ESAT - PERCDC PreBoard Aug 2008 1. An Ethernet bus is 200 meters long, uses a coaxial cable (velocity factor is 0.625), and a communication speed of 10 Mbps. Determine the total number of bits that would be sent by each station before it detects detects a collision, collision, if both stations stations begin begin to transmit transmit at the same time. a. 5 bits c. 11 bits b. 13 bits d. 25 bits 2. Broadcast station towers, by convention, is painted with colors___. a. white and red c. white and orange b. whit white e and and yell yellow ow d. oran orange ge and and yell yellow ow 3. A radio communication repeater has a transmitting output power of 1 KW, a 5 dB feedline loss, 6 dB duplexer and circulator loss, and a 10 dB antenna gain. Calculate the effective radiated power. a. 79.4 W c. 794 W b. 384 W d. 251 W 4. To demonstrate demonstrate the color picture of a television television set, a ____ is used. a. equali equalizin zing g transfor transformer mer c. coil trap trap b. rota rotati tion onal al indu inducto ctorr d. dega degauss ussin ing g coil coil 5. In radio communic communicati ation on system, system, the purpose purpose of AFC in an FM receiver is ____. a. to provide selectivity b. to establish establish the gain c. to increase increase the sensitivity sensitivity d. to help maintain the steady local oscillator frequency 6. A phase-locked loop has a VCO with a free-running frequency of 10 Mhz. As the frequency of the reference input is gradually raised from zero, the loop locks at 8 Mhz and comes out of lock again at 4 Mhz. Determine the lock range. a. 12 Mhz c. 4 Mhz b. 8 Mhz d. 6 Mhz 7. In Rado Rado Naviga Navigatio tion n System, System, the marker marker beacon beacon operate operates s at a carrier frequency of ____. a. 156.8 Mhz c. 145 Mhz b. 75 Mhz d. 123.8 Mhz 8. How many Hamming bits would have to be added to a data block containing 120 bits? a. 9 c. 6 b. 8 d. 7 9. In Radio Navigation, a navigation system which depends on time difference measurement and uses the lowest frequency application of radio transmission transmission is know as the ____. a. LORAN Radio Navigation System b. Global Position Satellite Navigation System c. DECCA Radio Navigation System d. OMEGA Radio Navigation System 10. Very small Aperture Satellite (VSAT) system operates within the frequency band called ____ band. a. K c. L b. X d. C 11. A hollow hollow metalli metallic c structur structure e throug through h which which microwa microwave ve energy energy propagates by reflection rather than conduction is a/an ____. a. microstrip c. optical fiber b. waveguide d. pipeline 12. For microwave application, the main advantage of traveling wave tube over a Klystron Klystron is _____. _____. a. lower cost c. readily available b. wide widerr bandw andwid idth th d. high igher power wer 13. In acoustics, the loudness sound level of the voice of a singing woman is 60 sones. What is its equivalent equivalent in phons? phons? a. 96 c. 98 b. 99 d. 100
14. 14. A microwa microwave ve commun communicat ication ion system system uses uses place place reflecto reflectors rs as passive repeaters. A parabolic antenna with 20 ft. diameter with an effecti effective ve area area of 250 ft was used. Calcul Calculate ate the reflect reflector or coupli coupling ng factor. a. 0.96 c. 1.12 b. 1.21 d. 0.706 15. The oscillator of a CB transmitter is guaranteed accurate to a plus or minus .005 percent. Calculate the maximum frequency at which it could actually transmit if it is set to transmit on channel 18, with a nominal carrier frequency of 27.175 Mhz. a. 27.2180 Mhz c. 27.2064 Mhz b. 27.1764 Mhz d. 27.1736 Mhz 16. An angstrom used to describe a lightwave is equal to 10 raised to minus _____ micrometer. a. 3 c. 6 b. 10 d. 4 17. In data communications, communications, the interfacing specifications specifications coveing pre-ISDN standards for basic rate access in an ISDN environment is the _____. a. B c. S b. L d. R 18. 