ECE Board Exam.Review Nov .97

1. Extra-terrestial noise is observable at frequencies from
A. 0 to 20 kHz
B. Above 2 GHz
(C) 8 to 1.43 GHz
D. 5 to 8 GHz
2. Band light waves, that are too short to be seen by human eye.
A. Visible
B. Infrared
(C) Ultraviolet
D. Amber
3. Two wires that are bent 90 degrees apart.
A. Hertz
(B) Dipole
C. Log-periodic
D. Rhomic
4. The first symbol in the designation of radio emission under the ITU rules refers to
A. nature of signal(S) modulating the main carrier
B. type of information to be transmitted
C. bandwidth
(D) type of modulation of the main carrier
5. Operating method in which the transmission is made alternately in each
direction of a telecommunication channel.
A. Semi-duplex operation
B. Duplex operation
(C) Half-duplex operation
D. Simplex operation
6. Production of radiation by a radio transmitting station.
A. Monitoring
(B) Emission
C. Radiation
D. Transmission
7. The third symbol in the designation of radio emission under the ITU rules refers to
A. type of the modulation of the main carrier
B. bandwidth
C. nature of the signal(s) modulating the main carrier
(D) type of information to be transmitted
8. A form of telecommunication for the transmission of transient images to fixed or
moving objects.
A. E-mail
(B) Television
C. Radio
D. Internet
9. Radiation pattern of a discone.
A. Unidirectional
B. Bidirectional
(C) Omnidirectional
D. Figure of eight
10. Another SEG function that allows a person to be superimposed on another scene.
A. Visual effect
B. Wiper
(C) Chroma keying
D. Special effect generation
11. What signal-to-noise ration is required for satisfaction telephone services?
(A) 50 dB
B. 30 dB
C. 40 dB
D. 20 dB
12. The use of telecommunication for automatic indicating or recording measurement
at the distance from the measuring instrument.
A. monitoring
B. Tracking
(C) Telemetry
D. Telecommand
13. The standard deviation of the variation in the transmission loss of a circuit should not exceed
A. 3dB
(B) 1 dB
C. 5 dB
D. 0.5 dB
14. Noise use by the thermal agitation of electrons is resistance.
A. All of these
B. Thermal noise
C. Johnson’s noise
(D) White noise
15. Unity gain antenna.
(A) Isotropic
B. Rhombic
C. Half-wave dipole
D. Dummy
16. The series of periodically recurrent pulses is modulated amplitude by the corresponding
instantaneous samples.
A. PFM
B. PWM
C. PDM
(D) PAM
17. This type of transmission permits communication in the frequency range from 30 to 60 MHz and
over distances from about 1000 to 2000 km.
A. Troposcatter
(B) Ionospheric scatter
C. Ducting
D. Microwave
18. A region in front of a paranoid antenna.
A. Transmission zone
(B) All of these
C. Fraunhofer
D. Fresnel
19. Designates the sensation of low or high in the sense of the base and treble.
A. Frequency
B. Intensity
(C) Pitch
D. SPL
20. A good example of a pilot tone system used in commercial frequency
modulation stations.
A. FDM
B. Time division
(C) Stereo multiplexing
D. Frequency modulation
21. Emission on a frequency or frequencies immediately outside the necessary bandwidth which
result from the modulation process except spurious emission.
A. radiation
B. Noise
(C) Out of the band
D. Interference
22. A helical antenna is used for satellite tracking because of _____________.
A. broad bandwidth
B. good front-to-back
C. maneuverability
(D) circular polarization
23. Background noise is the same as the following except
(A) impulse noise
B. white noise
C. thermal noise
D. Gaussian noise
24. An electric equipment used to measure standing wave ratio.
(A) Reflectometer
B. Waveneter
C. Altimeter
D. Multimeter
25. A single sideband emission in which the degree of carrier suppression enables
the carrier to be reconstituted and to be used for demodulation.
(A) Reduce carrier single sideband emission
B. Half carrier single sideband emission
C. Full carrier single sideband emission
D. Standard single sideband emission
26. Station in the mobile service not intended to be used while in motion.
A. Coast station
B. Fixed station
C. Base station
(D) Land station
27. The electric field lines in a plane perpendicular to the earth’s surface.
A. Elliptical polarization
B. Circular polarization
C. Horizontal polarization
(D) Vertical polarization
28. A digital carrier facility used to transmit a DSI-formatted signal at 1.544 Mbps.
A. T2
(B) T1
C. T4
D. T3
29. 12 voice channels are sampled at 8000 sampling rate and encoded unto 8 bit PCM word.
