Final Preboard Oct2017 Esatseta

Republic of the Philippines Professional Regulation Commission Board of Electronics Engineering

ECE Licensure Examination – Pre-Board Exam

1:00 pm – 5:00 pm

EST

page 1 of 7 SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil no. 2 only. NOTE:

Whenever you come across a caret (^) sign, it means exponentiation. Ex. x^2 means x2; (x+y)^(x-z) means (x+y) raised to the (x-z). Pi=3.1416

MULTIPLE CHOICE 1. When a wave greatest? a. when the b. when the c. when the d. when the 2. If a. b. c. d.

the the the the the

is reflected from a surface, energy is transferred. When is the transfer of energy incident incident incident incident

wave wave wave wave

is is is is

perpendicular to the surface. parallel to the surface.* coming from the air. coming from water.

wave passes from a less dense medium to a more dense medium, angle of refraction is less than the angle of incidence* angle of refraction is greater than the angle of incidence angle of refraction is equal to the angle of incidence angle of refraction depends on the nergy of the wave

3. How does density and temperature a. velocity increases as density b. velocity increases as density c. velocity increases as density d. velocity increases as density

affect the velocity of sound? increases and temperature increases decreaces and temperature decreaces decreaces and temperature increases* increases and temperature decreaces

4. A PCM system uses a uniform quantizer followed by a 7-bit binary encoder. The bit rate of the system is equal to 50 x 106 bits/sec. Determine the output signal to quantization noise ratio when a full load sinusoidal modulating wave of frequency 1 MHz is applied to the input. a. 23.6 dB b. 31.3 dB c. 43.8 dB* dB* d. 51.2 dB 5. The number of home users and small businesses that want to use the Internet is ever increasing. many are not happy with one address; many have created small networks with several hosts and need an IP address for each host. With the shortage of addresses, this is a serious problem. A quick solution to this problem is called _____ . This enables a user to have a large set of addresses internally and one address, or a small set of addresses, externally. A. Address Allocation C. network address translation* B. LOGICAL ADDRESSING D. Dynamic Host Configuration 6. An IPv6 address consists of how many bytes? a. 4 b. 8

c. 16* 16*

d. 32

7. A television signal with a bandwidth of 4.2 MHz is transmitted using binary PCM. The number of quantization levels is 512. Calculate the output signal to quantization noise ratio. a. 58.8 dB* dB* b. 34.4 dB c. 49.1 dB d. 28.9 dB 8. Naval communications within the hf band can be grouped into four general types of services: point-to- point, ship-to-shore, ground-to-air, and fleet broadcast. This service involves broadcast area coverage from shore-based transmitters to ships at sea. a. POINT-TO-POINT c. GROUND-TO-AIR b. SHIP-TO-SHORE d. FLEET BROADCASTS* BROADCASTS* 9. The GSM cellular radio system uses GMSK in a 200-kHz channel, with a channel data rate of 270.833 kb/s. Calculate the frequency shift between mark and space. a. 270.8 kHz b. 135.4 kHz* kHz* c. 222.2 kHz d. 111.1 kHz 10. A client/server protocol designed to provide physical address to logical address mapping. a. Reverse Address Resolution Protocol (RARP) b. Dynamic Host Configuration Protocol (DHCP) c. Bootstrap Protocol (BOOTP)* (BOOTP)* d. Internet Control Message Protocol (ICMP) 11. There are four networks networks in series. The first network has a gain of 15 15 dB, the second second has a loss of 4 dB, the third gain of 35 dB, and the fourth a loss of 5 dB. The input of the first network is +3dBm. What is the output to the last network in mW. a. 25118.9* 25118.9* b. 24231.2 c. 23017.2 d. 21212.7 12. The main advantage of a high-level modulation system compared to a low-level system is that it a. Allows more efficient amplification. * b. Allows use of low-powered intelligence signal. c. Provides higher modulation percentage. d. Is more economical.



