1.
Which US government agency divides the radio frequency spectrum into different bands?
Correct Answer
C. Federal Communications Commission (FCC).
Explanation
The Federal Communications Commission (FCC) is the correct answer because it is the US government agency responsible for regulating and dividing the radio frequency spectrum into different bands. The FCC is tasked with managing and allocating the limited radio spectrum resources to ensure efficient and interference-free communication for various industries and services, including broadcasting, telecommunications, and wireless technologies.
2.
High-frequency (HF) transmissions are normally conducted in which two operating modes?
Correct Answer
D. SSB and ISB.
Explanation
High-frequency (HF) transmissions are normally conducted in Single Sideband (SSB) and Independent Sidebands (ISB) operating modes. SSB is a modulation technique that suppresses the carrier and one of the sidebands, allowing for efficient use of bandwidth. ISB, on the other hand, is a technique where multiple sidebands are transmitted independently, enabling simultaneous transmission of multiple signals. Both SSB and ISB are commonly used in HF transmissions due to their efficiency and ability to transmit multiple signals.
3.
Which frequency band is most susceptible to jamming?
Correct Answer
C. High frequency (HF).
Explanation
High frequency (HF) is the correct answer because it is the frequency band that is most susceptible to jamming. This is because HF signals can travel long distances and can be easily disrupted by natural phenomena like solar flares or atmospheric disturbances. Additionally, HF signals can be easily intercepted and disrupted by intentional jamming devices, making this frequency band particularly vulnerable to interference.
4.
The ability of a receiver to reproduce the signal of a very weak station is characteristic of a receiver’s
Correct Answer
C. Sensitivity
Explanation
Sensitivity refers to a receiver's ability to detect and reproduce weak signals. A receiver with high sensitivity can pick up and amplify even very faint signals, allowing it to reproduce the signal of a weak station accurately. Fidelity refers to the accuracy with which a receiver reproduces the original signal, capacity refers to the maximum number of signals a receiver can handle, and selectivity refers to a receiver's ability to separate and tune in to a specific signal while rejecting others. Therefore, sensitivity is the most appropriate characteristic for a receiver's ability to reproduce the signal of a weak station.
5.
The ability of a receiver to reproduce the input signal accurately is characteristic of its
Correct Answer
A. Fidelity
Explanation
Fidelity refers to the ability of a receiver to reproduce the input signal accurately. It is a measure of how faithfully the receiver can reproduce the original signal without distortion or loss of information. A receiver with high fidelity will be able to accurately reproduce the input signal, while a receiver with low fidelity may introduce distortions or lose some of the original information. Capacity, sensitivity, and selectivity are not directly related to the accuracy of signal reproduction, making fidelity the correct answer.
6.
A combination transmitter and receiver, built as a single unit and shares common tuned circuits, is called a
Correct Answer
B. Transceiver.
Explanation
A combination transmitter and receiver, built as a single unit and sharing common tuned circuits, is referred to as a transceiver. This device is capable of both transmitting and receiving signals, making it a versatile and efficient tool for communication purposes. By integrating these functionalities into a single unit, a transceiver simplifies the setup and operation of communication systems, reducing the need for separate transmitter and receiver units.
7.
Conductor material resistance in a transmission line leads to this type of loss.
Correct Answer
A. Copper.
Explanation
The correct answer is Copper. The question is asking about the type of loss caused by the resistance of the conductor material in a transmission line. Copper is a commonly used conductor material, and it has a certain resistance. This resistance leads to power loss in the form of heat, known as copper loss.
8.
The amount of skin-effect loss is directly proportional to the
Correct Answer
B. Frequency
Explanation
The amount of skin-effect loss is directly proportional to the frequency. Skin-effect is the tendency of alternating current to concentrate near the surface of a conductor, resulting in increased resistance and power loss. As the frequency increases, the skin depth decreases, causing more current to flow near the surface of the conductor. This leads to higher resistance and increased skin-effect loss. Therefore, the frequency of the current is a determining factor in the amount of skin-effect loss experienced.
9.
Leakage loss in a transmission line is minimized by using a
Correct Answer
D. Very high-resistance dielectric.
Explanation
Using a very high-resistance dielectric minimizes leakage loss in a transmission line. Leakage loss occurs when some of the electrical energy is lost as heat due to the flow of current through the dielectric material. By using a high-resistance dielectric, the flow of current is reduced, resulting in lower leakage loss. This helps to improve the efficiency of the transmission line and minimize power losses. Thinner or thicker conductors do not directly affect leakage loss, and using a very low-resistance dielectric would actually increase leakage loss.
