This is the Section 5 Module 7 of the compiled Communications Coaching Materials taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize each questions to increase the chance of passing the ECE Board Exam.
Communications Engineering Coaching: Section 5 Module 7
1. 4:1 → Impedance matching ratio if a coax balun
2. No power is applied → When VSWR is equal to zero
3. Reflection Coefficient → Ratio of reflected voltage to the forward travelling voltage
4. 1 → The standing wave ratio is equal to __ if the load is properly matched with the transmission line
5. Resistive load at the resonant frequency → Transmission lines when connected to antennas have
6. 36 CCS → 1 Erlang
7. 83 ohms → For an Air dielectric, two wire line, the minimum characteristic impedance value is
8. 300-3400 Hz → Telephone channel has a band pass characteristic occupying the frequency range of
9. 0-4 kHz → Nominal Voice grade using PTN has an ideal passband of
10. 300 -3400 Hz → Standard analog telephone channel
11. G.122 → CCITT recommendation for a preparation of loss plan, a variable loss plans and a fixed loss plan
12. Quarter-wave Matching → One method of determining antenna impedance
13. VF Repeaters → __ are unidirectional amplifiers having 20-25 decibel gain that are placed about 75 km apart used to compensate for losses along the telephone line
14. Single-wire line → A single conductor running from the transmitter to the antenna
15. waveguides → The transmission lines which can convey electromagnetic waves only in higher modes isusually
16. to keep the waveguide dry → Why is nitrogen gas sometimes used in waveguide?
17. F3C and A3E → Emission designation for a facsimile
18. the line behaves as a parallel tuned circuit in relation to the generator → If a quarter-wave transmission line is shorted at one end
19. any convenient value → A 50 ohms transmission line is feeding an antenna which represents a 50 ohms resistive load. To shorten the line, the length must be
20. 120 ohms → Is not a common transmission impedance
21. transversely across the narrow dimension of the waveguide → A rectangular waveguide is operating in the dominant TE10 mode. The associated flux lines are established
22. at the beginning and at the end of the cable → The outer conductor of the coaxial cable is usually grounded
23. at a distance of one quarter wavelength from the sealed end → If a rectangular waveguide is to be excited in the dominant mode, the E-probe should be inserted
24. 1 → Desirable SWR on a transmission line
25. Reflectometer→ Measures SWR
26. 300 ohms → 214-056 twin lead which is commonly used for TV lead-in has a characteristics impedance of
27. 0 → Most desirable reflection coefficient
28. Phon → Unit of loudness level
29. Mel → Unit of Pitch
30. 115.56 dB SPL → 120 micro bars of pressure variation is equal to
31. ¼ → If the distance between the listener and the source of the sound is doubled, the intensity is reduced to
32. 4 times as great → If the distance between the listener and the source of the sound is decreased ½ the original amount, the intensity of the sound is
33. Threshold of hearing → The minimum sound intensity that can be heard is termed
34. Distortion → Is an undesired change in wave form as the signal passes through a device?
35. Distortion → Diagonal clipping in envelope detection will result in
36. Multiplication → Is a frequency change process, whereby the phase deviation and frequency deviation are multiplied by some fixed constant?
37. Frequency Modulation → The modulation system is ___ if the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant
38. Frequency Deviation → In FM, Carson’s Rule states that the bandwidth is equal to twice the sum of the modulating
frequency and __
39. triggered multivibrator → One implementation of a pulse averaging discriminator
40. higher value of operating power → The advantage of a high level modulated AM transmitter is
41. Interference to other radio services → Is the bad effect caused by over modulation in AM transmission?
42. have the same frequency → Two different signals can be coherent if they
43. 120 ohms → Not widely used impedance
44. Spectrum Analyzer → Test instrument that displays the carrier and the sidebands amplitude with frequency to frequency?
