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 above
ANS. 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. 2.2
ANS. 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 the
a. Gastrointestinal (GI) syndrome
b. Central Nervous System (CNS) syndrome c. Hematologic syndrome
d. Prodomal syndrome ANS. Hematologic syndrome
5. Ratio of incident to transmitted radiation through a grid ratio of patient dose with and without grid a. Bucky factor b. Damadian factor c. Grid ratio d. Roentgen equivalent
ANS. 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. 24kW ANS 42 Kw
Power rating=(0.7)x (mA x kVp)/1000 Power 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. Hounsfield ANS. Hounsfield
8. It is the study of the response of an image receptor to x-rays
a. sensitometry b. xeroradiography c. xeroradiometry d. spectrometry
ANS. Sensitometry
9. Ratio of radiographic contrast with a grid to that without a grid
a. grid ratio b. contrast improvement factor c. Collidge factor d. Bucky factor
ANS. 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 rad ANS. 600 rad
11.
ECG recording requires a bandwidth of 0.05 to ___Hza. 1000 b. 540 c. 100 d. 40 ANS.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 uV ANS. 309 uV E= QB/50πa E= ((175 cc.s)(250 G))/(50π(0.9cm)) E= 309 uV13. Period during which heart contracts.
a. Diastole b. Systole c. block mode d. Synapse
ANS. Systole
14. Apparatus for measuring blood pressure a. defibrillator b. electrocardiogram c. plethysmograph d. sphygmomanometer
ANS 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 MHz ANS. 10^10 MHz f= E/h f= (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 effect ANS. Photoelectric effect17.
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. Gray ANS. Roentgen
18. An optical electronic device that measures the color concentration of a substance in solution.
a. colorimeter b. flame photometer c. spectrophotometer d. chromatograph ANS.colorimeter
19. Recording of heart sounds
a. ultracardiography b. cardioacoustics c. electrocardiogram d. phonocardiography ANS. Phonocardiography
20. Recorder for measuring galvanic skin resistance a. electrodermograph b. electromyograph c. electrocorporealograph d. electrogalvanograph ANS.electrodermograph
**Digital and Data Communications**
1. It consists of 36 unique codes representing the 10 digits and 26 uppercase letters
a. Discrete code b. code 39 c. continuous code d. 20 code
ANS.code 39
2. The first fixed- length character code developed for machines rather than for people
a. ASCII Code b. Gray Code c. EBCDIC code d. Baudot Code
ANS.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 Baudot
ANS. Richard W. Hamming
4. The most reliable convolutional coding scheme for error detection
a. checksum b. LRC c. CRC d. VRC ANS.CRC
5. For the given parameters, determine the energy per bit-to noise power density ratio
C = 10e-12 W fb = 60 kbps N = 1.2 x 10e-14`W B = 120 kHz a. 16.2 dB b. 14.2 dB c. 20.2 dB d. 22.2 dB ANS.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. 0.678Vmax
ANS.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 errors
ANS.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. ADC
ANS.vocoder
9. A coding scheme that records the change in signal level since the precious sample
a. unipolar code b. PPM c. PCM d. delta modulation
ANS.delta modulation
10. Distortion created by using too low a sampling rate when coding an analog signal for digital transmission a. aliasing b. foldover distortion c. either a or b d. neither a nor b
ANS.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 Mbps ANS.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. 3.65
ANS6.35
SNRdB = 6.02nb + 1.76 = 40 n = 6.35
13. The thick coaxial cable implementation of standard Ethernet
a. 1000 Base-T b. 10 Base-T c. 10 Base 2 d. 10 Base 5
ANS.10 Base 5
14. A bit pattern or a character added to the beginning and the end of a frame to separate the frames a. Flag b. Firewall c. Frameguard d. Footprint ANS.Flag
15. An IPv4 has an address space of how many? a. 4294967296 b. 6927694924 c. 2449692769 d. 9672969442
ANS. 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 GHz
ANS.51.84 Mbps
17. A block coding technique in which four bits are encoded into a five bit code
a. Baudot b. 2B1Q Encoding c. 4B/5B Encoding d. 4A/5A Encoding
ANS.4B/5B Encoding
18. A national standards organization that defines standards in the United States
a. ANSI b. FCC c. ITU d. CCITT ANS.ANSI