18. In CMTS, CMTS, a man inside inside his car is operat operating ing his cellph cellphone one and uses frequency 825 Mhz. If he is traveling at a speed of 80 km/hr, what is the time between between signal fades? a. 7.27 ms c. 8.19 ms b. 9.81 ms d. 7.92 ms 19. In television using NTSC standard, the chrominance sub-carrier frequency is ____ Mhz. a. 3.5975 c. 2.785 b. 2.875 d. 3.5795 20. 20. In FM fax, fax, the the freq freque uenc ncie ies s for for blac black k and and whit white e are are ____ ____ respectively. a. 1500 1500 and and 3200 3200 Hz c. 2300 2300 and and 4200 4200 Hz b. 1500 1500 and and 2300 2300 Hz d. 2300 2300 and and 3200 3200 Hz 21. Calculate the time required to dial the number 932-51-74 using pulse dialing with 0.300 seconds interdigit time. a. 4.8 sec c. 4.9 sec b. 4.6 sec d. 4.1 sec 22. A type of diode popularly used as a microwave microwave oscillator is a ____ diode. a. avalance c. impatt b. tunnel d. gunn 23. 23. What layer of the Open Open System System Intercon Interconnec nectio tion n (OSI) (OSI) model model handles the transmission of bits over a communications channel? a. phys ic ic al al l ay ayer c . data link layer b. tr an ans po port layer d. net wo work layer 24. What is the effective height of a broadcast antenna if the voltage induced in the antenna is 2.7 volts and the measured field intensity received received in the antenna antenna site is 27 mV/m? a. 29.7 meters c. 72.9 meters b. 100 meters d. 127 meters 25. Medium Earth Orbit (MEO) satellite satellite operates in the ___ frequency band. a. 2 – 18 Ghz c. 1.2 – 1.66 Ghz b. 1.0 – 2.5 Ghz d. 6 – 12 Ghz 26. The normal design limitation of a telephone loop of its value of loop loop resi resist stan ance ce,, Rz, Rz, the the maxi maximu mum m valu value e of Rloo Rloop p must must not not exceed____. a. 5400 ohms c. 2300 ohms b. 1300 ohms d. 2800 ohms
27. Calculate the appropriate height of a GEO satellite using Kepler’s Third Law. (A = 42241.0979: P = 0.9972) a. 34, 416.40 km c. 36,000 km b. 35, 790 km d. 421, 164 km 28. In telecommunications, short haul connection refers to a connection not exceeding _____ kilometers. a. 200 c. 250 b. 150 d. 300 29. One of the following is not a system specification for third generation wireless system. a. TD/CDMA c. CDMA 2000 b. WCDMA d. IMT 2000 30. Bluetooth wireless technology uses ____ to produce the spreading function of spectrum signals. a. hybrid direct-sequences b. hybrid frequency-hopping c. direct sequence d. frequency-hopping 31. What is the characteristic impedance of a basic parallel wireline, if its diameter is 0.023 inches with spacing of 0.4 inches apart, if it uses a dielectric material made of continuous polyvinyl chloride? a. 128.7 ohms c. 234 ohms b. 99 ohms d. 188 ohms 32. Crosstalk in telephony, refers to unwanted coupling between signal paths and contribute to noise in the telephone receiver. Calculate the crosstalk coupling loss in dBx (one unit of crosstalk in dB above reference coupling) if the crosstalk coupling is 20 dBx. a. 60 c. 80 b. 70 d. 90 33. The critical maximum value of the external incident angle for which light will propagate in the fiber is known as ____. a. acceptance angle b.critical angle c. internal incident angle d. critical internal incident angle
