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ELECTRONICS SYSTEM & TECHNOLOGIES**Biomedical Technology**
1. A mammography service examined 327 patients during the third calendar quarter of 1996. 719 films were exposed during this period, eight of which were repeats. What is the repeat rate?a. 45.5% b. code 2.45% c. 1.1% d. 54.52%ANS. 1.1%
2. A type of luminescence where the visible light is emitted only during the stimulation of the phosphor.a. fluorescence b. phosphorescence c. after glow d. any of the aboveANS. Fluorescence
3. If a heart measures 12.5 cm from side to side at its widest point, and its image on chest radiograph measures 14.7 cm, what is the magnification factor?a. 0.85 b. 1.18 c. 0.15 d. 2.2ANS. 1.18
MF= (image size)/(object size)MF= (14.7 cm)/(12.5 cm)MF= 1.18
4. Radiation doses in the range of approximately200 to 1000 rad produce thea. Gastrointestinal (GI) syndromeb. Central Nervous System (CNS) syndromec. Hematologic syndromed. Prodomal syndromeANS. Hematologic syndrome
5. Ratio of incident to transmitted radiation through a grid ratio of patient dose with and without grida. Bucky factor b. Damadian factor c. Grid ratio d. Roentgen equivalentANS. Bucky factor
6. A radiographic single-phase unit installed in a private office has a maximum capacity of 100 milliseconds of 120kVp and 500mA. What is the power rating?a. 42 kW b. 60 kW c. 600W d. 24kWANS 42 Kw
Power rating=(0.7)x (mA x kVp)/1000Power rating=(0.7)x ((500)(120))/1000
Power rating=42 kW
7. Who completes the development of first computed tomographic (CT) scanner (EMI, Ltd.) in 1973?a. Mistretta b. Forssmann c. Kuhl
d. HounsfieldANS. Hounsfield
8. It is the study of the response of an image receptor to x-raysa. sensitometry b. xeroradiography c. xeroradiometry d. spectrometryANS. Sensitometry
9. Ratio of radiographic contrast with a grid to that without a grida. grid ratio b. contrast improvement factor c. Collidge factor d. Bucky factorANS. contrast improvement factor
10. Analysis of persons irradiated therapeutically with superficial x-rays has shown that the skin erythema dose required to affect 50% of persons so irradiated is about a. 200 rad b. 400 rad c. 600 rad d. 800 radANS. 600 rad
11. ECG recording requires a bandwidth of 0.05 to ___Hza. 1000 b. 540 c. 100 d. 40ANS.100
12. Find the potential generated if blood flowing in a vessel with radius 0.9 cm cuts a magnetic field of 250 G. Assume a volume flow rate of 175 cubic cm per second.a. 206 uV b. 309 uV c. 903 uV d. 260 uVANS. 309 uV
E= QB/50πaE= ((175 cc.s)(250 G))/(50π(0.9cm))E= 309 uV
13. Period during which heart contracts.a. Diastole b. Systole c. block mode d. SynapseANS. Systole
14. Apparatus for measuring blood pressurea. defibrillator b. electrocardiogram c. plethysmograph d. sphygmomanometerANS d. sphygmomanometer
15. Given the energy level of 6.624x10^-18 J imparted to an electron stream by an X-ray device, calculate the frequency in MHz.a. 10^6 MHz b. 45.29 MHz c. 10^10 MHz d. 300 MHzANS. 10^10 MHz
f= E/hf= (6.624x〖10〗^(-18) J)/(6.624x〖10〗^(-34) J-s)f= 10^10 MHz
16. It was first noted by Heinrich Hertz in 1887 and won Albert Einstein the Nobel Prize in 1905. It refers to the emission of electrons from a clean metallic surface (phototube) when electromagnetic radiation (light waves or X-rays) falls onto that surface.a. Photoelectric effect b. Compton effect c. Bremsstrahlung d. Mie effectANS. Photoelectric effect
17. Unit of radiation exposure or amount of X-ray radiation that will produce 2.08x10^9 ion pairs per cubic centimetre of air at standard temperature and pressure (STP).a. Curie b. Roentgen c. Radiation absorbed dose (rad) d. GrayANS. Roentgen
18. An optical electronic device that measures the color concentration of a substance in solution. a. colorimeter b. flame photometer c. spectrophotometer d. chromatographANS.colorimeter
19. Recording of heart soundsa. ultracardiography b. cardioacoustics c. electrocardiogram d. phonocardiographyANS. Phonocardiography
20. Recorder for measuring galvanic skin resistancea. electrodermograph b. electromyograph c. electrocorporealograph d. electrogalvanographANS.electrodermograph
**Digital and Data Communications**
1. It consists of 36 unique codes representing the 10 digits and 26 uppercase lettersa. Discrete code b. code 39 c. continuous code d. 20 codeANS.code 39
2. The first fixed- length character code developed for machines rather than for peoplea. ASCII Code b. Gray Code c. EBCDIC code d. Baudot CodeANS.Baudot Code
3. The early pioneer in the development of error-detection and correction procedures: a. Richard W. Hamming b. William R. Hamming c.
Emile Baudot d. Samuel BaudotANS. Richard W. Hamming
4. The most reliable convolutional coding scheme for error detectiona. checksum b. LRC c. CRC d. VRCANS.CRC
5. For the given parameters, determine the energy per bit-to noise power density ratio
C = 10e-12 W fb = 60 kbpsN = 1.2 x 10e-14`W B = 120 kHz
a. 16.2 dB b. 14.2 dB c. 20.2 dB d. 22.2 dBANS.22.2 dB
;
6. A signal at the input to a mu-law compressor is positive with its voltage one-half the maximum value. What proportion of the maximum output voltage is produced?a. 0.786Vmax b. 0.876Vmax c. 0.867Vmax d. 0.678VmaxANS.0.876Vmax
7. Inaccuracies caused by the representation of a continuously varying quantity as one of a number of discrete values.a. alias signal b. slope overload c. distortion d. quantizing errorsANS.quantizing errors
8. Circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced: a. vocoder b. codec c. sample-and-hold circuit d. ADCANS.vocoder
9. A coding scheme that records the change in signal level since the precious samplea. unipolar code b. PPM c. PCM d. delta modulationANS.delta modulation
10. Distortion created by using too low a sampling rate when coding an analog signal for digital transmissiona. aliasing b. foldover distortion c. either a or b d. neither a nor bANS.either a or b
11. A network with bandwidth of 10 Mbps can pass only an average of 12000 frames per minute with each frame carrying an average of 10000 bits. What is the throughput of this network?a. 1 Mbps b. 2 Mbps c. 3 Mbps d. 4 MbpsANS.2 Mbps
Throughput= (12 000 x 10 000)/60 = 2 Mbps 12. A telephone subscriber line must have an SNRdB
above 40. What is the minimum number of bits?a. 3.56 b. 5.63 c. 6.35 d. 3.65ANS6.35
SNRdB = 6.02nb + 1.76 = 40 n = 6.35
13. The thick coaxial cable implementation of standard Etherneta. 1000 Base-T b. 10 Base-T c. 10 Base 2 d. 10 Base 5ANS.10 Base 5
14. A bit pattern or a character added to the beginning and the end of a frame to separate the framesa. Flag b. Firewall c. Frameguard d. FootprintANS.Flag
15. An IPv4 has an address space of how many?a. 4294967296 b. 6927694924 c. 2449692769 d. 9672969442ANS. 4294967296
232 = 4294967296
16. What is the bit rate of STS – 1? a. 51.84 Mbps b. 64 kbps c. 100 Mbps d. 2.4 GHzANS.51.84 Mbps
17. A block coding technique in which four bits are encoded into a five bit codea. Baudot b. 2B1Q Encoding c. 4B/5B Encoding d. 4A/5A EncodingANS.4B/5B Encoding
18. A national standards organization that defines standards in the United Statesa. ANSI b. FCC c. ITU d. CCITTANS.ANSI
19. In asynchronous transmission, one or more bits to indicate the end of transmissiona. trailer b. flag c. escape byte d. stop bitANS.stop bit
20. What is the overhead (number of extra bits) in the DS-3 service? a. 1.368 Mbps b. 1.480 Mbps c. 2.048 Mbps d. 6.024 MbpsANS.1.368 Mbps
**Electronics/Communications**
1. The minimum sampling rate according to Nyquist Theorema. equal to the lowest frequency of a signalb. equal to the highest frequency of a signalc. twice the bandwidth of a signald. twice the highest frequency of a signalANS.twice the highest frequency of a signal
2. It is used in wireless applications in which stations must be able to share the medium without
interception by an eavesdropper and without being subject to jamming from a malicious intrudera. modulation b. Multiple accessc. multiple access d. Spread spectrumANS.spread spectrum
3. An error detection method which uses one’s complement arithmetica. Checksumb. CRCc. Simple-parity checkd. Two-dimensional parity checkANS.Checksum
4. It is a connecting device between two internetworks that use different modelsa. Bridgeb. Gatewayc. Repeaterd. router ANS.gateway
5. It is an undesired shift or width change in digital bits of data due to circuitry action which causes bits to arrive at different timesa. alias b. impulsec. jitter d. parityANS.jitter
6. In PCM system, it is the ratio of the maximum input voltage level to the smallest voltage level that can be quantized a. Dynamic rangeb. Figure of meritc. Quality factord. Noise figureANS.Dynamic range