Determine the rate of the data stream.
A. 354 kbps
B. 750 kbps
(C) 768 kbps
D. 640 kbps
30. The most common device used as a alight detector in fiber optic communication system.
A. LED
B. Darlington phototransistor
(C) APDs
D. PIN diode
31. If a fiber optic system has a rise time of 38.55 ns, the source rise time is 12 ns and the detector rise time
is 12 ns, what is the cable rise time?
(A) 34.61 ns
B. 14.55 ns
C. 53.55 ns
D. 26.25 ns
32. Nominal voice channel
A. 20 to 20 kHz
B. 16 to 16 kHz
C. 3 to 3 kHz
(D) 4 kHz
33. Two or more antennas separated by 9 wavelengths are used.
A. Hybrid diversity
(B) Space diversity
C. Polarized diversity
D. Frequency diversity
34. nif stands for
A. narrow intermediate frequency
B. noise interference figure
(C) noise improvement factor
D. non-intrinsic figure
35. Any small element of space in the path of a wave may be considered as a source of
secondary wavelet.
A. De Morgan’s Principle
B. Faraday’s Law
(C) Huygen’s Principle
D. Fresnel’s Law of optics
36. Modulation in which the modulated wave is always present.
A. Carrier modulation
B. Front-end
(C) Continuous modulation
D. Log-periodic modulation
37. Atmospheric noise is less at severe frequencies above
A. audio level
(B) 30 MHz
C. 10 GHz
D. 1 GHz
38. At height about 180 km above the earth exist only during daylight.
A. F2 layer
B. D layer
C. E layer
(D) F1 layer
39. Radiation characteristics of a dipole.
A. Figure of eight
B. Omnidirectional
(C) Bidirectional
D. Unidirectional
40. Determine the gain of a 6 ft. parabolic dish operating at 1800 MHz.
A. 30 dB
B. 11.2 dB
C. 15.5 dB
(D) 28.17 dB
41. An electromagnetic wave is _________ polarized when the electric field lies wholly in one plane
containing the direction of propagation.
A. horizontally
(B) linearly
C. circularly
D. vertically
42. A device that reduces the intensity of light in fiber optics communication systems.
A. Reducer
B. Quality factor
(C) Optical attenuator
D. Compressor
43. Propagation mode of microwave in a waveguide is known as ________.
A. TM
(B) TE
C. SW
D. TEM
44. A convenient method of determining antenna impedance.
A. Stub matching
B. Reactance circle
(C) Smith chart
D. Trial and error
45. Which of the following falls under the high frequency band of the radio spectrum?
(A) 8.2345 MHz
B. 150.50 MHz
C. 2.4555 MHz
D. 35.535 MHz
46. The electric field lies in a plane parallel to the earth’s surface.
A. Elliptical polarization
(B) Horizontal polarization
C. Vertical polarization
D. Circular polarization
47. The use of telecommunication for the transmission of signals to initiate, modify or terminate
functions of equipment at a distance.
A. Tracking
B. Telemetry
(C) Telecommand
D. Space telemetry
48. The product of the power supplied to the antenna and its gain relative to a half-wave
dipole in a given direction.
A. Peak envelope power
(B) ERP
C. Rated power
D. Carrier
49. Width measured in degrees of a major lobe between end of the lobe at which the relative
power is one half (-3dB) its value from the peak of the lobe.
A. Bandwidth
B. Wavelength
C. Radiation
(D) Beamwidth
50. The sinusoidal carrier is pulsed so that one of the binary states represented by a carrier
while the other is represented by its absence.
A. FSK
(B) ASK
C. PSK
D. QAM

ECE Board Exam.Review april 1997

1. What is the impedance of a balance 4-wire with a diameter of 0.25 cm and
spaced 2.5 cm apart using an insulator with a dielectric constant of 2.56?
(A) 100 Ω
B. 65 Ω
C. 75 Ω
D. 50 Ω
2. What is the impedance in ohms of a transformer marked for 25V, 4W, when the
secondary is correctly loaded?