19. In asynchronous transmission, one or more bits to indicate the end of transmission
a. trailer b. flag c. escape byte d. stop bit ANS.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 Mbps
ANS.1.368 Mbps
**Electronics/Communications**
1. The minimum sampling rate according to Nyquist Theorem
a. equal to the lowest frequency of a signal b. equal to the highest frequency of a signal c. twice the bandwidth of a signal
d. twice the highest frequency of a signal ANS.twice the highest frequency of a signal 2. It is used in wireless applications in which stations
interception by an eavesdropper and without being subject to jamming from a malicious intruder a. modulation b. Multiple access c. multiple access d. Spread spectrum ANS.spread spectrum
3. An error detection method which uses one’s complement arithmetic
a. Checksum b. CRC
c. Simple-parity check
d. Two-dimensional parity check ANS.Checksum
4. It is a connecting device between two internetworks that use different models
a. Bridge b. Gateway c. Repeater d. 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 times
a. alias b. impulse c. jitter d. parity ANS.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 range b. Figure of merit c. Quality factor d. Noise figure ANS.Dynamic range
7. A multiplexer combines four 100-kbps channels using a time slot of 2 bits, determine the frame duration.
a.
20µ sb.
50µ sc.
100µsd.
400µsANS.20µ s
8. Determine the Hamming distance for the codewords ( 10101, 11001) a. one b. two c. three d. five ANS. Two
10101 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. 232 b. 264 c. 296 d. 2128 ANS.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.123 c. H.321 d. H. 323 ANS.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 Gigabits b. 1. 2 Gigabits c. 120 Megabits d. 12 Megabits ANS.12 Megabits
1,200 times 1000 pixels x 10 bits = 12 Mb 1024 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 dBm
ANS.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 ratio
Rearranging the above to find NR gives: NR = (375/290) +1 = 2.29
The 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 totaltransmitted 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. 72 ANS. 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 MHz Mixer 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. 16 ANS. 10
3. A small variable capacitance in parallel with each section of ganged capacitor is called _______. a. trimmer b. converter c. padder d. autodyne
ANS. 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 λ
ANS.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 ns ANS. 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 = 0.26The 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 degrees ANS.108 degrees Θ = 360 td / T T =1/f = 1 / 4MHz = 250 ns Θ = 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-pair
ANS. microstrip
7. One complete revolution around a Smith Chart represents _________ wavelengths.
a. ½ λ b. ¼ λ c. 1 λ d. 2 λ
ANS.½ λ
8. A mismatched transmission line is also referred to as a ___________ line.
a. lossy b. lossless c. non-resonant d. resonant
ANS.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 ratio
ANS.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 6
ANS.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. 0.32 ANS.0.47 m = Em/ Ec Emax = Ec + Em ; Em = Emax – Ec = 125 – 85 = 40 V m = 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. 40kW ANS.66kW Pt = Pc ( 1 + m2/2) Pt = 50,000 ( 1 + 0.82 /2) Pt = 66,000 W Pt = 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 demodulate
ANS.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 modulator ANS.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 Hz ANS.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-multiplier
ANS. 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-aliasing
ANS. 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 sway ANS. 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. grounding
ANS.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 dBi ANS. 39.8 dBi G = 2 D2/ 2 = 3x108/ 4MHz = 0.075 m G = 0.6 2(3)2 0.0752 G= 9474.8 G = 10 log 9474.8 G = 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 effect
ANS.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 determined
ANS. The second antenna has a higher gain.\ 3. A half-wave dipole is sometimes called:
a. Marconi antenna b. Yagi antenna
c. Hertz antenna d. none of the choices