7. A multiplexer combines four 100-kbps channels using a time slot of 2 bits, determine the frame duration.a. 20sb. 50sc. 100sd. 400sANS.20s
8. Determine the Hamming distance for the codewords ( 10101, 11001)a. oneb. twoc. threed. five
ANS. Two10101 XOR 11001 = 01100 ( presence of two 1)
9. An address space is the total number of addresses used by the protocol, such as IPv4 and IPv6. What is the address space of IPv6?a. 232b. 264c. 296d. 2128ANS.2128
10. It is a standard designed by ITU to allow telephones in the public telephone network to talk to computers/terminals connected to the internet
a. H. 111b. H.123c. H.321d. H. 323ANS.323
11. A computer monitor has a resolution of 1200 by 1000 pixels. If each pixel uses 1024 colors, how many bits are needed to send the complete contents of a screen?a. 12 Gigabitsb. 1. 2 Gigabitsc. 120 Megabitsd. 12 MegabitsANS.12 Megabits
1,200 times 1000 pixels x 10 bits = 12 Mb1024 colors requires 10 bits , 210 = 1024
**Laws and Ethics, Analog and Digital Electronics, Microelectronics, Power Line Communications**
1. The sensitivity of a radio receiver is given in terms of dBm. If the receiver is receiving 200 mW, what is the corresponding dBm of this signal?a. 46dBm b. -46 dBm c. 23 dBm d. -23 dBmANS.23 dBm dBm for 200 mW = 10 log (200mW/1mW) = 23 dBm
2. An antenna with a noise temperature of 75 Kelvin is connected to a receiver input with a noise temperature of 300 K. Given the reference temperature T0 = 290 K, find the noise figure of the system. a. 0.97 dB b. 3.6 dB c. 6.02 dB d. 7.2 dB
ANS. 3.6 dB The total noise temperature of the antenna and receiver is NTtot = 75+ 300 = 375.The noise temperature is given by: where: NT – noise temp, NR = Noise ratioRearranging the above to find NR gives: NR = (375/290) +1 = 2.29The Noise figure is the decibel equivalent of the noise ratio, such that: NF = 10 log NR = 3.6 dB
3. The modulation index of an AM radio station is 0.75. If the carrier power is 500W, what is the total transmitted power?a. 391 W b. 438 W c. 641 W d. 688 W ANS.641 W
4. An FM transmitter system is using a 1MHz crystal oscillator to generate a very stable 108MHz final carrier frequency. The output of the crystal oscillator is fed to a x36 multiplier circuit then mixed with a 34.5 MHz signal. The sum output of the mixer is filtered out, while the difference is fed to another multiplier in order to generate the final carrier frequency. What is the multiplier value?a. 108 b. 3 c. 1.5 d. 72ANS. 72
Basic Block Diagram of the FM carrier generator:1 MHz carrier > x 36 > Mixer > Multiplier > 108MHz carrier
First Multiplier output: 1MHz x 36 = 36 MHzMixer output: 36MHz + 34.5 MHz = 70.5MHz (filtered output) 36MHz – 34.5 MHz = 1.5 MHz (difference fed to the next multiplier)Multiplier stage: Output = 108MHz Output = 1.5MHz x n N = 108/1.5 = 72
**Electronic Communications**
1. A/an _______ is a range of frequency in which the upper frequency is double the lower frequency.
a. bandwidth b. frequency doubler c. octave d. harmonics
ANS.octave
2. Determine the worst-case output S/N for a narrowband FM receiver with deviation maximum of 10 kHz and a maximum intelligence frequency of 3 kHz. The S/N input is 3:1.a. 10 b. 12 c. 14 d. 16ANS. 10
3. A small variable capacitance in parallel with each section of ganged capacitor is called _______.a. trimmer b. converter c. padder d. autodyneANS. trimmer
**EST**
1. How many wavelengths long are required for a pair of conductors to be considered as a transmission line?a. ½ λ b. ¼ λ c. 1/10λ d. 5/8 λANS.1/10λ
2. Determine the time taken for a signal to travel down a 10 m transmission line, if its velocity factor is 0.7.a. 23.33 ns b. 14.52ns c. 76.8 μs d. 47.6 nsANS. 47.6 ns
T= L/ (Vf x Vc)T= 10 m/ (0.7)(3x108 m/s)T= 47.6 ns
3. The maximum voltage standing wave of an RG-11/U foam coaxial cable is 52 V and its minimum voltage is 17 V. How many percent of the incident power is the reflected power?a. 51% b. 26% c. 3% d. 97%ANS.26% Г 2 = Pr/Pi
Г = SWR-1 ; SWR = Vmax/ Vmin = 52/17 = 3.05 SWR+1
Г = 3.05 – 1 = 0.51 3.05 +1 Thus : Г 2 = (0.51)2 = 0.26 The reflected power is 26 % of the incident power
:4. At exactly one-quarter wavelength, the short-circuited
transmission line behaves as a(an) ___________ circuit.
a. inductive b. capacitive c. parallel-resonant d. series-resonant
ANS.parallel-resonant
5. Determine the phase-shift represented by a 75 ns delay of a 4 MHz signal to a 75-ft cable with a dielectric constant of 2.3.a. 108 degrees b. 4.8 degrees c. 52 degrees d. 250 degreesANS.108 degrees
Θ = 360 td / T T =1/f = 1 / 4MHz = 250 nsΘ = 360 (75) / 250 = 108 degrees
6. Which of the following is a flat conductor separated by
an insulating dielectric from a large ground plane that is usually one-quarter or one-half wavelength long?a. stripline b. microstrip c. twin-lead wire d. shielded-pairANS. microstrip
7. One complete revolution around a Smith Chart represents _________ wavelengths.a. ½ λ b. ¼ λ c. 1 λ d. 2 λANS.½ λ
8. A mismatched transmission line is also referred to as a ___________ line.a. lossy b. lossless c. non-resonant d. resonantANS.resonant
. 9. It is the ratio of the speed of propagation on a line to
that of light in free-space.a. velocity factor b. refractive index c. dielectric constant d. standing-wave ratioANS.velocity factor
10. Which of the following is the most widely used UTP cable that can carry baseband data at rates up to 100 Mbps at a range up to 100m?a. CAT 4 b. CAT 5 c. CAT 5e d. CAT 6ANS.CAT 5
11. The modulated peak value of a signal is 125V and the unmodulated carrier value is 85V. What is the modulation index?a.0.47 b. 1.47 c. 0.68 d. 0.32ANS.0.47
m = Em/ Ec
Emax = Ec + Em ; Em = Emax – Ec = 125 – 85 = 40 Vm = 40V/ 85V = 0.47
12. The total transmitted power of an AM broadcast transmitter with a carrier power of 50kW when modulated 80 percent is:a. 62.5kW b. 66W c. 66kW d. 40kWANS.66kW
Pt = Pc ( 1 + m2/2)Pt = 50,000 ( 1 + 0.82 /2)Pt = 66,000 WPt = 66kW
13. One of the advantages of DSB is the savings of great deal of power. Which of the following is the reason why it is not widely used?a. the signal occupies a narrow bandwidth b. the signal has a low S/N c. the signal is weak at high frequencies d. the signal is difficult to demodulateANS.The signal is difficult to demodulate
14. If the input in a transmitter is collector-modulated, the system is called a _______________________.
a. low –level modulator b. high-level modulator c. differential- amplifier modulator d. lattice modulatorANS.high-level modulator
15. input to an FM receiver has a S/N of 2.8. What is the frequency deviation caused by the noise if the modulating frequency is 1.5KHz and the permitted deviation is 4KHz?a. 1,460.8 Hz b. 547.8 Hz c. 2.67 Hz d. 4,107.3 HzANS.547.8 Hz = fm = sin -1 N/S = sin -1 1/2.8 = 0.3652 = (0.3652)(1.5KHz) = 547.8 Hz
16. What circuit is used to return the frequency response of a signal to its normal, “flat” level?a. pre-emphasis b. de-emphasis c. carrier-recovery d. frequency-multiplierANS. de-emphasis
17. It is the most common means of overcoming the problems of quantizing error and noise.
a. multiplexing b. companding c. amplifying d. anti-aliasingANS. companding
18. ________________ means that the characteristics and performance of an antenna are the same whether the antenna is radiating or intercepting an electromagnetic signal.
a. antenna reciprocity b. antenna polarization c. antenna grounding d. tower swayANS. antenna reciprocity
19. Which of the following methods is used to lower the resonant frequency of a shortened vertical antenna?a. loading coil b. top hat loading c. drooping radials d. groundingANS.top hat loading
20. Calculate the gain (relative to an isotropic) of a parabolic antenna that has a diameter of 3 m, an efficiency of 60% and operates at a frequency of 4 GHz. a. 39.8 dBi b. 41.94 dBi c. 37.66dBi d. 79.53 dBiANS. 39.8 dBiG = 2 D2/ 2 = 3x108/ 4MHz = 0.075 mG = 0.62(3)2 0.0752G= 9474.8G = 10 log 9474.8G = 39.8 dBi
21. It is a phenomenon caused by any support insulators used at the ends of the wire antenna.a. skin effect b. end effect c. faraday effect d. miller effectANS.end effect
**Electronics System & Technologies**
1. A dipole antenna has a radiation resistance of 67 ohms and a loss resistance of 5 ohms, measured at the feedpoint. Calculate the efficiency.a. 90% b. 91% c. 92% d. 93%ANS. 93%
Efficiency = Rr / Rt = 67 / (67 + 5) = 93%
2. Two antennas have gains of 5.3 dBi and 4.5 dBd, respectively. Which has a greater gain?a. The first antenna has a higher gain.
