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REM C LVL 1 Flashcards

1
Q

Copper losses can be minimized and conductivity increased in an rf line by plating the line by what material?

A. Copper
B. Gold
C. Silver
D. Aluminum

A

C. Silver

Copper losses can be minimized and conductivity increased in an rf line by plating the line with silver. Since silver is a better conductor than copper, most of the current will flow through the silver layer. The tubing then serves primarily as a mechanical support.

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2
Q

The impedance of a coaxial line:

A. is greater for larger diameter line
B. is correct for only one size of line
C. changes with the frequency of the energy it carries
D. can be the same for different diameter line

A

D. can be the same for different diameter line

The Characteristic Impedance of coaxial cable is determined by the ratio of the outer conductor to the inner conductor. Different diameters of lines can have the der same Characteristic Impedance as long as the RATIO is preserved.

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3
Q

At very high frequencies, transmission lines are used as

A. antennas
B. tuned circuits
C. insulators
D. resistors

A

B. tuned circuits

At UHF and microwave frequencies where one-half wavelength is less than 1 ft, transmission lines are commonly used to replace conventionvider 2 tuned circuits

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4
Q

In what values are RF feed line losses expressed?

A. ohms per metre
B. dB per MHz
C. ohms per MHz
D. dB per unit length

A

D. dB per unit length

“Decibels per unit length”. In North els per unit le America, typically ‘dB per 100 ft’ or ‘dB per 30m’ at a given frequency. Loss rises proportionally with length. Loss goes up as frequency or goes up.

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5
Q

What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?

A. 600 ohm open-wire
B. coaxial cable
C. 75 ohm twin-lead
D. 300 ohm twin-lead

A

B. coaxial cable

Because the outer conductor of a coaxial cable is operated at ground potential, it can be buried der Parallel lines operate differently with both conductors at some voltage above ground.ed

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6
Q

For a resistive transmission line the reflection coefficient should be:

A. infinity
B. 0
C. 1
D. cannot be determined

A

B. 0

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7
Q

A balanced transmission line:

A. is made of two parallel wires
B. carries RF current on one wire only
C. is made of one conductor only
D. has one conductor inside the other

A

A. is made of two parallel wires

BALANCED. A ‘balanced’ transmission line operates with both conductors floating above ground potential (like all types of parallel lines: twin-lead, open-wire line). An ‘UNbalanced’ transmission line functions with vider? one conductor connected to ground (like coaxial cable or ‘coax’ for short).

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8
Q

TV twin-lead feed line can be used for a feed line in an amateur station. The impedance of this line is approximately:

A. 70 ohms
B. 50 ohms
C. 600 ohms
D. 300 ohms

A

D. 300 ohms

50 ohms is the common Characteristic Impedance of coaxial cable. 600 ohms is the common Characteristic Impedance of ‘open-wire line’ (a.k.a. ladder line). 300 ohms is the Characteristic Impedance of twin-lead transmission line used with yesteryear outside television antennas.

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9
Q

What does an SWR reading of less than 1.5:1 mean?

A. An impedance match which is too low
B. An impedance mismatch; something may be wrong with the antenna system
C. A fairly good impedance match
D. An antenna gain of 1.5

A

C. A fairly good impedance match

SWR is a measure of the impedance match in the antenna system. A Standing Wave Ratio (SWR) of ‘1.5 to 1’ is a total oder acceptable condition indicating little reflected energy. A ‘1 to 1’ ratio would indicate a perfect match while a very high SWR would indicate a short-circuit or an open-circuit somewhere along the transmission line.

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10
Q

A shorted quarter-wave line at the operating frequency acts like a(n).

A. omnidirectional series resonant circuit
B. parallel resonant circuit
C. capacitor
D. inductor

A

A. omnidirectional series resonant circuit

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11
Q

The characteristic impedance of a transmission line is determined by the:

A. load placed on the line
B. physical dimensions and relative positions of the conductors
C. length of the line
D. frequency at which the line is operated nhub

A

B. physical dimensions and relative positions of the conductors

Characteristic Impedance is determined by the physical dimensions of the line. Length, frequency or load have nothing to do with it.

