1C853A V2 Flashcards
1
Q
Radar stands for?
A
Radio Detection and Ranging
2
Q
the _______ supplies the timing signals that time the transmitted pulses, the indicator, & other circuits
A
synchronizer
3
Q
the ____________ generates electromagnetic energy in the form of short, powerful pulses
A
transmitter
4
Q
the ______ allows the same antenna to be used for transmitting and receiving
A
duplexer
5
Q
the _______ routes electromagnetic energy from the transmitter, radiates it, receives echoes, and routes the echoes to the receiver
A
antenna system
6
Q
the ______ amplifies the weak, electromagnetic pulses returned & reproduces them as video pulses
A
receiver
7
Q
the ______ produces a visual indication of the echo pulses furnishing range & azimuth info
A
indicator
8
Q
______ purpose is to control friendly aircraft, detect hostile aircraft, and control interceptors
A
Air Control and Warning (AC&W) radar
9
Q
______ assists a/c in making safe landings during poor wx conditions & is a key part of DATCALS
A
Precision Approach Radar (PAR)
10
Q
What does the “T” in TPN-19 designate?
A
Ground/Transportable
11
Q
What is used with proper receiving equipment to detect the presence of a distant object?
A
reflected energy
12
Q
At what speed do radio waves travel?
A
speed of light
162k NM/s
13
Q
How long does it take a radar pulse to travel one radar mile?
A
12.36 μs
14
Q
The _______ supplies timing signals to coordinate the operation of the complete system
A
synchronizer
15
Q
When a transmitter uses a high-power oscillator to produce the output pulse, what switches the oscillator on and off?
A
modulator high-voltage pulse
16
Q
A ______ permits the use of a single antenna for both transmitting and receiving
A
duplexer
17
Q
The two basic types of transmitters are _____ and _____
A
keyed-oscillator type; power-amplifier chain
18
Q
In addition to a flat top, what characteristics must a modulator pulse have?
A
steep leading and trailing edges
19
Q
The frequency range of magnetron oscillators of _________
A
600-30,000 MHz
20
Q
The three types of storage elements are most often used in modulators are _______, ______, ________
A
capacitor, artificial transmission line, pulse formed network
21
Q
What type of tube best meets the requirements of modulator switching element?
A
thyratron tube
22
Q
The _________ controls the rate at which the storage element charges
A
charging impedance
23
Q
The two forms of instability common in magnetrons are _______ and _________
A
mode skipping; mode shifting
24
Q
What is the typical frequency range about the center frequency of a tunable magnetron?
A
+/- 5 percent
25
In the power amplifier, what two signals are mixed to produce the output?
local oscillator & coherent oscillator
26
A ________ klystron is used as the final stage of a power amplifier transmitter
multi-cavity
27
What is the result of pulsing a pulsed RF amplifier when no RF is present?
oscillations at an undesired frequency
28
The two general classes of antennas are _______ and ______
omnidirectional; directional
29
_________ determines the width of the antennas main lobe
The system's purpose & degree of accuracy required
30
What is the directivity of a directional antenna?
the degree of sharpness of its beam
31
What are the two functions of a horn radiator?
impedance-matching & directional radiator
32
What are the functions of the antenna on transmit?
concentrate energy in predetermined beam shape, point in predetermined direction
33
What does it mean if an antenna is reciprocal?
transmit & receive patterns are identical
34
Why are reflector antennas extremely important and practical devices for use in radar systems?
economical method of distributing energy over large area, beams with high gain
35
Why is the paraboloid shape useful?
all rays leaving focal point & striking the reflector are reflected back along focal axis
36
What happens when you change the physical shape of the antenna?
gives fixed change to radiated beam pattern, but not continuous control or variation
37
How can you provide an amount of control over the received beam pattern?
two feedhorns, one active (low beam) & one passive (high beam)
38
What is the purpose of the passive feedhorn?
used only for receiving
39
What is an advantage of using MTI?