ANS. Hertz antenna 4. An antenna's beamwidth is measured
a. from +90° to –90° b. between half-power points
c. from front to back d. between the minor side-lobes
ANS. between half-power points
5. "Ground Effects" refers to the effects on an antenna's radiation pattern caused by
a. radio signals reflecting off the ground b. buildings and other structures on the ground c. fading
d. faulty connection of the feed cable ground ANS. radio signals reflecting off the ground 6. An antenna can be matched to a feed line using
a. a shorted stub b. an LC network
c. a loading coil d. all of the choices
ANS. all of the choices
7. As the length of a "long-wire" antenna is increased a. the number of lobes increases b. efficiency decreases
c. the number of nodes decreases d. none of the above
ANS. . the number of lobes increases 8. LPDA stands for
a. Low-Power Dipole Array b. Log-Periodic Dipole Array
c. Low-Power Directed Array d. Log Power Dipole Array
ANS. Log-Periodic Dipole Array
9. Field strength at a distance from an antenna is measured with
a. a slotted line b. an EIRP meter
c. a dipole d. a field-strength meter
ANS. a field-strength meter
10. A receiving antenna with a built-in preamplifier a. active antenna
b. passive antenna
c. coil d. LC antenna
ANS. 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-effective
c. mounting is easier d. support is easier
ANS. more cost-effective
12. The shape of the electromagnetic energy radiated from or received by an antenna is called the a. signal shape
b. electromagnetic pattern
c. radiation pattern d. antenna pattern
ANS. radiation pattern 13. Antennas that transmit an equal amount of energy in
the horizontal direction are called a. bi-directional b. unidirectional
c. omnidirectional d. unilateral
ANS. omnidirectional
14. The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as a. focal factor b. permittivity c. directivity d. horizontal range ANS. 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 a a. parasitic array
b. bi-directional array
c. half-wave dipole d. counterpoise
ANS. parasitic array
16. An antenna made up of a driven element and one or more parasitic elements is generally referred to as a a. Hertz antenna
b. Marconi antenna
c. collinear antenna d. Yagi antenna
ANS. Yagi antenna
17. Which antennas usually consist of two or more half-wave dipoles mounted end to end?
a. Hertz b. Marconi
c. collinear d. Yagi
ANS. collinear
18. A stacked collinear antenna consisting of half-wave dipoles spaced from one another by one-half wavelengths is the
a. broadside array b. end-fire array
c. wide-bandwidth array d. parasitic array
ANS. 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 1:10
c. minimum power transfer will take place d. maximum power transfer will take place ANS. 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 is a. a balun b. an autotransformer c. a Q section d. dummy load ANS. 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. 11.5m
ANS.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/s
ANS.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 m ANS. 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 choices
ANS.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. TE20 ANS. 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 mW ANS.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 µW ANS. 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 trap ANS.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 drum ANS.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 wavelength
c. is inversely proportional to the phase velocity d. is directly proportional to the group velocity ANSWER: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 latitude
ANS. 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. EIRP ANS. 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 effect b. The distance between the satellite and ground station is changing, causing the Bernoulli effect c. The distance between the satellite and ground station is changing, causing the Boyle’s Law effect d. The distance between the satellite and ground station is changing, causing the Doppler effect ANS. The distance between the satellite and ground station is changing, causing the Doppler effect
1. The most ambitious LEO constellation to date is ______.
a. Iridium b. NAVSTAR c. Teledesic d. Globalstar
ANS.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 Mm ANS.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 km ANS.39000 km
