EST | COACHING NOTES Flashcards
(140 cards)
1
Q
The total distance between two points on earth is 20 miles. What is earth’s curvature when surface refractivity is 250?
A. 52.4 mi
B. 54.2 mi
C. 30.1 mi
D. 10.8 mi
A
B. 54.2 mi
2
Q
Which of the following factors will affect the outer limits of the skip zone?
A. Frequency
B. Sunspot activity
C. Angle of transmission
D. All of the above
A
D. All of the above
3
Q
In relation to troposcatter system parameter, what is the typical transmitter power for path distance of 150-250 km at 1 GHz frequency?
A. 5 KW
B. 7 kW
C. 1 kW
D. 3 kW
A
C. 1 kW
4
Q
In signal processing, what is the simplest form of smoothing which simply replaces each data value with the average of neighboring values?
A. Direct average
B. Replacing average
C. Moving average
D. Substitution average
A
C. Moving average
5
Q
The critical angle for radio wave propagation depends on what two factors?
A. Angle of incidence and layer density only
B. Wavelength and antenna height only
C. Angle of incidence and wavelength only
D. Layer density and wavelength only
A
D. Layer density and wavelength only
6
Q
For a signal measurement of -42 dBm, a noise measurement of 16 dBrnC, and a -40 dBm TLP, determine the signal level in dBrnC.
A. 32 dBrnC
B. 40 dBrnC
C. 74 dBrnC
D. 48 dBrnC
A
D. 48 dBrnC
7
Q
In signal processing, what removes short-term variations, or “noise” to reveal the important underlying form of the data?
A. Filtering
B. Chopping
C. Smoothing
D. Leveling
A
C. Smoothing
8
Q
At what approximate time of day is the density of the ionospheric layers at its lowest level?
A. Afternoon
B. Just before sunrise
C. Sunset
D. Mid-morning
A
B. Just before sunrise
9
Q
Determine the noise current for a diode with a forward bias of 1 mA over a 100-kHz bandwidth.
A. 0.566 µA
B. 0.000566 µA
C. 0.00566 µA
D. 0.0566 µA
A
C. 0.00566 µA
10
Q
Radio waves above the MUF will experience what effect when refracted from the ionosphere?
A. They will overshoot the desired location
B. They will be absorbed by lower layers
C. They will fall short of the desired location
D. They will experience multipath fading
A
A. They will overshoot the desired location
11
Q
Which of the following is NOT a factor for radio wave refraction?
A. Ionization density of the layer
B. Frequency of the radio wave
C. The angle of incidence
D.Transmitter power
A
D. Transmitter Power
12
Q
The frequency of ultraviolet light passing through the atmosphere has what relationship to the ionospheric layer it ionizes?
A. It is inversely proportional during the day and directly proportional at night
B. It is inversely proportional
C. It is directly proportional
D. It is directly proportional during the day and inversely proportional at night
A
B. It is inversely proportional
13
Q
When sudden ionospheric disturbances (SID) occurs, which ionospheric layer is affected the most?
A. D
B. E
C. F₂
D. F₁
A
A. D
14
Q
Variations in the ionosphere resulting from changes in the sun’s activity are known as
A. Both regular and irregular variations
B. irregular variations
C. regular variations
D. seasons
A
A. Both regular and irregular variations
15
Q
Fading on the majority of the ionospheric circuits is a result of what particular type of fading?
A. Absorption
B. Selective
C. Weather
D. Multipath
A
D. Multipath
16
Q
What transform is similar to the Fourier transform in that it is a decomposition of a signal in terms of a basis set of functions?
A. Discrete Fourier transform (DFT)
B. Discrete Wavelet Transform (DWT)
C. Continuous Wavelet Transform (CWT)
D. Bilinear Transform
A
B. Discrete Wavelet Transform (DWT)
16
Q
What is the art and science of modifying acquired time-series data for the purposes of analysis or enhancement?
A. Signal Processing
B. Signal Gathering
C. Signal Sampling
D. Signal Acquisition
A
A. Signal Processing
17
Q
A 1004-Hz test tone is transmitted over a telephone circuit at 0 dBm and received at -16 dBm. Determine the 1004-Hz circuit gain.