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12
Q

What type of losses being described when some of the magnetic lines of force about a conductor do not return to the conductor when the cycle alternates. That is, power is supplied by the source, but is not available to the load.

A. Dielectric losses
B. Copper losses
C. Radiation losses
D. Induction losses

A

C. Radiation losses

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13
Q

The characteristic impedance of lines in actual use normally lies between:

A. 50 and 600 ohms
B. 60 and 120 ohms
C. 50 and 300 ohms
D. 200 and 300 ohms

A

A. 50 and 600 ohms

Figuring the actual impedance of a line having reactance is very similar, with inductance taking the place of the series resistors and capacitance taking the place of the shunt resistors. The characteristic impedance of lines in actual use normally lies between 50 and 600 ohms.

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14
Q

What does standing-wave ratio mean?

A. The ratio of maximum to minimum impedances on a feed line
B. The ratio of maximum to minimum voltages on a feed line
C. The ratio of maximum to minimum resistances on a feed line
D. The ratio of maximum to minimum inductances on a feed line

A

B. The ratio of maximum to minimum voltages on a feed line

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15
Q

Type of transmission loss that occurs whenever a connection is made to or from a transmission line or when two separate pieces of transmission line are connected together.

A. corona
B. coupling loss
C. dielectric heating loss
D. radiation loss

A

B. coupling loss

Corona is a luminous discharge that occurs between the two conductors of a transmission line when the difference of potential between them exceeds the breakdown voltage Provider 2018-013

Radiation loss occurs when the separation between the conductors of a transmission line is an appreciable fraction of a wavelength thus, acting like an antenna.

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16
Q

The lowest loss feed line on HF is:

A. coaxial cable
B. 300 ohm twin-lead
C. open-wire
D. 75 ohm twin-lead

A

C. open-wire

300 ohms is the Characteristic Impedance of TV twin-lead transmission line. The high Characteristic Impedances and greater separation of the conductors in parallel lines DO permit high power and high Standing Wave Ratio (SWR) BUT nearby metallic objects can affect them and impedance matching is most often necessary at the transmitter end. Their high Characteristic Impedance permits carrying power with less current (P = R* I squared), less current implies less losses due to resistance.

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17
Q

A transmission line that is not used for transmitting high frequency because of the high dielectric losses that occur in the rubber insulation.

A. Twin lead
B. Coaxial cable
C. Two-wire ribbon
D. Twisted pair

A

D. Twisted pair

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18
Q

What does the term “balun” mean?

A. Balanced antenna network
B. Balanced unloader
C. Balanced to unbalanced
D. Balanced unmodulator

A

C. Balanced to unbalanced

“Balun” is the contraction of “BALanced to UNbalanced”. Dipole (“doublet”) antennas and parallel lines operate in a BALanced mode (two conductors float above ground potential). A quarter-wave antenna, a ground-plane antenna and coaxial cable operate in an UNbalanced mode (with one side grounded). A BALUN interfaces balanced antenna to unbalanced transmission line OR balanced line to unbalanced line. A BALUN can also include impedance transformation.

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19
Q

What device can be installed to feed a balanced antenna with an unbalanced feed line?

A. A wavetrap
B. A loading coil
C. A triaxial transformer
D. A balun

A

D. A balun

“Balun” is the contraction of contractio “BALanced to UNbalanced”. Dipole (“doublet”) antennas and parallel lines operate in a BALanced mode (two conductors float above ground potential. A quarter-wave antenna, a ground-plane antenna and coaxial cable operate in an UNbalanced mode (with one side grounded). A BALUN interfaces balanced antenna to unbalanced transmission line OR balanced line to unbalanced line. A BALUN can also include impedance transformation.

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20
Q

What is an unbalanced line?

