telephone set to another telephone set in an adjacent room
- B. a two-wire or four-wire communication circuit between the customer’s premise and central office
- C. a four-wire circuit connecting a facsimile machine to a computer
- D. a group of wires connecting a telephone set to a modem
74. ECE Board Exam March 1996
In what region of the world is sporadic-E most prevalent?
- A. The equatorial regions
- B. The northern hemisphere
- C. The arctic regions
- D. The polar regions
75. ECE Board Exam March 1996
The process of assigning PCM codes to absolute magnitudes
- A. Overloading
- B. All of these
- C. Quantizing
- D. Multiplexing
76. ECE Board Exam March 1996
It is a measure of the microwave power radiated from an antenna as a function of angular direction from the antenna axis.
- A. Antenna pattern
- B. Polarization
- C. Beamwidth
- D. Sidelobes
77. ECE Board Exam March 1996
It is the made from semiconductor material such as aluminum-gallium-arsenide or gallium-arsenide-phosphide.
- A. APD
- B. Injection laser diode
- C. Light emitting diode
- D. Positive-intrinsic-negative
78. ECE Board Exam March 1996
Which one is not the basic electrical protection measures in the Philippine Electronics Code?
- A. Voltage/ current limiting and interrupting
- B. Undergrounding
- C. Grounding and bonding
- D. Shielding
79. ECE Board Exam March 1996
What does the noise weighting curve shows?
- A. Noise signals measured with a 144 handset
- B. Power levels of noise found in carrier systems
- C. The interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertz
- D. Interfering effects of signals compared with a 3-kHz tone
80. ECE Board Exam March 1996
What is the difference between phase and frequency modulation?
- A. Is purely theoretical because they are the same in practice
- B. Lies in poorer audio response of phase modulation
- C. Lies in the different definitions of the modulation index
- D. Is too great to make two systems compatible
81. ECE Board Exam March 1996
When a transmission line uses ground return, it is called a/an __________ line.
- A. ungrounded
- B. balanced
- C. unbalanced
- D. grounded
82. ECE Board Exam March 1996
What is the gain of four identically polarized antennas stacked one above the other and fed in phase?
- A. 3 dB over the gain of one antenna
- B. 10 dB over the gain of one antenna
- C. 4 dB over the gain of one antenna
- D. 6 dB over the gain of one antenna
83. ECE Board Exam March 1996
The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the same bandwidth.
- A. Reference audio output
- B. None of these
- C. Audio frequency response
- D. Residual noise level
84. ECE Board Exam March 1996
The ___________ filter attenuates signals but passes frequencies below and above that band.
- A. low pass
- B. band pass
- C. band stop
- D. high pass
85. ECE Board Exam March 1996
In a telephone system, the customer’s telephone directory numbering is from 000 to 999, what is the capacity of the system?
- A. 1000 lines
- B. 100,000 lines
- C. 10,000 lines
- D. 100 lines
86. ECE Board Exam March 1996
An absorption loss caused by valence electrons in the silica material from which fibers are manufactured.
- A. Modal dispersion
- B. Infrared absorption
- C. Ion resonance absorption
- D. Ultraviolet absorption
87. ECE Board Exam March 1996
In an FM receiver, which circuit removes amplitude variations?
- A. Exciter
- B. Mixer
- C. Discriminator
- D. Limiter
88. ECE Board Exam March 1996
A one-hop, full duplex, microwave system in a space diversity arrangement. Determine “how many receivers in all are used?”
- A. 8
- B. 2
- C. 4
- D. 6
89. ECE Board Exam March 1996
The frequency spectrum of the stereophonic FM signal.
- A. 67 kHz
- B. 59.5 to 74.5 kHz
- C. 19 to 38 kHz
- D. 30 to 53 kHz
90. ECE Board Exam March 1996
Termination means
- A. result of disconnecting a line from a transmitter
- B. result of cutting both ends of a conductor
- C. looking back impedance of a line with no load
- D. load connected to the output end of a transmission line
91. ECE Board Exam March 1996
Asynchronous protocol is
- A. message oriented
- B. clock oriented
- C. bit oriented
- D. character oriented
92. ECE Board Exam March 1996
Transmission lines are either balanced or unbalanced with respect to _________.
- A. negative terminal
- B. input
- C. ground
- D. positive terminal
93. ECE Board Exam March 1996
What is the velocity factor for non-foam dielectric 50 or 75 ohm flexible coaxial cable such as RG 8, 11, 58 and 59?
- A. 2.70
- B. 0.10
- C. 0.66
- D. 0.30
94. ECE Board Exam March 1996
Gain of an isotropic antenna
- A. -1 dB
- B. 1 dB
- C. 0 dB
- D. 2 dB
95. ECE Board Exam March 1996
In measuring noise in a voice channel at a 4 dB test point level, the meter reads -70 dBm (F1A weighted), convert the reading to pWp.
- A. 53
- B. 93
- C. 63
- D. 83
96. ECE Board Exam March 1996
Power is always __________.
- A. a definite amount of energy
- B. expressed in watts
- C. the rate at which energy is used
- D. all of these
97. ECE Board Exam March 1996
Radio fading resulting from obstruction losses.
- A. Log normal fading
- B. None of these
- C. Multi-path fading
- D. Rayleigh fading
98. ECE Board Exam March 1996
After the IF stages have been aligned, the next stage to align in FM receiver is.
- A. local oscillator
- B. limiter stage
- C. RF amplifier
- D. mixer stage
99. ECE Board Exam March 1996
___________ is a device in data transmission to interface data terminal equipment to an analogue transmission line.
- A. RS 232
- B. Connector
- C. Modem
- D. RJ-11 plug
100. ECE Board Exam March 1996
What is the primary advantage of DSBSC in AM?
- A. Reduce bandwidth over standard AM
- B. All of these
- C. It is simpler to transmit and receive than the standard AM
- D. No transmitter power is wasted in the carrier
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