b. The second antenna has a higher gain.c. Both antennas have the same gain d. Cannot be determinedANS. The second antenna has a higher gain.\
3. A half-wave dipole is sometimes called:a. Marconi antenna b. Yagi antennac. Hertz antenna d. none of the choicesANS. Hertz antenna
4. An antenna's beamwidth is measureda. from +90° to –90° b. between half-power pointsc. from front to back d. between the minor side-lobesANS. between half-power points
5. "Ground Effects" refers to the effects on an antenna's radiation pattern caused bya. radio signals reflecting off the ground b. buildings and other structures on the groundc. fading d. faulty connection of the feed cable groundANS. radio signals reflecting off the ground
6. An antenna can be matched to a feed line usinga. a shorted stub b. an LC networkc. a loading coil d. all of the choicesANS. all of the choices
7. As the length of a "long-wire" antenna is increaseda. the number of lobes increases b. efficiency decreasesc. the number of nodes decreases d. none of the aboveANS. . the number of lobes increases
8. LPDA stands fora. Low-Power Dipole Array b. Log-Periodic Dipole Arrayc. Low-Power Directed Array d. Log Power Dipole ArrayANS. Log-Periodic Dipole Array
9. Field strength at a distance from an antenna is measured witha. a slotted line b. an EIRP meterc. a dipole
d. a field-strength meterANS. a field-strength meter
10. A receiving antenna with a built-in preamplifiera. active antenna b. passive antennac. coil d. LC antennaANS. active antenna
11. Which of the following is not a reason why most half-wave antennas are mounted horizontally at low frequencies?a. physical construction is easier b. more cost-effectivec. mounting is easier d. support is easierANS. more cost-effective
12. The shape of the electromagnetic energy radiated from or received by an antenna is called thea. signal shape b. electromagnetic patternc. radiation pattern d. antenna patternANS. radiation pattern
13. Antennas that transmit an equal amount of energy in the horizontal direction are calleda. bi-directional b. unidirectionalc. omnidirectional d. unilateralANS. omnidirectional
14. The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to asa. focal factor b. permittivityc. directivity d. horizontal rangeANS. directivity
15. A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form aa. parasitic array b. bi-directional arrayc. half-wave dipole d. counterpoiseANS. parasitic array
16. An antenna made up of a driven element and one or more parasitic elements is generally referred to as aa. Hertz antenna b. Marconi antennac. collinear antenna d. Yagi antennaANS. Yagi antenna
17. Which antennas usually consist of two or more half-wave dipoles mounted end to end?a. Hertz b. Marconic. collinear d. YagiANS. collinear
18. A stacked collinear antenna consisting of half-wave dipoles spaced from one another by one-half wavelengths is thea. broadside array b. end-fire arrayc. wide-bandwidth array d. parasitic arrayANS. broadside array
19. When the characteristic impedance of the transmission line matches the output impedance of the transmitter and the impedance of the antenna itself,a. the SWR will be 10:1 b. the SWR will be 1:10c. minimum power transfer will take place d. maximum power transfer will take placeANS. maximum power transfer will take place
20. A one-quarter wavelength of coaxial or balanced transmission line of a specific impedance connected between a load and a source in order to match impedances isa. a balun b. an autotransformerc. a Q section d. dummy loadANS. a Q section
21. By how much should two antennas be separated for space diversity in the 11 GHz band? a. 5.5 m b. 7.5m c. 9.5m d. 11.5mANS.5.5 m
22. What is the phase velocity of a rectangular waveguide with a wall separation of 3 cm and a desired frequency of operation of 6 GHz?
a. 3.45 x 108 m/s b. 4.35 x 108 m/s c. 4.53 x 108 m/s d. 5.43 x 108 m/sANS.5.43 x 108 m/s
23. A transmitter and a receiver is 45 km apart. Suppose that there is an obstacle midway between the transmitter and receiver. By how much must the path between the towers clear the obstacle in order to avoid diffraction at a frequency of 11 GHz?a. 17.52 m b. 10.51 m c. 8.76 m d. 7.52 mANS. 10.51 m
24. How far from the transmitter could a signal be received if the transmitting and receiving antennas where 40 m and 20 m, respectively, above level terrain?a. 44.5 km b. 45.4 km c. 54.4 km d. None of the choicesANS.44.5 km
25. A signal propagated in a waveguide has a full wave of electric intensity change between two further walls, and no component of the electric field in the direction of propagation. The mode is a. TE11 b. TE10 c. TM22 d. TE20ANS. TE20
26. An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power is dissipated in the load?a. 1 W b. 851 mW c. 750 mW d. 638 mWANS.638 mW
27. An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power returns to the source? a. 250 mW b. 350 µW c. 535 µW d. 690 µWANS. 5.43 x 108 m/s
28. It is a microwave device that allows RF energy to pass through in one direction with very little loss, but absorbs RF power in the opposite direction.a. multiplexer b. circulator c. isolator d. wave trapANS.isolator
29. A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called a. radome b. shield c. shroud d. bass drumANS.shroud
30. The wavelength of a wave in a waveguide _________. a. is greater than in free space b. depends only on the waveguide dimensions and the free space wavelengthc. is inversely proportional to the phase velocity d. is directly proportional to the group velocityANSWER:is greater than in free space
31. Geostationary satellites are located at ____ with respect to the equator.a. 00 longitude b. 00 latitude c. 450 longitude d. 900 latitudeANS. 00 latitude
32. The quality of a space-link is measured in terms of the ______ ratio. a. S/N b. G/T c. C/N d. EIRPANS. G/T
33. Why does the downlink frequency appear to vary by several kHz during a low earth orbit satellite pass?a. The distance between the satellite and ground station is changing, causing the Kepler effectb. The distance between the satellite and ground station is changing, causing the Bernoulli effectc. The distance between the satellite and ground station is changing, causing the Boyle’s Law effectd. The distance between the satellite and ground station is changing, causing the Doppler effectANS. The distance between the satellite and ground station is changing, causing the Doppler effect
1. The most ambitious LEO constellation to date is ______.a. Iridiumb. NAVSTARc. Teledesicd. GlobalstarANS.Teledesic
2. A satellite-dish owner has a 3 meter dish designed for C-band (4 GHz) operation. The owner wants to use the same dish with a new feedhorn, for Ku-band (12 GHz) satellites. What effect will the change in
frequency have on the gain and beamwidth of the antenna?a. Gain increases by 9.54 dB, beamwidth decreases to 1/3 of its former value.b. Gain decreases by 9.54 dB, beamwidth decreases to 1/3 of its former value.c. Gain increases by 9.54 dB, beamwidth increases to thrice of its former value.d. Gain decreases by 9.54 dB, beamwidth increases to thrice of its former value.ANS. Gain increases by 9.54 dB, beamwidth decreases to 1/3 of its former value.
3. The moon orbits the earth with a period of approximately 28 days. How far away is it? Assume circular orbit.a. 380 Mm b. 382 Mm c. 384 Mm d. 386 MmANS.384 Mm
4. What is the length of the path to a geostationary satellite from an Earth station if the angle of elevation is 300? a. 6400 km b. 39000 km c. 42400 km d. 46000 kmANS.39000 km
5. What is the nominal uplink frequency for the Ku band?a. 6 GHzb. 4 GHzc. 14 GHzd. 12 GHzANS. 14 GHz
6. To cover all inhabited regions of the earth, the number of polar-orbit satellites required isa. 1 b. 2 c. 3 d. 5ANS.1
**Printing** 1. The highest frequency that can be used for skywave
propagation between two specific points on earth’s surface.a. Critical Frequency b. MUF c. Cut-off frequency d. mid frequencyANS. Critical Frequency
2. Variation in signal loss caused by natural weather disturbances.a. attenuation b. fading c. spreading loss d. weather lossANS. fading
3. Determine the radio horizon for a transmit antenna that is 200 m high and a receiving antenna that is 100 m higha. 99.5km b. 96.5 km c. 95.87 km d. 97.5 kmANS. 99.
