Communications Engineering Coaching Materials: Section 5 Module 21

This is the Section 5 Module 21 of the compiled Communications Coaching Materials taken from different sources including but not limited to Communications books, past Board Exams Questions, Journals and the Internet.

Communications Coaching Materials: Section  5 Module 21

This is the Section 5 Module 21 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 21



1. Ratio of incident to transmitted radiation through a grid ratio of patient dose with and without grid

Bucky Factor

2. ECG recording requires a bandwidth of 0.05 to ______


3. Period during which the heart contracts


4. Who completes the development of first computed CT scanner in 1973


5. Study of the response of an image receptor to x-rays


6. Ratio of Radiographic contrast with a grid to that without a grid

Contrast Improvement Factor

7. Type of luminescence where the visible light is emitted only during the stimulation of phosphor


8. A phenomenon caused by any support insulators used at the ends of the wire antenna

End effect

9. Process of converting an infinite number of possibilities to a finite number of conditions


10. Which of the following is NOT a reason why most half wave antennas are mounted horizontally at low frequencies

More cost-effective

11. A 4-wire gigabit Ethernet implementation

1000 base T

12. Radiation doses in the range approximately 200 to 1000 rad produce the _____ syndrome


13. Modulation technique in which the frequency of the modulated signal varies with the amplitude of the modulating signal


14. Highest layer in the hierarchy and is analogous to the general manager of the network by providing access to the OSI environment

Application layer

15. Handset is in cradle

On hook

16. Hartley’s law


17. A small variable capacitance in parallel with each section of ganged capacitor is called ____


18. Most commonly used digital modulation scheme


19. Form of redundancy error checking where each character has a numerical value assigned to it


20. An 8 bit fixed length character set developed in 1962 by IBM


21. 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 ______ rad


22. Designed to send characters of the message with the specified bit rate without any fixed timing relationship from one character to the next


23. Waveguide acts as a/an ____ filter

High pass

24. Data communication refers to the transmission of

All of the above

(data, audio, voice)

25. Token Ring standard


26. Error correction scheme that actually detect and corrects transmission errors when they are received without requiring a retransmission

Forward error correction

27. A/an _______ is a range of frequency in which the upper frequency is double the lower frequency


28. Often used to compare the performance of one digital modulation technique to another

Bandwidth Efficiency

29. One complete revolution around a Smith Chart represents ___wavelength


30. At exactly one wavelength, the short circuited transmission line behaves as a/an _______ circuit

Parallel resonant

31. A mismatched transmission line is also referred to as a ___ line


32. A flat conductor separated by an insulating dielectric from a large ground plane that is usually one quarter or one half wavelength long


33. How many wavelengths long are required for a pair of conductors to be considered as a transmission line

1/10 Lambda

34. Most common means of overcoming the problems of quantizing error and noise


35. The shape of the electromagnetic energy radiated from or received by an antenna is called the

Radiation pattern

36. Ratio of the speed of propagation on a line to that of light in free space

Velocity factor

37. This means that the characteristics and performance of an antenna are the same whether the antenna is radiating or intercepting an electromagnetic signal

Antenna reciprocity

38. Most widely used UTP cable that can carry baseband data at rates up to 100Mbps at a range up to 100m


39. Used to lower the resonant frequency of a shortened vertical antenna

Top hat loading

40. Optical electronic device that measures the color concentration of a substance in solution


41. Why DSB is not widely used

Signal is difficult to demodulate

42. Refers to the emission of electrons from a clean metallic surface when electromagnetic radiation falls onto that surface

Photoelectric effect

43. System wherein the input in a transmitter is a collector modulated

High level modulator

44. Recording of heart sounds


45. Unit of radiation exposure that will produce 2.08x10^9 ion pairs per cubic cm of air at STP


46. Recorder for measuring galvanic skin resistance


47. A digital process that allows several connections to share the high bandwidth of a link


48. Apparatus for measuring blood pressure


49. The government agency that regulates radio communications in the US


50. Antennas that transmit an equal amount of energy in the horizontal direction are called ___________


51. Circuit used to return the frequency response of a signal to its normal “flat” level


52. The oldest microwave tube design which is commonly used in radar transmitters where they can generate peak power levels in the megawatt range


53. A quarter wavelength of coaxial or balanced transmission line of a specific impedance connected between a load and a source in order to match impedance is

Q section

54. The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as ______


55. Which antenna usually consist of two or more halfwave dipoles mounted end to end


56. When the characteristic impedance of the transmission line matches the output impedance of the transmitter and the impedance of the antenna itself

