Z3D153 Volume 2 Ure

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  • 1/100 Questions

    This is the best way to orient line-of-sight (LOS) antennas.

    • Toward the true north bearing.
    • Away from the receiving station.
    • Away from the magnetic north bearing.
    • In a straight path to the receiving station.
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About This Quiz

Z3D153 Volume 2 URE assesses knowledge on US frequency regulations, high-frequency transmission modes, jamming vulnerabilities, and receiver characteristics. It's vital for professionals in telecommunications and radio frequency engineering.

Z3D153 Volume 2 Ure - Quiz

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  • 2. 

    Which statement best identifies the requirements for two transceivers to establish HAVE QUICK (HQ) communications?

    • They must be the same model number

    • They must be the same version of transceiver.

    • They must be use the same encryption variables.

    • They must have the same word of day (WOD) and time of day (TOD).

    Correct Answer
    A. They must have the same word of day (WOD) and time of day (TOD).
    Explanation
    The requirement for two transceivers to establish HAVE QUICK (HQ) communications is that they must have the same word of day (WOD) and time of day (TOD). This ensures that both transceivers are synchronized and can communicate effectively using the same encryption variables. The other statements, such as being the same model number or version of transceiver, are not relevant to the establishment of HQ communications.

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  • 3. 

    This occurs when a transmitted signal travels over two or more separate paths during transmission

    • Skip effects

    • Modulation

    • Multipathing

    • Magneton splitting

    Correct Answer
    A. Multipathing
    Explanation
    Multipathing refers to the phenomenon where a transmitted signal takes multiple paths during transmission. This can occur when the signal reflects off objects or encounters obstacles in its path. As a result, multiple versions of the signal reach the receiver at slightly different times, causing interference and signal degradation. This can lead to issues such as signal fading, ghosting, or poor reception in wireless communication systems.

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  • 4. 

    Which type of antenna radiates radio energy equally well in all directions?

    • Omni-directional.

    • Uni-directional.

    • Bi-directional.

    • Directional

    Correct Answer
    A. Omni-directional.
    Explanation
    Omni-directional antennas radiate radio energy equally well in all directions. Unlike uni-directional, bi-directional, or directional antennas, which focus the energy in a specific direction, omni-directional antennas are designed to provide a 360-degree coverage pattern. This makes them ideal for applications where the signal needs to reach multiple locations or devices from a central point without the need for precise aiming or alignment.

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  • 5. 

    The process of unscrambling encrypted information so that it is intelligible is known as

    • Decryption

    • Encryption

    • Cryptography

    • Cryptanalysis

    Correct Answer
    A. Decryption
    Explanation
    Decryption refers to the process of converting encrypted information back into its original, intelligible form. It involves using a key or algorithm to reverse the encryption process and make the data readable again. Encryption, on the other hand, is the process of converting plain text into an unreadable form to protect it from unauthorized access. Cryptography is the broader field that encompasses both encryption and decryption techniques. Cryptanalysis, on the other hand, refers to the study of cryptographic systems with the aim of breaking them and gaining unauthorized access to encrypted information.

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  • 6. 

    Which US government agency divides the radio frequency spectrum into different bands?

    • Federal Aviation Agency.

    • American National Standard Institute.

    • Federal Communications Commission (FCC).

    • Institute of Electrical & Electronics Engineers, Inc.

    Correct Answer
    A. Federal Communications Commission (FCC).
    Explanation
    The Federal Communications Commission (FCC) is the US government agency responsible for dividing the radio frequency spectrum into different bands. They regulate and allocate different frequencies to various users, such as television and radio broadcasters, wireless communication providers, and other industries that rely on wireless technology. The FCC ensures that these bands are used efficiently and that interference is minimized, enabling effective communication and the smooth operation of wireless devices and services.

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  • 7. 

    A combination transmitter and receiver, built as a single unit and shares common tuned circuits, is called a

    • Transmitter.

    • Transceiver.

    • Receiver

    • Coupler.

    Correct Answer
    A. Transceiver.
    Explanation
    A combination transmitter and receiver, built as a single unit and sharing common tuned circuits, is called a transceiver. This device is capable of both transmitting and receiving signals, making it a versatile and efficient solution for communication purposes. By integrating both functions into one unit, a transceiver simplifies the overall system design and reduces the need for separate components. It is commonly used in various applications such as telecommunications, radio systems, and wireless networks.