4. The height above the earth’s surface from which a refracted wave appears to have been reflected…a. actual height b. virtual height c. average height d. mean heightANS. virtual height
5. The highest frequency that can be used for skywave propagation between two specific points on earth’s surface.a. Critical Frequency b. MUF c. Cut-off frequency d. center frequency ANS. Critical Frequency
6. Electromagnetic waves that are directed above the horizon level.a. ground waves b. surface waves c. sky waves d. space wavesANS. sky waves
**Communications / Broadcast**1. An acoustical phenomenon wherein the sound
continues to persist after the cause of sound has stopped resulting in repeated reflections is called…a. echob. reverberationc. reflectiond. diffractionANS.reverberation
2. A group of filters has 1/3 octave of spacing. If the initial frequency is 25 Hz, what is the next frequency available for the filter? a. 50 Hzb. 12.5 Hzc. 75 Hzd. 31.5 HzANS. 31.5 Hzf2 = 2x f1 where x = 1/3, fraction of an octavef2 = 21/3 x 25 = 31.5 Hz
3. + 26 dBu is how many volts? a. 7.75 Vb. 15.5 Vc. 31 Vd. 62 VANS. 15.5 V
V (dBu) = 20 log [ voltage in Volts / 0.775 Volts ]26 = 20 log [ voltage in Volts / 0.775 V ]26 / 20 = log [ voltage in Volts / 0.775 V ] = 1.3Voltage = log-1 (1.3) x 0.775 VVoltage = 15.5 V
4. A type of microphone that uses the principle of a capacitor as a means of transduction. It uses a polarizing voltage of between 9 and 48 V of DC supply applied to its diaphragm by an external power supply.a. Dynamic b.Condenserc. Ribbon d.CarbonANS. Condenser
5. Determine the sound power in Watts produced by the bank’s alarm if a by-stander heard the alarm at a sound pressure level of 100 dB-SPL. The by-stander is 100 ft away from the bank. a. 56.85 Wb. 55.68 Wc. 58.56 Wd. 58.65 WANS. 58.65 WPWL = SPL + 20 log D(m) + 8PWL = 100 + 20 log (100/3.28) + 8 = 137.68 dB-PWL137.68 = 10 log W + 120W = log-1 [(137.68 – 120)/10]W = 58.65 Watts
6. A loudspeaker produces an SPL of 85dB-SPL at 1 meter distance and input electrical power of 1 W. How loud is the SPL at distance of 20 meters if this speaker is driven to 10 W of electrical power?a. 82 dB-SPLb. 69 dB-SPLc. 65 dB-SPLd. 79 dB-SPLANS. 69 dB-SPLSPL@1m/1W = 85 dB-SPL (given)SPL@20m/1W = 85 - 20 log (20m/1m) = 59 dB-SPLSPL@20m/10W = 59 + 10 log (10W/1W) = 69 dB-SPL
7. A number from 0 to 1 representing the ability of a surface material to absorb sound energy is known asa. Sound absorptionc. Absorption Coefficientb. Reflection coefficientd. Room ConstantANS.Absorption Coefficient
8. The difference in dB between the loudest level of sound and the softest passage of sound is known as a. Headroom b. signal-to-noise ratioc. gain d.dynamic rangeANS. dynamic range
**Satellite Communications**1. The height above mean sea level of a satellite in a
geosynchronous orbit around Earth is:a. 35,786 miles b. 35,786 NM c. 35,786 feet d. 35,786 kmANS.35,786 km
2. The location of a satellite is generally specified in terms ofa. azimuth & elevation b. latitude & longitude c. true morth d. bearingANS.latitude & longitude
3. A point in the orbit of an object orbiting the earth that is located closest to Earth.a. perigee b. apogee c. apex d. subsatellite pointANS. perigee
4. Find the velocity of a satellite in a circular orbit 500 km above the earth’s surface.a. 76 km/s b. 76 m/s c. 7.6 km/s d. 7.6 km/s2ANS. 7.6 km/s
Formula :
Where : v = velocity in meters per second d = distance above earth’s surface in km
= 7.6 km/s
5. Find the orbital period of a satellite in a circular orbit 36,000 km above the earth’s surface if the earth’s radius is 6400 km.a. 1440 mins b. 24 days c. 3,600 sec d. 1440 secANS. 1440 mins
Formula :
Where : T = orbital period
C = circumference v = orbital velocity
C = 2 r
= 2π ( 6400 + 36,000 ) = 266.4 x 106 m
or 1440 minutes
6. The outline of a communications satellite antenna pattern on the earth is known as:a. beam b. propagation pattern c. spot d. footprintANS. footprint
7. Calculate the length of the path to a geostationary satellite from an earth station where the angle of elevation is 30.(earth’s radius = 6400 km, height of satellite above earth is 36 X 103 km)a. 36,000 km b. 36,000 mi c. 39,000 km d. 39,000 mi.ANS.39,000 km
Formula :
8. A satellite access technique where each earth station
transmits a short burst of information during a specific time slot.a. FDMA b. DAMA c. TDMA d. SCADAANS. TDMA ( Time Division Multiple Access)
9. An earth station antenna look angle is determined by :a. azimuth & elevation b. longitude & latitude c. bearing d. true northANS. azimuth & elevation
10. An ITU radiocommunication standards for satellite services which provides information on the range of frequencies that can be used by fixed satellite service systems for emergency and disaster relief operations.a. ITU-R M1854 b. ITU-R S 009 c. ITU-R S.1001-2 d. ITU-R S.004ANS.ITU-R S.1001-2
**Communications / Broadcast Engineering and Acoustics**
1. As per Philippine standard, frequency allocation of AM Radio Broadcasting is from…a. 535 to 1605 kHzb. 526.5 to 1605 kHzc. 535 to 1705 kHzd. 526.5 to 1705 kHzANS. 526.5 to 1705 kHz
2. Part of broadcasting in a day that refers to that period of time between 1000 UTC to 2200 UTC. UTC stands for Universal Time Coordinates.a. daytime periodb. nighttime periodc. experimental periodd. primetime periodANS. nighttime period
3. An AM broadcast service area in which groundwave field of 1mV/m (60dBu) is not subject to objectionable interference or objectionable fading.a. primary service areab. secondary service areac. intermittent service aread. none among theseANS. primary service area
4. In antenna mast or tower construction, the required obstruction painting and/or lighting must be imposed on mast or tower more than … from the ground level.a. 100 ftb. 150 ftc. 200 ftd. 250 ftANS. 150 ft
5. Regarding the design of AM antenna, what should be the polarization of the radiator?a. horizontalb. verticalc. circulard. ellipticalANS. vertical
6. As per Phillipine standard, what is the minimum frequency separation in any service area for adjacent AM radio stations?a. 40 kHzb. 200 kHzc. 36 kHzd. 300 kHzANS. 36 kHz
7. What is the maximum power allowable for remote pick-up stations used as broadcast auxillary services for AM and FM broadcast stations? a. 10 Wb. 15 Wc. 35 Wd. 200 WANS. 35 W
8. What is the classification of an FM station having an ERP not exceeding 30kW?a. Class Ab. Class Bc. Class Cd. Class DANS. Class B
9. What is the modulation used for the stereophonic subcarrier of FM composite baseband signal?a. AM DSB FCb. AM DSB SCc. AM SSBd. AM VSBANS. AM DSB SC
10. What is the pilot subcarrier frequency used in FM stereophonic transmission?a. 15 kHzb. 19 kHzc. 30 kHzd. 38 kHzANS.19 kHz
11. The output power of an FM transmitter is 5 kW. If the power loss in transmission line is around 10 W and the antenna has a power gain of 6 dB, what is the ERP of the station in kW?a. 5 kWb. 30 kWc. 20 kWd. 19.96 kWANS. 19.96 kWGANT = 6 dB = 4ERP = (5000 – 10) x 4 = 4990 x 4 = 19,960 W or 19.96 kW
12. Frequency allocation of FM broadcast in the Philippines…a. 535 – 1605 kHzb. 88 – 108 MHzc. 50 – 15000 Hzd. 174 – 216 MHzANS. 88 – 108 MHz
13. What is the color TV system adopted by the Philippines?a. NTSCb. PALc. SECAMd. none among choicesANS.NTSC
14. Exact value of color subcarrier frequency (MHz) is …a. 3.579554b. 3.579455c. 3.580545d. 3.579545ANS. 3.579545
15. Determine the visual carrier frequency of TV channel 9a. 175.25 MHzb. 187.25 MHzc. 193.25 MHzd. 199.25 MHzANS.187.25 MHzfNLB = 174 + (N – 7)6, using Arithmetic Progressionf9LB = 174 + (9 – 7)6 = 174 + (2)6 = 174 + 12 = 186 MHz, low band frequency of channel 9fVC = 186 + 1.25 = 187.25 MHz, visual carrier frequency of channel 9
16. What is the maximum allowable ERPs for channels 7 – 13 in Metro Manila and Metro Cebu?a. 100 kWb. 316 kWc. 350 kWd. 1 MWANS. 1 MW
17. At NTSC standard, the number of lines per frame = ________ lines/framea. 485b. 525c. 625d. 585ANS. 525
18. At NTSC standard, line frequency = 15734.264 Hz. What is the equivalent line period?a. 66.556 usec b. 65.556 usecc. 63.556 usecd. 64.556 usecANS. 63.556 usecfH = 15734.264 Hz
H = 1 / fH = 1 / 15734.264H = 63.556 x 10-6 = 63.556 usec
19. Nominal RF bandwidth of NTSC TV channel…a. 4.2 MHzb. 4.5 MHzc. 6 MHzd. 5.35 MHz
ANS. 6 MHz
20. A land mobile station used for the transmission of TV program materials and related communications from the scenes of events occuring at remote points from TV broadcast station studios to TV broadcast station.a. TV Pick-up station b. TV STL stationc. TV Inter-city Relay stationd. TV Satellite link stationANS.TV Pick-up station
21. For a total capacity of 36 Mbps and 64-QAM of digital modulation, what is the ideal RF bandwidth? a. 4 MHzb. 5 MHzc. 6 MHzd. 7 MHzANS. 6 MHzFor a 64-QAM, the total number of symbol combinations is 64 symbols and the number of bits to produce this is…n = log2 64 = 6 bits per symbolTherefore the ideal RF bandwidth is…BW = fB / n = 36 Mbps / 6 bitsBW = 6 MHz
22. What is the mode of radio wave propagation that utilized ionosphere as a medium of transmission and / or reception of radio signals?a. ground waveb. sky wavec. space waved. all of theseANS.sky wave
23. What is the wavelength of a radio signal travelling at a frequency of 220 MHz in a coaxial line having Teflon foam as its dielectric, εr = 2?a. 1.0 mb. 0.85 mc. 0.96 md. 1.36 mANS. 0.96 m
c = 3 x 108 m/sec = 300 x 106 m/secvelocity factor vf = 1 / sqrt (εr) = 1 / sqrt (2) = 0.707 = vP / cTherefore the velocity of the radio signal in the coaxial line is …vP = 0.707c = 0.707 (300 x 106) = 212,132,034.36 m/sec (or 212 x 106 m/sec approx.)so that the wavelength of the signal is …λ = vP / f = 212 x 106 / 220 x 106 = 0.963636… m or 0.96 m approx.
