WorksheetsEST 2
Total questions: 50
Worksheet time: 17mins
What is the typical frequency used for communicating to submerged submarines?
100 Hz
500 Hz
4 kHz
200 Hz
Which frequency bands can be refracted during the day by the D layer?
VLF
MF
LF
Both VLF and LF
What height of an ionized layer is determined from the time interval between the transmitted signal and the ionospheric echo at vertical incidence?
Virtual height
Apparent height
Actual height
Effective height
During the night when the F2 layer combines with F1 layer it falls to what approximate height?
250 km
350 km
300 km
400 km
Which of the following is considered the most frequently used transmission line?
Two-wire open line
Twin lead
Rigid coaxial line
Flexible coaxial line
The antenna effective height is ____ to ____ of the actual height.
½ to 2/3
½ to ¾
¼ to 2/3
¼ to ¾
What is the propagation velocity of a signal in a transmission line whose inductance and capacitance are 5μH/m and 20μF/m respectively?
100 x 10^3 m/s
100 m/s
10 x 10^3 m/s
100 x 10^6 m/s
What is the phase coefficient in radians per unit length of a transmission line at the frequency of 10 MHz if the velocity of propagation is 2.5 x 108 m/s?
0.25
2.5
0.35
3.5
Determine the conductance of a two-wire open line with the following parameters: D = 4 in., d = 0.1 in. and ρ = 2.6×108 Ω-m.
2.76 x 10^-9 S/m
2.76 x 10^-6 S/m
2.76 x 10^-12 S/m
2.76 x 10^-3 S/m
What is the input impedance of a transmission line if its characteristic impedance is 300 Ω and the load is 600 Ω? Assume a quarter wavelength section only.
150 kΩ
150 mΩ
150 Ω
2 Ω
Determine the standing wave ratio of a 300-Ω line whose load is 400+j150 Ω.
3.55
1.67
5.53
3.35
What is the optimum volume per person of rooms for speech?
2.8
3.1
4.2
5.1
What happens to the beamwidth of an antenna as the gain is increased?
The beamwidth increases geometrically as the gain is increased.
The beamwidth increases arithmetically as the gain is increased.
The beamwidth is essentially unaffected by the gain of the antenna.
The beamwidth decreases as the gain is increased.
A superhet receiver has an IF of 455 kHz and is experiencing image-channel interference on a frequency of 1570 kHz. The receiver is tuned to
1115 kHz
660 kHz
2025 kHz
910 kHz
What is the end impedance of a half-wave dipole?
73 Ω
72 Ω
250 Ω
2500 Ω
What volume of the chamber is required to measure absorption coefficient at 100 Hz?
125 m^3
50 m^3
150 m^3
352 m^3
What is the optimum reverberation time at 500 Hz for a cinema?
0.8 – 1.2 sec.
0.9 – 1.3 sec.
0.6 – 0.8 sec.
0.45 – 0.55 sec.
An FM receiver whose intermediate frequency is 10.7 MHz, is experiencing image channel interference from a station transmitting on 121.1 MHz. If the local oscillator is tracking above, the receiver is tuned to
131.8 MHz
110.4 MHz
142.5 MHz
99.7 MHz
A 1 Mhz carrier is amplitude modulated by a pure 200-Hz audio test tone. Which of the following combinations of frequencies represent the total content of the AM signal?
1 MHz and 200 Hz
1 MHz and 1000.2 kHz
999.8 kHz, 1000 kHz, and 1000.2 kHz
999.8 kHz and 1000.2 kHz
What establishes the receiver bandwidth?
RF amplifier
Mixer
Local oscillator
IF amplifier
What noise type is observable between 8 MHz to somewhat above 1.43 GHz or up to 1.5 GHz?
Solar noise
Space noise
Galactic noise
Cosmic noise
Flicker noise is a poorly understood form of noise which may be completely ignored about above ____.
100 Hz
200 Hz
400 Hz
500 Hz
What is the typical gain of a rhombic antenna?
Between 15 to 60
Between 20 to 90
Between 50 to 75
Between 10 to 25
What illumination factor is normally considered in computing parabolic antenna gain in microwave communications?
0.54
0.65
0.75
0.85
How many voice band channels are there in a superjumbo group?