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  • 8. 

    This occurs when high-energy ultraviolet light waves from the sun enter the ionospheric region of the atmosphere and strike the gas atoms.

    • Ionization

    • Modulation

    • Conductivity

    • Recombination

    Correct Answer
    A. Ionization
    Explanation
    When high-energy ultraviolet light waves from the sun enter the ionospheric region of the atmosphere and strike the gas atoms, ionization occurs. This means that the UV light causes the gas atoms to lose or gain electrons, resulting in the formation of ions. This process increases the number of ions in the ionospheric region, affecting the electrical conductivity of the atmosphere. Therefore, ionization is the correct answer as it explains the phenomenon of high-energy UV light causing ion formation in the atmosphere.

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  • 9. 

    A transmission line that consists of a center conductor, placed inside a rigid metal tube that functions as the outer shield, is called 

    • Flexible coaxial cable.

    • Rigid coaxial cable.

    • Waveguide

    • Twin lead

    Correct Answer
    A. Rigid coaxial cable.
    Explanation
    A transmission line that consists of a center conductor, placed inside a rigid metal tube that functions as the outer shield, is called a rigid coaxial cable. This type of cable provides excellent shielding and is commonly used in applications that require high-frequency signals and low signal loss. The rigid outer shield ensures that the electromagnetic waves are contained within the cable, preventing interference and signal degradation.

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  • 10. 

    Radio waves that travel near the Earth’s surface are called

    • Earth waves

    • Global waves

    • Ground waves

    • Terrestrial waves

    Correct Answer
    A. Ground waves
    Explanation
    Ground waves are radio waves that travel near the Earth's surface. They are able to follow the curvature of the Earth and can travel for long distances. These waves are commonly used for broadcasting and communication purposes, as they can easily penetrate buildings and other obstacles. Therefore, ground waves are the correct term to describe radio waves that travel near the Earth's surface.

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  • 11. 

    How long is each word-of-day (WOD) used with the HAVE QUICK II (HQII) communications multiple word-of-day (MWOD)?

    • Until manually changed

    • 3 days

    • 48 hours

    • 24 hours

    Correct Answer
    A. 24 hours
    Explanation
    Each word-of-day (WOD) is used with the HAVE QUICK II (HQII) communications multiple word-of-day (MWOD) for a duration of 24 hours. This means that the WOD is automatically changed every 24 hours without any manual intervention.

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  • 12. 

    In sky-wave propagation, frequencies higher than the critical frequency are

    • Returned to Earth

    • Passed into space

    • The most desirable

    • Refracted by the F2 player

    Correct Answer
    A. Passed into space
    Explanation
    In sky-wave propagation, frequencies higher than the critical frequency are passed into space. This means that these frequencies are able to penetrate the ionosphere and continue traveling through space instead of being reflected back to Earth. This is because the ionosphere, a layer of charged particles in the Earth's atmosphere, acts as a medium through which radio waves can propagate. However, when the frequency of the radio wave exceeds the critical frequency, it becomes too high to be refracted by the ionosphere and instead passes through it, allowing the wave to continue its journey into space.

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  • 13. 

    The ability of an antenna to both receive and transmit equally well is known as the antenna’s

    • Bandwidth

    • Resonance

    • Reciprocity

    • Effectiveness

    Correct Answer
    A. Reciprocity
    Explanation
    Reciprocity refers to the ability of an antenna to both receive and transmit signals equally well. This means that the antenna's characteristics remain the same regardless of whether it is used for receiving or transmitting. In other words, if an antenna is efficient in receiving signals, it will also be efficient in transmitting signals, and vice versa. This property is important in various communication systems where the same antenna is used for both sending and receiving signals.

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  • 14. 

    This is one fundamental rule about camouflage.

    • Sawed-off branches and foliage should not be used.

    • Site should be visualized from above

    • Equipment should be widely separated.

    • Straight lines are obvious.

    Correct Answer
    A. Straight lines are obvious.
    Explanation
    Straight lines are obvious because they do not occur naturally in nature. In a natural environment, objects and shapes tend to have more organic and irregular forms. Straight lines can stand out and attract attention, making them easily detectable by observers. Therefore, when using camouflage techniques, it is important to avoid straight lines to blend in with the surroundings effectively.

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  • 15. 

    Which type of conventional land mobile radio (LMR) device maximizes the communications distance between lower-powered equipment items?

