1.
What characteristic of frequency does a radar target moving towards the radar exhibit?
Correct Answer
B. A higher frequency than the original broadcast
Explanation
When a radar target is moving towards the radar, it exhibits a higher frequency than the original broadcast. This is known as the Doppler effect. As the target moves closer to the radar, the waves are compressed, causing an increase in frequency. This change in frequency is detected by the radar system and used to determine the speed and direction of the target.
2.
What radar subassembly allows the radar system to transmit and receive from the same
antenna?
Correct Answer
D. Duplexer
Explanation
A duplexer is a radar subassembly that allows the radar system to transmit and receive from the same antenna. It is responsible for separating the transmitted and received signals, allowing them to be processed independently. This is important because it allows the radar system to alternate between transmitting and receiving signals without the need for separate antennas. By using a duplexer, the radar system can save space, reduce costs, and improve overall efficiency.
3.
An antenna is said to be reciprocal if
Correct Answer
D. Its transmit and receive patterns are identical
Explanation
A reciprocal antenna is one that exhibits the same transmit and receive patterns. This means that the antenna behaves the same way when transmitting a signal as it does when receiving a signal. In other words, the antenna has the same radiation pattern and characteristics regardless of whether it is transmitting or receiving. This is an important property for many practical applications, as it allows for efficient and reliable communication. None of the other options (nonlinearity, transmission of patterns, or ferrite devices) are directly related to the reciprocity of an antenna.
4.
Which feedhorn is used only for receiving?
Correct Answer
C. Passive
Explanation
Passive feedhorns are used only for receiving signals. Unlike active feedhorns, which can both transmit and receive signals, passive feedhorns are designed solely for the purpose of receiving signals. They do not have any active components or electronics that enable them to transmit signals. Therefore, the correct answer is "Passive".
5.
The shape of the beam of radar energy and its antenna pattern depend on the radar’s
Correct Answer
C. Purpose
Explanation
The shape of the beam of radar energy and its antenna pattern depend on the radar's purpose. Different radar systems are designed for different purposes, such as air traffic control, weather monitoring, or military surveillance. Each purpose requires a specific beam shape and antenna pattern to achieve optimal performance. For example, a radar system used for air traffic control needs a narrow beam and a focused antenna pattern to accurately track aircraft in a specific area. Therefore, the purpose of the radar system determines the shape of the beam and antenna pattern.
6.
The scanning method used by the radar system refers to the
Correct Answer
C. Motion of the antenna axis (of the beam) as the radar looks for an aircraft
Explanation
The correct answer is "motion of the antenna axis (of the beam) as the radar looks for an aircraft". This means that the radar system scans the area by moving the antenna axis in order to search for an aircraft. This motion allows the radar to cover a wider area and detect any potential targets within its range. By continuously scanning the surroundings, the radar system can track the movement of aircraft and provide accurate information about their location and trajectory.
7.
What scan is identified at the electronic countermeasure receiver by its regular intervals
between illuminations?
Correct Answer
C. Circular
Explanation
Circular scan is identified at the electronic countermeasure receiver by its regular intervals between illuminations. This type of scan involves the radar beam rotating in a circular pattern, illuminating the target at regular intervals as it completes each rotation. This allows for a systematic coverage of the surrounding area and provides a consistent and predictable scanning pattern.
8.
Which scan radar is also used in the acquisition phase by some airborne intercept radars?
Correct Answer
A. Raster
Explanation
Some airborne intercept radars use the Raster scan radar in the acquisition phase. The Raster scan radar is a type of radar system that scans the target area in a systematic pattern by sweeping a narrow beam in a series of horizontal and vertical lines. This scanning technique allows the radar to gather information about the target's position, velocity, and other characteristics. In the acquisition phase, the radar is searching for and acquiring targets, and the Raster scan radar is used for this purpose.
9.
What causes delayed, but separate, pulses?
Correct Answer
B. Near-simultaneous reception of pulse-type information
Explanation
Near-simultaneous reception of pulse-type information causes delayed, but separate, pulses. This means that the pulses are received at slightly different times, resulting in a delay between them. However, they are still separate and distinct pulses, not overlapping or simultaneous. This could occur, for example, when multiple signals are transmitted from different sources and received by the same antenna, causing a slight delay in the reception of each pulse.
10.
