Radar(2018) Flashcards
NAVEDTRA 14339
What does the acronym radar mean?
Radio Detection and Ranging.
What is the speed of electromagnetic energy when it travels through air?
Approximately the speed of light or 186,000 statute miles per second.
What is the minimum range for a radar system with a pulsewidth of 10.5 s, which has a recovery time of 0.5 s?
1,804 yards.
What is the range of target when the elapsed time for the radar pulse to travel to the target and return is 370.8 microseconds?
30 nautical miles.
What factors determine the minimum range of a pulse radar system?
Thepulsewidthofthetransmittedpulseandtherecoverytimeoftheduplexerand the receiver.
The maximum range of a pulse radar system depends upon what three factors?
Transmitted power, pulse repetition frequency (PRF), and receiver sensitivity.
Define range resolution of a radar system.
Range resolution of a radar system is the minimum resolvable separation in range of two targets at the same bearing.
What effect is achieved by increasing the length of a pulsewidth?
The longer the pulsewidth, the greater the range capabilities of the radar.
What term is used to describe the situation in which atmospheric temperature first in- creases with altitude and then begins to decrease?
Temperature inversion.
The bending of radar waves due to a change in density of the medium through which they are passing is known by what term?
Refraction.
A very high radar antenna indicates what type of frequency?
A low carrier frequency.
Radar frequency ranges are divided into sections referred to by what term?
Bands.
The ideal radar pulse shape should have what characteristics?
A square wave with very sharp leading and trailing edges.
What part of a radar pulse affects its range accuracy?
The leading edge.
What is the reciprocal of PRF?
PRT
What two RF generating devices have low interelectrode capacitance, low transit time, and the ability to handle very high levels of RF power?
Magnetron and klystron.
What is the duty cycle of a radar system that has an average power of 2 Megawatts and a peak power of 200 Megawatts?
0.01.
What radar transmission method does not depend on target motion or relative frequency of the returned signal?
Pulse modulation radar.
What is the purpose of radar synchronizer?
Provides proper timing pulses to components of the radar system.
What are the two synchronization classifications for a basic pulse radar system?
Self-synchronized or externally synchronized.
What are the two high-powered RF generators used in transmitters of pulse radar systems?
Magnetron and klystron.
Adding additional intermediate cavities between the input and output of a klystron has what affect on power output?
An increase in the power available at the output.
What is a duplexer and what is its purpose in a radar system?
An electronic switch that permits the use of one antenna for both transmit and receive functions.
What type of receiver mixes incoming signals with the receiver’s local oscillator signal to produce an intermediate frequency?
Superheterodyne.
What is the purpose of the AFC circuitry within the receiver?
To maintain a constant IF frequency out of signal mixer.
What function does the detector perform within the receiver?
Converts IF pulses into video pulses, which are applied to radar indicators.
What are the three types of radar indicators?
PPI, RHI, and A-scope.
The PPI provides what type of presentation?
A map-like presentation of the region scanned.
What are the nine major components that make up a typical pulse radar system?
Antenna, antenna servo system, duplexer, transmitter, receiver, modulator, power supplies, synchronizer, and indicator
What are the four positions on the SCAN SPD rotary switch on the C-10535/APS-130 Radar Set Control?
OFF, 25, 50, 100.
What are the four functional groups of the T-1396/APS-130 Transmitter?
Power supply group, modulator group, transmitter group, and BIT group.
What position is the DVRI located in?
ECMO 1.
The CV-2434 Analog-Digital Converter is a major component of what radar system?
The APS-130.
During update mode, what slew control has priority for all inputs?
ECMO 1.
The acronym radar is derived from what words?
Radio, detection, and ranging
Radar uses what form of energy to detect the presence of objects?
Electromagnetic energy
RF energy travels through air at approximately what speed?
186,000 statute miles per second
162,000 nautical miles per second
300 million meters per second
What is the time required for two-way travel of an RF pulse if the target is 15 miles from the radar unit?
185.4 μs
An increase in recovery time of a radar set will cause which of the following results?
Increase in minimum range and decrease in receiver sensitivity
A radar set has a pulsewidth of 3 μs. In order for the operator to see two separate blips that are directly on the same line of bearing, what minimum distance must separate the targets?
