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47 Cards in this Set

  • Front
  • Back
An RF mixer has what purpose in a radar system?
It converts a low level signal to a different frequency.
What frequency is the discriminator tuned to?
The 30 MHz or 60 MHz IF.
The usual intermediate frequency of a shipboard radar unit is:
30 or 60 MHz
The error voltage from the discriminator is applied to:
The repeller of the klystron.
What radar circuit determines the pulse repetition rate?
The timer (synchronizer circuit).
The output of an afc discriminator is:
AC is "on frequency" DC if "off frequency".
Power losses in cavity resonators are very low because:
Conducting furfaces are large
In a circular resonant cavity with flat ends, the E-field and H-field form with specific relationships. The:
E-Lines are perpendicular to the end walls.
Practical radar operation requires the use of microwave frequencies so that:
Stronger target echoes will be produced.
Airport wind shear radars depend upon:
The doppler effect to track rapid shifts in wind patterns.
The minimum range ofa radar is determined by?
The transmitted pulse width.
The major advantage of digitally processing a radar signal is:
Enhancement of weak target returns.
Which of the following is the most practical means of increasing the range ofa ship radar installation?
Increase tranmitter power, increase pulse width, and increase the time between transmitted pulses.
A shipboard radar uses a PFN driving a magnetron cathode through a step up transformer. This results in which type of modulation?
Pulse modulation.
What devices could be used as the local oscillator in a radar receiver?
A klystron and a Gunn Diode.
The klystron local oscillator is constantly kept on frequency by:
The Automatic Frequency control circuit.
Voltages used in CRT anode-circuits are in what range of value?
10-50 kV.
What type of video output tube is used in most marine radar units?
A plan position indicator (PPI).
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:
Connecting an inductor in series with the input capacitance and an inductor in parallel with the output capacitance.
The video detector in a pulse modulated radar system would most likely use a :
Diode detector.
When the receiver employs an MTI circuit:
Only moving targets will be displayed
To minimize video display saturation caused by RF energy from external sourses, such as jamming, a receiver might employ:
FTC circuits.
Pulse radars require precise timing for their operation. Which type circuit below might best be used to provide these accurate timing pulses?
A single swing blocking oscillator.
Standard vacuum tubes are not used at radar frequencies because:
The inductance of the leads is excessive.
To obtain an indication of target movement using the doppler principle, a CW radar receiver would most likely employ a :
Discriminator, tuned to the IF.
Solid state microwave amplifier devices operating at C-Band and above are typically made from:
Gallium Arsenide
The display of a 2-D airport surveillance radar typically provides:
Range, azimuth, and SSR responses.
On a basic syncro system, the angular information is carried on:
The stator lines.
In standard CMOS logic IC databooks, the parameter tTLH is considered to be:
Measured from the 10% to 90% points of the leading edge.
In a radar receiver, the RF power amplifier:
Does not exist.
What is the average range of a ships surface search radar unit?
40 miles.
A wavelength is equal to how many degrees of a sinewave?
360
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?
The waveguide compensation delay line needs adjusting.
The VSWR of a micro wave transmission lince device might be measured using?
A dual directional coupler, a power meter, and Network Analyzer.
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?
Video starage RAM or shift register.
An increase in magnetron current which coincides with a decrease in power output is an indication of what?
The external magnet weakening.
Low or no mixer current could be caused by?
All of these
A defective crystalin the AFC section will cause:
Bright flashing pie sections on the PPI.
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?
178 miliwatts/centimeters squared.
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:
150 kilmeters
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:
105 kilometers.
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:
More negatice.
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:
72 ohms.
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?
R=51 kilohms, C= 0.001 microfarad.
What is the most common type of radar antenna used aboard commercial maritime vessels?
Slotted array.
Long horizontal sections of waveguides are not desirable because:
Moisture can accumulate in the waveguide.
How is the signal removed from a waveguide or magnetron?
With a coaxial connector.