A. Feed line with neither conductor connected to ground
B. Feed line with one conductor connected to ground
C. Feed line with both conductors connected to ground
D. Feed line with both conductors connected to each other

A

B. Feed line with one conductor connected to ground

UNBALANCED. An ‘UNbalanced’ transmission line functions with one conductor connected to ground (like coaxial cable or ‘coax’ for short). A ‘balanced’ transmission line operates with both conductors floating above ground potential (like all types of parallel lines: twin-lead, open-wire line).

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21
Q

Adding a series inductance to an antenna would:

A. decrease the resonant frequency
B. have no change on the resonant
C. frequency
D. increase the resonant frequency
have little effect

A

A. decrease the resonant frequency

A series inductance in an antenna is termed a “loading coil”. It makes the antenna appear LONGER electrically than its physical size. Making the antenna longer brings down the resonant frequency.

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22
Q

The assembly is covered with a rubber of flexible composition coating that protects the line from moisture and mechanical damage. Outwardly, it looks much like the power cord of a washing machine or refrigerator.

A. Twin lead
B. Twisted pair
C. Coaxial cable
D. Shielded pair

A

D. Shielded pair

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23
Q

This type of parallel line is commonly used to connect a television receiving antenna to a home television set. This line is essentially the same as the two- wire open line except that uniform spacing is assured by embedding the two wires in a low-loss dielectric, usually polyethylene.

A. Two-wire open line
B. Two-wire ribbon hub
C. Twin lead and Two-wire ribbon
D. Twin lead

A

C. Twin lead and Two-wire ribbon

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24
Q

What would you use to connect a coaxial cable of 50 ohms impedance to an antenna of 35 ohms impedance?

A. An SWR meter
B. A low pass filter
C. A terminating resistor
D. An impedance-matching device

A

D. An impedance-matching device

The impedance mismatch (line with a Characteristic Impedance of 50 ohms to a load impedance of 35 ohms could be corrected by an ‘impedance-matching device’.