A. 150 Ω
(B) 156 Ω
C. 160 Ω
D. 165 Ω
3. A single conductor running from the transmitter to the antenna.
A. RG-8/U
(B) Single line wire
C. Twin-lead
D. Microstrip
4. If voltage change equal to twice its original value, what is its corresponding
change in dB?
A. 9 dB
(B) 6 dB
C. 10 dB
D. 3 dB
5. To couple a coaxial line to parallel line, it is better to use a ________.
A. slotted line
B. quarter-wave transformer
C. directional coupler
(D) balun
6. If you have available number of power amplifiers with a gain of 100 each, how
Many such amplifiers do you need to cascade to give an overall gain of 60 dB?
(A) 3
B. 4
C. 5
D. 2
7._______sets a limit on the maximum capacity of a channel with a given noise
level.
A. Hartley theorem
(B) Shannon-Hartley theorem
C. Nyquist theorem
D. Shannon theorem
8. Transmission sent both direction simultaneously.
A. Full duplex
(B) Duplex
C. Half duplex
D. Simplex
9. Industrial noise frequency is between ________.
A. 200 to 3000 MHz
(B) 15 to 160 MHz
C. 0 to 10 kHz
D. 20 GHz
10. Reference noise temperature.
A. 70 deg F
B. 30 deg C
(C) 290 Kelvin
D. 25 deg C
11. What is the reference frequency of CCITT psophometric noise measurement?
(A) 800 Hz
B. 1500 Hz
C. 290 Hz
D. 1000 Hz
12. Which does not affect noise in a channel?
A. none of these
B. bandwidth
C. temperature
(D) quantizing level
13. The random and unpredictable electric signals form natural causes, both interna
And external to the system is known as ________.
A. distortion
(B) noise
C. attenuation
D. interference
14. The most common unit of noise measurement in white noise testing.
A. dBw
B. dBk
C. dBm
(D) NPR
15. Unit noise power of psophometer
A. dBa
(B) pWp
C. dBm
D. dBmO
16. 100 % modulation in AM means a corresponding increase in total power by ______.
A. 25 %
B. 75 %
C. 100 %
(D) 50 %
17. If the modulation index of an AM wave is doubled, the antenna current is also
doubled, the AM system being used is
A. A5C
(B) A3J
C. A3H
D. A3
18. What particular circuit that rids FM of noise?
A. HPF
B. Phase Shifter
(C) Limiter
D. LPF
19. What is the advantage of PTM over PAM?
A. All of these
B. Low sampling rate is required
(C) Much better noise immunity
D. Simpler to generate
20. At 100% modulation, the sum of the effective voltages in both sidebands is
equal to _______ % of the unmodulated carrier voltage.
A. 50
(B) 71
C. 100
D. 25
21. A carrier signal has ________.
(A) constant peak amplitude
B. the information
C. frequency range of 20-20000 Hz
D. a varying amplitude
22. Which transmit only one sideband?
A. A3E
B. 3AJ
C. 11BE
(D) H3E
23. The final amplifier of either FM or AM transmitter operates as
A. class B
(B) class C
C. class A
D. class D
24. Modulation means
A. varying of information
B. utilization of a single transmission channel to carry multiple signals
(C) varying of some parameters of a carrier such as its amplitude to transmit
information
D. transmit pulses in DC form on a copper wire
25. What is the advantage of sidetone?
A. High transmission efficiency
B. Results to a strengthened signal
C. No energy dissipation
(D) Assures that the telephone is working
26. The standard test tone.
A. 0 dB
B. 10 dBm
(C) 0 dBm
D. 10 dB
27. One(1) Erlang is equal to ________.
A. 360 CCS
B. 100 CCS
(C) 36 CCS
D. 3.6 CCS
28. Transmission of printed material over telephone lines.
A. Video text
(B) Facsimile
C. Encoding
D. Xerox copy
29. 1-CCS is equal to
A. 60
(B) 100
C. 600
D. 1
30. 1 Erlang is _________.
A. 1000 TU
B. 10 TU
C. 100 TU
(D) 1 TU
31. When waves bend away from straight lines of travel, it is called _______.
(A) refraction
B. reflection
C. rarefraction
D. diffraction
32. Highest frequency that can be used for skywave HF communication between
two given points on earth.