5. What is the nominal uplink frequency for the Ku band? a. 6 GHz b. 4 GHz c. 14 GHz d. 12 GHz ANS. 14 GHz
6. To cover all inhabited regions of the earth, the number of polar-orbit satellites required is a. 1 b. 2 c. 3 d. 5
ANS.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 frequency
ANS. Critical Frequency
2. Variation in signal loss caused by natural weather disturbances.
a. attenuation b. fading c. spreading loss d. weather loss
ANS. fading
3. Determine the radio horizon for a transmit antenna that is 200 m high and a receiving antenna that is 100 m high
a. 99.5km b. 96.5 km c. 95.87 km d. 97.5 km
ANS. 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 height
ANS. 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 waves
ANS. 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. echo
b. reverberation c. reflection d. diffraction ANS.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 Hz b. 12.5 Hz c. 75 Hz d. 31.5 Hz ANS. 31.5 Hz
f2 = 2x f1 where x = 1/3, fraction of an octave f2 = 21/3 x 25 = 31.5 Hz
3. + 26 dBu is how many volts? a. 7.75 V
b. 15.5 V c. 31 V d. 62 V ANS. 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 ] = 1.3 Voltage = log-1 (1.3) x 0.775 V
Voltage = 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.Condenser
c. Ribbon d.Carbon
ANS. 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 W b. 55.68 W c. 58.56 W d. 58.65 W ANS. 58.65 W PWL = SPL + 20 log D(m) + 8 PWL = 100 + 20 log (100/3.28) + 8 = 137.68 dB-PWL 137.68 = 10 log W + 120 W = 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-SPL b. 69 dB-SPL c. 65 dB-SPL d. 79 dB-SPL ANS. 69 dB-SPL SPL@1m/1W = 85 dB-SPL (given) SPL@20m/1W = 85 - 20 log (20m/1m) = 59 dB-SPL SPL@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 absorption c. Absorption Coefficient b. Reflection coefficient d. Room Constant
ANS.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 range
ANS. 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 km
ANS.35,786 km
2. The location of a satellite is generally specified in terms of
a. azimuth & elevation b. latitude & longitude c. true morth d. bearing
ANS.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 point
ANS. 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/s2 ANS. 7.6 km/s Formula : v= 4x10 11 d+6400
(
)
Where : v = velocity in meters per second d = distance above earth’s surface in km
v= 4x10 11
(500+6400 )
= 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 sec ANS. 1440 mins Formula :
Τ =
C
v
Where : T = orbital period C = circumference v = orbital velocity C = 2 r = 2π ( 6400 + 36,000 ) = 266.4 x 106 m v= 4x1011 (36,000+6400 )=3.07km/s T=C v= 266.4x106m 3.07x103 m/s=24hrs 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. footprint
ANS. 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 :
d
=(
r
+
h
)
2−
(
r
c
o
s
θ
)
2−
r
s
i
n
θ
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. SCADA
ANS. 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 north
ANS. 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.004
ANS.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 kHz b. 526.5 to 1605 kHz c. 535 to 1705 kHz d. 526.5 to 1705 kHz ANS. 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 period b. nighttime period c. experimental period d. primetime period ANS. 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 area b. secondary service area c. intermittent service area d. none among these ANS. 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 ft
b. 150 ft c. 200 ft d. 250 ft ANS. 150 ft
5. Regarding the design of AM antenna, what should be the polarization of the radiator?
a. horizontal b. vertical c. circular d. elliptical ANS. vertical
6. As per Phillipine standard, what is the minimum frequency separation in any service area for adjacent AM radio stations? a. 40 kHz b. 200 kHz c. 36 kHz d. 300 kHz ANS. 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 W b. 15 W c. 35 W d. 200 W ANS. 35 W
8. What is the classification of an FM station having an ERP not exceeding 30kW?
a. Class A b. Class B c. Class C d. Class D ANS. Class B
9. What is the modulation used for the stereophonic subcarrier of FM composite baseband signal? a. AM DSB FC
b. AM DSB SC c. AM SSB d. AM VSB ANS. AM DSB SC
10. What is the pilot subcarrier frequency used in FM stereophonic transmission? a. 15 kHz b. 19 kHz c. 30 kHz d. 38 kHz ANS.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 kW b. 30 kW c. 20 kW d. 19.96 kW ANS. 19.96 kW GANT = 6 dB = 4 ERP = (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 kHz b. 88 – 108 MHz c. 50 – 15000 Hz d. 174 – 216 MHz ANS. 88 – 108 MHz