10.
A transmission line that consists of a center conductor, placed inside a rigid metal tube that functions as the outer shield, is called
Correct Answer
B. 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 better shielding and protection against interference compared to other options like flexible coaxial cable or twin lead. The rigid structure of the metal tube helps maintain the integrity of the signal being transmitted, making it suitable for applications that require high frequencies and low signal loss. Waveguide, on the other hand, is a different type of transmission line that uses a hollow metal tube to guide electromagnetic waves.
11.
A waveguide is a type of transmission line that you would use
Correct Answer
A. When the frequencies are so high that their wavelength is miniscule.
Explanation
A waveguide is a type of transmission line that is used when the frequencies of the signals being transmitted are very high, resulting in very short wavelengths. This is because waveguides are designed to efficiently transmit electromagnetic waves with high frequencies and short wavelengths, which cannot be effectively transmitted through traditional transmission lines. By using a waveguide, the signals can be contained and guided along the structure, allowing for efficient transmission at these high frequencies.
12.
All statements concerning waveguides are true except
Correct Answer
A. Their outer surface will arc from being very slightly damaged.
Explanation
This statement is false because the outer surface of waveguides will not arc from being very slightly damaged. Arcing occurs when there is a high voltage breakdown across a gap, but waveguides are designed to handle high power without arcing. Therefore, this statement is not true and is the exception among the given statements concerning waveguides.
13.
Which two transmission line properties determine its characteristic impedance (ZO)?
Correct Answer
B. Inductance and capacitance
Explanation
The characteristic impedance of a transmission line is determined by its inductance and capacitance. Inductance is the property that opposes changes in current flow, while capacitance is the property that opposes changes in voltage. These two properties work together to determine how well the transmission line can transmit signals without distortion or loss.
14.
This is the correct statement concerning a wavelength.
Correct Answer
A. Wavelength is inversely related to frequency.
Explanation
The correct answer is "Wavelength is inversely related to frequency." This means that as the frequency of a wave increases, the wavelength decreases, and vice versa. This relationship is based on the wave equation, where wavelength (λ) is equal to the speed of the wave divided by the frequency. Therefore, if the frequency increases, the wavelength must decrease in order to maintain a constant speed.
15.
Determine the wavelength of a 250 megahertz (MHz) signal.
Correct Answer
D. 1.2 meters
Explanation
The wavelength of a signal can be determined by dividing the speed of light by the frequency of the signal. In this case, the frequency is given as 250 megahertz (MHz), which can be converted to 250 million hertz (Hz). The speed of light is approximately 300,000,000 meters per second. Dividing the speed of light by the frequency gives us a wavelength of 1.2 meters.
16.
A nonresonant transmission line is one with
Correct Answer
B. No reflected waves
Explanation
A nonresonant transmission line is designed in such a way that there are no reflected waves. This means that the entire energy of the signal is transmitted without any portion being reflected back. In a nonresonant transmission line, the impedance is matched, allowing for efficient transfer of power. Therefore, there are no reflected waves in a nonresonant transmission line.
17.
When discussing resonant and nonresonant transmission lines,
Correct Answer
C. Maximum power transfer results from a nonresonant line
18.
This will likely result if a transmission line is terminated in an open.
Correct Answer
B. Signal loss would be significant.
Explanation
If a transmission line is terminated in an open, it means that the line is not connected to any load or device at the end. In this scenario, the signal will not be properly absorbed or reflected back, causing significant signal loss. The open termination prevents the signal from being effectively transmitted along the line, resulting in a weakened or distorted signal. Therefore, the correct answer is that signal loss would be significant.
19.
Direct waves are radio waves that travel
Correct Answer
D. 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 transmitter to receiver. This means that they do not require any obstacles or interruptions to propagate and can travel long distances without significant attenuation. Unlike other types of waves, direct waves do not rely on bouncing off the Earth's surface or being refracted by the atmosphere. Instead, they maintain a straight path, allowing for efficient long-distance communication.
20.
Radio waves that travel near the Earth’s surface are called
Correct Answer
C. Ground waves
Explanation
Radio waves that travel near the Earth's surface are called ground waves. These waves propagate by hugging the Earth's surface and following its curvature, allowing them to travel for long distances. Ground waves are commonly used for broadcasting and communication purposes, as they can easily penetrate buildings and other obstacles.
21.