| moving target indicator
can be used to reduce clutter
40
How is range gating adjusted in the 12-feedhorn system?
individually adjustable by 45 degrees in four azimuth quadrants, relative to north
41
Why is stacked-beam a good technique?
uses simultaneous pencil-beam radiation patterns to cover angles of interest
42
How many receivers are used for the pencil beam?
separate receiver for each pencil beam
43
How does the gain of the individual pencil beams compare to the fan-beam antenna?
provides a larger number of hits, higher data rate = higher gain
44
What phase-array ability is an important advantage if the required antenna is large?
steer a beam without needing to move a large mech structure
45
How does the two-dimensional planer array work in rectangular form; in circular aperture form?
rectangular; fan beams
| circular; pencil beams
46
________ is the greatest limiting factor in a receiver’s detectable range
noise
47
What type of receiver is “almost, always” in radar systems?
superheterodyne
48
Which component of the receiver produces the signal that is mixed with the received signal to produce the IF signal?
local oscillator
49
What is the one major disadvantage of the unbalanced crystal mixer?
unable to cancel local oscillator noise
50
Which receiver component converts the IF pulses to video pulses?
the detector
51
Why is AGC (automatic gain control) not used as frequently as other types of gain control?
widely varying amplitudes of radar return signals
52
How does FTC affect receiver gain, if at all?
no effect, greatly reduces effect of jamming
53
What type of target has a fixed phase relationship from one receiving period to the next?
stationary objects
54
What signal is used to synchronize the coherent oscillator to a fixed phase relationship with the transmitted pulse?
COHO locked pulse
55
What is the phase relationship between the delayed and undelayed video?
pulses will arrive at exactly the same time; opposite
56
When a large signal and a small signal are applied to a LIN-LOG amplifier at the same time, what is the effect on the small signal?
reduces amplification of small signal
57
The overall gain of a LIN-LOG amplifier _______ as each stage saturates
decreases
58
If a target is on the azimuth axis of the radiated beam, what is the input to the azimuth IF channel?
zero
59
What functions does the ASDP (advanced signal/data processor) provide for the radar?
S.REX.PC.T.WX
syncing, receiver/exciter (REX) control, pulse compression, target & wx processing
60
What does target processing in the ASDP consist of?
Doppler filtering, constant false alarm rate (CFAR) detection, sliding dwell binary integration, plot extraction, scan-to-scan
61
The _______ used to suppress large in-band interference returns produced by other radar sources
radar interference suppressor
62
What is the purpose of pulse compression in the ASDP?
recover radar range resolution w/ long pulse transmissions
63
What is the purpose of the CFAR function?
controls false alarms from fixed/moving clutter & system noise
64
When does the binary integrator output a detection?
2+ detections at same range in four processing intervals
65
What are permanent echoes used for?
monitoring primary surveillance radar performance
66
How does the weather processor remove second time around returns?
after 6 scans, maps are merged & data averaged
67
A___________ is used to coordinate timing events within the ASDP and REX
golf
field programmable gate array (FPGA)
68
What information does a plot consist of?
range & azimuth of target, quality measure
69
The ___________ collects the weather data for all 256 radials and assembles a weather map
plot processor
70
The primary radar can detect and process _______ aircraft in a single 360° scan
at least 700
71
4 reasons why it is important that minor lobes of radar antennas be small compared to the main lobe
High directivity
Reduce susceptibility to signal interference
Reduce detecting target in minor lobe
Reduce interference w/ other systems
72
How is the fictitious surface used?
aids in computing antenna performance; immediate front plane where radiation passes
73
How is the pattern of the antenna determined?
distribution of electromagnetic energy from antenna over aperture
74
3 primary performance parameters for an antenna?
gain
beamwidth
side-lobe level
75
Name two basic functions of the radar antenna.
launch & receive electromagnetic energy efficiently, direct the energy into appropriate beam shape
76
The ____________ determines the shape of the beam of radar energy and its antenna pattern
purpose of the radar
77
In the search radar, we need to measure _____ & ______, not ______.