600
900
10,800
3,600
In acoustics, what is the reference pressure in lb/ft2 unit?
2×10^-5
0.0002
2.089
2.980
Which of the following characterizes a properly terminated transmission line?
The line loss is minimum.
The standing wave ratio is minimum.
The input impedance is twice the load impedance.
The standing wave ratio is one.
What is the meaning of forward power?
The power traveling from the transmitter to the antenna
The power radiated from the top of an antenna system.
The power produced during the positive half of an RF cycle.
The power used to drive a linear amplifier.
What organization has published safety guidelines for the maximum limits of RF energy near the human body?
The American National Standards Institute (ANSI).
The Environmental Protection Agency (EPA).
The Federal Communications Commission (FCC).
The Institute Of Electrical and Electronics Engineers (IEEE).
When no signal is being received, the loudspeaker is not entirely silent as a result of the presence of
parasitic oscillations in some of the receiver stages.
negative feedback in each stage.
spurious frequencies as a result of improper neutralization.
internal receiver noise.
When measuring a transmitter’s frequency against a suitable standard, the frequency to be measured is taken from the
oscillator stage
intermediate amplifier
buffer stage
final RF stage
When the is the ionosphere most ionized?
Dusk
Midnight
Dawn
Midday
Cellular radios use FM with a maximum deviation of
± 30 KHz
± 75 KHz
± 25 KHz
± 12 KHz
What device measures the angle between two radio frequencies and also the direction of propagation of a wave?
Densimeter
Absorption wavemeter
Goniometer
Ergometer
An automated ship-to-shore distress alerting system using satellites and advanced terrestrial communications systems.
GPS
Iridium system
INMARSAT
GMDSS
What antenna can be used to minimize the effect of Faraday rotation of polarization?
Dipole
Parabolic
Helical
Rhombic
The presence of standing waves on a transmission line is the result of
a high level of attenuation on the line.
terminating the line by a resistive load equal in value to the surge impedance
reducing the input power to below its critical level.
an impedance mismatch between the load and the line.
What device measures rf power by measuring the heat the rf power generates?
Calorimeter
Goniometer
Spectrum meter
Oscilloscope
What is considered the most efficient mode in terms of energy transfer in waveguides?
Dominant mode
Normal mode
Conventional mode
Vertical mode
In acoustics, _____ is the apparent change in frequency or pitch when a sound source moves either toward or away from a listener.
flanking
reverberation
Doppler effect
echo
. Which of the following wavelengths where absorption of electromagnetic waves becomes peak due to vibrational resonances in the water vapor molecule?
1.35 cm and 1.7 mm
1.5 mm and 5mm
1.35 dm and 1.7cm
1.5 cm and 5 mm
Oxygen molecule absorption peaks to electromagnetic wave are at what wavelengths?
1.35 mm and 1.7 μm
1.35 cm and 1.7 mm
5 cm and 2.5 cm
5 mm and 2.5 mm
The approximate single-hop nighttime range of F2 layer is ____.
3000 km
3840 km
4130 km
2350 km
What ionospheric layer has a daytime approximate critical frequency of 8 MHz?
F2 layer
F1 layer
E layer
D layer
In cellular system, _____ defines the geographic distance that is required between cells using identical frequencies in order to avoid interference between the radio transmissions at these cells.
frequency-reuse ratio
distance-to-reuse ratio (D/R)
reuse format plan ratio
reuse factor
What do you call the ability of a mobile phone to change from one channel (frequency) to another?
Frequency agility
Frequency handoff
Frequency handover
Frequency switch
What mathematical plane figure is ideal in cellular system design and engineering it graphically and functionally depicts overlapping radio coverage between and among adjacent cell base stations?
Hexagon
Octagon
Pentagon
Nonagon
In cellular system, the average lead time to install a new base station is approximately ____ months to a year.
4
5
6
10
What is considered the threshold of audibility at 3000 Hz?
10^-12 W/m^2
10^-16 W/m^2
10^-12 W/cm^2
10^-15 W/cm^2
At one atmospheric pressure, what is the approximate speed of sound in steel?
5150 m/s
5150 ft/s
4990 m/s
4990 ft/s
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