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