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25
What is the best antenna feed line to use, if it must be put near grounded metal objects? A. Twin lead B. Ladder-line C. Twisted pair D. Coaxial cable
D. Coaxial cable Coaxial cable, with its shielded and grounded outer conductor, is not affected by nearby metallic objects.
26
It is the ratio of the actual velocity of propagation through a given medium to the velocity of propagation through free space. A. velocity factor B. propagation factor C. relative permittivity D. relative permeability
A. velocity factor Relative permittivity It is the ratio of the amount of stored electrical energy when a voltage is applied, relative to that stored by a vacuum. Relative permeability is the ratio of the permeability of a specific medium to the permeability of free space Propagation factor/constant is used to express the attenuation and phase shift per unit length of a transmission line
27
The velocity factor of a transmission line A. is higher for a solid dielectric than for air. B. is governed by the skin effect C. increases in velocity along the transmission line D. depends on the dielectric constant of the material used
D. depends on the dielectric constant of the material used
28
When dc flows through a conductor, the movement of electrons though the conductor's cross section is uniform, but when ac is applied the expanding and collapsing fields about each electron encircle other electrons. This phenomenon is called: A. Induction losses B. Radiation losses C. Mutual induction D. Self-induction
D. Self-induction
29
The VLF and LF bands use ______ propagation for communications. A. Space B. Ground C. Sky D. Line of sight
B. Ground
30
An elliptical zone between two microwave antennas, where the total path distance nowhere varies by more than half of the operating wavelength. A. Fresnel zone B. Optimum Zone C. Skip zone D. Dillinger zone
A. Fresnel zone
31
What two sub-regions of ionosphere exist only in the daytime? A. Troposphere and stratosphere B. Electrostatic and electromagnetic C. D and E D. F1 and F2
D. F1 and F2 SUB-REGIONS. The F1 and F2 layers present during the day combine at night to form the F layer. D and E are two distinct layers of their own.
32
All communication frequencies throughout the spectrum are affected in varying degrees by the: A. sun B. atmospheric conditions C. aurora borealis D. ionosphere
A. sun Because the Sun affects the ionosphere and the troposphere (e.g., temperature inversions), it can be said that it has an influence on all radiocommunications.
33
A change or variation in signal strength at the antenna, caused by differences in path lengths, is called: A. fading B. path loss C. absorption D. fluctuation
A. fading Parts of a wave arriving with difference in phases (Selective Fading) cause a fluctuation in the perceived signal. Signals with large bandwidths are more susceptible to Selective Fading. SSB is less affected.
34
Where would you connect a microphone for voice operation? A. To an antenna B. To a power supply C. To an antenna switch D. To a transceiver
D. To a transceiver Remember your transmitter block diagrams: the Microphone connects to the Speech Amplifier, the first stage in a voice transmitter.
35
What electromagnetic wave polarization does a Yagi antenna have when its elements are parallel to the earth's surface? A. Vertical B. Horizontal C. Circular D. Helical
B. Horizontal An electromagnetic wave comprises an electrical field and a magnetic field. Wave Polarization or describes the position of the ELECTRIC field with respect to the earth's surface. On a dipole antenna or on the 'driven' element of a Yagi, the electric field is developed between the tips of the radiating element.
36
When a signal is returned to earth. by the ionosphere, what is this called? A. Earth-moon-earth propagation B. Tropospheric propagation C. Ground-wave propagation D. Sky-wave propagation
D. Sky-wave propagation Sky Waves or 'ionospheric waves' rely on refraction in layers of the ionosphere.
37
Skip distance is the: A. the maximum distance reached by a signal after one reflection by the ionosphere B. the minimum distance reached by a signal after one reflection by the ionosphere C. the maximum distance a signal will travel by both a ground wave and reflected wave D. the minimum distance reached by a ground-wave signal
B. the minimum distance reached by a signal after one reflection by the ionosphere Skip Distance is the "nearest point where the sky wave returns".
38
The _____ is not used for voice communication: A. IS-95 system B. GPS C. Globalstar system D. Iridium system
A. GPS
39
For radio signals, the skip distance is determined by the: A. height of the ionosphere and the angle of radiation B. power fed to the final C. angle of radiation D. type of transmitting antenna used
A. height of the ionosphere and the angle of radiation How far one hop through the ionosphere reaches depends on the take-off angle of the wave with respect to ground (the lower, the further) AND the height of the layer where refraction takes place (the higher, the further). One hop via the E layer of the ionosphere can reach to 2000 km. One hop via the F2 layer can reach to 4000 km.
40