The Earth’s conductivity is determined by the type of
Correct Answer
C. Soil and water in the propagation path.
Explanation
The Earth's conductivity refers to its ability to conduct electrical currents. In the context of this question, it is being determined by the type of atmospheric conditions at the time of transmission. The conductivity of the Earth can be influenced by factors such as air and moisture content in the propagation path. However, the primary determinant of Earth's conductivity is the composition of the soil and water in the propagation path. Soil and water can significantly impact the conductivity of the Earth, affecting the transmission of electrical currents.
22.
This term is used to describe radio waves that bend as they travel from one medium to another that has different density
Correct Answer
C. Refraction
Explanation
Refraction is the correct answer because it refers to the bending of radio waves as they pass from one medium to another with different densities. This phenomenon occurs due to the change in speed and direction of the waves when they enter a different medium.
23.
The refractive index of air depends on moisture
Correct Answer
A. Atmospheric pressure, and temperature.
Explanation
The refractive index of air depends on atmospheric pressure and temperature. Atmospheric pressure affects the density of air, which in turn affects the speed of light passing through it. As the pressure increases, the density of air increases, causing the speed of light to decrease. Similarly, temperature also affects the density of air. As temperature increases, the density of air decreases, resulting in an increase in the speed of light. Therefore, both atmospheric pressure and temperature play a role in determining the refractive index of air.
24.
When comparing the radio and optical horizons, which one is farther away and by what percentage?
Correct Answer
B. Radio; 15.
Explanation
The correct answer is "Radio; 15." This means that the radio horizon is farther away than the optical horizon by 15%. The radio horizon refers to the maximum distance at which radio waves can travel before being absorbed by the Earth's atmosphere, while the optical horizon refers to the maximum distance at which objects can be seen with the naked eye. Therefore, the radio horizon extends further than the optical horizon, and it is 15% farther away.
25.
Which process permits communication in shadow regions behind obstacles?
Correct Answer
D. Diffraction
Explanation
Diffraction is the process that permits communication in shadow regions behind obstacles. It occurs when waves encounter an obstacle or an opening and bend around it, spreading outwards. This bending allows the waves to reach areas that are not directly in the line of sight, such as shadow regions. Reflection, scattering, and refraction do not specifically allow communication in shadow regions behind obstacles.
26.
Which frequency range will show little effect from precipitation?
Correct Answer
A. HF
Explanation
HF (High Frequency) is the correct answer because it refers to the frequency range between 3 and 30 MHz, which is relatively low compared to UHF (Ultra High Frequency), SHF (Super High Frequency), and EHF (Extremely High Frequency). Precipitation, such as rain or snow, tends to have a greater impact on higher frequency ranges. Therefore, HF frequencies will experience little effect from precipitation compared to the other options.
27.
Line-of-sight (LOS) radio waves that are guided through the air between two layers of the atmosphere are known as
Correct Answer
C. Ducting
Explanation
Ducting refers to the phenomenon where radio waves are guided through the air between two layers of the atmosphere. This allows for long-distance communication without the need for satellite or other infrastructure. Channeling, guiding, and piping do not accurately describe this specific process of radio wave propagation.
28.
Which condition gives sky-wave propagation its ability to communicate beyond the optical line-of-sight (LOS)?
Correct Answer
A. Refraction
Explanation
Refraction is the correct answer because it is the bending of radio waves as they pass through different layers of the atmosphere. This bending allows the waves to follow the curvature of the Earth and reach areas beyond the line-of-sight. Refraction occurs due to the variation in the density of the atmosphere, causing the radio waves to change direction and be able to communicate over longer distances. Reflection, Earth's conductivity, and atmospheric charge do not play a significant role in sky-wave propagation's ability to communicate beyond the optical line-of-sight.
29.
The angle at which a radio wave enters the ionosphere is known as the
Correct Answer
D. 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 a line perpendicular to the surface of the ionosphere. It determines how the wave will be reflected, refracted, or absorbed by the ionosphere. The angle of incidence is an important factor in understanding how radio waves propagate through the ionosphere and is used in various applications such as radio communication and radar systems.
30.
There are several critical sky-wave propagation angles and frequencies. Radio waves that angle too low are
Correct Answer
C. Absorbed before refraction occurs
Explanation
Radio waves that angle too low are absorbed before refraction occurs. This means that when the radio waves approach the ionosphere at a very low angle, they are absorbed by the ionosphere before they can be refracted or bent back towards the Earth's surface. This absorption prevents the radio waves from being reflected back to the Earth and instead they are lost or dissipated in the ionosphere.