13. What is the color TV system adopted by the Philippines?
a. NTSC b. PAL c. SECAM
d. none among choices ANS.NTSC
14. Exact value of color subcarrier frequency (MHz) is … a. 3.579554
b. 3.579455 c. 3.580545 d. 3.579545 ANS. 3.579545
15. Determine the visual carrier frequency of TV channel 9 a. 175.25 MHz b. 187.25 MHz c. 193.25 MHz d. 199.25 MHz ANS.187.25 MHz
fNLB = 174 + (N – 7)6, using Arithmetic Progression f9LB = 174 + (9 – 7)6 = 174 + (2)6 = 174 + 12 = 186 MHz, low band frequency of channel 9
fVC = 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 kW b. 316 kW c. 350 kW d. 1 MW ANS. 1 MW
17. At NTSC standard, the number of lines per frame = ________ lines/frame a. 485 b. 525 c. 625 d. 585 ANS. 525
18. At NTSC standard, line frequency = 15734.264 Hz. What is the equivalent line period?
a. 66.556 usec b. 65.556 usec c. 63.556 usec d. 64.556 usec ANS. 63.556 usec fH = 15734.264 Hz H = 1 / fH = 1 / 15734.264 H = 63.556 x 10-6 = 63.556 usec
19. Nominal RF bandwidth of NTSC TV channel… a. 4.2 MHz
b. 4.5 MHz c. 6 MHz d. 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 station
c. TV Inter-city Relay station d. TV Satellite link station ANS.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 MHz
b. 5 MHz c. 6 MHz d. 7 MHz ANS. 6 MHz
For 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 symbol Therefore the ideal RF bandwidth is… BW = fB / n = 36 Mbps / 6 bits BW = 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 wave b. sky wave c. space wave d. all of these ANS.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 m b. 0.85 m c. 0.96 m d. 1.36 m
ANS. 0.96 m
c = 3 x 108 m/sec = 300 x 106 m/sec
velocity factor vf = 1 / sqrt (εr) = 1 / sqrt (2) = 0.707 = vP / c
Therefore 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 θr
θr = 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. D b. E c. F1 d. F2 ANS. D
26. As per ITU-R Recc. V.431-6 Tables 1 & 2 Wavelength Classifications, what is the classification of Super High Frequency? a. metric b. decimetric c. centimetric d. millimetric ANS.centimetric SHF band: 3 GHz – 30 GHz λmax = 3 x 108 / 3 x 109 = 0.1 m = 100 cm λmin = 3 x 108 / 30 x 109 = 0.01 m = 1 cm
SHF 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 diversity b. space diversity c. angle diversity d. quadrature diversity ANS.space diversity
28. What is a diversity scheme that uses two (2) different frequencies in a simplex path?
a. frequency diversity b. space diversity c. angle diversity d. 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 MHz b. 12 MHz c. 13 MHz d. 14 MHz ANS.13 MHz
Nmax = 2 x 106 per cm3 = 2 x 106 x 106 per m3 = 2 x 1012 per m3
fc = 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 MHz b. 8.3 MHz c. 8.4 MHz d. 8.5 MHz ANS. 8.4 MHz
For flat terrain analysis, tan i = d/2hv
i = tan-1 [d/2hv] = tan-1 [500/2(110)] = tan-1 [2.273] = 66.25° angle of incidence
MUF = fc x sec i = fc / cos i = 4 / cos 66.25° = 4 / 0.40275 = 9.932 MHz via Secant Law
OWF = 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 law
b.
Snell’s lawc. Inverse Square law d. Gauss law
ANS.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. D
b. E c. F1 d. 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 Response
b.