What does maximum usable frequency mean? A. The highest frequency signal that is most absorbed by the ionosphere B. The lowest frequency signal that is most absorbed by the ionosphere C. The lowest frequency signal that will reach its intended destination D. The highest frequency signal that will reach its intended destination
D. The highest frequency signal that will reach its intended destination The Maximum Usable Frequency (MUF) is the highest frequency usable for sky wave propagation between two points on the globe. MUF varies with ionization levels (solar cycle, time of the day). Maximum Usable Frequencies (MUF) in the range of 30 to 50 MHz become possible during solar cycle peaks.
41
Occurs when the microwave is at the point of grazing over an obstacle. A. refraction B. absorption C. reflection D. Diffraction
D. Diffraction
42
What causes the ionosphere to form? A. Temperature changes ionizing the outer atmosphere B. Release of fluorocarbons into the atmosphere C. Lightning ionizing the outer atmosphere D. Solar radiation ionizing the outer atmosphere
D. Solar radiation ionizing the outer atmosphere Ultraviolet (UV) radiation and particles emanating from the Sun breaks down molecules in the ionosphere to form charged ions.
43
It is 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. A. multiplexer B. circulator C. isolator D. wave trap
C. isolator
44
What type of propagation usually occurs from one hand-held VHF transceiver to another nearby? A. Sky-wave propagation B. Auroral propagation C. Line-of-sight propagation D. Tunnel propagation
C. Line-of-sight propagation VHF, NEARBY. The two antennas "see" one another. 'Line-of-sight' is also known as 'direct waves' in contrast with 'sky wave'.
45
In a Yagi-Uda 3 element directional antenna, the ______ is the shortest radiating element. A. boom B. reflector C. driven element D. director
D. director
46
The measure of the antennas directivity. A. efficiency B. bandwidth C. beamwidth D. radiation resistance
C. beamwidth Bandwidth-frequency range of idth-frequency ra operation Radiation resistance is an ac antenna resistance and is equal to the ratio of the power radiated by the antenna to the feedpoint Efficiency of theon Provider 2 square of the current at its antenna is the ratio of the power radiated by an antenna to the sum of the power radiated and the power dissipated.
47
Indicate which of the following reasons for the use of an earth mat with antennas is false: A. improvement of the radiation pattern of the antenna B. protection of personnel working underneath C. provision of an earth for the antenna D. impossibility of a good ground conduction
A. improvement of the radiation pattern of the antenna
48
The fields surrounding the antenna do not collapse their energy back into the antenna but rather radiate it out into space. A. near field B. radiation field C. magnetic field D. induction field
B. radiation field Radiation field is the same as far field Induction field is the same as near field which are the fields close to the antenna
49
Radiation resistance is the ratio of _____. A. square of voltage to the square of current at any point in the antenna B. radiated power to antenna center current C. voltage to any point of the antenna D. radiated power to the square of the antenna center current
A. square of voltage to the square of current at any point in the antenna
50
Discone radiation pattern is: A. omnidirectional B. bi-directional C. figure of eight D. unidirectional
A. omnidirectional Discone antenna is a low gain antenna but it is omnidirectional. It is often employed as a VHF and UHF receiving and transmitting antenna.
51
What electromagnetic wave polarization does a half- wavelength antenna have when it is perpendicular to the earth's surface? A. Horizontal B. Parabolical C. Circular D. Vertical
D. Vertical An electromagnetic wave comprises an electrical field and a magnetic field. Wave Polarization describes the position of the ELECTRIC field with respect to the earth's surface. On a dipole antenna or on the 'driven' element of a Yagi, the electric field is developed between the tips of the radiating element
52
What does an antenna matching unit do? A. It helps a receiver automatically tune in stations that are far away B. It switches an antenna system to a transmitter when sending, and to a receiver when listening C. It matches a transceiver to a mismatched antenna system D. It switches a transceiver between different kinds of antennas connected to one feed line
C. It matches a transceiver to a mismatched antenna system The 'Antenna Tuner' provides variable impedance transformation: it can adapt the impedance of a the antenna system (which changes with antenna dimensions and operating frequency) to the design impedance of the transceiver. The 'Antenna Tuner' permits using an antenna on a frequency or band other than the one for which it was designed.
53
Polarization of an antenna is determined by: A. the electric field B. the magnetic field C. the type of antenna D. the height of the antenna
A. electric field An electromagnetic wave comprises an electrical field and a magnetic field. Wave Polarization describes the position of the ELECTRIC field with respect to the earth's surface. On a dipole antenna or on the 'driven' element of a Yagi, the electric field is developed between the tips of the radiating element.