    • Mobile

    • Portable

    • Repeater

    • Base station

    Correct Answer
    A. Repeater
    Explanation
    A repeater is a type of conventional land mobile radio (LMR) device that maximizes the communication distance between lower-powered equipment items. It receives a weak signal from a mobile or portable radio and then retransmits it at a higher power, allowing the signal to reach further distances. By acting as a relay station, a repeater extends the range and coverage of communication for LMR devices, making it an ideal choice for maximizing distance between lower-powered equipment items.

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  • 16. 

    Which Air Force instruction (AFI) requires communications squadrons to maintain installation notification and warning systems (INWS)?

    • AFI 10–2501, Air Force Emergency Management Program.

    • AFI 10–2801, Force Development Concepts.

    • AFI 33–115, Air Force Information Technology Service Management.

    • AFI 33–217, Voice Call Sign Program.

    Correct Answer
    A. AFI 10–2501, Air Force Emergency Management Program.
    Explanation
    AFI 10–2501, Air Force Emergency Management Program, is the correct answer because it specifically outlines the requirements for communications squadrons to maintain installation notification and warning systems (INWS). This instruction provides guidance on emergency management procedures and responsibilities within the Air Force, including the maintenance and operation of INWS. It ensures that communications squadrons are equipped to effectively communicate and respond to emergency situations, thereby enhancing the overall emergency management capabilities of the Air Force.

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  • 17. 

    The design frequency of a resonant antenna is 10 megahertz (MHz). What will be its frequency range?

    • 8–10 MHz.

    • 9–11 MHz

    • 9.5–10.5 MHz

    • 9.8–10.2 MHz.

    Correct Answer
    A. 9.8–10.2 MHz.
    Explanation
    The design frequency of a resonant antenna represents the frequency at which the antenna is designed to operate optimally. However, due to various factors such as manufacturing tolerances and environmental conditions, the actual frequency range in which the antenna will perform effectively may vary slightly from the design frequency. In this case, the correct answer suggests that the frequency range for the resonant antenna is expected to be between 9.8 and 10.2 MHz, indicating a slight deviation from the design frequency of 10 MHz.

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  • 18. 

    When siting a radio station, which type of foliage would have a more adverse effect on radio-wave propagation?

    • Broadleaf trees

    • Evergreen trees

    • Swamp grass

    • Sagebrush

    Correct Answer
    A. Broadleaf trees
    Explanation
    Broadleaf trees would have a more adverse effect on radio-wave propagation compared to evergreen trees, swamp grass, and sagebrush. This is because broadleaf trees have denser foliage and a higher water content, which can absorb and scatter radio waves more effectively. This absorption and scattering can result in a weaker signal and reduced coverage for the radio station. In contrast, evergreen trees, swamp grass, and sagebrush have less dense foliage and lower water content, allowing radio waves to pass through with less obstruction.

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  • 19. 

    The common name for the method of changing encryption keys over the radio channel in a two-way radio system is called

    • OTAR

    • Asymmetric

    • Symmetric

    • Off-line

    Correct Answer
    A. OTAR
    Explanation
    OTAR stands for Over-The-Air Rekeying, which is a method used to change encryption keys over the radio channel in a two-way radio system. This process allows for secure and efficient key management, ensuring that the communication remains protected from unauthorized access. By regularly changing encryption keys, the system reduces the risk of key compromise and enhances the overall security of the communication.

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  • 20. 

    Which type of site configuration was designed to provide coverage for a small geographical area?

    • Single-site

    • Multi-site

    • Simulcast

    • Multicast

    Correct Answer
    A. Single-site
    Explanation
    A single-site configuration is designed to provide coverage for a small geographical area. In this configuration, a single base station or repeater is used to cover the entire area, ensuring that users within the vicinity have reliable communication. This type of configuration is suitable for small businesses, campuses, or localized operations where a wide coverage area is not required. It allows for efficient use of resources and simplifies management since all communication devices operate on the same frequency and are connected to a single site.

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  • 21. 

    Which statement is not a benefit of having a trunking network?

    • Selective radio inhibit

    • Faster system access

    • Unbalanced channel loads

    • Better channel efficiency

    Correct Answer
    A. Unbalanced channel loads
    Explanation
    Having unbalanced channel loads is not a benefit of having a trunking network. Trunking networks are designed to efficiently allocate and manage resources, including channels, in order to optimize communication. Unbalanced channel loads can lead to congestion and inefficient use of resources. Therefore, it is not considered a benefit in a trunking network where the goal is to achieve better channel efficiency and equal distribution of traffic.