A. Gyro frequency
(B) Maximum usable frequency
C. Critical frequency
D. Virtual frequency
33. Electromagnetic radiation theory was profounded by ________.
A. Sir Edward Appleton
B. Sir Isaac Newton
(C) James Clerk Maxwell
D. Michael Faraday
34. Distance travelled by a wave in the time of one cycle.
A. Hop
B. Frequency
(C) Wavelength
D. Crest
35. Which region of the ionosphere is mainly responsible for long distance
night time communications?
A. A layer
B. D layer
C. E layer
(D) F layer
36. The polarization of a discone antenna is ________.
A. horizontal
(B) vertical
C. omni
D. directional
37. ________ is the horizontal pointing angle of an antenna.
A. Right angle
B. Angle of elevation
C. Bandwidth
(D) Azimuth
38. Which is properly terminated antenna?
(A) Rhombic
B. Hertz
C. Marconi
D. Dipole
39. _________is a device that detects both vertically and horizontally
polarized signals simultaneously.
A. Crystal
(B) Orthomode transducer
C. Light transducer
D. Optoisolator
40. How much does the radiated power of an antenna increases if its current
increased by 3.3 times?
A. 6.6 times
B. 3.3 times
(C) 10.89 times
D. 9.9 times
41. What do you call the energy that was not radiated into space or completely
transmitted?
A. Incident waves
B. captured waves
(C) Standing waves
D. Modulated waves
42. The minimum number of turns a helix antenna must have.
A. 4
B. 5
(C) 3
D. 6
43. A device that radiates electromagnetic energy and or intercepts
electromagnetic radiation.
(A) Antenna
B. Transmitter
C. Transmission line
D. Transceiver
44. Full duplex transmission means
A. one way transmission
B. 24-hour transmission
C. broadcast transmission
(D) two-way simultaneous transmission
45. Transmission system for a multidrop network.
A. Token passing
( B) Polling
C. Switching
D. CSMA/CD
46. The method of determining the bandwidth of any processing system is _______
A. bandwidth analysis
B. frequency spectrum
(C) spectral analysis
D. frequency analysis
47. It is a protocol used to connect the other packet switching network.
A. X.25
B. X.50
C. X.10
(D) x.75
48. Slowest communications hardware product.
A. synchronous
(B) Asynchronous
C. ETHERNET
D. INTERNET
49. Data is directly on the transmission cable.
A. Asynchronous
B. Synchronous
(C) Baseband
D. Broadband
50. Gateway can interconnect LANS that have ______ protocols and formats.
A. the same
B. different or the same
(C) totally different
D. none of these

ECE Board Exam.Review Nov.1996

1. Which frequency band is the standard AM radio broadcast?
A. HF
B. UHF
(C) MF
D. VHF
2. A system that performs parallel-to-serial and serial-to-parallel conversion of data link.
A. DCE
(B) DTE
C. Modem
D. PC
3. The line control unit (LCU) operates on the data in digital form.
A. Data communications equipment (DCE)
B. UART
C) Modem
(D) Data terminal equipment
4. Quantization noise is caused by
A) binary coding techniques
B. serial transmission errors
C. the synchronization between encoder and decoder
(D) the approximation of the quantized signal
5. Speaker is a device that ______.
(A) convert current variation into sound waves
B. none of these
C. concert electrical energy to mechanical energy
D. concert sound waves into current and voltage
6. An object farther from a converging lens than its focal point always has an _____ image.
A. virtual
B. the same in size
(C) inverted
D. smaller size
7. The loss in signal power as light travels down a fiber is
(A) attenuation
B. propagation
C. absorption
D. scattering
8. Energy that has neither been radiated into space nor completely transmitted
A. Captured waves
B. Incident waves
(C) Standing waves
D. Modulated waves
9. One of the reasons why FDM is being replaced by TDM is
(A) noise is amplified with voice when an FDM system is used
B. it is difficult to place channel side by side
C. there is more time than frequency
D. most available frequencies has been used
10. Which determine the number of sideband components in FM?
A. Modulation frequency
(B) Modulation index
C. Carrier frequency
D. All of these
11. When one stations is designated as master and the rest of the station are considered slaves message handling is _____.