54
What device might allow use of an antenna on a band it was not designed for? A. A low pass filter B. An SWR meter C. An antenna tuner D. A high pass filter
D. A high pass filter The 'Antenna Tuner' permits using an antenna on a frequency or band other than the one for which it was designed. The 'SWR Meter' measures antenna system efficiency. The 'Low-Pass Filter' reduces 'Harmonic Radiation'. The 'High-Pass Filter' protects TV receivers from being overloaded by HF transmissions.
55
Of the components in an HF station, which component would normally be connected closest to the antenna, antenna tuner and dummy load? A. Transceiver B. SWR bridge C. Low pass filter D. Antenna switch
C. Low pass filter The 'Antenna Switch' provides a convenient way to select a direct connection to an antenna, a connection through the 'Antenna Tuner' to other antennas or to the 'Dummy Load'. The HF Station block diagram begins with: Transceiver, Linear Amplifier, Low- Pass Filter, SWR Bridge, Antenna Switch, ....
56
A directional antenna with two or more elements is known as: A. array B. ground plane C. loop D. folded dipole
A. array Folded dipole is a single antenna, but it consists of two elements. The first is directly while the second is coupled inductively at the ends. Ground plane is also called as the Marconi antenna which is a quarter wavelength long antenna Loop antenna is simply a single turn coil of wire that is significantly shorter than one wavelength and carries RF current
57
When switching from receive to transmit: A. the power supply should be off B. the receiver should be muted C. the transmit oscillator should be turned off D. the receiving antenna should be connected
B. the receiver should be muted Switching from receive to transmit supposes FOUR actions: disconnect the antenna from the receiver, connect the antenna to the transmitter, silence the receiver and activate the Power Amplifier in the transmitter. A 'Relay' (a multiple-contact electrically-driven switch) frequently performs the antenna changeover an the enabling/ disabling of the transceiver sections.
58
Which of the following antennas is best excited from a waveguide? A. horn B. helical C. biconical D. discone
A. horn
59
What is meant by antenna bandwidth? A. The angle formed between two imaginary lines drawn through the ends of the elements B. The angle between the half-power radiation points C. The frequency range over which the antenna may be expected to perform well D. Antenna length divided by the number of elements
C. The frequency range over which the antenna may be expected to perform well 'Antenna Bandwidth' is the range of frequencies over which Standing Wave Ratio (SWR) is acceptable.
60
The field pattern that is close to the antenna. A. point of shoot B. far field C. figure of eight D. near field
D. near field Near field is also called induction field Far field refers to the field pattern that is at great distance from the antenna. It is also called radiation field. Point of shoot is the line bisecting the major lobe or pointing from the center of the antenna in the direction k of maximum radiation.
61
In a Yagi-Uda 3 element directional antenna, the ________ is not the longest nor the shortest radiating element. A. reflector B. boom C. director D. driven element
D. driven element
62
To lower the resonant frequency of an antenna, the operator should: A. centre feed it with TV ribbon feeder B. lengthen it C. ground one end D. shorten it
B. lengthen it Wavelength and frequency have an inverse relationship. Decreasing the resonant frequency (longer wavelength) can be achieved by lengthening the Cane radiating element.
63
The main characteristic of a vertical antenna is that it will: A. be very sensitive to signals coming from horizontal antennas B. receive signals equally well from all compass points around it C. require few insulators D. be easy to feed with TV ribbon feeder
B. receive signals equally well from all compass points around it An upright antenna element radiates equally well all around it in the horizontal plane. It is termed 'omni-directional'.
64
In a Yagi-Uda 3 element directional antenna, the ________ is the longest radiating element. A. reflector B. boom C. director D. driven element
A. reflector
65
It is the widest dimension of a waveguide and determines the range of operating frequencies. A. n B. a C. b D. m
B. a
66
Indicate which of the following cannot be followed by the word "waveguide": A. Coaxial B. Ridged C. Elliptical D. Flexible
B. Ridged
67
The inside surfaces of waveguides are often plated with ______ to reduce skin effect losses. A. Silver or gold B. Copper C. Tin D. Aluminum
A. Silver or gold
68
A waveguide may be considered as having upper and lower quarter-wave sections and a central section which is a solid conductor called a ______. A. Bus bar B. Solid bar C. None of these choices D. Square bar
A. Bus bar
69
The inner core of an optical fiber is in composition. A. Glass or plastic B. Copper C. Liquid D. Bimetalic
D. Bimetalic
70
It is the narrowest dimension of a waveguide which determines the power-handling capability of the waveguide. A. a B. m C. n D. b
D. b
71
