Communications Engineering 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

#	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

Communications Engineering Coaching Materials

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