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100 Cards in this Set
- Front
- Back
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Introduction to Basic Radar Systems
What is the reason any reflected pulses from close targets that return before the receiver is connected to the antenna would be undetected? |
Because a reflected pulse would not be received during the transmit pulse and subsequent receiver recovery time
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Introduction to Basic Radar Systems
What does the maximum range of the pulse radar system depend on? |
Carrier frequency, pick power of the transmitted pulse, pulse repetition frequency (PRF), receiver sensitivity and pulse repetition rate (PRR)
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Introduction to Basic Radar Systems
What determines the maximum range the pulse can travel to a target and still return as usable echo? |
the pick power of the pulse
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Introduction to Basic Radar Systems
What determines the frequency that the indicator is reset to the zero range? |
The PRR
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Introduction to Basic Radar Systems
What happens if the transmitted pulse is shorter than the time required for the echo to return? |
The target will be indicated at a false range in a different sweep
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Introduction to Basic Radar Systems
What can determine whether an echo is a true target or a false target? |
By simply changing the PRR
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Introduction to Basic Radar Systems
What is the ideal pulse shape? |
A square wave that has vertical leading and trailing edges
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Introduction to Basic Radar Systems
Although the pulse method is the most common method for transmitting radar energy, what are two other methods sometimes used for special applications? |
The continuous wave method and frequency modulation method
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Introduction to Basic Radar Systems
What does the continuous wave (CW) method use to detect the presence and speed of an object moving toward or away from the radar? |
The Doppler effect
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Introduction to Basic Radar Systems
Where is the frequencies modulation (FM) method used? |
In aircraft altimeters that gives a continuous reading of how high the aircraft is above the earth
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Introduction to Basic Radar Systems
What does the degree of range resolution depend on? |
The width of the transmitted pulse, the types and sizes of the targets and the efficiency of the receiver and the indicator
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Introduction to Basic Radar Systems
What part of the radar system generates all the necessary timing pulses (triggers) for use in the radar and its associated systems? |
The Modulator
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Introduction to Basic Radar Systems
Because the radar frequencies are very high and difficult to amplify, what is used to convert the echos to a lower frequency, called the intermediate frequency (IF), which is easier to amplify? |
A super-hetero dyne receiver
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Basic Radar Systems
What does the pulse radar system include? |
The basic pulse radar and the pulse Doppler radar
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Basic Radar Systems
How is the return echo signal mixed? |
With a local oscillator (LO)signal to produce an intermediate frequency (IF) signal at a lower frequency than the transmitter
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Basic Radar Systems
What causes a blind spot in the range? |
The higher PRF decreases the pulse repetition time (PRT) between pulses resulting in the possibility of the target echo returning at the time of the next transmission
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Basic Radar Systems
When does range ambiguity occur? |
If the echo from the first pulse returns after the second pulse is transmitted.
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Basic Radar Systems
How can the range blind spot and ambiguities be compensated? |
By changing the PRF over a wide range
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Basic Radar Systems
What a Doppler shift allow? |
Distinguishing between the target and the transmitter leakage
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Basic Radar Systems
What is the amount of Doppler shift also depended on? |
The wave length resulting from the transmitter frequency
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Basic Radar Systems
What method is used as a means of storing or controlling the transmitted phase required to provide coherent detection? |
A magnetron for the transmitter
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Basic Radar Systems
What happens when a basic continuous wave (CW) radar employs a continuous transmission that results into a continuous echo signal from a target? |
Determination of the target range is impossible
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Basic Radar Systems
What improves the isolation between the transmitted signal and the received echo signal in the CW radar? |
A separate antenna, and when a signal antenna uses it with a Ferrite circulator, it acts as a duplexer.