In an optical fiber, the inner core is _____ the cladding. A. Less dense than B. The same density as C. Denser than D. Another name for
C. Denser than
72
Which type of transmission lines can handle more power? A. Two-wire B. Waveguides C. Open wire D. Coaxial lines
D. Coaxial lines Power-handling capability is another advantage of waveguides. Waveguides can handle more power than coaxial lines of the same size because power-handling capability is directly related to the distance between conductors.
73
What is a coaxial cable? A. Two wires twisted around each other in a spiral B. Two wires side-by-side in a plastic ribbon C. A center wire inside an insulating material which is covered by a metal sleeve or shield D. Two wires side-by-side held apart by insulating rods
C. A center wire inside an insulating material which is covered by a metal sleeve or shield
74
What is the primary lower- frequency limitation of waveguides? A. Physical dimensions B. Frequency range C. Physical size D. Special couplings
C. Physical size : Physical size is the primary lower-frequency limitation of waveguides. The width of a waveguide must be approximately a half wavelength at the frequency of the wave to be transported. For example, a waveguide for use at 1 megahertz would be about 500 feet wide. This makes the use of waveguides at frequencies below 1000 megahertz increasing impractical. The lower frequency range of any system using waveguide is limited by the dimensions of the waveguides.
75
A detector that contains two or more sensors that tracks the corresponding products of fire, such as smoke, heat, flame, or carbon monoxide, an transmit signals to the fire alarm control panel, which shall mathematically evaluate them with preprogrammed algorithms to determine whether an alarm signal is warranted. A. Duct Detector B. Multi-criteria Detector C. Beam Detector D. Flame Detector
B. Multi-criteria Detector
76
Thermocouple is a ______. A. Secondary transducer B. None of these choices C. Primary device D. Tertiary transducer
C. Primary device Thermocouple is a device which converts thermal energy to electrical energy and it can be treated as a primary device.
77
What are transducers? A. They convert work to power B. They convert work from one form to another C. They convert energy from one form to another D. They convert power from one form to another
C. They convert energy from one form to another Transducers are devices that convert energy from one form to another. This energy can be either mechanical energy, light energy, heat energy or any other forms of energy.
78
Thermo couple cannot be used to measure ______. A. Temperature of liquid B. None of these choices C. IR radiation D. Temperature of gas
B. None of these choices Infra-Red radiation is characterized by temperature and thermocouple can be used to measure temperature.
79
A detector that detects particles of combustion, whether visible or invisible. A. Smoke Detector B. Carbon Monoxide Detector C. Heat Detector D. Duct Detector
A. Smoke Detector
80
What type of energy conversion does a piezoelectric transducer perform? A. It converts mechanical energy to electrical energy B. It converts mechanical energy to sound energy C. It converts electrical energy to mechanical energy D. It converts sound energy to to mechanical energy
A. It converts mechanical energy to electrical energy A piezoelectric transducer converts mechanical energy to electrical energy. They are generally used to detect a knock or any impulsive force. They are also used in electronic drum pads to detect the impulse provided by the drumsticks.
81
Operation of thermocouple is governed by ______. A. Seebeck effect B. Thomson effect C. All of these choices D. Peltier effect
C. All of these choices Operation of thermocouple is of thermocou based on three major effects- Peltier, Thomson and seebeck, all describe the relation between current flow and temperature between two different metal.
82
A secondary transducer can perform functions such as: A. Generating primary signals B. Amplifying the physical quantity C. Amplifying, filtering, and linearizing the signal D. Filtering the primary signal
C. Amplifying, filtering, and linearizing the signal
83
Which component of a PLC system allows communication between the PLC and external devices or other PLCs? A. Communication Interfaces B. Central Processing Unit (CPU) C. Programming device D. Memory
A. Communication Interfaces
84
Ethernet is primarily used for: A. Sending data over separate lines simultaneously B. Networking and connecting devices over a local area network (LAN) or the internet C. Converting analog signals to digital signals D. Serial communication between devices
B. Networking and connecting devices over a local area network (LAN) or the internet
85
Middleware acts as an intermediary layer between: A. Different software components or systems B. GUIS and CLIS C. Users and software applications D. Hardware devices and the operating system
A. Different software components or systems
86
Which effect arises due to the difference in length of sound path lines and hence causes time delay with respect to each other? A. Stereophonic B. Inductive C. Mesomeric D. Electromeric