40. A frequency modulation system requires a signal-to-noise ration of 40 dB at the detector output. The modulating frequency is 2 Khz and the deviation is 50 Khz. Determine the required minimum S/N at the detector input. a. 120 dB c. 80 dB b. 25 dB d. 83.3 dB 41. A typical separation distance between satellites in a geostationary orbit is 1839.7 miles. In terms of degrees, it is equivalent to ___ degrees. a. 7 c. 4 b. 6 d. 5 42. At 0 degrees elevation, geostationary satellite can cover a maximum of _____ percent of the earth’s surface. a. 64 c. 46 b. 42.5 d. 33.33 43. Luminance signals are adjusted to match the brightness sensation of human vision of color television. This is ____. a. 29 % red, 59 % green, and 12 % blue b. 30 % red, 59 % green, and 11 % blue c. 29 % red, 60 % green, and 11% blue d. 30 % red, 58 % green, and 12 % blue 44. What is the actual length in feet of a one-half wavelength of a coax with a velocity factor of 0.57 at 25 Mhz? a. 42.17 c. 41.12 b. 44.87 d. 43.25 45. The choir in the church composed of 20 members, sings “silent night”. A soloist sings in a passage and is then joined by the rest of the choir members singing with the same intensity. What is the difference in the sound intensity level in the two cases? a. 20 dB c. 2.0 dB b. 13 dB d. 1.3 dB 46. How many voice channels are there in a DS-2 Digital Signal Hierarchy for TDM signals? a. 672 c. 48 b. 24 d. 96
34. Calculate the peak envelope power of a single sideband (SSB) transmitter that produces a peak-to-peak voltage of 240 volts across a 100 ohm antenna load. a. 144 W c. 72 W b. 120 W d. 24 W
47. An optic fiber is made of glass with a refractive index of 1.54 and is clad with another glass with refractive index of 1.50. Launching takes place from air. Calculate the numerical aperture of the fiber. a. 0.352 c. 0.0352 b. 0.00352 d. 3.52
35. What is the purpose of an indirectly-heated cathode in a cathode ray tube? a. beam modulation c. beam focusing b. beam production d. beam deflection
48. In spread-spectrum frequency hopping system, a ____ circuit selects the frequency modulated by the synthesizer. a. frequency synthesizer c. PSN code generator b. FSK os ci llat or d. frequency s hif ter
36. The time transfer accuracy used with a reference to the Universal Transmitter Mercator Grid is _____. a. UTC c. GMT b. UTMG d. UTM
49. What synchronizes the horizontal of the TV picture tube? a. HSC c. HFC b. HAFC d. HAC
37. Determine the shot noise for a diode with a forward bias of 1.35 mA over a 110 Khz bandwidth. (1 = 1.6 x 10^-19 C) a. 0.006 uA rms c. 0.004 uA rms b. 0.005 uA rms d. 0.007 uA rms 38. The velocity of sound in dry air medium is 331.45 m/s. Calculate the new velocity if there is an increase of temperature equal to 10 degrees centigrade. a. 341.52 m/s c. 332.52 m/s b. 337.52 m/s d. 332 m/s 39. Another name used for optical density is _____. a. light density c. light flux b. flux density d. radiant flux
50. In FDM, how many voice band channels are there in a jumbo group? a. 7,200 c. 10,800 b. 3,600 d. 1,600 51. Using the NTSC standard, what is the aural carrier frequency of UHF TV channel 28? a. 558.75 Mhz c. 553.75 Mhz b. 559.75 Mhz d. 555.25 Mhz 52. An optical fiber and its cladding have refractive indexes of 1.55 and 1.32 respectively. Determine the acceptance angle. a. 52.38 degrees c . 51.37 degr ees b. 54.34 degrees d. 55. 68 degrees
53. Calculate the transmitted data stream for the following data and CRC generating polynomials: Data C(x) = x raised to the power of 7 + x raised to the power 5 + x raised to the power 4 + x raised to the 2nd power + x + one. P(x) = x raised to the power of 5 + x raised to the power 5 + x + one. a. 1011011111001 b. 1011011101001 c. 10110111000101 d. 1011010010001
b. 10 bits/cycle
d. 3 bits/cycle
65. The modulation technique used by DECT a. PSV c. GFSK b. ASK d. QAM 66. The carrier transmitted 1.25 Mhz above the bottom frequency in the Philippines TV channel is the ___. a. intercarrier c. picture b. sound d. sub-picture carrier
54. An AM transmitter uses a high level modulation. The RF power amplifier runs from a 12 volt source putting out a carrier power of 85 watts, with an efficiency of 85 percent, what load impedance is required in order for it to deliver the rated power? a. 0.85 ohms c. 1.7 ohms b. 80 ohms d. 83.6 ohms
67. Among the visible light rays of blue, green, yellow and orange, which has the longest wavelength? a. Green c. Yellow b. Blue d. Orange