Radiation Pattern c. Smith Chartd. FCC F(50,50) Graph ANS, 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 Ω b. 15 Ω c. 12 Ω d. 6.58 Ω ANS.6.58 Ω η = Rd/(Rd + Rloss) 0.82 = 30/(30 + Rloss) 0.82 (30 + Rloss) = 30 = 24.6 + 0.82 Rloss Rloss = (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. SID b. 11-year sunspot c. Sporadic E-layer d. Ionospheric storms ANS.11-year sunspot36. What should be done to increase the transmission distance at frequencies higher than HF bands? a. increase antenna gain
b. increase antenna height c. increase transmitter power
d. increase receiver sensitivity ANS. 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 terrain
b.
frequencyc. antenna polarization d. all choices
ANS.all choices
38. A radio station operates at 11 meter wavelength. What is the designated band of station’s frequency? a. MF
b. HF c. VHF d. UHF ANS.HF
SOLUTION (IF PROBLEM SOLVING): c = 3 x 108 m/sec
λ = 11 m = c / f
f = 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 km
b. 53.66 mi c. 18.97 km d. 18.97 mi ANS. 18.97 mi
SOLUTION (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 W c. 3 W d. 4 W ANS.3 W
From Inverse Square Law, PD = PR/4πd2
PR = PD x 4πd2 = 1.57 x 10-4 x 4π(50)2 = 4.93 W approx. is the radiated power
GANT = log-1 [2.15 dB/10] = 1.64 PR = PFED x GANT
PFED = 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 digits
ANS.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 service
ANS.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 cell d. the MTSO increases power level
ANS.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 segment ANS.cluster
6. In Celluar Telephone Systems, these are transmissions from base stations to mobile units (Downlink)
a. forward links b. reverse links c. TRX d. TRA
ANS.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 mW ANS.250 mW PT = -76 dB - PR Where: PT = transmitted power in dBm PR = 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 dB ANS. 0.8 dB
VNL = 0.2t + 0.4 dB Where:
VNL = minimum required via net loss in dB t = time delay in ms for propagation one way along line
VNL = 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 b b. 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 failure
c. occurs only on long-distance cables
d. 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 cable b. shielded twisted-pair copper wire d. fiber-optic ANS.twisted-pair copper wire 13. In DTMF, the four vertical frequencies are ____.
a. 1209Hz, 1336Hz,1477Hz,1633Hz b. 697Hz,770Hz,852Hz,941Hz c. 679Hz,770Hz, 852Hz, 941Hz d. 1208Hz,1336Hz,1747Hz,1633Hz ANS. 697Hz,770Hz,852Hz,941Hz 14. In DTMF, the Horizontal frequencies are
a. 1209Hz, 1336Hz,1477Hz,1633Hz b. 697Hz,770Hz,852Hz,941Hz c. 679Hz,770Hz, 852Hz, 941Hz d. 1208Hz,1336Hz,1747Hz,1633Hz ANS.1209Hz, 1336Hz,1477Hz,1633Hz 15. In Celluar Telephone Systems, these are
transmissions from mobile units to base stations (Uplink)
a. forward links b. reverse links c. TRX d. TRA
ANS.reverse links
16. In DTMF, the horizontal frequencies is also known as a. low group frequencies
b. high group frequencies c. mid group frequencies d. top group frequencies ANS.high group frequencies
17. In DTMF, the Vertical frequencies is also known as a. low group frequencies
b. high group frequencies c. bottom group frequencies d. top group frequencies ANS.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 multiplexed d. all of the above
ANS. 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 center b. regional center d. all of the above ANS.regional center
20. In Cellular Radio, AMPS stand for: a. American Mobile Phone System b. Analog Mobile Phone Service
C. Advanced Mobile Phone System d. Advanced Mobile Phone Service ANS.Advanced Mobile Phone Service
21. In Cellular Radio, BSC stands for:
a. Base Station Controller c. Basic Service Contract b. Base Signal Controller d. Basic Service Code ANS.Base Station Controller
22. In Cellular Radio, MSC stands for:
a. Mobile Switching Center c. Maximum Signal Carrier b. Mobile Service Cellular d. Minimum Signal Carrier ANS.Mobile Switching Center
23. In GSM, voice channels are called: a. traffic channels c. bearer channels b. voice channels d. talking channels ANS.traffic channels
24. In Mobile Communications, GSM uses: a. frequency hopping c. CDMA
b. direct-sequence modulation d. all of the above ANS.frequency hopping 25. In Mobile Communications, IMSI stands for:: a. Integrated Mobile Subscriber Identification b. International Mobile Subscriber Identification c. Interim Mobile Subscriber Identification d. Intermodulation System Interference
ANS.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. Ultraviolet ANS.Infrared
2. In the telecommunications industry, the most commonly used fiber(s) are
a. 50 micron b. 62.5 micron c. 50 and 62.5 micron d. 125 micron ANS. 50 and 62.5 micron
3. The abrupt change in refractive index from core to cladding of fiber-optic cable is called the
