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NAVEDTRA 14190A
RADAR PRINCIPLES CH 1, 2, 4
| Question | Answer |
|---|---|
| Which term is used to refer to electronic equipment that detect the presence, direction, height, and distance of objects by using reflected electromagnetic energy? | radar |
| What is used by radar sets to determine the direction and distance of the reflecting object? | echo |
| What is the line from the radar set directly to the object referred to as? | line of sight (los) |
| What is the angle called between horizontal plane and the los? | elevation angle |
| Approximately how many statute miles per second does electromagnetic energy travel through the air? | 186,000 mps |
| Approximately how many nautical miles are equal to 186,000 statute miles? | 162,000 nm |
| Approximately how many feet are there per nautical mile? | 6,080 ft |
| What is radar timing usually expressed in? | microseconds |
| Approximately how many feet per microsecond does radiated energy from a radar test set travel at? | 984 ft |
| The range in nautical miles to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by what number? | 12.36 |
| Which pulse property determines the maximum range that the pulse can travel to a target and still return a usable echo? | peak power |
| What is the smallest signal called that is detectable by a receiver system that an be processed and presented on an indicator? | usable echo |
| What is the frequency of the rf energy in the pulse radiated by a radar referred to as? | carrier frequency |
| What is used to calculate both peak power and average power of a radar system? | duty cycle |
| Which radar target property is the angle between true north and a line pointed directly at the target? | true bearing |
| Which radar systems are designed to determine only the range and bearing of an object? | 2D |
| Which type of search radar system detects altitude as well as range and bearing? | 3D |
| Which radar property is defined as its ability to distinguish between targets that are very close together in either range or bearing? | target resolution |
| Which two categories is resolution usually divided into? | range and bearing |
| What is the ability referred to as of a radar system to distinguish between two or more target on the same range but at different bearings? | azimuth resolution |
| What is a measure of the ability of a radar system to determine the correct range, bearing, and in some cases, height of an object? | radar accuracy |
| What is the bending of electromagnetic waves caused by a change in the density of the medium through which the waves are passing? | refraction |
| What ensures that all circuits connected with the radar system operate in a definite timed relationship? | synchronizer |
| What is essentially an electronic switch that permits a radar system to use a single antenna to both transmit and receive? | duplexer |
| What is the systematic movement of a radar beam in a definite pattern while searching for or tracking a target? | scanning |
| Which type of scanning is unsuitable for use as a tracking radar? | single-lobe |
| What are the two basic methods of beam scanning? | mechanical and electronic |
| Which type of scanning is used in fire control tracking radars? | monopulse |
| What can occur as the target maneuvers or moves and the radar pulses bounce off different areas of the target and causes random reflectivity and may lead to tracking errors? | scintillation |
| What is a requirement for any Doppler radar to function? | coherence |
| What is the heart of a missile guidance system? | radar system |
| Which type of radar is designed to continuously scan a volume of space to provide initial detection of all targets? | search radar |
| Which type of radar provides continuous range, bearing, and elevation data on one or more targets? | track radar |
| Which type of radar systems detect the presence of surface craft and low flying aircraft and to determine their presence? | surface search radars |
| Which type of radar systems detect and process only moving targets? | moving target indicators |
| The maximum range of air search radar can exceed how many miles? | 300 mi |
| Which type of radar computes accurate ranges, bearings, and altitudes of aircraft targets detected by air search radars? | height-finding radar |
| Which type of radar system provides the information used to guide a missile to a hostile target called? | guidance radar |
| What is often referred to as the "heart" of the radar system because it controls and provides timing for the operation of the entire system? | synchronizer |
| What is the function of the majority of circuits in radar? | timing and control |
| Which types of waves will be generated by the multivibrator if it is symmetrical? | square |
| What produces the short duration high-power rf pulses of energy that are radiated into space by the antenna? | transmitter |
| What controls the radar pulse width by means of a rectangular dc pulse of the required duration and amplitude? | modulator |
| Magnetron oscillators are capable of generating rf pulses with very high peak power at frequencies ranging from 600 to how many megahertz? | 30,000MHz |
| Pulse-forming networks are often insulated by immersing each circuit element in what? | oil |
| Typical DC power supplies for radar modulators use a half-wave rectifier, a full-wave rectifier, or which other type rectifier? | bridge rectifier |
| What does the keyed-oscillator transmitter most often use as the power oscillator? | magnetron |
| What are the two main types of magnetron mode instability? | mode skipping and mode shifting |
| Which condition occurs when the magnetron changes from one mode to another during pulse time? | mode shifting |
| Which condition occurs when the magnetron fires randomly in an undesired, interfering mode during some pulse times, but not in others? | mode skipping |
| What are used in radar systems with a wide band of transmitted frequencies because they are stable over a wider frequency range? | amplitrons |
| What allows the transmitter to radiate a large number of discrete frequencies over a relatively wide band? | frequency synthesizer |
| Which term refers to the discharge of electricity through a gas-filled electron tube? | glow discharge |
| Which type of duplexers are the most common in radar systems? | waveguide and hybrid-ring |
| What is used as a duplexer in high-power radar systems? | hybrid-ring |
| Which term refers to a condition of the receiver in which the voltage pulse at the receiver input is too large? | blocking |
| The superheterodyne receiver is almost always used in which type of radar systems? | microwave radar |
| Most radar receivers use a 30MHz or which intermediate frequency? | 60 MHz |
| Which very stable microwave oscillator can be tuned by changing the repeller voltage? | reflex klystron |
| Which circuit is used by most radar systems to control the output of the local oscillator? | automatic frequency control (AFC) |
| Which part of a microwave receiver serves to convert the IF pulses into video pulses? | detector |
| What is the simplest form of detector and the one most commonly used in microwave receivers? | diode detector |
| What is fundamentally an RC coupled amplifier that uses high-gain transistors or pentodes? | video amplifier |
| What is the appearance on a radar indicator of confusing, unwanted echoes which interfere with the clear display of desired echoes? | clutter |
| Which type of non-saturating amplifier does not ordinarily use any special gain-control circuits? | lin-log amplifier |
| Radar energy is distributed more or less symmetrically over a band of frequencies. What is this frequency distribution of energy known as? | frequency spectrum |
| What presents a graphic display of energy versus frequency? | spectrum analyzer |
| What does the distribution of power over the radar frequency spectrum depend on? | modulation |
| The electronic frequency counter, wavemeter, along with what else are the devices used to determine the basic carrier frequency of a radar transmitter? | echo box |
| What is defined as the weakest signal that produces a visible receiver output (on a scope)? | MDS (most discernable signal) |
| A typical receiver sensitivity reading on a modern radar should be in the vicinity of what? | -105dBm |
| What is defined as the frequency spread between the half-power points on the receiver response curve? | receiver bandwidth |
| When present on transmission lines and waveguides what indicates an impedance mismatch between a transmitter or receiver to its antenna. | standing waves |
| A high vswr (what or higher) indicates that the characteristic impedance of a transmitter line differs greatly from the terminating impedance? | 1.5 to 1 |
| Most AC power distribution systems in naval systems in naval vessels are how many-volt, 60 Hz, 3 phase, 3 wire, ungrounded systems? | 440v |
| Which type of equipment is used to provide power to vital loads? | automatic bus transfer (ABT) |
| What do microwave components require, such as waveguides, cavities, and power amplifiers, to prevent arcing and internal corrosion? | dry air |
| What is one of the best mediums for cooling high-power components, and in many cases the only medium that may be used? | distilled water |
Created by:
nng7294
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