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47 Cards in this Set
- Front
- Back
An RF mixer has what purpose in a radar system?
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It converts a low level signal to a different frequency.
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What frequency is the discriminator tuned to?
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The 30 MHz or 60 MHz IF.
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The usual intermediate frequency of a shipboard radar unit is:
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30 or 60 MHz
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The error voltage from the discriminator is applied to:
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The repeller of the klystron.
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What radar circuit determines the pulse repetition rate?
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The timer (synchronizer circuit).
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The output of an afc discriminator is:
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AC is "on frequency" DC if "off frequency".
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Power losses in cavity resonators are very low because:
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Conducting furfaces are large
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In a circular resonant cavity with flat ends, the E-field and H-field form with specific relationships. The:
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E-Lines are perpendicular to the end walls.
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Practical radar operation requires the use of microwave frequencies so that:
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Stronger target echoes will be produced.
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Airport wind shear radars depend upon:
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The doppler effect to track rapid shifts in wind patterns.
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The minimum range ofa radar is determined by?
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The transmitted pulse width.
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The major advantage of digitally processing a radar signal is:
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Enhancement of weak target returns.
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Which of the following is the most practical means of increasing the range ofa ship radar installation?
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Increase tranmitter power, increase pulse width, and increase the time between transmitted pulses.
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A shipboard radar uses a PFN driving a magnetron cathode through a step up transformer. This results in which type of modulation?
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Pulse modulation.
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What devices could be used as the local oscillator in a radar receiver?
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A klystron and a Gunn Diode.
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The klystron local oscillator is constantly kept on frequency by:
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The Automatic Frequency control circuit.
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Voltages used in CRT anode-circuits are in what range of value?
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10-50 kV.
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What type of video output tube is used in most marine radar units?
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A plan position indicator (PPI).
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In video amplifiers, compensation for the input and output stage capacitances must be accomplished to prevent distorting the video pulses. This compensation is normally accomplished by:
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Connecting an inductor in series with the input capacitance and an inductor in parallel with the output capacitance.
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The video detector in a pulse modulated radar system would most likely use a :
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Diode detector.
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When the receiver employs an MTI circuit:
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Only moving targets will be displayed
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To minimize video display saturation caused by RF energy from external sourses, such as jamming, a receiver might employ:
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FTC circuits.
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Pulse radars require precise timing for their operation. Which type circuit below might best be used to provide these accurate timing pulses?
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A single swing blocking oscillator.
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Standard vacuum tubes are not used at radar frequencies because:
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The inductance of the leads is excessive.
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To obtain an indication of target movement using the doppler principle, a CW radar receiver would most likely employ a :
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Discriminator, tuned to the IF.
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Solid state microwave amplifier devices operating at C-Band and above are typically made from:
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Gallium Arsenide
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The display of a 2-D airport surveillance radar typically provides:
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Range, azimuth, and SSR responses.
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On a basic syncro system, the angular information is carried on:
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The stator lines.
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In standard CMOS logic IC databooks, the parameter tTLH is considered to be:
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Measured from the 10% to 90% points of the leading edge.
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In a radar receiver, the RF power amplifier:
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Does not exist.
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What is the average range of a ships surface search radar unit?
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40 miles.
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A wavelength is equal to how many degrees of a sinewave?
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360
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While examining hte shipboard radar sets, you notice on a particular indicator that hte video representing the pier is distorted closest to the center of the PPI. This is a primary indication of what?
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The waveguide compensation delay line needs adjusting.
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The VSWR of a micro wave transmission lince device might be measured using?
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A dual directional coupler, a power meter, and Network Analyzer.
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In a radar using digital video processing, a bright, wide ring appears at a fixed distance from the center of hte sidplay on all digital ranges. The transmitter is operating normall. What receiver circuit would you suspect is causing hte problem?
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Video starage RAM or shift register.
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An increase in magnetron current which coincides with a decrease in power output is an indication of what?
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The external magnet weakening.
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Low or no mixer current could be caused by?
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All of these
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A defective crystalin the AFC section will cause:
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Bright flashing pie sections on the PPI.
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US Regulations limit exposure to microwave energy to a power density of 5 mW?centimeters squared. What is the average enery density tranmitted by a radar across a one square foot surface area with the following pulse parameters: 1000 pulses per second, 55 kilowatts peak power, and a 3 microsecond pulse width?
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178 miliwatts/centimeters squared.
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A continuous Wave radar is frequency modulated with a 50 Hz sinewave. At the output of the receiver phase detector, a phase delay of 18 degrees is measured. This indicates a target range of:
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150 kilmeters
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On an "A" scope presentation, range markers are displayed at 200 microsecond intervals. A target pulse appears exactly half way between the third and fourth range marks. The target slant range is:
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105 kilometers.
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A radar tranmitter is operating on 2.5 GHz and hte reflex klystron local oscillator, operating at 2.56 GHz, developps a 60 MHz IF. If ht5e magnetron drifts higher in frequency, the AFC system must cause the klystron repeller plate to become:
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More negatice.
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A certain length of transmission line has a characteristic impedance of 72 ohms. If the line is cut at its center, each half of the transmission line will have a Zo of:
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72 ohms.
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Given a square wave with a frequency of 1000 heartz to be converted to trigger pulses by an RC network, which combination of R and C will provide the sharpest pulses?
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R=51 kilohms, C= 0.001 microfarad.
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What is the most common type of radar antenna used aboard commercial maritime vessels?
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Slotted array.
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Long horizontal sections of waveguides are not desirable because:
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Moisture can accumulate in the waveguide.
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How is the signal removed from a waveguide or magnetron?
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With a coaxial connector.
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