24. What is the angle of refraction in a Teflon (εr2 = 2) medium of a radio wave from air (εr1 = 1.0) if its angle of incidence is 45°?a. 24°b. 26°c. 28°d. 30°ANS. 30°
Using Snell’s Law…Sqrt (εr1) sin θi = Sqrt (εr2) sin θr Sqrt (1) sin 45° = Sqrt (2) sin θrθr = sin-1 [(Sqrt (1) sin 45°) / Sqrt (2)] = sin-1 (0.5) = 30°
25. An ionosphere layer also termed as “absorption layer” because it absorbs most of the frequencies above 100 kHz is known as the … layer.a. Db. Ec. F1d. F2ANS. D
26. As per ITU-R Recc. V.431-6 Tables 1 & 2 Wavelength Classifications, what is the classification of Super High Frequency?a. metricb. decimetricc. centimetricd. millimetricANS.centimetricSHF band: 3 GHz – 30 GHzλmax = 3 x 108 / 3 x 109 = 0.1 m = 100 cmλmin = 3 x 108 / 30 x 109 = 0.01 m = 1 cmSHF band wavelength classification is ranging from 1 cm to 100 cm. Therefore it is centimetric wave.
27. What is a diversity scheme that uses two (2) separate antennas and receivers for each single transmitter? a. frequency diversityb. space diversityc. angle diversityd. quadrature diversity
ANS.space diversity
28. What is a diversity scheme that uses two (2) different frequencies in a simplex path?a. frequency diversityb. space diversityc. angle diversityd. quadrature diversity
ANS. frequency diversity
29. What is the critical frequency of a layer if the maximum value of electron density is 2 x 106 per cm3?a. 11 MHzb. 12 MHzc. 13 MHzd. 14 MHzANS.13 MHz
Nmax = 2 x 106 per cm3 = 2 x 106 x 106 per m3 = 2 x 1012 per m3fc = 9 x sqrt (Nmax) = 9 x sqrt (2 x 1012)fc = 12.73 MHz or 13 MHz approx.
30. A radio communication link is to be established via the ionosphere. The maximum virtual height of the layer is 110 km. at the midpoint of the path and the critical frequency is 4 MHz. If the distance between the radio stations is 500 km, what is the suitable value for the optimum working frequency? Use flat terrain analysis.a. 8.2 MHzb. 8.3 MHzc. 8.4 MHzd. 8.5 MHzANS. 8.4 MHz
For flat terrain analysis, tan i = d/2hvi = tan-1 [d/2hv] = tan-1 [500/2(110)] = tan-1 [2.273] = 66.25° angle of incidenceMUF = fc x sec i = fc / cos i = 4 / cos 66.25° = 4 / 0.40275 = 9.932 MHz via Secant LawOWF = 0.85 x MUF = 0.85 (9.932) = 8.4422 MHz or 8.4 MHz approx.
31. The power density is inversely proportional to the square of the distance from the source. This law is known as…a. Faraday’s lawb. Snell’s lawc. Inverse Square lawd. Gauss lawANS.Inverse Square law
32. The lowest portion of the ionosphere that is useful for long-distance communication by amateurs; about 100 to 115 km above the earth is known as the… layer. This is often termed as the Kennely-Heavyside layer.a. Db. Ec. F1d. F2
ANS. E
33. A graph which shows the radiation in actual field strength of electromagnetic fields at all points which are at equal distance from the antenna is known as…a. Frequency Responseb. Radiation Patternc. Smith Chartd. FCC F(50,50) GraphANS, Radiation Pattern
34. The efficiency of an antenna is 82 %. Its radiation resistance is 30 Ω. What is the value of its loss resistance?a. 75 Ωb. 15 Ωc. 12 Ωd. 6.58 ΩANS.6.58 Ωη = Rd/(Rd + Rloss)0.82 = 30/(30 + Rloss)0.82 (30 + Rloss) = 30 = 24.6 + 0.82 RlossRloss = (30 – 24.6) / 0.82 = 6.5854 Ω or 6.58 Ω approx.
35. A phenomenon on the surface of the sun with appearance and disappearance of dark irregularly shaped areas.a. SIDb. 11-year sunspotc. Sporadic E-layerd. Ionospheric stormsANS.11-year sunspot
36. What should be done to increase the transmission distance at frequencies higher than HF bands?a. increase antenna gainb. increase antenna heightc. increase transmitter powerd. increase receiver sensitivityANS. increase antenna height
37. Which of the following factors must be considered in the transmission of a surface wave to reduce attenuation?a. electrical properties of the terrainb. frequencyc. antenna polarizationd. all choicesANS.all choices
38. A radio station operates at 11 meter wavelength. What is the designated band of station’s frequency?a. MF b. HFc. VHFd. UHFANS.HFSOLUTION (IF PROBLEM SOLVING):c = 3 x 108 m/secλ = 11 m = c / ff = 3 x 108 / 11 = 27 MHz approx., which is within 3 – 30 MHz range designated as HF band
39. What is the total radio horizon distance between an 80 ft transmitting station and a 20 ft receiving station?a. 53.66 kmb. 53.66 mic. 18.97 kmd. 18.97 miANS. 18.97 miSOLUTION (IF PROBLEM SOLVING):dRH (TOT) = sqrt (2 x hT) + sqrt (2 x hR)dRH (TOT) = sqrt (2 x 80) + sqrt (2 x 20)dRH (TOT) = 18.97 mi
40. A power density of 1.57 x 10-4 W/m2 is measured 50 meters from a test antenna whose directive gain is 2.15 dB. How much power was fed into the test antenna?a. 1 W b. 2 Wc. 3 Wd. 4 WANS.3 WFrom Inverse Square Law, PD = PR/4πd2PR = PD x 4πd2 = 1.57 x 10-4 x 4π(50)2 = 4.93 W approx. is the radiated powerGANT = log-1 [2.15 dB/10] = 1.64PR = PFED x GANTPFED = PR / GANT = 4.93 / 1.64 = 3.007 W or 3 W approx.