a. Total internal reflection b. Numerical aperture c. Dispersion d. Step index
ANS. Step index
4. A technique that is used to minimize the pulse dispersion effect is to
a. Use a higher frequency light source b. Use plastic cladding
c. Minimize the core diameter d. All the above
ANS. 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 called
a. Modal dispersion b. Material dispersion c. Waveguide dispersion d. Cable dispersion
ANS. Waveguide dispersion
7. Recent laser developments for fiber-optic communication include
a. Distributed feedback (DFB)
b. Vertical cavity surface emitting (VCSEL) c. Heterojunction
d. 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 time b. Power levels c. Temperature sensitivity d. Failure characteristics ANS.Response time
9. In 1815, the correct explanation of diffraction was given by
a. Maxwell b. Rayleigh c. Fresnel d. Snell
ANS.Fresnel
10. It is the central part of the optical communication system
a. Light Source b. Optical Fiber c. Photodetector d. none of the above ANS.Optical Fiber
11. The light energy that is always emitted or absorbed in discrete units
a. Light Ray b. Boson c. Quanta d. Light
ANS.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 & c ANS.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 fibers
a. 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. Azimuth ANS.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. Feeding ANS.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. Diplexer c. Reciprocity d. Repeatability ANS.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. Polarizing ANS.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. waveguide ANS.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 doublet
ANS.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 array
ANS.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. aperture
ANS.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 above ANS.Resonant antenna
12.
An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with arefractive 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. 0.235
ANS. 0.352
By equation (20.10), the fractional difference between the indexes is:
∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258
By 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. 23.6◦
ANS. 20.6◦
By equation (20.10), the fractional difference between the indexes is:
∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258
By equation (20.11), the numerical aperture is found to be:
NA=n1√(2∆)
=1.55√[(2)(0.0258)] = 0.352
By 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. -30dBm ANS. -35dBm P=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) =0.316µW P(dBm)= 10log = -35dBm15. 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 Mbps ANS.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 Sensitivity
ANS.Responsivity
17. A phenomenon also called stress corrosion resulting if the glass fiber is exposed to long periods of high humidity?
a. Static fatigue b. Absorption c. Scattering loss d. Dispersion ANS. 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 effect b. Planck’s law
c. Photoemission effect d. Ray Theory of light ANS.Planck’s law
19. The science of measuring only light waves that are visible to the human eye
a. Radiometry b. Photometry c. Optometry d. Optics ANS. 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 spreading b. Wavelength distortion c. Rayleigh scattering d. Microbending ANS.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
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 WAVE
1. The electric field intensity is measured in:
a. V/m b. V-m c. C/m
d. 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. potential d. potential difference
ANSWER polarization
3. It refers to the maximum antenna gain
a. directivity b. directive gain c. power gain d. 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 distance d. 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. dipole
c. 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 modulation
b. 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 performance
b. Bandwidth requirements of the channel c. Ionospheric fading characteristics d. 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 pattern
b. Constellation pattern c. Statistical concentration d. Loopback
ANSWER:a. Eye pattern
5. The type of radio transmission that uses
pseudorandomly switched transmissions is known as a. Facsimile
b. Spread spectrum c. Synthesizing d. Compression ANSWER: b. Spread spectrum
6. The acronym CDMA refers to ________.
a. Channel-division multiple-access systems b. Carrier-division multiple-access systems c. 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 Multiplexing c. Optional Frequency Division Modulation d. Orthogonal Frequency Division
Modulation
ANSWER: Orthogonal Frequency Division Multiplexing 8. Using radio to transmit gathered data on some particular phenomenon without human monitors is known as