31.
In sky-wave propagation, frequencies higher than the critical frequency are
Correct Answer
B. Passed into space
Explanation
In sky-wave propagation, frequencies higher than the critical frequency are passed into space. Sky-wave propagation refers to the reflection and refraction of radio waves by the ionosphere, allowing them to travel long distances. The critical frequency is the maximum frequency that can be refracted back to Earth by the ionosphere. Frequencies higher than the critical frequency cannot be refracted and instead pass through the ionosphere into space. Therefore, they are passed into space rather than being returned to Earth or refracted by the F2 layer.
32.
The term frequency of optimum transmission (FOT) is also referred to as the
Correct Answer
C. Optimum traffic frequency.
Explanation
The term frequency of optimum transmission (FOT) refers to the frequency at which the transmission of data or signals is most efficient and effective. It is also known as the optimum traffic frequency because it represents the ideal frequency for transmitting traffic or data. The other options mentioned in the question, such as outbound traffic frequency and optimum tropospheric frequency, do not accurately describe the concept of FOT. Therefore, the correct answer is optimum traffic frequency.
33.
In sky- and ground-wave propagation, the area of silence where no signals are received is known as the
Correct Answer
D. Skip zone
Explanation
The skip zone refers to an area where no signals are received in sky- and ground-wave propagation. This occurs when the signal is too far for ground-wave propagation and not far enough for sky-wave propagation to occur. In this zone, the signal is neither reflected back to the Earth nor able to reach the receiver directly, resulting in no signal reception.
34.
This occurs when a transmitted signal travels over two or more separate paths during transmission
Correct Answer
C. Multipathing
Explanation
Multipathing refers to the phenomenon when a transmitted signal takes multiple paths during transmission. This can happen due to reflections, refractions, or diffractions in the environment. As a result, the receiver receives multiple versions of the signal at slightly different times and amplitudes. Multipathing can cause interference, signal distortion, and reduced signal quality. It is a common issue in wireless communication systems, especially in urban areas with tall buildings and obstacles that cause signal reflections.
35.
How many layers make up the Earth’s atmosphere?
Correct Answer
D. 5
Explanation
The Earth's atmosphere is composed of five layers. These layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer has its own unique characteristics and plays a vital role in the Earth's climate and weather patterns. The troposphere is the lowest layer and is where weather occurs, while the exosphere is the outermost layer and gradually transitions into space.
36.
This occurs when high-energy ultraviolet light waves from the sun enter the ionospheric region of the atmosphere and strike the gas atoms.
Correct Answer
A. Ionization
Explanation
Ionization is the process in which high-energy ultraviolet light waves from the sun enter the ionospheric region of the atmosphere and collide with gas atoms, causing them to lose or gain electrons and become ions. This process increases the number of ions in the atmosphere, leading to ionization.
37.
The atmospheric recombination process is dependent on the
Correct Answer
B. Time of day (TOD)
Explanation
The atmospheric recombination process refers to the process in which ions in the atmosphere combine with electrons to form neutral molecules. This process is dependent on the time of day (TOD) because the concentration of ions and electrons in the atmosphere varies throughout the day. During the day, there is more sunlight and ionizing radiation, which leads to the production of more ions and electrons. As the day progresses and sunlight decreases, the concentration of ions and electrons decreases as well. Therefore, the time of day plays a crucial role in the atmospheric recombination process.
38.
Which layer of the ionosphere is most important for high-frequency (HF) communications?
Correct Answer
C. F
Explanation
The F layer of the ionosphere is the most important for high-frequency (HF) communications. This layer is located between 150 and 400 km above the Earth's surface and is responsible for reflecting HF radio waves back to the Earth. It is the highest ionospheric layer and has the highest electron density, allowing it to refract and reflect HF signals over long distances. This makes it crucial for long-range HF communication, such as international broadcasting and long-distance radio transmissions.
39.
During which season do we have the wider range of critical frequencies and less absorption of all frequencies?
Correct Answer
B. Winter
Explanation
During winter, the air is colder and denser, which leads to a wider range of critical frequencies. The colder air also has less moisture, resulting in less absorption of all frequencies. This combination of factors allows sound waves to travel further and with less attenuation, making winter the season with the wider range of critical frequencies and less absorption of all frequencies.
40.
