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Unit 5-1

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(801) The range resolution of a radar set is determined by what characteristic?
Transmitted Pulse Width
(801) Azimuth resolution is directly related to what radar set characteristic?
Antenna beam width.
(801)What is the width of the azimuth scan for the AN/GPN-22 precision approach radar?
20 degrees
(802) While siting an airport surveillance radar, the approach path, including touchdown, should be in the line of sight. If it is impossible to include the touch-down point, there should be a line-of-sight path at least to the point corresponding to the
minimum instrument flight rule (IFR) altitude for the base.
(802) The AN/GPN-22 precision approach radar accuracy is impaired if the setback distance is more than...
6,000 feet.
(802) The most commonly used and normally maintenance free reflector used for the AN/GPN-22 precision approach radar is the...
reference reflector
(803) In the AN/GPN-22 precision approach radar, frequency diversity is used in the scan mode to eliminate...
large target fluctuations and provide target enhancement.
(803) In the AN/GPN-22 precision approach radar, the coherent and non-coherent input to signal data converter is...
bipolar video
(804) Once a track is established in the AN/GPN-22 precision approach radar, what device uses error data obtained from the received signal to predict where the target will be during the next track interval?
Target Data Computer (TDC)
(804) How many narrow band filters does the AN/GPN-22 precision approach radar (PAR) employ to convert a shift in IF to a range error signal?
24
(805) During the target tracking cycle, in the AN/GPN-22 precision approach radar, the computer updates the computation of azimuth, elevation, and slant range coordinates on how many targets?
Six
(805) At what interval does the target data computer (TDC) perform system fault monitoring?
Once every 2 seconds.
(806) In the AN/GPN-22 precision approach radar (PAR), what are the three modes of operation with respect to data loop operation?
Command, input, and output.
(806) The data loop interface logic circuitry used in each of the subsystems is commonly called....
repeaters logic.
(807) Which of the following is not part of the siting information requested by the target data computer (TDC) from the computer data entry (CDE)?

a. Safety zone
b. Elevation angle
c. Distance to centerline
d. Distance to touchd
Distance to centerline
(807) The operator collects what type of data for the acquisition word by positioning the trackball symbol to lead the target return slightly?
Range and elevation.
(807) What is the time duration (usec) of the local oscillator (LO) chirp?
1.3usec
(807) The refresh memory provides a flicker-free presentation of the target symbol on the radar display by refreshing at a...
30-cycle rate.
[801] Into what three categories can ATC radar systems be divided?
(1) Air route traffic control radar.
(2) Terminal control area radar.
(3) Precision approach radar.
[801] In which ATC radar category is an ASR used?
Terminal control area radar.
[801] Define range resolution.
The ability of a radar system to distinguish between two close but separate targets at the same azimuth but different ranges.
[801] Define azimuth resolution.
The ability of a radar system to distinguish between two close but separate targets at the same range but different azimuths.
[801] Typically, what is the range and azimuth resolution of the PAR?
Typically range resolution is 100 feet and azimuth resolution is 1°.
[802] What is the optimum distance between ASR site and the touchdown point?
More than 1/2 mile from the touchdown point.
[802] Why is the receiver recovery time a factor in choosing an ASR site?
So that these areas do not fall within the area on the scope that is blanked out by receiver recovery time.
[802] What is the maximum allowable separation of receiver and indicator with most landline remoting equipment?
10,000 to 12,000 feet
[802] Define the term "Runway centerline".
It is the line an aircraft follows during its landing approach that bisects the runway and extends beyond it.
[802] What is meant by the term "left of runway"?
It describes the possible PAR siting area from the view of a pilot on a landing approach.
[802] Define the term "Touchdown"
An arbitary point that has been designated as the point at which an aircraft would touch the ground if it were to maintain the glide path and couse line given by the final controller during the landing procedure
[802] List the azimuth scan limits of the AN/GPN-22 (PAR).
The PAR scans 20° in azimuth, from +10° to -10° with 0° being the center of the antenna.
[802] How can more than one runway be provided radar coverage when the PAR unit has such definite scan limits?
With the use of a turntable at the base of the antenna cappable of moving 360°, bringing other runways into the radar scan.
[802] If you need to cover two runways but can provide optimum coverage for only one, how should you site the PAR?
Locate the PAR so that it gives you the best coverage to your most important runway.
[802] What is the purpose of a radar reflector?
The radar reflector provides a fixed target at precisely known position adjacent to the touchdown point of each runway. These are used to properly line up the PAR sytem to the runway under use.
[802] Which of the available reflectors for the GPN-22 are the most commonly used and the most critical to its operation?
Tracking reflector
[803] List the two normal operating modes of the GPN-22.
Search mode and track mode.
[803] How many scan beam positions elapse before the radar goes into track mode?
24
[803] Why is frequency diversity used in the scan mode?
To eliminate large target fluctuations and provide target enhancement.
[804] How many targets can the radar track during a single track interval?
Three
[804] What term describes differences in azimuth and elevation prediction errors during tracking?
Angle errors
[804] Decribe the characteristics of the signal called "chirp".
1 usec RF burst swept 120 MHz within the operating frequency band.
[804] How many narrow band filters does the AN/GPN-22 PAR employ to convert a shift in IF to a range error signal?
24
[805] Which signal is responsile for interrupting the TDC 1200 times a second?
The beam interrupt signal.
[805] During the tracking cycle, how many targets can the TDC update azimuth, elevation, and slant range?
Six separate targets.
[805] Name the technique used to track the touchdown reflector as well as utilizing all six track channels.
Use of the "phantom" track channel, which is rotated and time-shared with the six other channels.
[805] Name the two off-line test programs used for diagnostics.
System Performance Assesment (SPA) and Diagnostic Test progams
[805] Which off-line test is used solely for the diagnostics of the TDC?
Diagnostic Test
[806] List the three modes of operation associated with the data loop operation.
Command, input, and output.
[806] What action does the TDC take whenever a peripheral that is addressed is busy?
The computer performs an alternate operation in order to conserve system operational time.
[806] Which mode of data loop operation allows the TDC to recieve data from a peripheral?
Input mode.
[806] How many bits are conatined in the data word from a peripheral?
32-bits
[806] List the three different ways the repeater logic must perform in a peripheral when responding to the TDC's request.
(1) Repeat all input address, data and control signals.
(2) If the peripheral is addressed, must accept data.
(3) If the peripheral is addressed, it must put data on-line to allow a rebound to the computer.
[807] From where does the informaiton that is entered into the site parameter panel switches come from?
The initial site survey.
[807] What is the destination of siting information from the computer data entry (CDE)?
The Target Data Computer (TDC)
[807] How often is the site parameter data processed by the TDC?
Once every 2 seconds.
[807] After selection of a target to be tracked, what action does an operator take to make the formal tracking request?
The operator depresses the "Acquire Target" pushbutton.
[807] What action does the refresh memory take to identify the display making a request?
Includes a file identification code within the 32-bit Acquisition word.
[807] What factor predicts the next track beam position and chirped local oscillator range?
The predicted target position
[807] What method does the refresh memory use to provide a flicker-free display of the target symbol?
It uses a 30-cycle refresh rate.

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