A. Stereophonic Stereophonic effect can be obtained by the use of two microphones at source of sound, one for each of two ears. Stereophonic effect arises due to the difference in length of sound path lines and hence time delay with respect to each other. In general, several microphones may be used in place of one to represent each ear.
87
Which type of isolation utilizes light to transmit signals between isolated input and output circuits? A. Signal Multiplexing B. Transformer Isolation C. Optical Isolation D. Electrical Isolation
C. Optical Isolation
88
Which of the following is the main block of digital TV receiver? A. MCU (Microcontroller unit) B. MPRT(Motion picture response time) C. CCU (central control unit) D. MTR (Mean time to repair)
C. CCU (central control unit) The main block of the system is the Central Control Unit (CCU), a micro-computer based device that controls and coordinates all the circuits and signal processing functions and provides a user interface. This permits the user to control receiver functions, display teletex and obtain multiple picture-in-picture displays for simultaneous viewing of different programs and even zooming of the picture.
89
Analog Multiplexing is primarily used for: A. Switching between digital communication protocols B. Switching between different transducer outputs to sample and convert analog signals into digital data C. Converting analog signals to digital format D. Amplifying analog signals
B. Switching between different transducer outputs to sample and convert analog signals into digital data
90
For best protection from electrical shock, what should be grounded in an amateur station? A. The AC power line B. All station equipment C. The power supply primary D. The antenna feed line
B. All station equipment An external ground connection on each cabinet serves as a backup to the normal electrical outlet ground (the 'green' wire in a three-lead power cord).
91
In control system excessive bandwidth is not employed because: A. It leads to low relative stability B. Noise is proportional to bandwidth C. It leads to slower time response D. Noise is proportional to the square of the bandwidth
B. Noise is proportional to bandwidth In closed loop system the bandwidth of the system is more as compared to the open loop system and this is so required as higher the bandwidth means lower the selectivity and hence higher the noise.
92
A control system working under unknown random actions is called ______. A. Digital data system B. Computer control system C. Adaptive control system D. Stochastic control system
D. Stochastic control system A control system is a system which is having feedback and can be both positive and negative and working under unknown random actions is called stochastic control system.
93
Which of the following is an open loop control system? A. Metadyne B. Ward Leonard control C. Stroboscope D. Field controlled D.C. motor
D. Field controlled D.C. motor Open loop control systems are the systems that have no feedback and cannot be used to obtain the desired response and field controlled system is an open loop control system.
94
The SCADA systems are used to: A. Both of these choices B. None of these choices C. Monitor D. Control
A. Both of these choices SCADA systems are used to control and monitor the equipment or plant in industries such as energy, telecommunications, etc.
95
What is the minimum voltage which is usually dangerous to humans? A. 2000 volts B. 30 volts C. 1000 volts D. 100 volts
B. 30 volts Under certain circumstances, even 30 VOLTS can be dangerous. If the human heart is part of the electrocution path, even one tenth of an Ampere can lead to cardiac arrest. Wet skin or cuts to the skin and the exact path of the current are all factors that determine the severity of electrocution.
96
What should you do for safety if you put up a UHF transmitting antenna? A. Make sure that RF field screens are in place B. Make sure the antenna will be in a place where no one can get near it when you are transmitting C. Make sure you connect an RF leakage filter at the antenna feed point D. Make sure the antenna is near the ground to keep its RF energy pointing in the correct direction
B. Make sure the antenna will be in a place where no one can get near it when you are transmitting RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. Never point antennas at anyone. Never look into antennas. Disconnect transmission lines before working on antennas (to further reduce the odds of an error at the station exposing to RE)
97
In a control system the output of the controller is given to: A. Comparator B. Final control element C. Amplifier D. Sensor
B. Final control element In control system the output of the controller is given to the final control element it may be the plant or any other controller which-ever is used in the control circuit.
98
Which multiplex system is used for the broadcasting of stereo sound? A. AM-AM B. FM-FM C. AM-FM D. FM-PM
B. FM-FM The broadcasting of the stereo sound is done by FM-FM stereo Multiplex system where only one FM transmitter is used to tater or broadcast both the left and right channel audio signals. The signal (L+R) is obtained by combining directly the left and right signals while the (L-R) signal is obtained on frequency translation.

EST (10 decks)

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