As ionospheric solar variations, sunspots are disturbances that appear and disappear
Correct Answer
B. On the sun’s surface.
Explanation
Sunspots are disturbances that appear and disappear on the sun's surface. These dark spots are caused by intense magnetic activity, which inhibits the flow of heat from the sun's interior, resulting in cooler temperatures and reduced brightness. Sunspots can vary in size and can last from a few days to several months. They are closely monitored by scientists as they are indicators of solar activity and can have an impact on Earth's climate and communication systems.
41.
On which regular ionospheric variation do sunspots occur?
Correct Answer
D. 11-year cycle.
Explanation
Sunspots occur on an 11-year cycle. Sunspots are dark spots on the surface of the sun that are caused by intense magnetic activity. These spots appear and disappear over time, following a cycle of approximately 11 years. During the peak of the cycle, the number of sunspots is at its highest, and during the minimum, the number is at its lowest. This 11-year cycle is known as the solar cycle and is closely linked to other solar phenomena, such as solar flares and coronal mass ejections.
42.
In a basic communication system, this is used to convert radio frequency (RF) current oscillation into electric and magnetic fields of force.
Correct Answer
A. Antenna
Explanation
An antenna is used in a basic communication system to convert radio frequency (RF) current oscillation into electric and magnetic fields of force. It acts as a transducer, converting electrical signals into electromagnetic waves that can be transmitted and received. The antenna plays a crucial role in transmitting and receiving signals efficiently and effectively in a communication system.
43.
The concept where alternating current (AC) changes in magnitude, and reverses its direction during each cycle, is
Correct Answer
C. 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. Alternating current is used in radio transmission because it can be easily transformed into different voltages, allowing for the efficient transmission of signals over long distances. This concept is essential for the functioning of radio communication systems.
44.
At which point do magnetic fields around a wire no longer have time to collapse completely between alternations?
Correct Answer
C. 10,000 cps.
Explanation
At 10,000 cycles per second (cps), the magnetic fields around a wire do not have enough time to collapse completely between alternations. This means that the magnetic field does not have enough time to fully dissipate before the next alternation occurs. As a result, the magnetic field will not collapse completely and will persist between alternations at this frequency.
45.
In radio-wave creation, which type of field detaches from the antenna and travels through space at great distances?
Correct Answer
A. Radiation
Explanation
Radio waves are a form of electromagnetic radiation that is created by the antenna. Electromagnetic radiation is a type of energy that detaches from the antenna and travels through space at great distances. It does not require a medium to propagate and can travel through a vacuum. Therefore, the correct answer is radiation.
46.
Which types of polarization do most satellite communication terminals transmit and receive?
Correct Answer
C. Transmit right-hand circular and receive left-hand circular polarizations.
Explanation
Most satellite communication terminals transmit and receive right-hand circular polarizations. This type of polarization is commonly used in satellite communication because it provides better resistance to signal degradation caused by atmospheric conditions and other obstacles. By transmitting right-hand circular polarization and receiving left-hand circular polarization, the terminals can effectively communicate with satellites and ensure reliable signal transmission.
47.
A resonant antenna effectively radiates a radio signal for frequencies close to its designed frequency. Which percentage range, plus or minus, is it usually within?
Correct Answer
B. 2
Explanation
A resonant antenna is designed to operate at a specific frequency, and it is most effective in radiating radio signals within a certain range around that frequency. This range is usually within a percentage of plus or minus the designed frequency. Therefore, the correct answer is 2, indicating that the resonant antenna is usually within a range of plus or minus 2% of its designed frequency for effective signal radiation.
48.
The design frequency of a resonant antenna is 10 megahertz (MHz). What will be its frequency range?
Correct Answer
D. 9.8–10.2 MHz.
Explanation
The correct answer is 9.8–10.2 MHz. This is because the frequency range of a resonant antenna is typically slightly higher and lower than its design frequency. In this case, the design frequency is 10 MHz, so the frequency range would be 9.8–10.2 MHz.
49.
The lowest frequency at which an antenna resonates is known as its
Correct Answer
B. Fundamental
Explanation
The lowest frequency at which an antenna resonates is known as its fundamental frequency. This frequency is the primary or base frequency at which the antenna can vibrate or oscillate most easily. It is the fundamental mode of vibration for the antenna and determines its resonant characteristics.
50.
The ability of an antenna to both receive and transmit equally well is known as the antenna’s
Correct Answer
C. Reciprocity
Explanation
Reciprocity refers to the ability of an antenna to receive and transmit signals equally well. It means that the antenna's characteristics remain the same regardless of whether it is used for receiving or transmitting signals. This property is essential for efficient communication systems as it allows for bidirectional communication without the need for separate antennas for transmitting and receiving.