A. +16 dB
B. 32 dB
C. 0 dB
D. -16 dB
A
D. -16 dB
17
Q
What converts a finite list of equally-spaced samples of a function into the list of coefficients of a finite combination of complex sinusoids, ordered by their frequencies, that has those same sample values?
A. Discrete Wavelet Transform (DWT)
B. Continuous Wavelet Transform (CWT)
C. Wigner Transform
D. Discrete Fourier transform (DFT)
A
D. Discrete Fourier transform (DFT)
18
Q
During the 27–day sunspot cycle, which ionospheric layer experiences the greatest fluctuations in density?
A. F₁
B. D
C. E
D. F₂
A
D. F₂
19
Q
In what portion of the atmosphere does the majority of weather phenomena take place?
A. Exosphere
B. Mesosphere
C. Stratosphere
D. Troposphere
A
D. Troposphere
19
Q
The regular variations in the ionosphere can be separated into how many classes?
A. Four
B. Two
C. Three
D. Five
A
A. Four
20
Q
A certain tropospheric system has scatter angle components of 0.2 and 0.3 radians respectively. Determine the scatter angle oftentimes called the angular distance between antennas.
A. 0.06 rad
B. 0.25 rad
C. 0.50 rad
D. 0.24 rad
A
C. 0.50 rad
21
Q
What is used in digital signal processing and discrete-time control theory to transform continuous-time system representations to discrete-time and vice versa?
A. Continuous Wavelet Transform (CWT)
B. Wigner Transform
C. Bilinear transform
D. Discrete Wavelet Transform (DWT)
A
C. Bilinear transform
22
What transform maps a 1D time signal U(t) into a 2D time-frequency representation?
A. Hilbert Transform
B. Wigner Transform
C. Continuous Wavelet Transform (CWT)
D. Fourier Transform
B. Wigner Transform
23
The value of the resistor creating thermal noise is doubled. The noise power generated is therefore _____.
A. halved
B. quadrupled
C. doubled
D. unchanged
D. unchanged
24
In an SSB transmitter, if the peak envelope power (PEP) is 500 W then what is typical range of the average power?
A. 167 W to 250 W
B. 100 W to 200 W
C. 125 W to 250 W
D. 125 W to 167 W
D. 125 W to 167 W
25
What is the typical power of educational FM stations?
A. 10 W
B. 15 W
C. 20 W
D. 5 W
A. 10 W
26
In frequency modulation, determine the possible frequency deviation produced by noise. Assume a maximum modulating frequency and a desirable S/N for voice transmission.
A. 859 Hz
B. 28.65 Hz
C. 85.9 Hz
D. 859 kHz
A. 859 Hz
27
An AM signal is being measured by an oscilloscope. The following are the readings:
V_max(p-p) = 6.9 divisions from the graticule on the scope
V_min(p-p) = 2.2 divisions from the graticule on the scope
If the vertical scale is 1.5 V per division, what is the carrier voltage?
A. 7.05 V
B. 6.825 V
C. 13.65 V
D. 3.525 V
B. 6.825 V
27
When radiowave signals follow the curvature of the earth, this is known as ______.
A. troposheric scatter
B. ducting
C. ionospheric reflections
D. the faraday effect
B. ducting
27
Indicate the noise whose source is in a category different from that of the other three.
A. Atmospheric noise
B. Solar noise
C. Cosmic noise
D. Galactic noise
A. Atmospheric noise
28
An SSB transmitter produces a peak-to-peak voltage of 200 V across a 100-Ω antenna load. What is the peak envelope power?
A. 200 W
B. 100 W
C. 50 W
D. 400 W
C. 50 W
29
AM BC signals are normally having ________ polarization.
A. horizontal
B. vertical
C. random
D. circular
B. vertical
30
In SSB generation, filter method is the simplest method to eliminate one of the two sidebands. Find the Q required of the filter to have an effective 80 dB sideband suppression. Assume a carrier of 15 MHz and 200 Hz separation between two sidebands.
A. 1875 x 10⁶
B. 187.5 x 10⁶
C. 18.75 x 10⁶
D. 1.875 x 10⁶
D. 1.875 x 10⁶
31
The AM spectrum consists of ________.
A. All of the choices
B. upper side band frequency
C. carrier frequency
D. lower side band frequency
A. All of the choices
32
In high level amplitude modulation,
A. collector modulation method is high level amplitude modulation
B. power amplifiers are used to boost the carrier and modulating signals before modulation
C. modulation is done at high power of carrier and modulating signal
D. All of the choices
D. All of the choices
32
The only roadblock to having a complete receiver manufactured on an integrated circuit is ______.