**Wireline and wireless **
1. Identical telephone numbers in different parts of a country are distinguished by their ___.a. language digits b. area codes c. central office codes d. access digitsANS.area codes
2. Telephone traffic is measured ____
a. in erlangs c. with echo cancellers b. by the relative congestion d. in terms of the grade of serviceANS.in erlangs
3. In a cellular telephone system, each cell site contains a ____.a. touch tone processors c. repeater b. control computer d. direct link to a branch exchange ANS.repeater
4. When the signal from a mobile cellular unit drops below a certain level, what action occurs?a. the cell site switches antennas b. the call is terminated c. the unit is “handed off” to a closer celld. the MTSO increases power levelANS.the unit is “handed off” to a closer cell
5. In a cellular telephone system, group of cells is called ___. a. sector b. Cluster c. site d. cell segmentANS.cluster
6. In Celluar Telephone Systems, these are transmissions from base stations to mobile units (Downlink)a. forward links b. reverse linksc. TRX d. TRAANS.forward links
7. A CDMA mobile measures the signal strength from the base as -100 dBm. What should the mobile transmitter power be set to as a first approximation, considering - 76 dB at mobile power contol?a. 150 mW b. 200 mW c. 250 mW d. 300 mWANS.250 mW PT = -76 dB - PRWhere:PT = transmitted power in dBmPR = received power in dBm
PT = -76 dB - PR = -76 dB – (-100dBm) = 24 dBm = 250 mW
8. A telephone signal takes 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.a. 0.2 dB b. 0.4 dB c. 0.6 dB d. 0.8 dBANS. 0.8 dB VNL = 0.2t + 0.4 dBWhere:
VNL = minimum required via net loss in dBt = time delay in ms for propagation one way along lineVNL = 0.2t + 0.4 dB = 0.2 X 2 + 0.4 = 0.8 dB
9. The typical voltage across a telephone when on-hook is:
a. 48 volts DC c. 90 volts DC b. 48 volts, 20 hertz AC d. 90 volts, 20 hertz AC
ANS.48 volts DC
10. Central offices are connected by: a. local loops c. both a and bb. trunk lines d. none of the above ANS.trunk lines
11. In telephony, call blocking is:a. cannot occur in the public telephone network b. occurs on the local loop when there is an electrical power failurec. occurs only on long-distance cablesd. occurs when the central office capacity is exceeded ANS.occurs when the central office capacity is exceeded
12. The cable used for local loops in telephone system is mainly:a. twisted-pair copper wire c. coaxial cableb. shielded twisted-pair copper wire d. fiber-opticANS.twisted-pair copper wire
13. In DTMF, the four vertical frequencies are ____. a. 1209Hz, 1336Hz,1477Hz,1633Hz b. 697Hz,770Hz,852Hz,941Hzc. 679Hz,770Hz, 852Hz, 941Hzd. 1208Hz,1336Hz,1747Hz,1633HzANS. 697Hz,770Hz,852Hz,941Hz
14. In DTMF, the Horizontal frequencies area. 1209Hz, 1336Hz,1477Hz,1633Hz b. 697Hz,770Hz,852Hz,941Hzc. 679Hz,770Hz, 852Hz, 941Hzd. 1208Hz,1336Hz,1747Hz,1633HzANS.1209Hz, 1336Hz,1477Hz,1633Hz
15. In Celluar Telephone Systems, these are transmissions from mobile units to base stations (Uplink)a. forward links b. reverse linksc. TRX d. TRAANS.reverse links
16. In DTMF, the horizontal frequencies is also known asa. low group frequenciesb. high group frequenciesc. mid group frequenciesd. top group frequenciesANS.high group frequencies
17. In DTMF, the Vertical frequencies is also known asa. low group frequenciesb. high group frequenciesc. bottom group frequenciesd. top group frequenciesANS.low group frequencies
18. The bandwidth of voice-grade signals on a telephone system is restricted in order to:a. allow lines to be "conditioned" b. prevent "singing" c. allow signals to be multiplexedd. all of the aboveANS. allow signals to be multiplexed
19. This is the highest-ranking office in the DDD network in telephony in terms of the size of the geographical area served and the trunking options available.a. section center c. primary centerb. regional center d. all of the aboveANS.regional center
20. In Cellular Radio, AMPS stand for:a. American Mobile Phone System b. Analog Mobile Phone Service C. Advanced Mobile Phone Systemd. Advanced Mobile Phone ServiceANS.Advanced Mobile Phone Service
21. In Cellular Radio, BSC stands for:
a. Base Station Controller c. Basic Service Contractb. Base Signal Controller d. Basic Service CodeANS.Base Station Controller 22. In Cellular Radio, MSC stands for:a. Mobile Switching Center c. Maximum Signal Carrierb. Mobile Service Cellular d. Minimum Signal Carrier
ANS.Mobile Switching Center
23. In GSM, voice channels are called:a. traffic channels c. bearer channelsb. voice channels d. talking channelsANS.traffic channels
24. In Mobile Communications, GSM uses:a. frequency hopping c. CDMAb. direct-sequence modulation d. all of the aboveANS.frequency hopping
25. In Mobile Communications, IMSI stands for::
a. Integrated Mobile Subscriber Identificationb. International Mobile Subscriber Identificationc. Interim Mobile Subscriber Identificationd. Intermodulation System InterferenceANS.International Mobile Subscriber Identification
** Electronics and Communications**1. The most common light used in fiber-optic links is
a. Infrared b. Red c. Violet d. UltravioletANS.Infrared
2. In the telecommunications industry, the most commonly used fiber(s) area. 50 micron b. 62.5 micron c. 50 and 62.5 micron d. 125 micronANS. 50 and 62.5 micron
3. The abrupt change in refractive index from core to cladding of fiber-optic cable is called thea. Total internal reflection b. Numerical aperture c. Dispersion d. Step indexANS. Step index
4. A technique that is used to minimize the pulse dispersion effect is toa. Use a higher frequency light sourceb. Use plastic claddingc. Minimize the core diameterd. All the aboveANS. Minimize the core diameter
5. Which is not an important characteristic of a light detector?a. Responsitivity b. Dark current c. Power consumption d. Response speed ANS. Power consumption
6. The dispersion of light in fiber-optic cable caused by a portion of the light energy traveling in the cladding is calleda. Modal dispersionb. Material dispersionc. Waveguide dispersiond. Cable dispersionANS. Waveguide dispersion
7. Recent laser developments for fiber-optic communication includea. Distributed feedback (DFB)b. Vertical cavity surface emitting (VCSEL)c. Heterojunctiond. Distributed feedback (DFB) and vertical cavity surface emitting (VCSEL)ANS.Distributed feedback (DFB) and vertical cavity surface emitting (VCSEL)
8. Which of the following considerations is important when deciding between using a diode laser or an LED?a. Response timeb. Power levelsc. Temperature sensitivityd. Failure characteristicsANS.Response time
9. In 1815, the correct explanation of diffraction was given bya. Maxwell b. Rayleigh c. Fresnel d. Snell ANS.Fresnel
10. It is the central part of the optical communication systema. Light Source b. Optical Fiber c. Photodetector d. none of the aboveANS.Optical Fiber
11. The light energy that is always emitted or absorbed in discrete unitsa. Light Ray b. Boson c. Quanta d. LightANS.Quanta
12. Which of the following Ethernet fiber optic standard uses synchronous, Centralized Clock?a. 10 Base-FL (Link) b. 10 Base-FB (Backbone) c. 10 Base-FP (passive) d. Both a & cANS.10 Base-FB (Backbone)
13. It is a mixed, multiple-service standard to allow the transmission of voice and video over an FDDJ network.
a. FDDI - II b. FDDI - I c. Hi PPI d. Escon ANS. FDDI - II
14. It is a layer of plastic that surrounds a fiber or group of fibersa. Buffer Tube b. Bulkhead c. Cladding d. Jacket ANS. Buffer Tube
** Signal Processing and Control Systems **1. The angular separation between the two half-power
points on the power density radiation pattern.a.Bandwidth b Beamwidth c. Footprint d. Azimuth ANS.Beamwidth
2. Refers to the direction in space of electric vector of the electromagnetic wave radiated from an antenna and is parallel to the antenna itself.a.Propagation b. Coordinates c. Polarization d. AzimuthANS.Polarization
3. Placing a metallic array on the antenna effects to increase the current at the base of the antenna, and also to make the current distribution more uniform. What is this called?a.Reflector b. Grounding c. Top loading d. FeedingANS.Top loading
4. What principle that states that the properties of an antenna are independent of whether it is used for transmission or reception.a.Alternation b. Diplexerc. Reciprocity d. RepeatabilityANS.Principle of reciprocity
5. Calculate the beam width between nulls of a 2-m paraboloid reflector used at 6GHz. Note: such reflectors are often used at that frequency as antennas outside broadcast television microwave links.
a.140 b. 70 c. 3.50 d. 0.8750 ANS.3.50
6. This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts.
a. Splicing b. Zoning c. Curving d. PolarizingANS.Zoning
7. A structure-generally metallic and sometimes very complex-designed to provide an efficient coupling between space and the output of a transmitter or input to a receiver.a.Stub b. Antenna c. Transmission line d. waveguideANS.antenna
8. The ratio comparing the power density generated by a practical antenna in some direction, with that due to an isotopic antenna radiating the same total power.a. directivity b. Directive gain c. bandwidth d. Elementary doubletANS.Directive gain(b)
9. Any array that is directional at right angles to the plane of the array is said, by inference, to have __________.a.Broadside b. Broadside array c. Broadside action d. End-fire arrayANS.Broadside action
10. The ratio of the focal length to the mouth diameter is called __________ of the parabola, just as in camera lenses.a. focus b. resolution c. feed d. apertureANS.Aperture
11. Corresponds to a resonant transmission line, and the dipole antennas describe so far have been resonant.a. Non-resonant antenna b. Resonant antenna c. Antenna arrays d. None of the aboveANS.Resonant antenna
12. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air. What numerical aperture does the fiber have?a. 0.852 b. 0.352 c. 1.032 d. 0.235ANS. 0.352
By equation (20.10), the fractional difference between the indexes is:∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258By equation (20.11), the numerical aperture is found to be:NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352
13. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air. What is the acceptance angle?a. 22.8 b. 18.6 c. 20.6 d. 23.6ANS. 20.6By equation (20.10), the fractional difference between the indexes is:∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258By equation (20.11), the numerical aperture is found to be:NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352By equation (20.8), the acceptance angle is:Θ0(max)=sin-1NA= sin-10.352=20.6
14. For a single-mode optical cable with 0.25-dB/km loss, determine the optical power 100km from a 0.1-mW light source.a. -25dBm b. -45dBm c. -35dBm d. -30dBmANS. -35dBmP=0.1mW x 10-[(0.25)(100)]/(10)=1 x 10-4 x 10[(0.25)(100)]/(10)]=(1 x 10-4)(1 x 10-25)=0.316µWP(dBm)= 10log = -35dBm
15. For an optical fiber 10km long with a pulse-spreading constant of 5ns/km, determine the maximum digital transmission rates for return-to-zero.a. 10Mbps b. 20 Mbps c. 50 Mbps d. 5 MbpsANS.20Mbps
16. In fiber optics, it is a measure of the conversion efficiency of a photodetector. It is the ratio of the output current of a photodiode to the input optical power and has the unit of amperes per watt
a. Dark current b. Responsivity c. Spectral Response d. Light SensitivityANS.Responsivity
17. A phenomenon also called stress corrosion resulting if the glass fiber is exposed to long periods of high humidity?a. Static fatigueb. Absorptionc. Scattering lossd. DispersionANS. Static fatigue
18. The theory which states that when visible light or high-frequency electromagnetic radiation illuminates a metallic surface, electrons are emitted.a. Photoelectric effectb. Planck’s lawc. Photoemission effectd. Ray Theory of lightANS.Planck’s law
19. The science of measuring only light waves that are visible to the human eyea. Radiometryb. Photometryc. Optometryd. OpticsANS. Photometry
20. The process of constructing an ILD that is similar to LED except that the ends are highly polished.a.epitaxially grown b. Planar diffusion c. lasing d. None of the above ANS.Lasing
21. A phenomenon in optical fibers communication system that is caused by the difference in the propagation times of light rays that take different paths down the fiber.a. Pulse spreadingb. Wavelength distortionc. Rayleigh scatteringd. MicrobendingANS.Pulse spreading
Data comms
1. Is an OSI Layer which is responsible for providing error-free communications across the physical link connecting primary and secondary stations (nodes)