Attempts to reduce multipath effects on radar tracking accuracy include the use of
Correct Answer
B. Frequency agility
Explanation
Frequency agility refers to the ability of a radar system to rapidly change its operating frequency. By doing so, the radar can avoid or mitigate the effects of multipath interference, which occurs when radar signals bounce off objects and create additional echoes. By changing the frequency, the radar can minimize the impact of these echoes and improve tracking accuracy. This technique is commonly used in radar systems to enhance their performance in challenging environments with multiple reflections.
11.
What type of radar system uses a B-scan indicator?
Correct Answer
C. Precision approach
Explanation
A radar system that uses a B-scan indicator is typically used for precision approach. Precision approach radar systems are specifically designed to provide accurate and detailed information about an aircraft's position and altitude during the final stages of landing. The B-scan indicator is a display feature that shows a cross-sectional view of the aircraft's altitude profile, allowing for precise monitoring and adjustment of the aircraft's descent path. This type of radar system is crucial for ensuring a safe and accurate landing, particularly in low visibility conditions or at airports with challenging terrain.
12.
What target information is provided by a plan-position indicator?
Correct Answer
C. Range and azimuth
Explanation
A plan-position indicator provides information about the range and azimuth of a target. Range refers to the distance between the radar and the target, while azimuth refers to the horizontal angle between the radar and the target. By providing both range and azimuth information, a plan-position indicator can give a complete picture of the target's location in relation to the radar. This information is crucial for tracking and identifying targets in radar systems.
13.
In a Raster scan indicator, how many vertical scan periods does it take to produce one
complete picture?
Correct Answer
B. 2
Explanation
In a raster scan indicator, it takes two vertical scan periods to produce one complete picture. This is because the raster scan works by scanning the image from top to bottom, line by line. The first scan period covers half of the picture, scanning every other line, while the second scan period completes the picture by scanning the remaining lines. Therefore, it requires two vertical scan periods to display the entire image on the screen.
14.
The vacuum in a cathode-ray tube (CRT)
Correct Answer
D. Prevents collisions between electrons in the beam and air molecules
Explanation
The vacuum in a cathode-ray tube (CRT) prevents collisions between electrons in the beam and air molecules. In a CRT, an electron beam is generated and accelerated towards a phosphor coating, which emits light when struck by the electrons. The vacuum inside the CRT ensures that there are no air molecules present to hinder the movement of the electrons, allowing them to travel freely and accurately hit the phosphor coating. If there were air molecules present, the electrons would collide with them, causing scattering and distortion of the electron beam, ultimately affecting the display quality.
15.
An X pulse is present in a selective identification feature code train when
Correct Answer
B. The aircraft is a pilotless drone or missile
Explanation
The presence of an X pulse in a selective identification feature code train indicates that the aircraft is a pilotless drone or missile. This is because the X pulse is specifically associated with pilotless drones or missiles, and it serves as a way to identify their position or presence. The other options mentioned, such as receiving a Mode 4 reply, declaring a military emergency, or being requested by the radar operator, do not directly correspond to the presence of an X pulse.
16.
Which selective identification feature special response explains a 7500 reply?
Correct Answer
D. Hijacking
Explanation
The special response that explains a 7500 reply is hijacking. When an aircraft transmits the code "7500" to air traffic control, it indicates that the aircraft has been hijacked or is under the threat of hijacking. This code is part of the selective identification feature used in aviation communication systems to quickly and discreetly alert authorities of a hijacking situation.
17.
What is the AN/UPM–155 radar test set capable of testing?
Correct Answer
A. Interrogators and associated components
Explanation
The AN/UPM-155 radar test set is capable of testing interrogators and associated components. This means that it can assess the performance and functionality of the equipment used for interrogating other radar systems. It can verify the proper functioning of the interrogators and ensure that they are able to effectively communicate with other radar systems. Additionally, the test set can also evaluate the associated components that are used in conjunction with the interrogators, such as antennas, signal processors, and data links.
18.
What factor determines the spacing of the sidebands in an amplitude modulated signal?
Correct Answer
B. Frequency of the modulating signal
Explanation
The spacing of the sidebands in an amplitude modulated signal is determined by the frequency of the modulating signal.
19.
In frequency modulation, the amount of oscillator frequency change is
Correct Answer
B. Directly proportional to the amplitude of the modulating signal
Explanation
In frequency modulation, the amount of oscillator frequency change is directly proportional to the amplitude of the modulating signal. This means that as the amplitude of the modulating signal increases, the frequency deviation of the carrier signal also increases. This relationship is due to the fact that the frequency of the carrier signal is varied in proportion to the instantaneous amplitude of the modulating signal. Therefore, a higher amplitude modulating signal will result in a greater change in the frequency of the carrier signal.