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  • 22. 

    In the giant-voice system, this controls the system’s signal routing and power distribution.

    • Landline board

    • Control board

    • Radio board

    • Encoder

    Correct Answer
    A. Control board
    Explanation
    The control board is responsible for managing the signal routing and power distribution in the giant-voice system. It is the central component that oversees and regulates the flow of signals and power throughout the system. Without the control board, the system would not be able to properly route signals or distribute power to the necessary components. Therefore, the control board is crucial for the overall functioning and operation of the giant-voice system.

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  • 23. 

    In sky- and ground-wave propagation, the area of silence where no signals are received is known as the

    • Propagation distance

    • Skip distance

    • Dead zone

    • Skip zone

    Correct Answer
    A. Skip zone
    Explanation
    The skip zone refers to the area where no signals are received in sky- and ground-wave propagation. This occurs due to the phenomenon of signal skipping, where the signal is refracted or reflected away from the receiver. As a result, there is a region where the signal does not reach the receiver, leading to a silence or dead zone. Therefore, the correct answer is skip zone.

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  • 24. 

    During which season do we have the wider range of critical frequencies and less absorption of all frequencies?

    • Fall

    • Winter

    • Spring

    • Summer

    Correct Answer
    A. Winter
    Explanation
    In winter, the air is colder and denser, which affects the propagation of sound waves. The colder air allows for a wider range of critical frequencies, meaning that a broader range of frequencies can be heard more clearly. Additionally, the colder air has less absorption of all frequencies, allowing sound waves to travel further without being absorbed or attenuated. Therefore, winter is the season when we have a wider range of critical frequencies and less absorption of all frequencies.

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  • 25. 

    As ionospheric solar variations, sunspots are disturbances that appear and disappear

    • In the sun’s atmosphere

    • On the sun’s surface.

    • In the ionosphere.

    • Beneath the sun’s surface.

    Correct Answer
    A. On the sun’s surface.
    Explanation
    Sunspots are disturbances that appear and disappear on the sun's surface. These dark spots are cooler regions caused by intense magnetic activity. They are associated with the sun's magnetic field and are often seen in groups or pairs. Sunspots are important because they can affect space weather and have an impact on Earth's ionosphere.

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  • 26. 

    In radio-wave creation, which type of field detaches from the antenna and travels through space at great distances?

    • Radiation

    • Induction

    • Gravitational

    • Electromotive

    Correct Answer
    A. Radiation
    Explanation
    Radio-wave creation involves the generation of electromagnetic waves, which detach from the antenna and travel through space at great distances. This process is known as radiation. Electromagnetic radiation is characterized by the oscillation of electric and magnetic fields perpendicular to each other and to the direction of propagation. These waves carry energy and information, allowing for the transmission of radio signals over long distances.

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  • 27. 

    Which type of polarization is used to radiate a signal using a helical satellite antenna?

    • Horizontal

    • Vertical

    • Circular

    • Linear

    Correct Answer
    A. Circular
    Explanation
    Circular polarization is used to radiate a signal using a helical satellite antenna. This type of polarization involves the rotation of the electric field of the signal in a circular motion. It is advantageous for satellite communication as it allows for better signal reception and transmission, regardless of the orientation of the receiving antenna. Circular polarization also helps to minimize signal interference and multipath effects, resulting in improved signal quality and reliability.

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  • 28. 

    This is the most effective type of antennas in mountainous terrain that has a mountain between you and the distant end.

    • Whip

    • Dipole

    • Discone

    • Near-vertical incidence sky-wave

    Correct Answer
    A. Near-vertical incidence sky-wave
    Explanation
    The near-vertical incidence sky-wave antenna is the most effective type of antenna in mountainous terrain with a mountain between you and the distant end. This type of antenna is specifically designed to transmit and receive signals that are reflected off the ionosphere at a near-vertical angle. This allows the signals to bypass obstacles like mountains and reach the distant end effectively. The whip, dipole, and discone antennas are not specifically designed for mountainous terrain and may not perform as well in such conditions.

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  • 29. 

    Which tactical data link (TDL) is a secure, full-duplex, point-to-point digital data link that uses satellite, microwave, or terrestrial cable, as opposed to a modulated waveform, to transmit data?