1:00 pm – 5:00 pm

EST

page 2 of 7 SET A

13. When the input to an ideal nonlinear device is an AM waveform consisting of a carrier and its sidebands, the output of nonlinear mixing produces the original intelligence because a. The intelligence signal is one of its inputs. b. A dc component is also produced. c. The difference between the carrier and its sidebands is the original intelligence frequency.* d. The intelligence frequencies are the upper and the lower sideband frequencies. 14. A nonlossy transmission line terminated with a short circuit has an a. In-phase reflected voltage that is equal in magnitude to the incident voltage b. Opposite-phase reflected voltage that is equal in magnitude to the incident voltage* c. In-phase reflected voltage that is smaller in magnitude than the incident voltage d. Opposite-phase reflected voltage that is smaller in magnitude than the incident voltage 15. The ground wave eventually disappears, as one moves away from the transmitter, because of a. interference from the sky wave b. loss of line-of-sight conditions c. maximum single-hop distance limitation d. tilting* 16. When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is a. the same as in free space b. the same as the wavelength perpendicular to the wall c. shortened because of Doppler effect d. greater than in the actual direction of propagation* 17. In a satellite communications system, free space conditions may be assumed. The satellite is at a height of 36,000 km above earth, the frequency used is 4000 MHz, the transmitting antenna gain is 15 dB, and the receiving antenna gain is 45 dB. Calculate the received power when the transmitted power is 200 W. A. 5 pW* B. 10 pW C. 15 pW D. 20 pW 18. Channel 4 in Philippine TV uses ____ as its visual carrier frequency. A. 67.25 MHz* B. 70.83 MHz C. 71.75 MHz D. 72 MHz 19. A microwave communication system uses plane reflectors as passive repeaters. A parabolic antenna with 20 ft. diameter with an effective area of 250 ft was used. Calculate the reflector coupling factor. A. 0.96 B. 1.21 C. 1.12 * D. 0.706 20. A radio communication repeater has a transmitting output power of 1 kW, a 5dB feedline loss, 6dB duplexer and circulator loss, and a 10 dB antenna gain. Calculate the effective radiated power. A. 79.4 W B. 394 W C. 794 W * D. 251 W 21. What is the reliable measurement for comparing amplifier noise characteristics? A. signal-to-noise C. nosie factor * B. thermal agitation noise D. noise margin 22. A parallel tuned circuit, having a Q of 20, is resonated to 200 MHz with a 10 picofarad capacitor. If this circuit is maintained at 17 C with bandwidth of 10 kHz, what noise voltage will a wideband voltmeter measure when placed across it? A. 31.64 nV C. 18.75 uV B. 25.25 nV D. 15.97 uV* 23. The serial binary data is mixed with higher-frequency pseudorandom binary code at a faster rate and the result is used to phase modulate the carrier. A. Spread spectrum C. Frequency hopping B. Time division multiplexing D. Direct sequence* 24. A three-stage has stages with the following specifications: First stage with power gain and noise figure of 10 and 2 respectively, 25 and 4 for the second stage and 30 and 5 for the third stage. Find the noise temperature. A. 382 K* B. 435 K C. 328 K D. 358 K 25. The radiated beam from a parabolic "dish" transmitting antenna is: A. Collimated* C. dispersed B. phased D. none of the above 26. A modulating signal is amplified by a 80% efficiency amplifier before being combined with a 20 kW carrier to generate an AM signal. The required DC input power to the amplifier, for the system to operate at 100% modulation, would be (A) 5 kW (B) 8.46 kW (C) 12.5 kW* (D) 6.25 kW 27. A TDM link has 20 signal channels and each channel is sampled 8000 times/sec. Each sample is represented by seven binary bits and contains an additional bit for synchronization. The total bit rate for the TDM link is (A) 1180 K bits/sec (C) 1180 M bits/sec (B) 1280 K bits/sec* (D) 1280 M bits/sec 28. Which of the following amplifiers is used between the carrier oscillator and the final power amplifier to isolate the oscillator from the load? A. class A buffer* C. high-power linear B. class B push-pull D. class C