(A) polling
B. WAN
C. LAN
D. OSI
12. How many satellite orbital slots are requested by the Philippine government from ITU?
A. 2
(B) 6
C. 5
D. 3
13. The output of a balanced modulator is _____.
(A) LSB and USB
B. LSB
C. USB
D. Carrier
14. A special service circuit connecting two private branch exchanges (PBX)
A. Phantom line
B. Private line
(C) Tie trunk
D. Tandem trunk
15. What is the baseband frequency of standard FDM basic supergroup?
(A) 312 to 522 kHz
B. 300 to 600 kHz
C. 60 to 2540 kHz
D. 60 to 108 kHz
16. What is the data rate of the ISDN Basic access B Channel?
A. 192 kbps
B. 32 kbps
(C) 64 kbps
D. 144 kbps
17. What is the transmission rate of a GSM cellular system
A. 64 kbps
B. 240 kbps
C. 128 kbps
(D) 270 kbps
18. Pulse carrier at the radio of 8000 pulses/sec is amplitude modulated by an analog signal, this type of modulation is
(A) PAM
B. ADM
C. DM
D. PCM
19. Collects very weak signals from a broadcast satellite.
(A) Satellite dish
B. LNB
C. Yagi-Uda antenna
D. Satellite receiver
20. A seven-bit character can represent one of _____ possibilities.
A. 14
B. 64
(C) 128
D. 7
21. The maximum power suggested by KBP on 919-1312 Am broadcast station in Metro Manila is
A. 10 kW
(B) 20 kW
C. 15 kW
D. 5 kW
22. When the clearance above the obstruction is equal to the radii of even fresnel zone at the point of reflection the RSL is:
A. remain the same
B. above threshold
(C) decreased
D. increased
23. A______ interconnects LAN having identical protocols at the physical and data link layers.
A. all of these
(B) Bridge
C. router
D. gateway
24. Both frequency and phase modulation utilize ______ modulation.
A. phase
B. AM and FM
C. digital
(D) angle
25. An invitation from the primary to secondary to transmit a message.
A. Retransmission
B. Selection
C. Reuse
(D) Polling
26. An agency of the United Nations that formulates standards and recommended practices for all civil aviation.
(A) ICAO
B. CAA
C. IATA
D. ATO
27. The transformer signal coding method for T1 carrier is
A. binary
B. NRZ
C. Manchester
(D) bipolar
28. When the value of k increases, the effective result is ____ of the equivalent curvatures.
A. downward curvatunes
(B) flattening
C. bulging
D. sharp curvature
29. An electromagnetic wave consist of
A. a magnetic field only
(B) both electric and magnetic fields
C. an electric field only
D. non magnetic field only
30. Satellite signal transmitted from a satellite transponder to earth’s station.
A. Vertically polarized
B. Uplink
(C) Downlink
D. RHCP
31. Which stands for dB relative level?
A. dBm
B. dBm
(C) dBr
D. dBa
32. What is the maximum color TV bandwidth?
A. 1.6 MHz
B. 0.5 MHz
C. 1.0 MHz
(D) 1.3 MHz
33. Digital modulation technique used in modems.
A. ASK
(B) PSK
C. FSK
D. all of these
34. Which of the following is not a baseband signal of modulation.
(A) RF carrier
B. Video system
C. Audio signal
D. Binary coded pulses
35. When was the UHF (14-83) of television were added?
A. 1852
B. 1904
C. 1947
(D) 1952
36. Multiplexing in a time division multiplexer occurs based upon
A. the position of a frame within a group of frames
(B) the positioning of data within a frame
C. the priority assigned to a connected device
D. the activity of a connected device
37. Which is the non-resonant antenna?
A. Broadside antenna
B. Folded dipole
(C) Rhombic antenna
D. End fire array
38. The first commercial satellite.
A. Explorer
B. Sputnik
C. Telstar
(D) Early bird
39. What band does VSAT first operate?
A. X-band
(B) C-band
C. Ku-band
D. L-band
40. The wavelength of light has no role in
A. diffraction
B. interference
C. resolving power
(D) polarization
41. Luminous efficiency is least for a
A. mercury vapor lamp
(B) low-wattage light bulb
C. high-wattage light bulb
D. fluorescent tube
42. What is the equivalent output of a circuit in dBm, if it is has an output of 10 watts?
A. 145.6 dB
B. 138.5 dB
C. 135.5 dB
(D) 140.89 dB
43. Satellite engine use
A. liquid fuel
B. jet propulsion
(C) ion propulsion system
D. solar jet
44. Electromagnetic waves travel at ____ in free space.
(A) 300,000 km/sec
B. 100,000 km/sec
C. 400,000 km/sec
D. 200 km/sec
45. Codes must be
(A) agreed upon in advance between sender and receiver
B. eight bit per character
C. the same in all modern computer
D. either seven or eight bits per character
46. What is the stage of the sand becoming a silicon?
A. Hot
B. Gas
C. Liquid
(D) Molten
47. Noise reduction system used for film sound in movie.
A. dBx
(B) dolby
C. dBa
D. dBm
48. Combination of modulator, channel, and detector.
A. Tranceiver
(B) Discrete Channel
C. T/R channel
D. Transponder
49. What is the type of emission used by standard AM radio broadcast?
A. A0
B. F3
(C) A3
D. A5C
50. Top loading is used in an antenna in order to increase its _____.
A. input capacitance
B. beamwidth
C. bandwidth
(D) effective height

ECE Board Exam.Review 1996

1. That dielectric material of an optical fiber surrounding the core
(A) Cladding
B. Armor
C. Shield
D. Cover
2. An antenna that is circularly polarized is the ______.
A. parabolic reflector
(B) helical
C. Yagi-uda
D. small circular loop
3. A word in telegraphy consist of _____ Characters plus a word space
A. 11
(B) 7 and ½
C. 8
D. 5
4. The number of voice band channels in a master group per CCITT standard is ______.
(A) 300
B. 480
C. 600
D. 120
5. The power of standard test tone is normally ______.
A. 1 dB
B. 0 mW
(C) 1 mW
D. 1 W
6. LORAN is a navigation system used primarily for
A. approach control
(B) obtaining fixes over large distances
C. blind landing
D. automatic collision warning
7. At what power level does a 1kHz tone cause zero interference (144 weighted)?
A. -90 dB
(B) -90 dBm
C. 90 dBm
D. 90 dB
8. One character or a sequence of characters forming a part, or the whole of a message with a specific meaning.
A. Signs
B. Call sign
(C) Code
D. Identifier
9. The K-factor under normal atmospheric conditions in a microwave radio data profile calculation is equal to ______.
A. 2/3
B. 0
(C) 4/3
D. infinity
10. What is the IBM’s asynchronous data link protocol designation?
(A) 83 B
B. 8A1/8B1
C. 93 B
D. 9 A1/9B1
11. EIRP stands for _______.
A. effective isotropic refracted power
B. efficient and ideal radiated power
C. effective isotropic reflected power
(D) effective isotropic radiated power
12. The modulation system used for telegraphy is
(A). frequency-shift keying
B. two-tone modulation
C. pulse-code modulation
D. single-tone modulation
13. The standard that specifies a balanced interface cable that will operate bit rates up to 10 Mbps with a span distances up to 1200 m.
(A) RS-423A
B. RS-422A
C. RS-550A
D> RS-449A
14. The antenna which is not resonant at s particular frequencies and so can be used over a wide band of frequencies is called
(A) aperiodic
B. boresight
C. cassegrain
D. top-loaded
15. ______ occurs when the microwave beam is at point of grazing over an obstacle.
(A) Diffraction
B. Refraction
C. Absorption
D. Reflection
16. Atmospheric condition is controlled by
A. humidity
B. pressure
C. temperature
(D) all of these
17. The characteristic impedance of a transmission line does not depend uponits ____.
A. conductor spacing
B. conductor diameter
(C) length
D. conductor radius
18. The point on the satellite orbit, closest to the earth is
A. progade
(B) perigee
C. zenith
D. apogee
19. The potential difference between any exposed structured to ground in any electrical installation should not exceed ______ volts RMS.
A. 10
(B) 45
C. 0
D. 30
20. The capture area of an antenna is directly proportional to the
A. frequency of the received signal
B. distance between transmitter and receiver
(C) gain of antenna
D. power density of the signal
21. Modems are required to connect computer to telephone lines because _______.
A. telephone company rules required them
B the telephone network bandwidth is too high
C. none of the above
(D) the telephone network will pass direct current
22. The standard reference antenna for the directive gain is ________.
A. elementary doublet
(B) isotrophic antenna
C. half-wave dipole
D. infinitesimal dipole
23. It is a spacecraft placed in orbit around the earth carrying onboard microwave
receiving and transmitting equipments.