    • Link 4

    • Link 11

    • Link 11b

    • Link 16

    Correct Answer
    A. Link 11b
    Explanation
    Link 11b is a secure, full-duplex, point-to-point digital data link that uses satellite, microwave, or terrestrial cable to transmit data. It is different from other options like Link 4 and Link 16, which use modulated waveforms for data transmission.

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  • 30. 

    In high-frequency (HF) communications, your station’s automatic link establishment (ALE) self-address is the address

    • the user programmed for his or her station.

    • it shares with other members.

    • Of an unprogrammed station

    • Of other stations in the net

    Correct Answer
    A. the user programmed for his or her station.
    Explanation
    In high-frequency (HF) communications, the automatic link establishment (ALE) self-address refers to the address that the user has programmed for their station. This self-address is unique to each station and is used for communication purposes. It is not shared with other members or stations in the network.

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  • 31. 

    This will likely result if a transmission line is terminated in an open.

    • Signal loss would be negligible.

    • Signal loss would be significant.

    • Current would be maximum at the termination.

    • Voltage would be minimum at the termination

    Correct Answer
    A. Signal loss would be significant.
    Explanation
    If a transmission line is terminated in an open, it means that there is no load connected to the line. In this scenario, the signal would encounter a significant loss because there is no impedance matching between the source and the line. This mismatch causes a reflection of the signal, resulting in a loss of energy. Therefore, the correct answer is that signal loss would be significant.

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  • 32. 

    The angle at which a radio wave enters the ionosphere is known as the

    • Skip angle

    • Critical angle

    • Angle of entrance

    • Angle of incidence

    Correct Answer
    A. Angle of incidence
    Explanation
    The angle at which a radio wave enters the ionosphere is known as the angle of incidence. This is the angle between the incident wave and the normal to the surface of the ionosphere. It determines how the wave will be refracted or reflected as it passes through the ionosphere. The angle of incidence is an important factor in understanding the behavior of radio waves in the ionosphere and is used in various calculations and models related to ionospheric propagation.

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  • 33. 

    How many layers make up the Earth’s atmosphere?

    • 2

    • 3

    • 4

    • 5

    Correct Answer
    A. 5
    Explanation
    The Earth's atmosphere is composed of five layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer has its own unique characteristics and plays a crucial role in the Earth's climate and weather patterns.

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  • 34. 

    The concept where alternating current (AC) changes in magnitude, and reverses its direction during each cycle, is

    • An unproven hypothesis.

    • The definition of propagation

    • What makes radio transmission possible.

    • What led to the discovery of direct current (DC).

    Correct Answer
    A. What makes radio transmission possible.
    Explanation
    The concept where alternating current (AC) changes in magnitude, and reverses its direction during each cycle, is what makes radio transmission possible. Radio transmission relies on the ability of AC to oscillate and change direction, allowing the transmission of information through electromagnetic waves. This concept is fundamental to the functioning of radio technology and is the basis for the transmission and reception of radio signals.

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  • 35. 

    Where is the primary high frequency global communications system (HFGCS) network control station located?

    • Offutt, Nebraska.

    • Grand Forks, North Dakota

    • Andrews AFB, Maryland

    • Croughton, England.

    Correct Answer
    A. Andrews AFB, Maryland
    Explanation
    The primary high frequency global communications system (HFGCS) network control station is located at Andrews AFB, Maryland.

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  • 36. 

    High-frequency (HF) transmissions are normally conducted in which two operating modes?

    • Frequency modulation (FM) and independent sidebands (ISB).

    • Continuous wave (CW) and amplitude modulation (AM).

    • Single side band (SSB) and FM.

    • SSB and ISB.

    Correct Answer
    A. SSB and ISB.
    Explanation
    High-frequency (HF) transmissions are normally conducted in two operating modes: Single sideband (SSB) and independent sidebands (ISB). SSB is a modulation technique that transmits only one sideband of the signal, resulting in more efficient use of bandwidth. ISB, on the other hand, transmits both sidebands independently, allowing for simultaneous transmission of multiple signals. These operating modes are commonly used in HF communications to maximize efficiency and improve signal quality.

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  • 37. 

    Which frequency band is most susceptible to jamming?

    • Low frequency (LF)

    • Medium frequency (MF).