range & azimuth; not height
78
A practical beamwidth is ______ degrees and vertical height is about ________ degrees
1 to 2; 30 to 35
79
A ___________ is used to shape the radar beam
parabolic reflector
80
The ___________ refers to the motion of the antenna axis (of the beam) as the radar looks for an aircraft
scanning method
81
When using a conical scan, what component of the return signal modulation is used by the radar system to maintain track in both azimuth and elevation?
the phase
82
_____________ is identified at the ECM receiver by its regular intervals between illuminations
circular
83
A scan in which a thin beam covers a rectangular area by sweeping it horizontally with the angle of elevation being incrementally stepped up or down with each horizontal sweep of the sector is a ____________
raster scan
84
The ___________ radar gets its name from the fact that each echo pulse from the aircraft being tracked yields a new azimuth and elevation correction signal
monopulse
85
A ______ scan is one in which the antenna rotates on an azimuth sweep, while the elevation angle rises slowly from 0° to 90°
helical
86
What happens to the speed of electromagnetic energy traveling through air as the altitude increases?
small, uniform increase
87
What effects can ducting have on radar coverage?
extend coverage or create holes
88
Name 4 types of propagation anomalies?
ducting
subrefraction
superrefraction
multipathing
89
__________ is the propagation of a wave from one point to another by more than one path
Multipathing
90
When multipath occurs in radar, of what does it consist?
a direct path & one or more indirect paths reflecting from earth surface or large man-made structures
91
When may a multipath also include more than one path through the ionosphere?
frequencies below 40MHz
92
What can near-simultaneous reception of “pulse-type” information cause?
delayed but separate pulses
93
When a low-altitude target is illuminated by a radar system, or for higher-angle situations involving appreciable antenna sidelobes, by what two paths can energy enter the tracking antenna?
direct path from target
| indirect path from energy reflection of earth surface
94
What attempts are made to reduce multipath effects on radar tracking accuracy?
freq & polarization agility
high res antennas
clutter fences
angle-processing techniques
95
___________ provides critical information to provide ample time to prepare or evacuate in response to natural disturbances
Weather radar
96
The “P” in GPN–30 designates _______
Radar
97
It takes radio frequency (RF) _______ microseconds to travel one radar mile
12.36
98
The time from one pulse to the next that the radar sends out is called ______________
pulse recurrence time (PRT).
99
___________ amplifies the weak, electromagnetic (EM) pulses returned from the reflecting object and reproduces them as video pulses
Receiver
100
____________ controls the radar pulse width (PW) by means of a rectangular direct current (DC)
Modulator
101
In addition to a flat top, what characteristics must a modulator pulse have?
think mesa
Very steep leading edge and trailing edge
102
What type of modulator is most commonly used in modern radar systems?
Line-pulsed
103
What type of tube best meets the requirements of a modulator-switching element?
Thyratron
104
If the magnetic field strength is too high on the magnetron, the magnetron will
not oscillate
105
The power gain of an antenna is the ratio of its radiated power to
reference dipole
106
Which pattern is usually specified and measured for a reciprocal antenna?
Transmit
107
What is the most common reflector shape?
Paraboloid
108
What do you call the use of contiguous beams stacked in elevation?
Stacked beam radars
109
What is an advantage of the individual pencil beams when handling rain clutter or chaff?
Limits the volume of space observed
110
Which array is particularly useful in radar applications?
Two-dimensional planar
111
Which waveguide antenna is more suited for one-dimensional scanning than scanning in two coordinates?
Waveguide slot array
112
What intermediate frequencies are usually used in radar receivers?
30 MHz or 60 MHz
113
What receiver circuit/stage actually produces the intermediate frequency (IF)?
Mixer
114
Which stage of the intermediate frequency (IF) section is the most critical?
Input (1st stage)
115
Immediately after the transmitter fires, sensitivity time control (STC) reduces the receiver gain to what level?