A. Fiber optic equipment
(B) Communications satellite
C. Wireless radio system
D. Coaxial cable system
24. One type of pulse communications system uses pulse that appear as a group,
and which vary in number according to the loudness of the voice. This type of
Pulse modulation is called
(A) pulse duration modulation
B. pulse amplitude modulation
C. pulse code modulation
D. pulse position modulation
25. A device to be connected across the headset in telephone receivers to reduce
the effects of acoustic shock.
A. Ground
(B) Two rectifiers in parallel with opposite polarities
C. Protector
D. Fuse
26. Judgment on the case against an ECE shall become final and executory after
A. 10 days
B. 60 days
(C) 30 days
D. 15 days
27. The equivalent noise temperature of the amplifier is 25 K. What is the noise
figure?
A. 1.86
B. 0.1086
(C) 1.086
D. 10.86
28. The letter-number designation B8E is a form of modulation also known as
_________.
A. pilot-carrier system
(B) independent sideband emission
C. lincomplex
D. vestigial sideband transmission
29. When the transmission and receiving antennas are in line-of-sight of each other,
the mode of propagation is _________ wave.
(A) space or direct
B. ground
C. surface
D. sky
30. According to the Nyquist theorem, the sampling rate that can be used in a PCM
system is _______ the highest audio frequency.
A. once
B. eight times
(C) twice
D. thrice
31. Passive crossover components cause some frequencies to be delayed with
respect to the other frequencies at the crossover point.
(A) Phase shift
B. Phase correction
C. Phase-error correction
D. Time alignment
32. A car horn outdoors produces a sound intensity level of 90 dB at 10 ft away. At
this distance, what is the sound power in watt?
A. 12 W
(B) 0.12 W
C. 0.012 W
D. 1.2 W
33. What is one principal difference between synchronous and asynchronous
transmission?
A. the pulse height are different
( B) the clocking is derived from the data in synchronous transmission
C. the clocking is mixed with the data in asynchronous
D. the bandwidth required is different
34. The lowest layer is the ionosphere.
(A) D
B. F2
C. E
D. F1
35. What is the number of pins in the RS-232C interface?
(A) 25
B. 15
C. 20
D. 20
36. SSB transmission requires only _______ of the bandwidth for a DSBFC
transmission.
A. ¼
B. 2/3
(C) ½
D. ¾
37. The method of generating FM used by broadcasting station i
A. direct
B. all of these
(C) indirect
D. insertion
38. What is the transmission rate of a system for transmitting the output of a
microcomputer to a line printer operating at a speed of 30 lines/minute?
assume that the line printer has 8 bits of data per character and prints out 80
characters/line.
A. 800 bps
B. 400 bps
(C) 320 bps
D. 640 bps
39. Communications code is _________.
A. eight bits per character
(B) agreed upon in advance between sender and receiver
C. the same in all modern computers
D. either seven or eight bits per character
40. What is the reference tone level for dBm?
A. -82 dBm
B. -85 dBm
C. -67 dBm
(D) -90 dBm
41. A type of an undergrounded antenna is a/an _________ antenna.
(A) Hertz
B. isotropic
C. parabolic
D. Marconi
42. Which of the following pulse modulation systems is analog?
A. Delta
B. Differential PCM
(C) PWM
D. PCM
43. TACAN is a navigational aid providing _________.
(A) bearing and distance indication
B. speed and height indication
C. bearing and weather information
D. instrument-landing glide paths
44. In ________ transmission, a unique SYN character is transmitted at the
beginning of each message.
A. asynchronous
(B) synchronous
C. digital
D. analogue
45. If the terminating impedance is exactly equal to the characteristic impedance of
the transmission line the return loss is _______.
A. zero
B. one
(C) infinite
D. none of these
46 What is the main purpose of a communication systems?
A. None of these
B. To have a frequency assignment
C. For modulation
(D) To provide an acceptable replica of the information at the destination.
47. In the phase shift method, how many circuits must be balanced?
A. none of these
(B) 1
C. 4
D. 2
48. The carrier swing necessary to provide 80% modulation in the FM broadcasting
band is ________.
A. 150 kHz
B. 120 kHz
C. 60 kHz
(D) 75 kHz
49. The correctness and accuracy of the transmitted message content is
A. verified by the modem
(B) communication system
C. determined by the sender and receiver
D. ensured by use of digital technique
50. After the IF stages have been aligned, the next stage to align in FM receiver is
(A) local oscillator
B. limiter stage
C. RF amplifier
D. mixer stage