    • High frequency (HF).

    • Very high frequency (VHF).

    Correct Answer
    A. High frequency (HF).
    Explanation
    High frequency (HF) is the correct answer because it is the range of frequencies that are most susceptible to jamming. This is because HF signals can travel long distances through the ionosphere, making them ideal for long-range communication. However, this also makes them more vulnerable to interference and jamming from natural phenomena like solar flares or man-made sources. Additionally, HF signals can be easily disrupted by atmospheric conditions, making them more susceptible to jamming compared to other frequency bands.

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  • 38. 

    A waveguide is a type of transmission line that you would use 

    • When the frequencies are so high that their wavelength is miniscule.

    • to transmit on frequencies too low for ground propagation.

    • for high power at frequencies up to 30 megahertz (MHz) primarily.

    • To receive television frequencies over the air.

    Correct Answer
    A. When the frequencies are so high that their wavelength is miniscule.
    Explanation
    The correct answer is when the frequencies are so high that their wavelength is miniscule. This is because waveguides are designed to handle high-frequency signals and are most effective when the wavelength of the signal is small, such as in the microwave and millimeter wave frequency ranges. Waveguides provide a means of guiding and confining the electromagnetic waves within a structure, allowing for efficient transmission of high-frequency signals without significant loss or interference.

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  • 39. 

    On which regular ionospheric variation do sunspots occur?

    • 11-day cycle

    • 11-week cycle

    • 11-month cycle

    • 11-year cycle.

    Correct Answer
    A. 11-year cycle.
    Explanation
    Sunspots occur on an 11-year cycle. Sunspots are dark areas on the surface of the sun that are cooler than their surroundings. These spots are caused by intense magnetic activity on the sun, which follows an 11-year cycle known as the solar cycle. During this cycle, the number of sunspots increases and decreases, reaching a maximum and minimum every 11 years. This variation in sunspots has an impact on the ionosphere, which is the upper part of the Earth's atmosphere, causing regular ionospheric variations.

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  • 40. 

    Electromagnetic (EM) deception, as it applies to electronic warfare (EW), is

    • Controlling the information an enemy receives.

    • Eliminating some, or all, of an adversary’s electronic defenses.

    • Conveying misleading information to an enemy through the deliberate radiation of EM energy.

    • Degrading, or interfering with, the enemy’s use of the EM spectrum to limit an enemy’s combat capabilities

    Correct Answer
    A. Conveying misleading information to an enemy through the deliberate radiation of EM energy.
    Explanation
    The correct answer is conveying misleading information to an enemy through the deliberate radiation of EM energy. In electronic warfare, electromagnetic deception involves intentionally emitting electromagnetic energy to deceive the enemy by conveying false or misleading information. This can be done by mimicking friendly signals, creating false targets, or distorting enemy sensor readings. By manipulating the electromagnetic spectrum, the goal is to confuse and mislead the enemy, making it difficult for them to accurately assess the situation and make informed decisions.

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  • 41. 

    The ability of a receiver to reproduce the input signal accurately is characteristic of its

    • Fidelity

    • Capacity

    • Sensitivity.

    • Selectivity

    Correct Answer
    A. Fidelity
    Explanation
    Fidelity refers to the ability of a receiver to reproduce the input signal accurately. It measures how well the receiver can maintain the integrity of the original signal without any distortion or loss of information. A receiver with high fidelity will be able to faithfully reproduce the input signal, ensuring that the output is a true representation of the original signal. Therefore, fidelity is the characteristic that determines the accuracy of signal reproduction by a receiver.

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  • 42. 

    Direct waves are radio waves that travel

    • Long distances with few interruptions.

    • From point to point along the Earth’s surface.

    • No more than 20 miles to the receive antenna

    • Through the air in a straight line from transmitter to receiver

    Correct Answer
    A. Through the air in a straight line from transmitter to receiver
    Explanation
    Direct waves are radio waves that travel through the air in a straight line from the transmitter to the receiver. This means that there are no obstacles or interruptions in the path of the waves, allowing them to travel long distances without being obstructed. The statement "from point to point along the Earth's surface" is incorrect because it suggests that the waves travel along the surface, whereas direct waves travel through the air. The statement "no more than 20 miles to the receive antenna" is also incorrect because direct waves can travel much farther distances without significant loss of signal strength.

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  • 43. 