a.Data Link Layer b. Transport Layer c. Session Layer d. Presentation Layer
ANSWER: a. Data Link layer
2. Is the ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the digital-to-analog converter.
a. Step size b. Quantization Error c. Resolution d. Dynamic range
ANSWER: d. Dynamic range
3. Is a PCM system which uses a single bit PCM code to achieve digital transmission of analog signals
a.Trellis Coding b. Delta modulation c. Differential PCM d. QAM
ANSWER: b. Delta modulation
4. Is a redundancy error detection scheme that uses parity to determine if a transmission error has occurred within a message and is sometimes called message parity.
a. Longitudinal redundancy check b. Vertical redundancy check c. Character Parity Check d. Checksum
ANSWER: a. Longitudinal redundancy check
5. Is an n-bit data register inside the UART that keeps track of the UART’s transmit and receive buffer registers
a. Control Register b. Status Word register
c. Control and Status Register d. Command registerANSWER: b. Status Word register
6. Is an access method used primarily with LANs configured in a bus topology.
CSMA/CD b. CSMA c. CSMA/CA d. MA
ANSWER: a. CSMA/CD
7. IP version 4 address length is
32 bits b. 24 bits c. 40 bits d. 48 bits
Ans. 32 bits
8. Is a multiport bridge that provides bridging function.
a. Repeater b. hub c. Router d. Switch ANSWER: d. Switch
9. Is a device which operates in the Network layer and it makes forwarding decisions on the basis of network addresses
a. Repeater b. hub c. Router d. Switch
ANSWER: c. Router
10. OC-1 (STS-1) line rate is
a. 51.84 Mbps b. 1.544 Mbps c. 3 Mbps d. 2.048 Mbps
ANSWER: a. 51.84 Mbps
11. Is one in which all computers share their resources with all the other computers on the network.
a. Dedicated client server network b. Peer-to-peer client/server network c. Peer-to-peer network d. All of the above
ANSWER: b. Peer-to-peer client/server network
12. Is used to interface DTEs to digital transmission channels
a. Data modem b. Router c. Splitter d. Channel service unit
ANSWER: d. Channel service unit
13. Modulation which combines encoding and modulation to reduce the
probability of error.
a. DPSK b. FSK c. QAM d. TCM
ANSWER: d. TCM
14. Is an empirical record of a system’s actual bit error performance
a. ER b. BER c. EER d. BERT
ANSWER: b. BER
15. Is an error-correcting code used for correcting transmission errors in synchronous data streams.
a. Trellis Code b. EBCDIC c. Bisync Code d. Hamming code
ANSWER: d. Hamming code
RADIO WAVE1. The electric field intensity is measured in:
a. V/m b. V-m c. C/md. V/C
ANSWER:a. V/m
2. It is a result of an increase in the charge density in dielectric materials.
a. polarization b. dipole moment c. potentiald. potential difference
ANSWER polarization
3. It refers to the maximum antenna gain
a. directivity b. directive gain c. power gaind. power density
ANSWER: a. directivity
4. The maximum horizontal distance between the transmitter and the receiver for line of sight propagation is known as:
a. radio horizon b. range c. single hop distanced. service region
ANSWER: a. radio horizon
5. Typical mode of radiation of helical antenna is:
a. end fire b. normal c. common mode d. differential mode
ANSWER: a. end fire
6.The electric field is perpendicular to the earth’s surface, the polarization is:
a. vertical b. normal c. horizontal d. circular
ANSWER:a. vertical
7. In what major RF band is ground wave basically applied?
a. MF b. HF c. VHF d. UHF
ANSWER a. MF (Medium Frequency)
8. A measure of mismatch in a transmission line
a. reflection coefficient b. propagation delay
c. standing wave ratio d. all of these
ANSWER:c. standing wave ratio
9. The highest frequency that can be set back to earth by the ionosphere, if wave is sent vertically upward.
a. maximum usable frequency (muf) b. propagating frequency
c. critical frequency d. cut-off frequency
ANSWER: critical frequency
10. Travel in a straight line from the transmitting antenna to the receiving antenna
a. ground wave b. scatter c. space wave d. sky wave
ANSWER:c. space wave
11. VLF waves are for some types of services because
a. of low powers required b. the transmitting antennas are of convenient size
c. they are very reliable d. they penetrate the ionosphere easily
ANSWER:c. they are very reliable
12. It is the distance between two wave fronts having the same phase at any given instant.
a. wavefront b. wavelength c. wave distance d. field intensity
ANSWER:b. wavelength
13. It is a piece of transmission line which is normally short-circuited at the far end.
a. terminator b. stub c. quarter wave transformer d. none of these
ANSWER: b. stub
14. A 50 ohms transmission line is connected to a 30 ohm resistive load. Calculate the reflection coefficient.
a. 0.35 b. 0.25 c. 0.10 d. 0.15
ANSWER: b. 0.25
SOLUTION ( IF PROBLEM -SOLVING)
Ref Coeff = (30 – 50)/(30 + 50) = 0.25
15. The characteristic impedance of a transmission line does not depend upon its
a. conductor spacing b. conductor diameter
c. length d. conductor radius
ANSWER: c. length
16. Characteristic 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
ANSWER:a. input
17. Which region of the ionosphere is mainly responsible for long-distance night time communications?
a. D layer b. E layer c. A layer d. F layer
ANSWER: d. F layer
18. Which is properly terminated antenna?
a. rhombic b. dipolec. marconi d. hertz
ANSWER: a. rhombic
19. Occurs when the radio beam is at point of grazing over an obstacle.
a. diffraction b. refraction c. absorption d. reflection
ans: diffraction
20. A microwave communications system, space loss calculation formula is
a. 92.4 + 10 log F + 20 log D b. 94.2 + 10 log F + 20 log D c. 92.4 + 20 log F + 20 log Dd. 94.2 + 20 log F + 20 log D
ANSWER:
c. 92.4 + 20log F + 20 log D
DATA
1. The technique that uses the BPSK vector relationship to generate an output with logical 0s and 1s determined by comparing the phase of two successive data bits is
a. CSU/DSU b. DPSK c. TDM d. CVSD
ANSWER: b. DPSK
2. A special digital modulation technique that achieves high data rates in limited-bandwidth channels is called
a. Delta modulationb. Pulse-coded modulation (PCM)c. Quadrature amplitude modulation (QAM)d. Pulse amplitude modulation (PAM)
ANSWER: c. Quadrature amplitude modulation (QAM
3. FSK systems are much superior to two-tone amplitude-modulation systems with respect to
a. Noise performanceb. Bandwidth requirements of the channelc. Ionospheric fading characteristicsd. Power consumption
ANSWER: c. Ionospheric fading characteristics
4. Using an oscilloscope to display overlayed received data bits that provide information on noise, jitter, and linearity is called a
a. Eye patternb. Constellation patternc. Statistical concentrationd. Loopback
ANSWER:a. Eye pattern
5. The type of radio transmission that uses pseudorandomly switched transmissions is known as
a. Facsimileb. Spread spectrumc. Synthesizingd. Compression
ANSWER: b. Spread spectrum
6. The acronym CDMA refers to ________.
a. Channel-division multiple-access systemsb. Carrier-division multiple-access systemsc. Capture-division multiple-access systems
d. Code-division multiple-access systems
ANSWER:Code-division multiple-access systems
7. The acronym OFDM refers to ________.
a. Orthogonal Frequency Division Multiplexing
b. Over Frequency Division Multiplexingc. Optional Frequency Division Modulationd. Orthogonal Frequency Division
ModulationANSWER: Orthogonal Frequency Division Multiplexing
8. Using radio to transmit gathered data on some particular phenomenon without human monitors is known as
a. Radio facsimileb. Radio telemetryc. Radio teletyped. Radio multiplexing
ANSWER: Radio telemetry
9. The acronym for the form of data transmission in which the modulating wave shifts the output between two predetermined frequencies is _____.
