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Communications Engineering Coaching Materials: Section 5 Module 2

Communications Coaching Materials: Section 5 Module 2

This is the Section 5 Module 2 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 2


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Questions

Answers

102

Impedance matching ratio of coaxial balun

4:1

103

Energy neither radiated nor transmitted

Standing waves

104

Transmission lines are either balanced or unbalanced with
respect to

ground

105

Apparent speed of propagation along a waveguide based on the
distance between wavefronts along the walls of the guide

phase velocity

106

Coaxial are grounded

Both input and output

107

Why concentric transmission lines sometimes field with
nitrogen?

keep moisture out and prevent oxidation

108

Conductance takes place in a waveguide

through electromagnetic and electrostatic fields in the walls
of the waveguide

109

If a ¾ wavelength transmission is shortened at one end,
impedance at the open will be

infinite

110

To be properly matched the ratio of a maximum voltage along a
transmission line should be equal to 0

1

111

The ratio between energy absorbed to the total energy received

absorption coefficient

112

The higher the gauge number

the higher the resistance, smaller the diameter

113

Short length of transmission line used to eliminate standing
waves

lambda/4 transformer

114

gain of half wave dipole

2.15 dB

115

TACAN is a navigational aid providing

bearing and distance indicator

116

glideslope

329.30 to 335.00 MHz

117

Localizer

108.10-111.95 MHz

118

DME

962 MHz to 1213

119

Compandor

compressing

120

45 baud

22 kbps

121

One half of the spacing between the start positions for
scanning even and odd fields

exact interlacing

122

What is Selective fading effect?

A fading effect caused by phase differences between radio wave
components of the
same transmission, as experienced at the receiving
point

123

lowest frequency

fundamental

124

exchange of predetermined signal

Huffman code

125

Which computer terminal can be reprogrammed to perform new
functions?

Intelligent terminal

126

Luminous efficiency is least for

low-wattage light bulb

127

each point on a wavefront maybe regarded as a new source of
secondary wavelength

Huygen’s Principle

128

Nearest distance from satellite orbit to earth

Perigee

129

Antenna is continuously adjusted with respect to satellite

despun antenna

130

Maximum radiation mr/week

100

131

Device to measure exposure to hazardous environment

dosimeter

132

When the earth’s atmosphere is struck by meteor, a cylindrical
region of free electrons is formed at what layer of the ionosphere?

E layer

133

What is the propagation effect called when phase differences
between radio wave components of the same transmission are experienced at the
recovery station?

selective fading

134

occurs when the refractive index of the air decreases with
height much more rapidly than normal

superrefraction

135

region in which superrefraction occur

duct

136

When the magnetic field is perpendicular to ground

Horizontal polarization

137

Metric subdivision for VHF

metric

138

SSB compared to AM and FM measurement

peak positive, rms values respectively

139

Layer that disaapears at night, no effect on sky wave
propagation

D layer

140

highest frequency that will be returned down to earth

critical frequency

141

best frequency used that will be returned down to earth

optimum usable frequency

142

E layer

4 MHz

143

F2 layer

8 MHz

144

gyniometer

145

what emission modes suffer the most from selective fading?

FM and double sideband AM

146

Band that operates in sky wave propagation

3 MHz to 30 MHz

147

Which band does channel 14 of the TV channel belong?

UHF

148

What propagation condition is usually indicated when a VHF
signal is received from a station 500 miles away?

Tropospheric ducting

149

What happens to a radio wave as it travels in space and
collides with other particles?

Kinetic energy is given up by the radio wave

150

What is the maximum range for signals using transequatorial
propagation?

About 5,000 miles

151

The band of frequencies least susceptible to atmospheric noise
and interference is

300-3,000 MHz

152

What is the relationship in degrees of the electrostatic and
electromagnetic fields of an antenna?

90 degrees

153

What is the best time of day for transequatorial propagation?

Afternoon or early evening

154

The propagation of radio wave

is the same direction as the electrostatic field of the antenna

155

What is knife-edge diffraction?

Allows normally line of sight signals to bend around sharp
edges, mountain ridges,
building and other obstructions

156

Skip distance can be maximized by using the ____ radiation
angle possible and the _____ frequency that will be refracted at that angle

lowest, highest

157

To obtain the most reliable sky wave propagation the
___________should be used

Optimum useable frequency (OUF)

158

Troposcatter is a method of sky wave propagation for which of
the following frequency
bands?

300 MHz to 3 GHz

159

What is the major cause of selective fading?

Phase differences between radio wave components of the same
transmission, as
experienced at the receiving station

160

A means of beyond the line of sight propagation of UHF signals

Troposcatter propagation

161

Which of the following is most affected by knife edge
refraction?

VHF and UHF frequencies

162

The ionosphere causes radio signals to be

refracted

163

The ionosphere has its greatest effect on signals in what
frequency range?

3 to 30 MHz

164

Maritime Communications Law

RA 3396

165

services of ECE’s

DO 88

166

autopilot

autopilot may sharply turn left or right

167

ratio of the maximum deviation frequency to modulating
frequency

Deviation Ratio

168

Modulation index

169

Neglecting line losses, the RMS voltage along an RF
transmission line having no standing waves

Is the product of the surge impedance and the line current

170

A technique of feeding a parabolic antenna using a small
reflector to beam waves to a larger parabolic reflector

Cassegrain feed

171

The process of interchangeability of receiving and
transmitting operations of antennas is known as

Reciprocity

172

A grid dip meter measures the resonant frequency of tuned
circuit

without power being applied to the tuned circuits

173

What gives more forward gain?

director

174

With similar size, which has the greatest gain?

Parabolic

175

Which is longer?

Reflector

176

What type of antenna receives signal equally well from all
horizontal directions?

Circular

177

How do parasitic element differ in length from a lambda/2?

5%

178

Testing of equipment

during experimental period

179

When a capacitor is connected in series with a Marconi antenna

antenna resonant frequency increases

180

In telephony, combination of

call waiting tone

181

How is it possible to lower the resonant frequency of hertz
dipole antenna?

by connecting an inductor

182

radiation pattern of isotropic antenna

sphere

183

Atmospheric attenuation is due to

water vapor and oxygen

184

Permits signal to travel in one direction

Ferrite isolator

185

Ascending pass for a satellite

pass from south to north

186

descending pass for a satellite

pass from north to south

187

What is the first letter in the ITU emission designation?

type of modulation of the main carrier

188

Fading is allowed

Secondary Service

189

Velocity of sound in wood

3300 m/s

190

NTT

191

Satellite of the same velocity as earth

Geostationary Satellite

192

Localizer

108.10- 119.95 MHz

193

Glide slope

329.30 – 335.00 MHz

194

Noise observed at frequency 8 to 1.4 GHz

Space Noise

195

antenna consisting of a reflector in the form of parabolic
cylinder, fed by a sectoral horn

hoghorn

196

What kind of impedance does a ¼ wavelength transmission line
present to a generator when the line is shorted at the far end?

a very high impedance

197

Concentrate the radiated power in a very small geographic
areas

Spot Beams

198

Black body is a perfect emmiter and absorber

True

199

Tonal quality of sound

Timbre

200

Longitudinal waves

Back and forth

201

What is the most important specification of loudspeakers and
microphones?

frequency response

202

strong FM signal dominating weaker signal on a common
frequency

Capture Effect

Complete List of Communications Engineering Coaching Materials

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