    The atmospheric recombination process is dependent on the

    • Season

    • Time of day (TOD)

    • Regular variation

    • Irregular variations

    Correct Answer
    A. Time of day (TOD)
    Explanation
    The atmospheric recombination process refers to the process in which ions and free electrons in the atmosphere recombine to form neutral molecules. This process is dependent on the time of day (TOD) because the concentration of ions and free electrons in the atmosphere varies throughout the day. During the day, the ionization rate is higher due to the presence of sunlight, which leads to more ions and free electrons in the atmosphere. As the day progresses and sunlight decreases, the ionization rate decreases, resulting in a decrease in the concentration of ions and free electrons. Therefore, the time of day plays a crucial role in the atmospheric recombination process.

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  • 44. 

    Which layer of the ionosphere is most important for high-frequency (HF) communications?

    • D

    • E

    • F

    • Topside

    Correct Answer
    A. F
    Explanation
    The F layer is the most important layer of the ionosphere for high-frequency (HF) communications. It is located at an altitude of about 150 to 400 km above the Earth's surface. The F layer is responsible for reflecting HF radio waves back to the Earth, allowing long-distance communication over large areas. It is also known for its ability to refract radio waves, allowing them to travel beyond the horizon. The F layer is further divided into two sub-layers, F1 and F2, with the F2 layer being the most significant for HF communications.

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  • 45. 

    In frequency-hopping (FH) operations, the interval at which each transmitter remains on a given frequency for a specific time is known as

    • Dwell time

    • Hopping rate

    • Frequency offset

    • Transmitter velocity

    Correct Answer
    A. Dwell time
    Explanation
    In frequency-hopping (FH) operations, the interval at which each transmitter remains on a given frequency for a specific time is known as dwell time. This refers to the duration that a transmitter stays on a particular frequency before hopping to the next frequency. It is an important parameter in FH systems as it determines the amount of time spent on each frequency and affects the system's performance in terms of interference, capacity, and reliability.

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  • 46. 

    Which type of cryptographic algorithm permits the encryption key to be public?

    • Asymmetric

    • Symmetric

    • Encoder

    • Secret

    Correct Answer
    A. Asymmetric
    Explanation
    Asymmetric cryptographic algorithms allow the encryption key to be public. In this type of encryption, there are two different keys: a public key and a private key. The public key is used for encryption, and it can be freely shared with others. The private key, on the other hand, is kept secret and is used for decryption. This allows for secure communication between parties, as anyone can encrypt a message using the recipient's public key, but only the recipient with the corresponding private key can decrypt and read the message.

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  • 47. 

    All statements concerning waveguides are true except

    • Their outer surface will arc from being very slightly damaged.

    • Their conductive material construction is easily dented.

    • Their effectiveness is hindered by moisture.

    • They can be destroyed by corrosion.

    Correct Answer
    A. Their outer surface will arc from being very slightly damaged.
    Explanation
    The given answer states that "their outer surface will arc from being very slightly damaged" is not a true statement concerning waveguides. This means that waveguides do not experience arcing on their outer surface even if they are slightly damaged.

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  • 48. 

    Which frequency range will show little effect from precipitation?

    • HF

    • UHF

    • SHF

    • EHF

    Correct Answer
    A. HF
    Explanation
    HF stands for High Frequency and refers to the frequency range between 3 to 30 MHz. This frequency range is less affected by precipitation because the radio waves in this range are able to penetrate through rain, snow, and other forms of precipitation with minimal attenuation. Therefore, HF signals can travel longer distances and are less likely to be disrupted by weather conditions compared to higher frequency bands like UHF, SHF, and EHF.

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  • 49. 

     Line-of-sight (LOS) radio waves that are guided through the air between two layers of the atmosphere are known as

    • Channeling

    • Guiding

    • Ducting

    • Piping

    Correct Answer
    A. Ducting
    Explanation
    Ducting refers to the phenomenon in which radio waves are guided through the air between two layers of the atmosphere. This allows for the transmission of signals over long distances, even beyond the normal line-of-sight range. Ducting is commonly observed in situations where there are temperature inversions in the atmosphere, causing the radio waves to follow a curved path due to differences in air density. This allows for communication over longer distances than what would be possible with line-of-sight transmission alone.

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Quiz Review Timeline (Updated): Mar 20, 2023 +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • Mar 20, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Mar 28, 2017
    Quiz Created by
    Trevormayer88
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