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Basic Radar Systems
Why are the circulators limited to a low power CW radars? |
The amount of leakage from the transmitter to the receiver is about 20-30 decibels (dB) down from the transmitter power level
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Basic Radar Systems
What are the two most common techniques used in fire control radars? |
Mono-pulse (simultaneous lobing) scanning and phase scanning
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Basic Radar Systems
Which scanning does not move the transmitted beam? |
Mono-pulse scanning, instead the echo signal is scanned or compared
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Basic Radar Systems
What does mono-pulse scanning produce? |
A narrow circular beam of post RF energy at a high PRR
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Basic Radar Systems
What is scintillation? |
The rapid fluctuation of the echo signal amplitude as the target maneuvers or moves resulting in radar beam bouncing of different areas of the target and causing random reflectivity which may lead to tracking errors
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Basic Radar Systems
What does phasing scanning control? |
The phase of the RF signal fed to multiple feed horns, dipoles or radiators
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Basic Radar Systems
What are the two categories of the high power tubes? |
Crossed-field and linear beam
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Basic Radar Systems
What type of non-resonant crossed-field tube has found a wide use in radar application? |
The crossed-field amplifier (CFA), which is non-resonant backward wave and re-entrant
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Basic Radar Systems
When is the sensitivity time-control (STC) used? |
To control the gain of a radar receiver as a function of range
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Basic Radar Systems
What is the purpose of the AGC circuit? |
It detects the output of the IF amplifier and produces a voltage proportional to the strength of the detected signal and noise
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Basic Radar System
What substance is used for cooling klystron amplifiers? |
Distilled water for very high power amplifiers, and low and medium power klystrons use a mixture of ethylene glycol and water
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Basic Radar System
What is synchronous tuning? |
When a klystron amplifier tube delivers high gain and narrow bandwidth if all the cavities are tuned to the same frequency
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Basic Radar System
What is asynchronous tuning? |
If the cavities are tuned to slightly different frequencies, the gain of the klystron amplifier will be reduced and the bandwidth may be appreciably increased
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Basic Radar System
What is an important item that is required for a high power klystron amplifier operation? |
An axial magnetic field (a magnetic field paralleled to the axis of the klystron)
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Basic Radar System
What field is used to overcome beam spreading in klystron amplifiers? |
An axial magnetic field, which exerts a force on the electrons that keeps them focused into a narrow beam
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Basic Radar System
What is the primary use for TWTs? |
Voltage amplification
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Basic Radar System
What is a TWT also used as? |
A micro-wave mixer and has the added advantage of providing gain as well as simply acting as a mixer.
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Basic Radar System
What path follows the echo signal after it enters through the antenna? |
The duplexer and it is amplified by the low-noise amplifier (LNA)
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Basic Radar System
What is the function of the mixer stage in many receivers? |
To translate the RF to a lower intermediate frequency, usually 30 or 60 MHz by hetero-dyning the returning RF signal echo with a local oscillator signal and a non-linear device (mixer) and extracting the signal component at a difference frequency
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Basic Radar System
what is the difference frequency system? |
The automatic frequency control (AFC) system normally used to keep the receiver in tune with the transmitter
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Basic Radar System
What is a highly important factor in a receiver operation? |
The tracking stability of the local oscillator which generates the frequency that beats the coming signal to produce the IF.
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Basic Radar System
What is another requirement of a local oscillator? |
It must be tunable over a range of several MHz to compensate for the changes in both the transmitter frequencies and its own frequencies
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Basic Radar System
What system is becoming more common in radar systems today? |
A frequency synthesizer system
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Basic Radar System
What detects any deviation from the correct IF signal? |
The AFC frequency discriminator, which, in turn, generates a error voltage.
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Basic Radar System
How are most low power klystron amplifiers cooled? |
By air
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Basic Radar System
What is main source of power and heat in the klystron amplifier package? |
Beam power supply
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Basic Radar System
What happens if the electro-magnet cooling fails? |
The focus coil power supply must be shut off very quickly
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Basic Radar System
What does modulator mean? |
To shape as well as to control
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Basic Radar System
What is the simplest type of radar mixer? |
Single-ended or unbalanced crystal mixer.
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Basic Radar System
What can reflex klystron also be used as? |
Drivers for RF power amplifier and when used, the frequency and the amplitude stability are much more critical.
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Basic Radar System
What does phase-coding the transmitted pulse involve? |
Shifting the phase of the transmitter RF during the pulse width.
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Liquid Cooling Systems
In types 2 and 3 liquid cooling systems, where is chilled water taken from? |
The supply main of the air-conditioning chilled water system
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Liquid Cooling Systems
What total number of liquid cooling system does the US Navy use? |
3
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Liquid Cooling Systems
What is the type One liquid cooling system? |
A sea water/distilled water (SW/DW) heat-exchanger with a SW/DW heat-exchanger stand-by
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Liquid Cooling Systems
What is the type One liquid cooling system used for? |
Electronic system installations that can be operated satisfactorily with sea water temperature as high as 95 degrees F, which should result in a distilled water supply temperature to the electronics of approximately 104 degrees F.
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Liquid Cooling Systems
What is size load is the heat-exchanger designed to handle? |
The full cooling load of electronic equipment, plus a 20% margin.
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Liquid Cooling Systems
What is installed at the output of the demineralizer to prevent the carry-over of chemicals in to the systems and to remove existing solids? |
A sub-micron filter (less than one millionth of a meter)
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Liquid Cooling Systems
Where is the type Two liquid cooling system used? |
In installations that cannot accept a DW temperature higher than 90 degrees F.
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Liquid Cooling Systems
What is the major difference between the secondary liquid cooling system of the type Two liquid cooling system to that of the type One secondary liquid cooling system? |
The operation of the SW/DW heat-exchanger.