1:00 pm – 5:00 pm

page 3 of 7

EST

SET A

29. Which of the following IPs can two different hosts connected to the internet have? (1) 10.12.14.10 (2) 172.16.5.12 (3) 192.168.32.51 (4) 202.144.131.5* 30. Telephone switch that connects only to other switches, and not to individual customers. A. central office B. tandem office * C. toll station D. PSTN 31. Microstrip is a flat conductor separated by an insulating dielectric from a large conducting ground plane. The microstrip is usually onequarter or one-half wavelength long. As the distance between copper trace and the ground plane increases, the value of the characteristic impedance of your stripline A. increases* C. decreases B. remains constant D. Zo is temperature dependent 32. The half wave dipole is formed from a conducting element which is wire or metal tube which is an electrical half wavelength long. It is typically fed in the centre where the impedance falls to its lowest. In this way, the antenna consists of the feeder connected to two quarter wavelength elements in line with each other. The voltage and current levels vary along the length of the radiating section of the antenna. This occurs because standing waves are set up along the length of the radiating element. At the feedpoint of this antenna, the current is A. maximum* B. minimum C. remains constant D. zero current 33. Assertion (A): Free space does not interfere with normal radiation and propagation of radio waves Reason (R): Free space has no magnetic or gravitational fields. A. Both A and R are correct and R is correct explanation of A* B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D. A is wrong but R is correct 34. Consider the following statements 1. The amplitude of an FM wave is constant 2. FM is more immune to noise than AM 3. FM broadcasts operate in upper VHF and UHF frequency ranges 4. FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments Which of the above are correct? A. 1, 2, 3, 4 B. 1, 2, 3*

C. D.

2, 3, 4 1, 3, 4

35. A satellite-dish owner has a 3 meter dish designed for C-band (4GHz) operation. The owner wants to use the same dish with a new feedhorn, for Ku- band (12GHz) satellites. What effect will the change in frequency have on the gain and beamwidth of the antenna? A. Gain decreases by 9.54 dB, beamwidth decreases three times of its former value. B. Gain increases by 9.54 dB, beamwidth decreases three times of its former value. C. Gain decreases by 9.54 dB, beamwidth decreases 1/3 of its former value. D. Gain increases by 9.54 dB, beamwidth decreases 1/3 of its former value. * 36. In AT&T’s FDM heirarchy. To lessen the number of carriers the channels are grouped. How many group dose a jumbogroup have? A. 60 * B. 600 C. 1800 D. 10800 37. In this encoding method, the duration of the bit is divided into two halves. The voltage remains at one level during the first half and moves to the other level in the second half. The transition at the middle of the bit provides synchronization. A. B8ZS B. Manchester * C. AMI D. pseudotenary 38. One problem with TDM is how to handle a disparity in the input data rates. Sometimes the bit rates of sources are not multiple integers of each other. A solution is to make the highest input data rate the dominant data rate and then add dummy bits to the input lines with lower rates. This will increase their rates. This technique is called a. Multilevel Multiplexing c. Pulse Stuffing* b. Multiple-Slot Allocation d. Frame Synchronizing 39. It provides independence to the application processes by addressing any code or syntax conversion necessary to present the data to the network in a common communications format. It specifies how end-user should format the data. This layer provides for translation between local representations of data and the representation of data that will be used for transfer between end users. The results of encryption, data compression, and virtual terminals are examples of the translation service. A. Session Layer B. Presentation Layer* C. Transport Layer D. Physical layer 40. What is the new designation for PAM? A. J3F B. M3E

C. K3E

*

D. L3E

41. The best terrain between antennas is_____which will prevent reflection effects on the hop. A. rocky B. plain and flat* C. forested D. water surface 42. Given the pulse-spreading constant equal to 10 ns/m and the cable length equal to 100 meters, determine the maximum bit rate in Mbps for UPRZ transmission. A. 500 Mbps B. 1.0 Mbps * C. 1000 Mbps D. 0.5 Mbps