A. phase-locked loops
B. cost
C. tuned circuits and volume controls
D. ceramic filters
C. tuned circuits and volume controls
33
Which one of the following types of noise becomes of great importance at high frequencies?
A. Impulse noise
B. Transit-time noise
C. Shot noise
D. Random noise
B. Transit-time noise
34
A double-tuned IF amplifier with optimum coupling has a critical coupling of 0.02 and a resonant frequency of 5 MHz. Find the overall bandwidth.
A. 150 kHz
B. 50 kHz
C. 200 kHz
D. 100 kHz
A. 150 kHz
34
Amplitude modulation is used for broadcasting because ______.
A. compared with other system it requires less transmitting power
B. no other modulation system can provide the necessary bandwidth for high fidelity
C. it is more noise immune than other modulation system
D. it use avoids receiver complexity
D. it use avoids receiver complexity
34
What is another name for signals in the HF range?
A. RF waves
B. Microwaves
C. Shortwaves
D. Millimeter waves
C. Shortwaves
35
If the 3-dB bandwidth of a tuned circuit is 10 MHz then what is its actual noise bandwidth?
A. 3.18 MHz
B. 15.7 MHz
C. 31.4 MHz
D. 20 MHz
B. 15.7 MHz
36
What is the purpose of a buffer amplifier stage in a transmitter?
A. It prevents transmitters from producing spurious frequencies in the output signals.
B. It provides power amplification with high efficiency.
C. It amplifies audio frequencies before modulation occurs.
D. Its high input impedance prevents oscillators from drifting of frequency.
D. Its high input impedance prevents oscillators from drifting of frequency.
36
An FM receiver rarely works satisfactorily without an RF amplifier because ______.
A. FM receivers do not have very much gain in their IF amplifier stages
B. FM receivers typically work with smaller input signal levels due to their noise characteristics
C. FM receivers need RF amplifier stages to be able to decode stereo signals
D. FM receivers have a narrower bandwidth
B. FM receivers typically work with smaller input signal levels due to their noise characteristics
36
In amplitude modulation, suppose the unmodulated antenna current is 2.5 A and the modulated antenna current is 2.8 A, what is the modulation index?
A. 0.65
B. 0.71
C. 0.90
D. 0.35
B. 0.71
36
A tuned circuit has a capacitance of 25 pF and a dynamic resistance of 1.6 kΩ. Determine the noise bandwidth.
A. 0.625 MHz
B. 625 MHz
C. 62.5 MHz
D. 6.25 MHz
D. 6.25 MHz
37
If a receiver has poor capacity of blocking adjacent channel interference then the receiver has ______.
A. poor sensitivity
B. poor signal to noise ratio
C. poor selectivity
D. poor front end
C. poor selectivity
37
A high-level modulation AM transmitter has a DC supply to the final RF power amplifier of 50 V. If the total current is 5 A and the efficiency is 85%, how much AF power is required for 100% modulation?
A. 62.5 W
B. 250 W
C. 500 W
D. 125 W
D. 125 W
37
In amplitude modulation, bandwidth is _____ the audio signal frequency.
A. twice
B. thrice
C. four times
D. none of the choices
A. twice
38
The primary advantage of phase modulation over frequency modulation is that phase modulation has better carrier _______.
A. frequency stability
B. amplitude stability
C. directional stability
D. power stability
A. frequency stability
39
Indicate the false statement regarding the Armstrong modulation system,
A. Equalization is unnecessary.
B. the system is basically phase and not frequency, modulation.
C. Frequency multiplications must be used
D. AFC is not needed, as the crystal oscillator is used.
A. Equalization is unnecessary.
39
What does the term y(-1) indicate especially in an equation that represents the behavior of the causal system?
A. Response of the system to its initial input
B. Negative initial condition of the system
C. Negative feedback condition of the system
D. Initial condition of the system
D. Initial condition of the system
40
A stripline is a flat conductor sandwiched between two ground planes. Find its characteristic impedance with the following information given: PCB dielectric is 2.2.; d = 0.5 in; w = 0.3 in; t = 0.2 in and h = 0.4 in.