Maximum power transfer will take place

57. An antenna made up of a driven element and one or more parasitic elements is generally referred to as _______


58. Noise that is primarily caused by lightning, sometimes referred to as static noise

Atmospheric noise

59. A modulation process wherein both frequency and phase remains constant while the amplitude changes


60. Allows a wide variety of computers to share the same network


61. A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form a

Parasitic array

62. An antenna consisting of halfwave dipoles spaced from one another by one-half wavelength is the

Broadside array

63. Error correcting code used for correcting transmission errors in synchronous data streams

Hamming code

64. Horizontal frequencies for DTMF

1209 Hz, 1336 Hz, 1477Hz,1633Hz

65. Using DTMF, #8

852Hz and 1336 Hz

66. In DTMF, horizontal frequencies are also known as ______ frequencies

High group

67. In DTMF, vertical frequencies are also known as ______ frequencies

Low group

68. In PCM, it translates the quantized samples into digital code words


69. An error detection technique in which a redundant bit is appended to every data unit so that the total number of 1’s in the unit (even the parity bit) becomes even

Vertical redundancy check

70. Reception of portions of a signal from one channel in another channel


71. Type of digital modulation that uses two or more different output frequencies


73. Primary purpose is to serve as structural guideline for exchanging information between computers, workstations and network


74. A LAN topology in which the individual terminal, microcomputers or workstations are connected directly to a central computer


75. Loss of data that occurs when two stations transmit on a network at the same time


76. A network topology in which data circulates from one computer to the next in sequence


77. Combination of amplitude and phase modulation


78. Means of transmitting data by shifting the phase angle of the transmitted signal


79. 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


80. Telephone switch that connects only to other switches and not to individual customers

Tandem office

81. A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called ______


82. The wavelength of a wave in a waveguide

Is greater than in free space

83. The most common circuit used for demodulating binary FSK signal


84. Geostationary satellites are located at ______ with respect to the equator

0 degrees latitude

85. The quality of a space-link is measured in terms of _____ ratio


86. The nominal uplink frequency for the Ku-band

14 Ghz

87. The downlink frequency appear to vary by several kHz during a LEO satellite pass due to the change in the distance between the satellite and ground station, which is referred to as

Doppler effect

88. A satellite dish owner has a 3m 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

Gain increases by9.54 dB, beamwidth decreases to 1/3 of its value

89. The most ambitious LEO constellation to date is


90. Antenna 1 has a gain of 5.3 dBi while antenna 2 has a gain of 4.5 dBd. Which of the following is true?

Antenna2 has a higher gain

91. Beamwidth is measured

Between half power points

92. A half-wave dipole is sometimes referred to as

Hertz antenna

93. An antenna can be matched to the feedline using

All of the above (shorted stub, LC network, loading coil)

94. “Ground Effect” refers to the effects on an antenna’s radiation pattern caused by

Radio signals reflecting off the ground

95. LPDA stands for

Log Periodic Dipole Array

96. As the length of a “long-wire” antenna increases

The number of lobes increases

97. A receiving antenna with a built-in preamplifier

Active antenna

98. Field strength at a distance from an antenna is measured with

Field strength meter

100. Cable used for local loops in telephone system is mainly

Twisted pair copper wires

101. Transmission from mobile unit to base station

Reverse link

102. The bandwidth of voice grade signals on a telephone system is restricted to

Allow signals to be multiplexed

103. 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

Regional center

104. AMPS

Advanced Mobile Phone Service

105. MSC

Mobile Switching Center

106. IMSI

International Mobile Subscriber Identification

107. BSC

Base Station Controller

108. In GSM, voice channels are called


109. In Mobile Communications, GSM uses

Frequency hopping

110. An acoustical phenomenon wherein the sound continues to persist even after the cause of the sound has stopped resulting in repeated reflections is called _____


111. A type of microphone that uses the principle of a capacitor as a means of transduction. It uses a polarizing voltage of between 9 to 48V DC supply applied to its diaphragm by an external power supply


112. A number from 0 to 1 representing the ability of a surface material to absorb sound energy

Absorption Coefficient

113. The difference in dB between the loudest level of sound and the softest passage of sound is known as

Dynamic range

114. Refers to the direction in space of electric vector of the electromagnetic wave radiated from an antenna and is parallel to the antenna itself


115. Placing a metallic array on the antenna effects to increase the current at base of the antenna, and also to make the current distribution more uniform is called ________

Top Loading

116. What principle states that the properties of an antenna are independent of whether it is used for transmission or reception

Principle of reciprocity

117. Often used to cure the problem of great thickness required of lenses used at lower microwave frequencies


118. 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


119. Any array that is directional at right angles to the plane of the array is said to have _____

Broadside action

120. The ratio of the focal length to the mouth diameter is called ________ of the parabola, just as in camera lense


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