1:00 pm – 5:00 pm

page 4 of 7

EST

SET A

43. What usually happens to radio waves with frequencies below the MUF and above the LUF when they are sent into the ionosphere? A. They are bent back to the Earth* B. They pass through the ionospher C. They are amplified by interaction with the ionosphere D. They are bent and trapped in the ionosphere to circle the Earth 44. What does the term "critical angle" mean as used in radio wave propagation? A. The long path azimuth of a distant station B. The short path azimuth of a distant station C. The lowest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions D. The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions* 45. Which of the following is a function of OSI network layer? a. Logical addressing* c. Flow control b. Synchronization of bits d. Segmentation and reassembly 46. What type of antenna can be used rotation? A. A linearly polarized antenna B. A circularly polarized antenna*

to

minimize

the

effects

of

spin

modulation

and

Faraday

C. An isotropic antenna D. A log-periodic dipole array

47. What is blanking in a video signal? A. Synchronization of the horizontal and vertical sync pulses B. Turning off the scanning beam while it is traveling from right to left or from bottom to top* C. Turning off the scanning beam at the conclusion of a transmission D. Transmitting a black and white test pattern 48. An AM signal is detected using an envelope detector, the carrier frequency and modulating signal frequency are 1 MHz and 2 kHz respectively. An appropriate value for the time constant of the envelope detector is A. 500 μ sec C. 0.2 μ sec B. 20 μ sec* D. 1 μ sec 49. In a double side-band (DSB) full carrier AM transmission system, if the modulation index is doubled, then the ratio of total sideband power to the carrier power increases by a factor of ____. A. 2 B. 3 C. 4* D. 5 50. How does the maximum distance of ground-wave propagation change when the signal frequency is increased? A. It stays the same C. It decreases* B. It increases D. It peaks at roughly 14 MH 51. The characteristic impedance of a transmission line is determined by the: A. length of the line B. physical dimensions and relative positions of the conductors * C. frequency at which the line is operated D. load placed on the line 52. A receiver designed for SSB reception must have a BFO (beat frequency oscillator) because ____ A. it beats with the received carrier to produce the other sideband B. it reduces the passband of the IF stages C. the suppressed carrier must be replaced for detection * D. it phases out the unwanted sideband signal 53. The sequence of operations in which PCM is done is A. Sampling, quantizing, encoding * C. Quantizing, encoding, sampling B. Quantizing, sampling, encoding D. None of the above 54. In of A. B.

an optical fiber, the concept of Numerical aperture is applicable in describing the ability ______ Light Collection * C. Light Scattering Light Dispersion D. Light Polarization

55. If a fiber operates at 1400nm with the diameter of about 10 μm, n1 = 1.30, Δ = 0.80% , V = 3.5, then how many modes will it have? A. 6.125 * C. 9.655 B. 12.95 D. 16.55 56. If a noisy channel has a bandwidth of 4 MHz with signal to noise ratio of about 1, what would be the maximum capacity of the channel? A. 2 Mb/sec B. 4 Mb/sec * C. 6 Mb/sec D. 8 Mb/sec 57. Guard band is A. The small unused bandwidth between the frequency channels to avoid interference * B. The bandwidth allotted to the signal C. The channel spectrum D. The spectrum acquired by the noise between the signal



