This is the Section 1 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 1 Module 7
1. Speech power – typically ¼ to 1/3 of PEP
2. CATV channels – between channels 6 and 7 (wideband); above channel 13 (superband)
3. VCR data – FM modulation
4. Superjumbo group – 10,800 channels
5. GPS – user segment, space segment, control segment; main control – Falcon Air Base, Colorado, USA
6. Magic T – hybrid T
7. Feed horn – horn amplifier that feeds a reflector
8. 100 dB exposure – 20 mins
9. Datawire – term for the communication channel over which data is transmitted
10. Slope detector – vulnerable to noise degradation
11. Ratio detector – more amplitude dependent but lower demodulated signal level (50%)
12. Varactor diode (for direct FM) – 12:1 ratio of capacitance
13. IF amp – most of the receiver’s selectivity/gain
14. SSB signals – more prone to frequency distortion because there’s no carrier to serve as reference
15. Lattice modulator – most commonly used SSB modulator
16. Losses in fiber optic cable – material/absorption losses, scattering losses, dispersion losses
17. Splice is better that connectors because there is no air gap
18. PCS – plastic-clad silica; uses silicon plastic
19. Fiber construction:
Glass – low attenuation; brittle
Plastic – high attenuation
20. Radar – 2 types: continuous wave (CW) and pulsed
21. TACS – 1G system used in England; 8 kbps data rate
22. LIDAR – optical version of radar; light direction and ranging
23. Frequencies directly above 300 GHz – millimetric waves
24. Sunlight radiation – 300 nm - 2000 nm (UV to infrared)
25. Human ear – best response – 1- 4 kHz
26. If the desired area to capture cannot fit into the camera’s field of view, use a lens with shorter focal length
27. Ultor – main accelerating anode
28. Grid-dye meter/detector – for measuring RF current/power in antenna; for measuring resonant frequency of RF circuits
29. Hamming code – corrects 1 bit only
30. TDD – time division duplexing – 2 way communication channels are separated in time via time slots
31. Microwave communication is being used because of wide bandwidth
32. To protect against fading – frequency diversity; space diversity
33. Fresnel reflection – reflection of waves through 2 media; involves materials w/ different index of refraction; also involves angle; reflection of part of incident light
34. Initial payload – main satellite in the satellite launch
35. 8-VSB – standard for digital TV
36. Why digital TV? – possibly less BW, more immunity to noise, more signal processing
37. For UHF frequencies, transmission lines are used in place of LC networks.
38. Interlacing – technique to reduce flicker of TV picture w/o increasing BW
39. No. of scanning lines (conventional TV) – 525
40. Effective no. of scanning lines – (utilization factor) (525) = resolution of picture
41. HDTV – up to 1125 lines; 5 times more video info compared to conventional TV picture
42. Video signal w/o sync pulse – noncomposite video signal
43. Commercial (analog) telephone service – NTT, 1979
44. Problem of 1G – a phone’s code can be stole and copied – clone fraud
45. Why is it hard to transmit music using SSB? – it is difficult to produce 90° phase shift for AF in the 5-10 kHz range
46. Modern pool – alternative to having a dedicated modem + telephone line connection for each workstation
47. Inertial Navigation Systems (INS) – part of most aircraft/ships today
48. Republic and Titanic (1910 and 1912) – sinking led to mandatory 24-hr ship-to-shore communications
49. Anisochronous – no relationship in the time interval (“chronous”) between Tx and Rx data
50. Dolby AC-3 surround sound – sound with compressed data rates
51. Microphones:
Carbon – economical
Dynamic
Condenser – weak response
52. Broadband wireless access for fixed, nomadic, mobile:
In MHz:
450-470 2400-2483 5150-5350
1900-1910 2500-2700 5470-5850
1980-1990 3400-3600 10150-10650
53. SUF for 3G (per MHz, M-million):
Frequency paired unpaired
5 MHz P 5M P 3M
5th-10th 8M 6M
10th-15th 10M 8M
>15th 15M 12M
54. Ambiophony – adjusting reverberation by providing loudspeaker feedback
55. 2% of main signal – to provide minimum interference
56. Bluetooth – IEEE 802.15; 720 kbps; 1mW
57. Wimax – 802.16
58. Zigbee – 802.15.4; cost-efficient; low power; low data rate
59. Wifi – 802.11b; 11 Mbps; 54 Mbps
60. Vinton Cerf – father of internet
61. ITU-T – telecommunications standards bureau
62. William Gibson – 1984; coined “cyberspace” in “Neuromancer”
63. EO 467 – national policy on the operation and use of international satellite.
64. EO 205 – regulation of CATV
65. EO 101 – improvement of LEC service
66. EO 469 – satellite; March 17, 1998
67. 1% harmonic distortion for CATV
68. Range of CDMA – 13 miles; BW = 1.23 MHz
69. Birth of WWW – 1991
70. 1918 – superheterodyne receiver; Edwin Armstrong
71. 820 nm – 2.5 dB Rayleigh loss
72. 0.7 μm – 100 μm – IR wavelength
73. Radio Act of 1910 – first attempt at radio regulation
74. Hydrazine – fuel for jet thrusters
75. Middle C – 262 Hz
76. Cavity resonator – high Q parallel LC circuit
77. Hoghorn – parabolic cylinder plus horn antenna
78. 15 yrs – max permit length of CATV operator authentication
79. Iridium – 780 km; 66 satellites
80. 1978 – first GPS satellite launched
81. L band – used for navigation
82. 3G – “2 to 4 times” 2G
83. 2G – 3000-20,000 people per cell site
84. 1G – 1000 people, 50 radio channels
85. Cell site – 10-50W
86. П-L network/ inductive coupling – against harmonics/ greatest harmonic suppression
87. Digital microwave – PSK/QAM
88. Cable TV supplying power and signals – 30 Vac or 60 Vac
89. UWB – 20/30 ft.; 500 MHz or 20% of center frequency
90. Randall and Boot – some type of magnetron
91. Beamwidth of horn antenna – 10° - 60°
92. Thick Ethernet – 10 Base 5 (old thick Ethernet)
93. Thin Ethernet – “cheapernet”
94. Button microphone – used in telephones
95. Telemetry – 481.25 - 481.725; 486.25 - 486.725
96. CB – 26.965-27.475 MHz
97. International AM station – min 50 kW
98. P 900 – license fee for head-end licensing
99. F-type connector – commonly used for TV, etc.; cheap
100. Cyan – 90° leading color burst
101. 125 μm – cladding diameter
102. Highest sunlight power – at 500 nm
103. IS-136 – North American digital cellphone standard
104. IS-95 – CDMA
105. Gyrotron – high power; >100GHz; USSR 1971
106. Backward-wave oscillator (BWO) – TWT + slow wave structure (RF + e-beam)
107. CB antenna height – 60 ft. above ground; 20 ft. above building
108. Jabber – random data sent by NIC
109. 9 pm - 7 am - no push/broadcast messages in paid subscription for such messages
110. For 2 kW transmit power, 2860W power
111. Velocity factor – 0.9 – twin lead; 0.9 – open wire; 0.5-0.9 in general
112. Shift register – used as bit-splitter
113. Phase splitter – push-pull amplifier
114. Input of quadrature phase detector – differential amplifier
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