20.
In phase modulation, the carrier’s
Correct Answer
A. pHase shifts at the rate of the modulating signal
Explanation
In phase modulation, the phase of the carrier signal changes in accordance with the changes in the modulating signal. This means that the phase of the carrier signal shifts at the same rate as the modulating signal. The amplitude of the carrier signal, on the other hand, remains constant. Therefore, the correct answer is "phase shifts at the rate of the modulating signal."
21.
What size bit combinations are allowed when using 16–phase shift keying?
Correct Answer
C. 4 bit
Explanation
16-phase shift keying allows for 4-bit combinations. This means that each symbol in the transmitted signal can represent 4 bits of information. With 4-bit combinations, a total of 16 different symbols can be used to convey data.
22.
How is the parity bit used in asynchronous transmission?
Correct Answer
A. By the receiving device to verify that the transmission was received correctly
Explanation
The parity bit is used by the receiving device to verify that the transmission was received correctly. Parity bit is an extra bit added to a binary code to make the total number of 1s either odd or even. The transmitting device adds the parity bit to the data, and the receiving device checks if the number of 1s in the received data matches the expected parity. If they don't match, it indicates that there was an error in the transmission. Therefore, the receiving device uses the parity bit to verify the correctness of the received transmission.
23.
How does synchronous transmission reduce the overhead costs of data transmission?
Correct Answer
B. Blocks many characters together for transmission
Explanation
Synchronous transmission reduces the overhead costs of data transmission by blocking many characters together for transmission. This means that multiple characters are sent as a single unit, reducing the number of control bits and increasing the amount of message data that can be sent. By transmitting multiple characters together, the transmission process becomes more efficient and reduces the overall overhead costs.
24.
When using forward error control as a method of error correction, where does error
correction take place?
Correct Answer
A. Receiving end
Explanation
Error correction takes place at the receiving end when using forward error control as a method of error correction. This means that the errors are detected and corrected after the data has been transmitted and received. The receiving end is responsible for identifying any errors in the received data and applying the necessary corrections to ensure accurate and reliable data transmission.
25.
Which statement describes an advantage of using fiber optic cable?
Correct Answer
C. Electromagnetic fields do not affect fiber optic cables
Explanation
Fiber optic cables are not affected by electromagnetic fields. This is because they use light signals to transmit data, rather than electrical signals. Unlike copper cables, which can experience interference from electromagnetic fields, fiber optic cables are immune to this type of interference. This advantage makes fiber optic cables more reliable and less prone to signal degradation, making them ideal for use in environments with high levels of electromagnetic interference, such as near power lines or in industrial settings.
26.
Which statement describes a security feature of using fiber optic cable?
Correct Answer
C. Virtually impossible to tap a fiber optic cable unnoticed
Explanation
Fiber optic cables are virtually impossible to tap unnoticed because they do not emit any electromagnetic signals that can be intercepted. Unlike metallic cables, which can be tapped by attaching a device to the cable and intercepting the electrical signals, fiber optic cables use light pulses to transmit data, making it extremely difficult for someone to tap into the cable without being detected.
27.
Most fiber optic links use infrared light and consist of what frequency range?
Correct Answer
B. 750 to 1500 nm
Explanation
Most fiber optic links use infrared light because it has a longer wavelength and can transmit data over long distances without significant loss. The frequency range of 750 to 1500 nm falls within the infrared spectrum, making it the correct range for fiber optic links. The other options, 400 to 750 nm and 400 to 750 mm, are not within the infrared spectrum and are therefore incorrect.
28.
When considering light wave propagation, what is the name of the angle between the
normal in the first material and the ray that is bounced back in the first material?
Correct Answer
C. Angle of reflection
Explanation
The angle between the normal in the first material and the ray that is bounced back in the first material is called the angle of reflection.
29.
What is the principle on which fiber optics work?
Correct Answer
A. Total internal reflection
Explanation
Fiber optics work on the principle of total internal reflection. This occurs when light traveling through a medium with a higher refractive index encounters the boundary with a medium of lower refractive index at an angle greater than the critical angle. Instead of being refracted, the light is reflected back into the medium. In fiber optics, this phenomenon allows the transmission of light signals through the fiber by bouncing the light off the walls of the fiber core, ensuring minimal loss of signal strength.
30.
What occurs because of imperfections in an optical fiber’s basic structure?