1:00 pm – 5:00 pm

page 5 of 7

EST

SET A

58. The advantages of FDMA over TDMA includes 1. Division is simpler 2. Propagation delays are eliminated 3. Cheaper filters with less complicated logic functions 4. Linearity A. 1, 2 and 3 are correct C. 1 and 2 are correct * B. 1 and 4 are correct D. All four are correct 59. A transmission line differs from an ordinary circuit or network in communications or signaling devices in one very important way. That important aspect is: A. capacitive reactance C. inductive reactance B. propagation delay * D. resistance 60. Losses occurring on a transmission line between transmitter and antenna results in: A. an SWR reading of 1:1 C. less RF power being radiated * B. reflections occurring in the line D. the wire radiating RF energy 61. What does an SWR reading of 1:1 mean? A. The best impedance match has been attained * B. An antenna for another frequency band is probably connected C. No power is going to the antenna D. The SWR meter is broken 62. If an antenna is made longer, what happens to its resonant frequency? It decreases* B. It increases C. It stays the same D. It disappears 63. Approximately how much gain does a half-wave dipole have over an isotropic radiator? A. 1.5 dB B. 3.0 dB C. 6.0 dB D. 2.1 dB * 64. If you made a quarter-wavelength vertical antenna for 21.125 MHz, how long would it be? A. 3.6 metres (11.8 ft) C. 3.36 metres (11.0 ft) * B. 7.2 metres (23.6 ft) D. . 6.76 metres (22.2 ft) 65. In a frequency modulation transmitter, the ________is in between the speech amplifier and the oscillator. A. modulator * C. power amplifier B. microphone D. frequency multiplier 66. What circuit has a variable-frequency oscillator connected to a driver and a power amplifier? A. A crystal-controlled transmitter C. A VFO-controlled transmitter * B. A single-sideband transmitter D. A packet-radio transmitter 67. The input power to the final stage of your transmitter is 200 watts and the output is 125 watts. What has happened to the remaining power? A. It has been dissipated as heat loss * C. It has been used to provide greater efficiency B. It has been used to provide negative feedback D. It has been used to provide positive feedback 68. How does the range of sky-wave propagation compare ground-wave propagation? A. It is much shorter C. It is about the same B. It depends on the weather D. It is much longer * 69. What is the maximum distance along the earth's surface that is normally covered in one hop using the F2 region? A. None; the F2 region does not support radio-wave propagation B. 2160 km (1200 miles) C. 4500km (2500 miles) * D. 325 km (180 miles) 70. What does maximum usable frequency mean? A. The lowest frequency signal that will reach its intended destination B. The highest frequency signal that is most absorbed by the ionosphere C. The lowest frequency signal that is most absorbed by the ionosphere D. The highest frequency signal that will reach its intended destination* 71. Find the minimum bandwidth for an ASK signal transmitting at 2000 bps. The transmission mode is half-duplex. A. 1000 Hz B. 500 Hz C. 2000 Hz D. 4000 Hz 72. A short-circuited half-wavelength line acts like a A. Parallel resonant circuit B. Oscillator

C. Series Resonant Circuit * D. LC circuit

73. If the two towers of a 950-kHz antenna are separated by 120 electrical degrees, what is the tower separation in feet? A. 231 ft. C. 235 ft. B. 176 ft. D. 345 ft.*



1:00 pm – 5:00 pm

page 6 of 7

EST

SET A

74. The figure in a receiver's specifications which indicates its sensitivity is the: A. signal plus noise to noise ratio * C. audio output in watts B. bandwidth of the IF in kilohertz D. number of RF amplifiers 75. A receiver receives an incoming signal of 3.54 MHz, and the local oscillator produces a signal of 3.995 MHz. To which frequency should the IF be tuned? A. 7.435 MHz C. 3.995 MHz B. 455 kHz * D. 3.54 MHz 76. A communications receiver has four filters installed in it, one at 250 Hz, one at 500 Hz, one at 2.4 kHz, and one at 6 kHz. If you were listening to single sideband, which filter would you utilize? A. 250 Hz B. 2.4 kHz C. 6 kHz D. 500 Hz 77. The data rate for IEEE 802.11b is _____. A. 10 Mbps C. 1.544 Mbps B. 2.048 Mbps D. 11 Mbps * 78. Why is it that the uplink is always higher in frequency than the downlink? A. Because the uplink suffers greater spreading or free-space loss of frequency than its lower counterpart B. Since an earth station aims upward with well-controlled antenna sidelobes C. A and B are correct * D. None of these 79. A fiber-optic cable has a loss of 15 dB/km. The attenuation in a cable 1000 ft. long is A. 4.57 dB * B. 9.3 dB C. 24 dB D. 49.2 dB 80. Which type of fiber-optic cable has the least modal dispersion? A. Single mode step-index * C. Multimode step-index B. Single-mode graded-index D. Multimode graded-index 81. Which causes a quantization noise in PCM system? A. Serial transmission errors B. The approximation of the quantized signal * C. The synchronization between encoder and decoder D. Binary coding techniques 82. The front-end of a television receiver, having a bandwidth of 7Mhz, and operating at a temperature of 27˚C , consists of an amplifier having a gain of 15 followed by a mixer whose gain is 20. The amplifier has a 300 Ω input resistor and a shot noise equivalent resistance of 500Ω; for the mixer, these values are 2.2kΩ and 13.5kΩ respectively, and the load resistance of the mixer is 470 kΩ. Calculate the equivalent noise resistance for this television receiver. A. 8760 Ω B. 875 Ω * C. 8.76 Ω D. 0.876 Ω 83. A receiver connected to an antenna whose resistance is 50 Ω has an equivalent noise resistance of 30Ω. Calculate its equivalent noise temperature if the noise figure is equal to 1.6. A. 17.4 K B. 174 K * C. 1.74 K D. 17 K 84. What is the effect on the signal to noise ratio of a system (in considering all other parameters to remain unchanged except the S/N will be A. Increased by a factor of 2 C. Decreased by B. Increased by a factor of 4 D. Decreased to