45. Buffer → Stage in a radio transmitter that isolates the oscillator from the load
46. 3 components → A single tone amplitude modulated wave has
47. 1300 ohms → The resistance limit for No. 2 Crossbar Exchange (US)
48. 0.51 dB/1000 ft → AWG # 26 has a typical loss of
49. Crosstalk → Cause a herringbone pattern in facsimile
50. 12 → How many simultaneous calls does each DECT system can support?
51. 1983 → Cellular mobile system was first operated in
52. 3 → RG-58 cable has a loss of about __ dB at cellular frequencies up to 15 feet length
53. 10 mW → Power output of Personal Communications System (PCS)
54. 1000 → TACS is a cellular system with ___ channels
55. 45 MHz → Frequency separation between the transmitter and receiver
56. 825.015/870.015 MHz → For channel 1, transmit/receive frequency
57. 666 → The number of transmit/receive channels in the cellular system is
58. 80 km → The transmission range of cellular telephony is generally about
59. Calling channel → Hailing channel
60. MTSO → All of the cell base stations are linked together by __ which serves as the central office and management node for the group
61. Echo Suppressor → Is a voice operated device that inserts a high loss in the opposite direction of transmission of the talking party
62. TPS → Type of connector arrangement wherein a customer may move to another location and still retain the telephone number
63. Poisson → Block calls held condition specified the held probability at time period equal to an average holding time
64. TDMA → Multiple access used by DECT
65. GFSK → Modulation technique used by DECT
66. Digital AMPS → Voted cellular digital standard at TIA
67. 416 → Number of channels for Band A and for Band B in Digital AMPS
68. Jaynes maximum entropy principle → __ of a data reduction says that when reducing a set of data into the form of an underlying mode, one should be maximally non-commital with respect to missing data
69. 6000 Hz → Supervisory Audio Tone (SAT) has __ frequency
70. 100000 → System capacity of AMPS
71. 0 dBm = 0 V.U. → A sine wave
72. Sound Intensity → What is the sound energy per unit area at right angles to the propagation direction per unit time?
73. Sound Intensity → Is the average rate of transmission of sound energy in a given direction through a cross section area of 1 sq. m. At right angles to the direction
74. 1 → Maximum Voltage to be perfectly matched in transmission line
75. 1 to 100 GHz → Microwave frequencies are normally regarded as those in the range of
76. to keep the electrons from spreading out → What is the purpose of the electromagnetic field which surrounds travelling wave tube?
77. Klystrons → High power TWT are replacing what in microwave amplifiers?
78. Blue → Color Code for Channel 1 in Light Spectrum
79. 6 dB → What is the increase in SPL in dB if the pressure is doubled?
80. Base to Mobile → In PCS, Forward Channel is
81. Reverse Channel → Mobile to Base in PCS
82. Terahertz → Photonics
83. 900 → How many groups are the in a super jumbo groups?
84. 564 – 3084 kHz → FDM U600 Mastergroup
85. No refraction will occur → If Angle of incidence is zero
86. Huffman Code → A source code whose average world length approaches the fundamental limit set by the entropy of a discrete memory less source
87. 10 → Peak power level for klystron amplifier
88. 1.55 micro meters → “Windows” longest wavelength
89. Non- resonant → The impedance measured at the input of the transmission line when its length is infinite or when it is terminated by its own impedance is known as the characteristic impedance in a ____ line
90. Dissipation Factor → Relative Energy loss level of a capacitor
91. Installation → In fiber optic, ___ range is critical
92. It is relatively free of spurious signal → Control oscillator synthesizer is preferred over direct one because
93. the MTSO checks your SID in the data base → In cellular telephony, roaming?
94. 10-20 dB/km → Optical fiber loss?
95. 300 – 3400 Hz → Voice grade channel
96. 140 → Amplitude characteristic of a video signal, where pure white is define in IRE, it has a total of
97. IMPATT → Low power radar uses
98. Operational Amplifier → Use in oscillator, amplifier, negative feedback, etc.
99. DVB-T → Modulation technique in Europe
100. 10 mW → FCC AM broadcast channel 10 has a power of
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