55. Find the frequency to which a 400 Hz baseband frequency will be translated for channel 7 of a group of FDM system. a. 84.4 Khz c. 84 Khz b. 80 Khz d. 83.6 Khz
68. An AM signal has the following characteristics: carrier frequency = 150 Mhz; modulating frequency = 3 Mhz; peak carrier voltage = 40 volts and peak modulation voltage is 30 volts. Calculate the peak voltage of the lower sideband frequency. a. 15 volts c. 70 volts b. 10 volts d. 20 volts
56. The radio wavelength known as ____ falls within the medium frequency range. a. centimetric waves c. hectometric waves b. decametric waves d. myriametric waves 57. Single sideband full carrier emission type: a. H3E c. J3E b. R3E d. B8E 58. A telephone signal takes 2 quarters of a second to reach its destination. Calculate the via net loss necessary for an acceptable amount of echo. a. 104 dB c. 100 dB b. 10.4 dB d. 100.4 dB 59. The power of any conducted spurious emission shall be attenuated below the maximum level of carrier frequency in accordance with the following formula: a. Attenuation (dB) = 43 + 20logP b. Attenuation (dB) = 43 + logP c. Attenuation (dB) = 43 + 10logP d. Attenuation (dB) = 43 + log(P/10) 60. When measuring he voice channel at a -4dB test point level, the meter reads -76dBm. Calculate the reading in dBrnC0. a. 80 c. 8 b. 18 d. 28 61. An uplink transmitter of a satellite system operates at 6 Ghz with a transmitter power of 12 kW and an antenna gain of 50 dBi. The receinver in a geostationary satellite has an antenna gain of 40 dBi. The elevation angle to the satellite from the ground is 45 degrees, calculate the received signal strength at the satellite (height of the satellite above the equator is 365,000 km., earth radius is 6400 km) a. 38.7 dBm c. -70.8 dBm b. 70.89 dBm d. -38.7 dBm 62. What kind of battery panels are used in some advanced satellite: a. silicon based panels b. Germanium based panels c. Gallium phosphate solar panel array d. Gallium arsenide solar panel array 63. Give the audio power of 500 W which will modulate an RF amplifier to 50 percent modulation. Find the DC power input. a. 1000 W c. 5000 W b. 250 W d. 4000 W 64. If the transmission rate of a digital communication system of 10 Mbps modulation scheme used is 16 QAM, determine the bandwidth efficiency. a. 5 bits/cycle c. 4 bits/cycle
69. A diagram which shows the relationship between the RF signal phase and maximum bunching of the electron beam in velocitymodulated devices. a. Applegate diagram c. S-parameter diagram b. Smith chart d. Venn diagram 70. What is the result of a balanced modulator if not perfectly balanced? a. the lower sideband is transmitted b. both sidebands are transmitted c. the carrier is transmitted d. the SB is filtered 71. The period for a single time slot in the GSM-TDMA slot structure is ____microsecond. a. 577 c. 377 b. 477 d. 277 72. An example of Marconi type antenna is ____. a. Quarter wave vertical tower b. Yagi c. Collinear d. Rhombic 73. The scientist who profounded the theory of electro-magnetic radiation is: a. Thomas Edison c . J ames Maxwel l b. Guglielmo Marconi d. Heinrich Hertz 74. At the ends of the half-wave antenna, what values of current and voltage exist compared to the remainder of the antenna? a. minimum voltage and maximum current b. minimum voltage and minimum current c. equal voltage and minimum current d. maximum voltage and minimum current 75. Which of the following is an example of a traveling wave antenna? a. Yagi-Uda c. Discone b. Log-periodic d. Rhombic 76. The amplitude of a sine wave which is modulated by a musical program will: a. be complex and contain fundamental and harmonic frequencies b. contain harmonic frequencies c. be complex d. contain fundamental frequencies 77. Radiation resistance is the ratio of ____. a. radiated power to the antenna center current.