492 yards
Apulse radar’s range resolution is a function of the transmitted pulsewidth, while azimuth resolution is a function of what?
Antenna beamwidth
In order for two targets at the same range to appear as two targets instead of one target on the radar’s indicator, what minimum distance must separate the two targets?
One beamwidth
The maximum power of a RF transmitted pulse is referred to by what term?
Peak power
Radar performance is affected by which of the following factors?
- Prevailing atmospheric conditions
- The quality of maintenance performed on the equipment
- The operator’s knowledge of the equipment’s capability
Although high-frequency energy from a transmitter travels essentially in a straight line and a constant speed, refraction and speed change are known to occur. Which of the following atmospheric conditions cause this to happen?
Temperature, pressure, and vapor content
Which of the following conditions is formed by a temperature inversion and/or by a moisture lapse that may extend or reduce the range of radar?
Ducting
The elapsed time between the start of one transmitted pulse and the start of the next is known as which of the following terms?
PRT
In addition to certain power considerations, the output pulse of a radar transmitter should possess which of the following characteristic shapes in order to present nearby targets on an indicator?
Narrow with a sloping trailing edge
Generally, the maximum range of pulse type radar is determined by what element
Pulse repetition frequency
The PRF of a radar must be low enough to eliminate ambiguous targets, but high enough that the antenna’s speed of rotation does not interfere with what factor?
The transmitted frequency
A radar set with a PRF of 2,000 PPS and an antenna rotation of 20 rpm produces what maximum number of pulses per degree?
16.6
Which of the following statements is correct concerning peak power and average power of a pulsed radar system?
Peak power is expended during the transmission of a pulse, and average power is the power expended over the pulse repetition time
Which of the following formulas expresses the duty cycle of a radar set?
PW x PRF
Which of the following methods of transmitting RF energy uses the Doppler principle for radar detection?
Continuous-wave
Frequency-modulated radars transmit a wave that is continuously varying from a fixed reference frequency. When frequency modulation is used, how is the target detected?
Comparing the frequency of the signal that
is presently being transmitted with the
received frequency that has been reflected
from the target
Continuous-wave radar, which employs the Doppler effect, is best suited in detecting which of the following targets?
Targets with a high degree of bearing resolution
Which of the following components of a radar system determines the timing for all components of the radar?
Synchronizer
What is the purpose of the modulator in a typical pulse radar system?
To supply high voltage, rectangular pulses
to drive the transmitter
What modulator circuitry determines the voltage level and width of the pulse generated?
The pulse forming network
Which of the following tubes should be used as the power amplifier in a radar transmitter?
Klystron
The process whereby some electrons are accelerated, some are decelerated, and others are unaffected in the movement of the electron beam towards the collector end of a klystron is referred to by what term?
Bunching
What is the primary function of radar duplexing system?
To permit the use of one antenna for
transmission and reception
A defective duplexer will likely cause damage to which of the following radar components?
The receiver
Because of the difficulty in amplifying high-frequency signals received in most radar receivers, it is necessary to generate an intermediate-frequency signal by a process referred to by which of the following terms?
Heterodyning
The Azimuth Elevation Range Indicator IP-1060A/APQ-148 is located at what station?
ECMO 1
How many slew controls are there with the APS-130 radar system?
2
What are the four ranges on the PPI RNG rotary switch on the RCP?
15, 30, 75, 150
The Radar Set Control C-10535/APS-130 (RCP) is located at which of the following stations?
ECMO 1
The intermediate frequency is produced in what stage of a microwave receiver?
Signal mixer
What section of a radar receiver usually determines the overall bandwidth?
IF amplifier/detector
The IF amplifier stages of a radar receiver determines which of the following receiver characteristics?
- The gain
- Signal-to-noise ratio
- Converts IF pulses to video pulses
Which of the following radar displays provides a map-like presentation that is practically an exact replica of the region scanned by the radar antenna?
PPI
On a RHI display, what is represented by the vertical axis?
Elevation
On an A-scope presentation, what is displayed on the horizontal axis?
Range only
Which component provides a crystalcontrolled clock and digital timing loop to generate PRF trigger, sweep triggers, range markers, and precision range line signal?
RSG