Zero
116
What signal is used to synchronize the coherent oscillator (COHO) to a fixed phase relationship with the transmitted pulse?
Coherent oscillator lock pulse
117
What is the phase relationship between the delayed and non-delayed video?
Opposite polarity
118
What happens to the overall gain of a linear logarithmic (LIN-LOG) amplifier as each stage saturates?
Gain decreases
119
How many separate channels does a monopulse receiver have?
Three
120
What is used to interface target and weather channel signals to the signal processor?
Azimuth beam/sensitivity time control (STC) interface
121
What unit’s primary function is to accept the output of the receiver/exciter (REX), and decide, for every range and azimuth cell in the radar coverage area, whether a moving target is present or not?
Target processor
122
How many permanent echoes are permitted by the advanced signal data processor (ASDP)?
25
123
What processor function attempts to correlate plots to existing tracks?
Track processor
124
What type of reflector is used to shape the radar beam?
Parabolic
125
What refers to the orientation of the electromagnetic (EM) wave as it travels through space?
Polarization
126
What refers to the motion of the antenna axis (of the beam) as the radar looks for an aircraft?
Scanning method
127
What precision radar system uses continuous rotation of a pencil beam (narrow angle in both dimensions) around the aircraft and uses the phase of the return signal modulation to maintain track in both azimuth and elevation?
Conical scan
128
When using a conical scan, what component of the return signal modulation is used by the radar system to maintain track in both azimuth and elevation?
Phase
129
What scanning method is identified at the electronic countermeasure (ECM) receiver by its regular intervals between illuminations?
Circular
130
Which radar gets its name from the fact that each echo pulse from the aircraft being tracked yields a new azimuth and elevation correction angle?
Monopulse scan
131
What happens to the speed of electromagnetic (EM) energy traveling through air as the altitude increases?
Signal speed increases
132
The bending of electromagnetic (EM) waves caused by a change in the density of the medium through which the waves are passing is referred to as
refraction
133
What is it called when temperature first increases with height and then begins to decrease?
Temperature inversion
134
What do you call propagation of a wave from one point to another by more than one path?
Multipathing
135
When would you use an electrostatic instead of an electromagnetic CRT?..
requirements for lightweight, compact equipment
136
How is information presented on an A-scan indicator?
vertical deflection from horizontal baseline
137
How is time represented on an A-scan indicator?
horizontal distance between start trigger & input signal
138
How is the video presented on a B-scan indicator?
electron beam presents target as bright spot on the screen
139
What type of radar uses the B-scan indicator?
precision approach radar for azimuth & elevation
140
What target information does a PPI scan present?
range & azimuth in polar coordinates
141
What type of pattern does a Raster scan indicator use to scan the CRT?
electron beam scans CRT screen left to right and top to bottom
142
What components do all indicators have regardless of type?
```
Power supplies
Data processing circuits
Video circuits
Deflection circuits
CRT (cathode ray tube)
Front panel controls
```
143
What furnishes the operating voltages for the CRT?
high voltage power supply
144
List the three functions performed by the data processing circuits.
control ops & data calcs
interface
data distribution
145
How do the video circuits protect the CRT during certain malfunctions?
disabling CRT high voltage power supply
146
How do the data processing circuits specify beam position?
using X & Y coordinates, with origin at center of CRT screen
147
List the two types of CRTs.
electrostatic, electromagnetic
148
What part of a CRT shields the electron beam from unwanted electric fields?
aquadag
149
What is the primary hazard involved with high-vacuum CRTs?
dangerous implosions
150
What do indicator front panel controls allow the operator to do?
select input signals/messages, enter op parameters, adjust indicator format
151
What are the SIF modes used to interrogate an aircraft?
Modes 1, 2, 3/A, C
152
What is the spacing between P1 and P3 pulses for the four SIF modes?