A. 56 Ω
B. 36 Ω
C. 112 Ω
D. 75 Ω
B. 36 Ω
40
An SWR meter measures the degree of match between transmission line and antenna by:
A. comparing forward and reflected voltage
B. measuring radiated RF energy
C. measuring the conductor temperature
D. inserting a diode in the transmission line
A. comparing forward and reflected voltage
40
In the spectrum of a frequency modulated wave:
A. the carrier frequency cannot disappear
B. the carrier frequency disappears when the modulation index is large
C. the amplitude of any sideband depends on the modulation index
D. the total number of sidebands depend on the modulation index
C. the amplitude of any sideband depends on the modulation index
41
Which of the following types of modulation is a form of amplitude modulation?
A. Continuous-wave
B. Frequency
C. Angle
D. Phase
A. Continuous-wave
42
In tropospheric scatter propagation, if the surface refractivity at the transmitting section is 205 and at the receiving section is 201 then what is the actual surface refractivity?
A. 403
B. 203
C. 406
D. 205
B. 203
43
An equalizer used to compensate the distortion in the communication system by faithful recovery of an original signal is nothing but an illustration of _________.
A. dynamic system
B. static system
C. Continuous-wave
D. invertible system
D. invertible system
44
What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?
A. None; the F2 region does not support radio-wave propagation
B. 2160 km
C. 4000km
D. 325 km
C. 4000km
44
In the stabilized reactance modulator AFC system, _____.
A. the discriminator must have a fast time constant to prevent demodulation
B. the higher the discriminator frequency, the better the oscillator frequency stability
C. phase modulation is converted into FM by the equalizer circuit
D. the discriminator frequency must not be too low, or the system will fail
D. the discriminator frequency must not be too low, or the system will fail
45
Which among the following belongs to the category of non-recursive systems?
A. Non-causal IIR Systems
B. Non-causal FIR Systems
C. Causal IIR Systems
D. Causal FIR Systems
D. Causal FIR Systems
46
A coaxial line has an inner diameter of 0.2 in. and a center conductor of 0.06 in. diameter. If the insulation is polyethylene then what is its characteristic impedance?
A. 48 Ω
B. 144 Ω
C. 40 Ω
D. 50 Ω
A. 48 Ω
47
The characteristic impedance of a parallel wire transmission line does not depend on the:
A. velocity of energy on the line
B. center to center distance between conductors
C. dielectric
D. radius of the conductors
A. velocity of energy on the line
48
Why does coaxial cable make a good antenna transmission line?
A. It can be used near metal objects, and its impedance is higher than that of most amateur antennas
B. You can make it at home, and its impedance matches most amateur antennas
C. It is weatherproof, and its impedance matches most amateur antennas
D. It is weatherproof, and its impedance is higher than that of most amateur antennas
C. It is weatherproof, and its impedance matches most amateur antennas
49
A basic parallel-wire line has a diameter of 0.023 in. with a spacing of 0.5 in. apart. The dielectric is a continuous polyvinyl chloride (PVC). What is its characteristic impedance?
A. 286 Ω
B. 301 Ω
C. 249 Ω
D. 452 Ω
C. 249 Ω
50
What causes the ionosphere to form?
A. Lightning ionizing the outer atmosphere
B. Release of fluorocarbons into the atmosphere
C. Temperature changes ionizing the outer atmosphere
D. Solar radiation ionizing the outer atmosphere
D. Solar radiation ionizing the outer atmosphere
51
A microstrip transmission line is to be used as a capacitor of 4 pF at 800 MHz. The PCB dielectric is 3.6. The microstrip dimensions are h = 0.0625 in., w = 0.13 in., and t = 0.002 in. What is the characteristic impedance of the line?
A. 276 Ω
B. 49 Ω
C. 50 Ω
D. 75 Ω
B. 49 Ω
51
In an SSB transmitter, one is most likely to find a ______.
A. tuned modulator
B. class B RF amplifier
C. class A RF output amplifier
D. class C audio amplifier
B. class B RF amplifier
51
Modulation produced in the plate circuit of the last radio stage of a system is known by what term?
A. Radio frequency modulation
B. High-level modulation
C. Final-amplifier modulation
D. Low-level modulation
B. High-level modulation
51
What are some reasons not to use parallel-conductor transmission line?