dB) if the bandwidth is doubled normal thermal noise only. The ½ its value * ¼ its value

85. In a microwave communications system, determine the noise power in dBm for an equivalent noise bandwidth of 10 MHz. A. -104 dBm * C. -114 dBm B. -94 dBm D. -174 dBm 86. The free space attenuation between two microwave antennas 40 km apart operating at 8 GHz is A. 146.7 dB C. 142.55 dB * B. 82.5 dB D. 86.7 dB 87. If the correction factor k equals 4/3 of the earth’s curvature, the microwave beam would have a curvature that is ___________ than that of the earth. A. More * C. Less B. Equal D. Not related 88. When the clearance above the obstruction is equal to the radii of even fresnel zones at the point of reflection. The RSL is A. Increased C. Decreased * B. Constant D. Above threshold 89. If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of A. square root of 2 B. 2 C. 4 * D. 8 90. A situation when there is no change in attenuation or “no gain, no loss” occurs when ________ % of the first Fresnel radius clears a path obstruction in microwave systems. A. 45% B. 60% * C. 75% D. 85% 91. A Fade Margin of 28 dB has a reliability of A. 99% B. 99.9% * C. 99.99%

D. 99.999%



1:00 pm – 5:00 pm

page 7 of 7

EST

SET A

92. Serial and parallel transmission A. Differ in how many bits are transferred per character B. Are used in synchronous and asynchronous systems, respectively C. Both a and b D. Differ in whether the bits are on separate wires or on one * 93. What is the approximate bandwidth occupied by the chrominance video signal for color TV? A. 0.8 MHz B. 1.8 MHz * C. 8.1 MHz D. 1.6 MHz 94. The video carrier and the audio carrier are separated by ____ MHz. A. 4.5 * B. 5.5 C.6.5 D. 7.5 95. Dividing the data block by a constant produces a remainder that is used for error detection. It is called the A. Vertical redundancy check C. Horizontal redundancy check B. Block check character D. Cyclic redundancy check * 96. The OSI layer that provides the control functions necessary to establish, manage and terminated the connections as required to satisfy the user request. A. Application layer C. Network layer B. Session layer * D. Physical layer 97. The total noise power present in a 1-Hz bandwidth . A. Noise density * C. Noise figure B. Noise limit D. Noise intensity 98. Unipolar, bipolar, and polar encoding are types of ___________ encoding. A. Digital-to-digital * C. Digital-to-analog B. Analog-to-analog D. Analog-to-digital 99. When a signal is returned to earth by the ionosphere, what is this called? A. Tropospheric propagation C. Ground-wave propagation B. Sky-wave propagation * D. Earth-moon-earth propagation 100. What is the bandwidth required to transmit at a rate of 10Mbits/sec in the presence of a 28 dB S/N ratio? A. 107.5 kHz C. 3.57 MHz B. 357.14 kHz D. 1.075 MHz *

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Final Preboard Oct2017 Esatseta

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