Correct Answer
B. Scattering
Explanation
Imperfections in an optical fiber's basic structure cause scattering. Scattering refers to the phenomenon where light waves are deflected and dispersed in different directions due to variations in the refractive index of the fiber. These imperfections can be in the form of impurities, irregularities in the fiber's core or cladding, or structural defects. Scattering leads to the loss of signal strength and can result in reduced transmission quality and distance in optical communication systems.
31.
What is reduced through the use of index matching fluids on fiber optic connectors?
Correct Answer
C. Fresnal reflection
Explanation
The use of index matching fluids on fiber optic connectors helps to reduce Fresnel reflection. Fresnel reflection occurs when there is a mismatch of refractive index between the fiber and the connector, leading to the loss of light signal. Index matching fluids minimize this reflection by matching the refractive indices of the fiber and the connector, allowing for efficient transmission of light signals through the fiber optic system.
32.
What is the most useful way to classify fiber optic cable?
Correct Answer
D. Refractive index profile and number of modes
Explanation
The most useful way to classify fiber optic cable is based on the refractive index profile and the number of modes. The refractive index profile refers to the way the refractive index changes across the core of the fiber, which affects the way light propagates through the cable. The number of modes refers to the number of different paths that light can take within the fiber. These two characteristics are important in determining the performance and capabilities of the fiber optic cable.
33.
Which feature of the Fluke 8025A multimeter do you use to select various measurement
functions?
Correct Answer
B. Rotary switch
Explanation
The rotary switch is the feature of the Fluke 8025A multimeter that allows you to select various measurement functions. By turning the rotary switch, you can choose the specific measurement function you want to use, such as voltage, current, resistance, or continuity. This feature provides convenience and ease of use, allowing you to quickly switch between different measurement options without the need for additional buttons or settings.
34.
Which current range on the Fluke 8025A do you select to measure 250 milliamps
alternating current (AC)?
Correct Answer
D. Milliamps/amp AC
Explanation
To measure 250 milliamps alternating current (AC) on the Fluke 8025A, you would select the "Milliamps/amp AC" current range. This range is specifically designed to measure alternating current in milliamps.
35.
What is caused by low-insulation resistance between conductors?
Correct Answer
A. High-attenuation, crosstalk, and noise
Explanation
Low-insulation resistance between conductors can cause high-attenuation, crosstalk, and noise. When the insulation resistance is low, it means that there is a leakage of current between the conductors. This leakage can result in a decrease in signal strength, leading to high-attenuation. Additionally, the leakage current can interfere with adjacent conductors, causing crosstalk, which is the unwanted transfer of signals between them. Furthermore, the leakage current can introduce unwanted electrical noise into the system, leading to noise interference. Therefore, low-insulation resistance can cause these issues.
36.
When will insulation resistance increases?
Correct Answer
C. Thickness of the insulating material increases
Explanation
Insulation resistance increases when the thickness of the insulating material increases. This is because a thicker insulating material provides a greater barrier to the flow of electric current, reducing the chances of leakage or short circuits. It effectively prevents the current from passing through the insulation and ensures that the conductive material is well insulated. As a result, the insulation resistance increases, improving the overall safety and performance of the electrical system.
37.
When using the AN/PSM–2 megger, how do you apply the correct regulated output
voltage?
Correct Answer
D. Turn the hand-crank at a rate to keep the indicator lights at a steady glow
38.
What type of megohmmeter do you use on paper insulated conductor cable?
Correct Answer
A. 500 volt
Explanation
The correct answer is 500 volt. This is because paper insulated conductor cables typically have lower insulation resistance compared to other types of cables. Therefore, a lower voltage megohmmeter, such as a 500 volt one, is sufficient to measure the insulation resistance accurately without causing any damage to the cable.
39.
How many probes are normally used for an earth ground tester?
Correct Answer
B. 3
Explanation
An earth ground tester typically uses 3 probes. These probes are used to measure the resistance between the grounding system and the earth, ensuring that the electrical system is properly grounded. By using 3 probes, the tester can obtain more accurate measurements and detect any potential issues with the grounding system.
40.
What is the earth ground standard for communications facilities?
Correct Answer
A. 10 ohms or less
Explanation
The earth ground standard for communications facilities is 10 ohms or less. This means that the resistance between the earth ground and the communications facility should be 10 ohms or lower. This is important for ensuring proper grounding and protection against electrical faults or surges. A lower resistance value indicates a better and more effective grounding system, which helps to prevent damage to equipment and ensure safety.
41.
Which probe does not need to actually make contact with the circuit under test?