A. It is difficult to make at home, and it does not work very well with a high SWR
B. You must use an impedance-matching device with your transceiver, and it does not work very well with a high SWR
C. It does not work well when tied down to metal objects, and you should use a balun and may have to use an impedance-matching device with your transceiver
D. It does not work well when tied down to metal objects, and it cannot operate under high power
C. It does not work well when tied down to metal objects, and you should use a balun and may have to use an impedance-matching device with your transceiver
51
Which kind of frequency spectrum/spectra is/are obtained from the line spectrum of a continuous signal on the basis of Polar Fourier Series Method?
A. Continuous in nature
B. Sampled in nature
C. All of the choices
D. Discrete in nature
D. Discrete in nature
51
What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?
A. They are bent back to the Earth
B. They are changed to a frequency above the MUF
C. They pass through the ionosphere
D. They are completely absorbed by the ionosphere
A. They are bent back to the Earth
51
In transmission engineering, longitudinal balance is an important parameter when dealing with transmission lines carrying baseband signals such as subscriber loops. When the open circuit longitudinal voltage is 12 V and the metallic voltage is 5 V, determine the longitudinal balance of the line.
A. -7.6 dB
B. 7.6 dB
C. 3.8 dB
D. -3.8 dB
B. 7.6 dB
51
A 75 ohm transmission line could be matched to the 300 ohm feed point of an antenna:
A. by inserting a diode in one leg of the antenna
B. by using a 4 to 1 impedance transformer
C. by using a 4 to 1 trigatron
D. with an extra 250 ohm resistor
B. by using a 4 to 1 impedance transformer
52
Calculate the gain, with respect to an isotropic antenna, of a half-wave dipole with an efficiency of 90% that is placed one-quarter-wavelength from a plane reflector that reflects 100% of the signal striking it.
A. 8.76 dBi
B. 8.67 dBi
C. 7.86 dBi
D. 7.68 dBi
D. 7.68 dBi
53
If an antenna is too short for the wavelength being used, what electrical compensation must be introduced for the antenna to achieve resonance?
A. Lumped resistance
B. More power
C. Lumped inductive reactance
D. Lumped capacitive reactance
C. Lumped inductive reactance
54
A standard AM receiver tunes from 535 to 1605 kHz. Determine its frequency tuning range.
A. 2.04
B. 2.08
C. 2.03
D. 2.05
B. 2.08
54
Calculate the aperture-to-medium coupling loss for two 30-ft antennas, one at each end of the path, with a 2ᵒ scatter angle and a 900-MHz operating frequency.
A. 3.67 dB
B. 3.18 dB
C. 5.37 dB
D. 5.65 dB
A. 3.67 dB
55
All antennas regardless of their shape or size have how many basic characteristics?
A. 5
B. 2
C. 4
D. 3
C. 4
56
Marconi antennas are used for operating frequencies below what level?
A. 4 MHz
B. 10 MHz
C. 2 MHz
D. 6 MHz
C. 2 MHz
57
What effect do ionospheric storms have on the range of frequencies and the working frequency used for communications?
A. increase, increase
B. increase, decrease
C. decrease, increase
D. decrease, decrease
D. decrease, decrease
57
What is the typical channel capacity of a troposcatter system for 1 GHz frequency and path distance of 250-320 km?
A. 240 channels
B. 36 channels
C. 84 channels
D. 72 channels
B. 36 channels
58
Calculate the length of a practical half-wave dipole for a frequency of 15 MHz.
A. 7.5 m
B. 10.5 m
C. 9.5 m
D. 8.5 m
C. 9.5 m
58
What is the antenna beamwidth in degrees if the power gain is 30 dB?
A. 8.4ᵒ
B. 5.4ᵒ
C. 6.4ᵒ
D. 7.4ᵒ
C. 6.4ᵒ
58
A sector log–periodic array can act as an antenna for a minimum of what number of transmit or receive systems?
A. 4
B. 5
C. 6
D. 7
A. 4
59
Hertz antennas are designed to operate at what wavelength in relationship to their operating frequency?
A. Full-wave
B. Quarter-wave
C. Three quarter-wave
D. Half-wave
D. Half-wave
60
When a person is standing in an rf field, power in excess of what level will cause a noticeable rise in body temperature?
A. 10 mW
B. 5 mW
C. 15 mW
D. 20 mW
A. 10 mW
61
Distributed constants in a transmission line are distributed in which of the following ways?