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Liquid Cooling Systems
Where is the type Three liquid cooling system used? |
In installations where temperature range is critical.
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Liquid Cooling Systems
What is the secondary cooling that floats through the heat-exchanger? |
Distilled water
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Liquid Cooling Systems
Why is a single pass counter flow heat-exchanger more efficient than the double pass heat-exchanger? |
Because there is a more uniform gradient of temperature difference between the two fluids
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Liquid Cooling Systems
What prevents contamination of the distilled water and permits the monitoring of water loss due to tube leakage? |
A void space between the double-tube sheets.
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Liquid Cooling Systems
What should you on the look-out to detect that indicates a failure of a tube joint? |
Leakage at the telltale tube drains.
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Liquid Cooling Systems
How does a leak in one of the tubes show up? |
A loss of water in the secondary site of the liquid cooling system, because it operates at a higher pressure than the primary.
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Liquid Cooling Systems
What type of heat-exchangers are the ones in the distilled water cooling systems that cool electronic equipment? |
Either liquid to air or cooling jacket
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Liquid Cooling Systems
What must you do first when filling the pressurized expansion tank? |
Isolate the tank from the cooling system and the air supply before you vent the air pressure off through the vent pipe at the top of the tank.
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Liquid Cooling Systems
What type of cooling system the Orifice plate is primary found? |
Sea water
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Liquid Cooling Systems
In what position is the Orifice plate normally installed from the heat-exchanger? |
Upstream
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Liquid Cooling Systems
What is the use of an Orifice plate limited to? |
Whether the input water pressure is essentially constant, such as ship's fire main
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Liquid Cooling Systems
When used with chilled water system where is the constant flow regulator (variable Orifice) installed? |
Downstream from the heat-exchanger.
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Liquid Cooling Systems
What are the main operating parts of the cooling system low flow switch? |
A hermetically sealed reed switch and a permanent magnet attached to an internal shuttle.
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Liquid Cooling Systems
What is the rota-meter? |
A variable area orifice meter that maintains a constant differential pressure with varying flow
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Liquid Cooling Systems
What are the circulating pumps used in liquid cooling systems? |
Single-stage centrifugal pumps, closely coupled to a constant-speed electrical motor
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Liquid Cooling Systems
What are the two major elements of the centrifugal pump? |
The impeller rotating on the extension of the electric motor shaft and the casing (the impeller chamber).
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Liquid Cooling Systems
On all pumps as output pressure increase, what does the output flow do? |
Decrease
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Liquid Cooling Systems
The sub-micron filter is used to remove particles that have size greater than what? |
.5 micron
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Liquid Cooling Systems
What are the three types of cartridges used in the demineralizers? |
Organic removal, oxygen removal and mixed bed
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Liquid Cooling Systems
What cartridge emits a urine odor when is near exhaustion? |
The oxygen removal cartridge
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What is a computer program that provides test capabilities suited to subsystem testing?
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The programmed Operational and Functional Appraisal (POFA).
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What are memory call-up tests?
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Tests used to monitor up to 12 randomly selected or consecutive computer memory locations and to display them on the A/N displays.
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What type of information is available for viewing by the operator as long as it is on the screen of the display?
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Soft-copy
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What is the length of time or duration that the display remains on the screen after the phosphor is hit with electrons known as?
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Persistence.
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What happens when a small AC voltage is applied to the filament to heat the cathode?
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The electrons are to be freed from the cathode.
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What happens when the control grid is negative with respect to the cathode?
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The electron beam is turned off, or blanked.
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A change in what voltage will result in a change in the diameter of the electron beam?
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Focus grid.
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What are the two most common types of deflection systems used in CRTs?
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Electromagnetic deflection and Electrostatic deflection.
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What does electromagnetic deflection used to move the beam across the CRT?
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A magnetic field generated by four coils.
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What CRTs is electromagnetic deflection most commonly found?
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Those that use a raster-scan type display.
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How many coils does the yolk assembly of a CRT contain?
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Four.
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Current flow through the coil produces a magnetic field at what angle to the coil?
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Right (90 degrees).
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In the electrostatic deflection CRT, how many plates are located inside the CRT?
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Four.
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What is the description of electrostatic deflection CRT?
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An electrical charge is applied to plates to direct the beam to the proper area of the CRT.
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What is the creation of a display known as?
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A scan.
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What signal is used in the generation of symbology?
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The Z (unblank) signal.
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What are the major differences between color and monochrome CRTs?
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The phosphor coating of the CRT, the electron gun(s), and the high voltage requirements.
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Basic Display Devices and Systems
What is the timing period called that the symbol is painted in? |
P-time
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