Correct Answer
A. Current probe
Explanation
A current probe is a type of probe that does not need to make physical contact with the circuit under test. It uses a magnetic field to measure the current flowing through a conductor without interrupting the circuit. This is achieved by placing the current-carrying conductor inside the probe's magnetic field. The probe then detects the magnetic field and converts it into a measurable current. This non-contact method makes it convenient and safe to measure high currents or currents in circuits where direct contact is not possible or desirable.
42.
Sampled data points are stored in the memory of a digital storage oscilloscope as
Correct Answer
B. Waveform points
Explanation
The answer "waveform points" is correct because in a digital storage oscilloscope, sampled data points are stored in memory as waveform points. These waveform points represent the amplitude values of the waveform at specific time intervals. By storing the waveform points, the oscilloscope can accurately recreate and display the waveform on the screen for analysis. Sequential records, record lengths, and record points are not the correct terms to describe the storage of sampled data points in a digital storage oscilloscope.
43.
What is the frequency range of an audio signal generator?
Correct Answer
B. 20 Hz to 20 kHz
Explanation
The frequency range of an audio signal generator is typically 20 Hz to 20 kHz. This range covers the audible frequencies for human hearing, allowing the generator to produce a wide range of tones and sounds within the normal hearing range. Frequencies below 20 Hz and above 20 kHz are generally considered to be outside of the audible range for most people.
44.
Which one of these is not an application of a radio frequency generator?
Correct Answer
D. Aligning galvanometers
Explanation
Aligning galvanometers is not an application of a radio frequency generator. A radio frequency generator is used for various purposes related to radio frequencies, such as verifying transmitter frequencies, troubleshooting receivers, and checking antenna systems. However, aligning galvanometers is not directly related to radio frequencies but rather involves calibrating and adjusting the sensitivity of galvanometers, which are instruments used to measure small electrical currents.
45.
How is a radio frequency generator used?
Correct Answer
B. Align telemetry receivers
Explanation
A radio frequency generator is used to align telemetry receivers. This means that it is used to adjust the settings and parameters of the receivers in order to optimize their performance and ensure accurate reception of telemetry signals. By aligning the receivers, any potential issues or inaccuracies in the reception can be identified and corrected, resulting in improved overall functionality and reliability of the telemetry system.
46.
What does a power reading that uses the abbreviation dBm indicate?
Correct Answer
A. Ratio of decibels relative to a 1-milliwatt standard
Explanation
A power reading that uses the abbreviation dBm indicates the ratio of decibels relative to a 1-milliwatt standard. This means that the power level being measured is compared to the power level of 1 milliwatt. The dBm unit is commonly used in telecommunications and signal strength measurements to express power levels in a logarithmic scale. It provides a convenient way to compare power levels and signal strengths.
47.
If someone says, “we doubled our transmitter power;” how much is the gain in dB?
Correct Answer
A. 3 dB
Explanation
When someone says "we doubled our transmitter power," it means that the power has been increased by a factor of 2. In terms of decibels (dB), a doubling of power corresponds to an increase of 3 dB. This is because the dB scale is logarithmic, and a 3 dB increase represents a doubling of power. Therefore, the gain in dB when the transmitter power is doubled is 3 dB.
48.
The measurable frequency and power ranges of the HP 436A power meter system are
determined by the
Correct Answer
B. Selected sensor
Explanation
The measurable frequency and power ranges of the HP 436A power meter system are determined by the selected sensor. Different sensors have different capabilities and specifications, such as frequency range and power handling capacity. Therefore, by selecting a specific sensor for the power meter system, the user can determine the frequency and power ranges that can be measured accurately.
49.
Which measurement is not made with a spectrum analyzer?
Correct Answer
B. Peak-peak voltage
Explanation
A spectrum analyzer is a device used to measure and display the frequency spectrum of a signal. It is commonly used to analyze the amplitude and frequency characteristics of signals. However, it is not designed to directly measure peak-peak voltage, which is the difference between the maximum positive and negative amplitudes of a waveform. Peak-peak voltage is typically measured using an oscilloscope, which is specifically designed for this purpose. Therefore, peak-peak voltage is not made with a spectrum analyzer.
50.
Which electronic counter measurement represents the average bit-to-bit time of an input
signal?
Correct Answer
A. Period
Explanation
Period represents the average bit-to-bit time of an input signal. It is the time taken for one complete cycle of a repeating waveform. In the context of electronic counter measurement, the period refers to the time it takes for a signal to complete one full cycle. Therefore, it represents the average bit-to-bit time of the input signal.