A. Along the length of the line
B. According to the thickness of the line
C. Between ground and any single point on the line
D. According to the cross-sectional area of the line
A. Along the length of the line
62
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64
65
65
65
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67
68
What determines the gain and directivity of a rhombic antenna?
A. Transmitter power
B. Transmitted frequency
C. Radiated wave interaction
D. Antenna height
C. Radiated wave interaction
68
Using Carson’s rule, what is the bandwidth of an FM signal with 5 kHz maximum frequency deviation and 2.5 kHz maximum modulating frequency?
A. 35 kHz
B. 10 kHz
C. 20 kHz
D. 15 kHz
D. 15 kHz
68
A 10 MHz crystal oscillator in a PLL frequency synthesizer has been calibrated to a reference standard known to be accurate to 5 ppm. The oscillator is guaranteed to drift no more than 10 ppm per month. A year later, what are the maximum and minimum frequencies that the oscillator could be producing?
A. 10.00125 MHz, 9.99875 MHz
B. 20.0153 MHz, 75.265 MHz
C. 10.125 MHz, 9.8875 MHz
D. 15.00145 MHz, 10.1257 MHz
A. 10.00125 MHz, 9.99875 MHz
68
Skin effect is classified as which of the following types of loss?
A. Induction
B. Copper
C. Voltage
D. Dielectric
B. Copper
68
Determine the power savings in percent when the carrier is suppressed in an AM signal modulated to 80%.
A. 96.52%
B. 75.76 %
C. 83.33%
D. 77.75%
B. 75.76 %
68
Of the following methods, which is NOT used to feed a cylindrical paraboloid reflector?
A. A quarter-wave stub
B. A thin waveguide radiator
C. A slit in the side of a waveguide
D. A linear array of dipoles
A. A quarter-wave stub
68
For an AM receiver, if the capacitance tuning range is 10, what is the frequency tuning range?
A. 5
B. 100
C. 3.16
D. 20
C. 3.16
68
Capacitive top-loading helps to increase which of the following antenna characteristics?
A. Radiation efficiency
B. Bandwidth
C. Power-handling
D. Directivity
B. Bandwidth
68
When a dc voltage is applied to a transmission line and the load absorbs all the energy, what is the resulting relationship between current and voltage?
A. They are in phase with each other
B. They are evenly distributed along the line
C. They are equal to Z₀ of the line
D. They are out of phase with each other
B. They are evenly distributed along the line
69
Frequencies above what level pass through the E layer unaffected?
A. 150 MHz
B. 200 MHz
C. 50 MHz
D. 100 MHz
A. 150 MHz
70
For a total rain attenuation of 11 dB, what is the sky noise at 20 GHz? Assume that the mean absorption temperature of the attenuating medium is 275 K.
A. 253.16 K
B. 255.19 K
C. 221.18 K
D. 273.18 K
A. 253.16 K
71
In microwave communications using plane reflectors as passive repeaters, compute the parabola/reflector coupling factor when the diameter of parabolic antenna is 20 ft and the effective area of the passive reflector is 320 ft²?
A. 0.05
B. 0.99
C. 0.91
D. 0.70
B. 0.99
72
Copper I²R losses are reduced by what physical property of waveguides?
A. Small surface area
B. Shape of the waveguides
C. Large surface area
D. Waveguide material being used
C. Large surface area
73
What microwave transmission line is analogous to a parallel-wire line consisting of the top strip and its image below the ground plane?
A. Waveguide
B. Stripline
C. PCB
D. Microstrip line
D. Microstrip line
74
What is known as the "spatial period" of the wave?
A. Wavelength
B. Period
C. Cycle
D. Frequency
A. Wavelength
75
In a non-diversity microwave communication link covering 20 mi, what is the reliability when the operating frequency is 6 GHz and with 45 dB of assigned fade margin? Assume a very smooth terrain and hot humid climate.
A. 99.9 %
B. 99.999 %
C. 99 %
D. 99.99 %
B. 99.999 %
76
77
Calculate the overall noise temperature of a receiver fed by a low-noise amplifier with a gain of 60 dB and a noise temperature of 100 K. The noise figure of the receiver is 10 dB.