b. radiated power to the square of the antenna center current c. voltage to any point of the antenna d. square of voltage to the square of current at any point in the antenna 78. A ship-to-ship communication system is plagued by fading. The best solution seems to be the use of ____. a. a more directional antenna b. frequency-diversity c. a broadcast antenna d. space diversity 79. Light loading as defined in the Philippines Electronics Code refer to the loading taken as the resultant stress due to wind and dead weight for ___ km per hour (kph) wind velocity a. 140 c. 160 b. 150 d. 120 80. What is the persistence of sound in an enclosed space, as a result of multiple reflections or scattering after the sound source has stopped? a. interference c. crosstalk b. echo d. reverberation 81. Calculate the highest and lowest frequencies for a subcarrier signal at 629 Khz with bandwidth of + or – 500 Khz. a. 112 and 1129 Khz c. 150 and 1120 Khz b. 1129 and 129 Khz d. 130 and 1150 Khz 82. Which resolution produces the quality fax? a. 300 lpi c. 96 lpi b. 400 lpi d. 200 lpi 83. A telephone line has a bandwidth of 3.2 Khz and signal-to-noise ration of 34 dB. A signal is transmitted down this line using a fourlevel code. What is the maximum theoretical data rate? a. 72.6 kbps c. 36.3 kbps b. 12.8 kbps d. 25.6 kbps 84. What is the horizontal scanning time for 2 pixels? a. 0. 25 mic ros ec. c . 15 mic ros ec. b. 0.125 microsec. d. 2.5 microsec. 85. What is known as Johnson’s noise? a. cosmic noise c. solar noise b. white noise d. static noise 86. The frequency band used by cellular telephones and mobile communication services is ____. a. UHF c. VHF b. EHF d. VLF 87. An octave is an interval of ration of two frequencies of what proportion? a. 3:1 c. 8:1 b. 1:1 d. 2:1 88. Find the distance in yards to an object if the display of a radar signal measures 4.4 microseconds. a. 164 c. 360.8 b. 1443.2 d. 721.6 89. A rectangular waveguide has a width of 0.6 inches. Calculate the waveguide cut-off frequency. a. 8 Ghz c. 10 Ghz b. 6 Ghz d. 12 Ghz 90. Audio signals are not propagated directly to space because ___. a. to do so will entail additional costs. b. the signal will be highly attenuated c. the will require antennas that are too long d. the signal that will be propagated will be too weak
91. A filter-type SSB generator uses an ideal bandpass filter with a center frequency of 5.0 Mhz and a bandwidth of 2.7 Khz. What frequency should be used for the carrier oscillator if the generator is to produce a USB signal with a baseband frequency response having a lower limit of 280 Hz. a. 4990.37 Khz. C. 5001.35 Khz b. 4996.65 kHz d. 5001.63 Khz 92. A 500-candle power that is located 12 feet from a surface provides how many lux? a. 3.648 c. 500 b. 0.3048 d. 37.57 93. By definition, speech power is equal tot v.u. reading minus_____. a. 1.8 dB c. 1.4 dB b. 4 dB c. 3 dB 94. The range of speech power is_______. a. 1-10 W c. 100-1000 mW b. 10-100 mW d. 10-1000 uW 95. The aspect ration of the 6 Mhz NTSC television standard is ____. a. 1.63 c. 0.75 b. 1.66 d. 1.33 96. A portable radio transmitter has to operate at temperature from -5 degrees C to 35 degrees C. If its signal is derived from a crystal oscillator with temperature coefficient of -1 ppm per degree C, and it transmits at exactly 145 Mhz at 20 degrees C, find the transmitting frequency at 35 degrees C. a. 144.9942 Mhx c. 145.0029 Mhz b. 144. 9956 Mhz d. 145. 00435 Mhz 97. A transistor has a power dissipation rating of 30 W. Assuming that the transistors is the only element that dissipates power in the circuit, calculate the power an amplifier, using this transistor, could deliver to the load if it operates as class-A with an efficiency of 30 percent. a. 35.7 W c. 22.5 W b. 7.5 W d. 12.86 W 98. What is the reliable measurement for comparing amplifier noise characteristics? a. signal-to-noise ration b. thermal agitation c. noise factor d. noise margin 99. Philippines belongs to what ITU region? a. 1 c. 2 b. 3 d. 4 100. In CMTS, the most important database in a GSM network is ________. a. VLR b. BSC-D
c. AUC d. HLR