a. FSKb. PSKc. FPF
FSAANSWER: a. FSK
10. Pseudorandom implies a sequence that can be _____ but has the properties of randomness.
a. decodedb. detectedc. re-createdd. minimizedANSWER: re-created
11. ______ implies that both analog and digital signals share the same channel bandwidth.
a. AMb. Hybridc. FMd. RF
Ans: hybrid
12. Telemetry may be defined as _____ metering.
a. distanceb. specializedc. remoted. data
ANSWER: Remote
13. Which is not a type of pulse modulation?
a. Pulse-amplitude modulation (PAM)b. Pulse-width modulation (PWM)c. Pulse-frequency modulation (PFM)d. Pulse-position modulation (PPM)
ANSWER: Pulse-frequency modulation (PFM)
14. PPM and PWM are superior to PAM systems in
a. Noise characteristicsb. Bandwidth characteristicsc. Simplicity in designd. Frequency response of the intelligence
signalANSWER: Noise characteristics
15. A procedure that decides which device has permission to transmit at a given time is called
a. Line controlb. Protocolc. Flow control
d. Sequence control
ANSWER: Line Control
16. The major difficulty faced by delta modulators is
a. Excessive noise producing errorsb. Slope overloadc. Insufficient frequency response of the
intelligence signald. Complexity of design
ANSWER: Slope overload
17. The AT&T T1 lines
a. Use 16-bit PCM code and include 24 voice channels
b. Use delta modulation and include 48 voice channels
c. Use 8-bit PCM code and include 24 voice channels
d. Use delta modulation and include 24 voice channels
ANSWER: Use 8-bit PCM code and include 24 voice channels
18. The ground wire in a USB cable is ______
a. Yellowb. Bluec. Redd. Brown
ANSWER: Brown
19. A(n) ________ is used to allow a digital signal to be transmitted on an analog channel.
a. codecb. aliasc. modemd. PSK
ANSWER: Modem
20. The bit ________ is the amount of power in a digital bit for a given amount of time.
a. errorb. energyc. jouled. hp
ANSWER: energy
21. The relationship for bit rate to ________ bandwidth is defined by the Shannon-Hartley theorem.
a. modemb. codecc. channeld. amplifier
ANSWER: Channel
22. In an S/H circuit, the time that it must hold the sampled voltage is
a. Aperture timeb. Acquisition timec. Flat-top timed. Dmin
ANSWER: Aperture time
23. Error signals associated with the sampling process are called
a. Foldover distortionb. Aliasingc. Nyquist rated. Foldover distortion and aliasing
ANSWER: Fold over distortion and aliasing
24. A(n) ________ is a single LSI chip containing both the ADC and DAC circuitry
a. modemb. DSPc. codecd. ASIC
ANSWER: codec
25. The NRZ digital signal-encoding format has a ________ component in the waveform.
a. dcb. sinusoidalc. harmonicd. parity
ANSWER: dc
Reed–Solomon codes utilize a technique called ________ to rearrange the data into a nonlinear ordering scheme to improve the chance of data correction
a. pseudorandomb. BSCc. interleavingd. quantizing
ANSWER: interleaving
1. .For an electronic device operating at a temperature of 17°C with a bandwidth of 10 kHz, determine the thermal noise power in dBm .
a. 134dBm b. 130dBm c. -134dBm d. – 130dBm
ANSWER: c. -134dBmSOLUTION (IF PROBLEM-SOLVING)
N = KTB T(kelvin) = 17°C + 273° = 290 K B = 1 x 104 Hz = (1.38 x 10-23)(290)(1 x 104) = 4 x 10-17 W
N(dBm) = 10log (4 x 10 -17 ) = -134 dBm 0.0012. A 300Ω resistor is connected across the 300Ω antenna input of a television receiver. The bandwidth of the receiver is 6MHz, and the resistor is at room temperature .Find the noise voltage applied to the receiver input. a. 5.4 V b. 3.12 V c. 4.5 V d. 6.7 VANSWER: a. 5.4 µVSOLUTION (IF PROBLEM-SOLVING)
VN =
= 4(1.38 x 10-23 J/K)(293 K)(6 x 106 Hz)(300
Ω) = 5.4 x 10-6 V = 5.4 µV 3. The signal power at the input to an amplifier is 100µW and the noise power is 1 µW. At the output, the signal power is 1W and the noise power is 30mW. What is the amplifier noise figure, as a ratio?
a. 3.5 b. 4.5 c. 3 d. 4SOLUTION (IF PROBLEM-SOLVING)
(S/N)p = 100µW = 100 1µW (S/N)o = 1W = 33.3 0.03W NF (ratio) = 100 = 3 33.54. It is desired to operate a receiver with NF = 8dB at S/N = 15 dB over a 200-KHz bandwidth at ambient temperature. Calculate the receiver’s sensitivity
a. -84dBm b. -98dBm c. -80dBm d. -75dBm
SOLUTION (IF PROBLEM-SOLVING)
S = Sensitivity = -74dBm + NF + 10log∆f + desired S/N S = -174 + 8 + 10log(200,000) + 15 S = -98 dBm5. A Satellite receiving system includes a dish antenna ( Teq = 35 K) connected via a coupling network (Teq= 40 K) to a microwave receiver (Teq=52 K referred to its input). What is the noise power to the receiver’s input over a 1-MHz frequency range?
a. 1.75 x 10-15W b. 1.75 x 10-12W c. 1.15 x 10-15W d. 1.15 x 10-12W
SOLUTION (IF PROBLEM-SOLVING)
PN = KT∆f = 1.38 x 10-23 J/K (35 + 40 + 52)K (1MHz) = 1.75 x 10-15 W6. Equivalent temperature of a passive system having the same noise power output of a given system.
a. Noise figureb. Total temperaturec. Equivalent temperatured. Noise temperature
Answer:d. noise temperature
7. The noise voltage produced across a 50Ω is input resistance at a temperature of 302°C with a bandwidth of 6 MHz is ______.
a. 5.15 µV b. 3005mV c. 2124mV d. 2.24µV
SOLUTION (IF PROBLEM-SOLVING
VN = = 4(1.38 x 10-23)(302)(6
x 106)(50) = 2.24µV8. Determine the worst-case output S/N for a broadcast FM program that has a maximum intelligence frequency of 5 kHz. The input S/N is 2
a. 2.5 b. 30 c. 3 d. 25
SOLUTION (IF PROBLEM-SOLVING)
ᵟ = φ x fi
= 0.5 x 5 kHz = 2.5 kHz75 kHz = 302.5 kHz
** Signal Processing and Control Systems**
1. Suppose that energy Q is required to accelerate a car from rest to v, neglecting friction. How much added energy would be required to increase the speed from v to 2v?a. Q b.2Q c. 3Q d.4Q
ANS. 3Q
Using the energy equation W=KE2 – KE1
Q = 0.5mv2 – 0 - condition 1
W = 0.5m(2v)2 – 0.5mv2 - condition 2
W=2mv2 – 0.5mv2 = 3(0.5mv2) = 3Q
2. Suppose you want to store 1.00 J of electric potential energy in a volume of 1.00 m3 in vacuum. What is the magnitude of the required electric field?a. 0.475 MV/m b. 0.336MV/m c. 0.225TV/m d. 0.113TV/m
ANS.E=0.475 MV/m
u=1.00J/1.00m3 = 1.00J/m3
E=0.475 MV/m (a)
3. Material a is a water and material b is a glass with index of refraction 1.52. If the incident ray makes an angle of 60o with the normal, find the direction of the reflected ray.a. 49.3o b. 91.3o c. 60o d. 34.7o
ANSWER: 60o
4. The wavelength of the red light from a helium-neon sensor is 633 nm in air but 474 nm in the aqueous humor inside our eyeballs. Calculate the speed of light in this substance.a. 2.25 x 108 m/s b. 3.25 x 108 m/s
c. 3.00 x 108 m/s d. 1.25 x 108 m/s
ANS. 2.25 x 108 m/s
5. A spaceship moving away from Earth with speed of 0.900c fires a robot space probe in the same direction as its motion, with speed of 0.700c relative to the spaceship. What is the probe’s velocity relative to the Earth?a. 0.900c b. 0.345c c. 0.700c d. 0.982c
ANS. 0.982c
6. In optics, this effect refers to the blurring of the image produced on a concave mirror due to the convergence of rays far from the mirror to other points on the principal axis. What do you call this effect?a. spherical aberration b. focal divergence c. parallax error d. Snell’s effect
ANS.spherical aberration
7. In fluid mechanics, this shows that the pressure of a fluid decreases as the speed of the fluid increases. In addition, the pressure of a fluid decreases as the elevation increases.a. Clairut’s equation b. Bernoulli’s equation
c. Maxwell’s equation d. Hyrdofluid equation
ANS.Bernoulli’s equation
8. In electrodynamics, what term refers to the average speed of the charge carriers?a. drag velocity b. molecular-kinetic speed
c. drift speed d. charge velocity
ANS.drift speed
9. In electromagnetics and wave theory, what refers to waves, commonly generated by electronic devices, whose wavelengths ranges from approximately 0.3m to 10-4 m. Due to their short wavelengths these are often used in radar systems and for studying the atomic and molecular properties of matter.a. Radio waves b. Microwaves
c. AM waves d. Radar waves
ANS.microwaves