A. 90 K
B. 125 K
C. 100 K
D. 85 K
C. 100 K
77
What is the open-circuit voltage in a λ/2 dipole when 25 W at 170 MHz is radiated from another λ/2 dipole 100 km distant? Assume an effective length of λ/π.
A. 282 mV
B. 197 μV
C. 197 mV
D. 282 μV
B. 197 μV
78
What designation of ITU is the basic AM modulation scheme?
A. B8E
B. R3E
C. J3E
D. A3E
D. A3E
78
In microwave radio system, what is the amount of loss contributed to a reliability objective of 99.9999%?
A. 50 dB
B. 120 dB
C. 60 dB
D. 4.34 dB
C. 60 dB
78
In the radio spectrum, which of the following frequencies are used for deep space radio communications?
A. 2.4 GHz to 2.5 GHz
B. 2.12 GHz to 2.3.1 GHz
C. 2.5 GHz to 2.7 GHz
D. 2.29 GHz to 2.3 GHz
D. 2.29 GHz to 2.3 GHz
79
What is the typical duty cycle (fraction of total time during which the magnetron is actually ON) of magnetron for pulse work in radar systems?
A. 0.1 percent
B. 0.3 percent
C. 0.2 percent
D. 0.4 percent
A. 0.1 percent
80
A ground screen is a series of conductors buried 1 or 2 feet below the surface in a radial pattern and is usually of what length in comparison to the wavelength being used?
A. One-half wavelength
B. Full wavelength
C. Three-quarter wavelength
D. One-quarter wavelength
A. One-half wavelength
81
In microwave radio system, determine the multipath effect for a distance of 30 km so that fade margin can be estimated for that particular link using 6 GHz of frequency and an objective of 99.999%.
A. 30.31 dB
B. 92.45 dB
C. 54.31 dB
D. 44.31 dB
D. 44.31 dB
82
What pairs of linear differential equations known to describe the voltage and current on an electrical transmission line with distance and time?
A. Heaviside`s Theory
B. Steinmitz`s Equations
C. Telegraph Equations
D. Maxwell`s Equations
C. Telegraph Equations
83
In antennas, dBi means dB gain over isotropic antenna and dBd means dB gain with respect to a perfect dipole, thus to find dBi, take the dBd figure and add ____.
A. 1.5
B. 2.5
C. 1.6
D. 2.2
D. 2.2
84
In transmission lines, the ______________ of the wave is the equivalent of the angular frequency but with respect to the distance variable.
A. phase constant
B. propagation constant
C. dielectric constant
D. attenuation constant
B. propagation constant
85
In microwave communications, what Fresnel zone must be kept largely free from obstructions to avoid interfering with the radio reception?
A. The third zone
B. The fourth zone
C. The second zone
D. The first zone
D. The first zone
86
In collinear array antenna, where is the maximum radiation directed?
A. Parallel to the axis of the elements
B. Equally in all directions.
C. Perpendicular to the axis of the elements
D. Bidirectional or figure 8 pattern.
C. Perpendicular to the axis of the elements
87
What is the frequency-deviation constant for a Clapp oscillator frequency-modulated for which the unmodulated frequency is 50 MHz with a fixed bias of 15 V and n = 0.1?
A. 337 kHz/V
B. 733 kHz/V
C. 373 kHz/V
D. 733 Hz/V
B. 733 kHz/V
88
What is the only feasible method of modulation for recording video to and retrieving video from magnetic tape without extreme distortion?
A. AM
B. PCM
C. FM
D. Phase modulation
C. FM
89
What is the equivalent noise temperature for an antenna whose spectrum density of the available noise signal received is 20 aW/Hz?
A. 1.45 x 10⁶ K
B. 15 K
C. 20 K
D. 145 K
A. 1.45 x 10⁶ K
90
“Incoming light is partially absorbed and partially transmitted equally in all directions”. This statement is known as
A. The Snell's reflection
B. The Fresnel reflection
C. The Lambertian reflection
D. The law of light reflection
C. The Lambertian reflection
91
In transmission lines (coaxial or two-wire), what velocity is the speed with which a point of constant phase in the wave appears to move?
A. Real velocity
B. Phase or group velocity
C. Phase velocity
D. Group velocity
B. Phase or group velocity
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93
At what frequencies does the combination of the earth’s surface and the D layer act as a waveguide?
A. LF
B. MF
C. VLF
D. HF
C. VLF
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