Mode 1 - 3 μs
Mode 2 - 5 μs
Mode 3 - 8 μs
Mode C - 21 μs
153
Explain the contents of the mode 4 preamble.
four pulses & a blank space
| each pulse 0.5 μs wide, 2 μs apart
154
What is the transmitted frequency of interrogation pulses?
Interrogator to a/c - 1030 MHz
| A/C to interrogator - 1090 MHz
155
What is the purpose of transmitting a P2 pulse?
To eliminate sidelobe reception
156
What is the limit of total possible codes in mode 1?
32
157
What is the largest single digit for any SIF modes 1, 2, and 3/A reply?
7
158
What type of code and what are the increments of the altitude information received in mode C?
Gray Code; 100' altitude increments
159
What terms are used for the first and last pulse present in a SIF?
bracket/framing pulses
160
What is the bracket pulse spacing on a normal SIF code train?
20.3 μs apart, width of 0.45 μs
161
What signifies that the SIF reply has been transmitted by a missile or drone?
X pulse in reply code train
162
What is the purpose of a reply pulse that is 4.35 μs after the last bracket pulse of a SIF code train?
I/P (id position) response by a/c requested by operator
163
What is the only IFF/SIF mode that can decode civilian emergencies?
Mode 3/A
164
How is a communications failure emergency received by the ground station?
7600 emergency code
165
Which modes will decode military emergencies?
Any SIF mode (1,2,3,C)
166
What type of aircraft can present a single-arc IFF reply on the scope?
US military aircraft
167
What are the seven functions within the AN/UPM–155 test set?
CI.I.M.I.F.O.P
```
Control and interface
IFF simulator
measurement system
interface
front panel
oscilloscope
power distribution
```
168
AN/UPM–155: Used for automatic testing
Interface
169
AN/UPM–155: Used to view signals under test
Oscilloscope
170
AN/UPM–155: Provides overall control
Control and Interface
171
AN/UPM–155: Measure VSWR (Voltage Standing Wave Ratio)
Measurement
172
AN/UPM–155: Simulates interrogations
IFF Simulator
173
AN/UPM–155: Provides all required voltages
Power Distribution
174
AN/UPM–155: Contains keyboard and display
Front Panel
175
What is used to couple the components between waveguide sections to prevent RF leakage?
Waveguide choke joints
176
What process is used on waveguides to prevent arcing?
air compressors supply dry air to waveguide components to pressurize
177
How are waveguides pressurized in fixed environments?
with air or inert gases
178
Explain how a rotary joint works.
allows one waveguide section to remain stationary while other rotates, suppress unwanted RF signals
179
What component allows the waveguide system to be connected to both transmitter and receiver, while allowing them to share a common antenna?
duplexer
180
After the majority of the RF energy enters one port of a circulator, where will it exit?
next highest # port of circulator
181
What is the purpose of the TR (transmit-receive) tube?
closes RF system to receiver during transmission to protect the receiver from high-power transmitter pulses
182
When a radar set uses dual transmitting channels, what is needed to properly route the RF signals between the waveguide, antenna, and dummy load?
RF switch
183
Explain the differences between a low-power and high-power diplexer.
high-power -- sulfur hexafluoride
| low-power -- no pressure windows/gas fittings/normal air
184
The RF filters will filter out all frequencies except what frequency?
the desired frequency of the circuit
185
State the purpose of the directional coupler.
enable mx to monitor signals, inject test signals into waveguide system
186
What important factor must you consider when making directional coupler measurements?
loss of signal strength when sampling/injecting, indicated on coupler
187
What component reduces precipitation and clutter to nearly zero?
polarizer
188
Explain the differences in radar returns from raindrops and aircraft.
Rain drops will return constant amplitude/same energy; a/c will show wide/irregular variations as polarization changes
189
Name the two most commonly used mediums to remote radar equipment.
cable/land lines & radio microwave links (RML)
190
What is the distance restriction when remoting radar systems with coaxial cable?
12,000'
191
What two things can assist a technician in determining the operational usability and troubleshooting of a radar system?
performance monitors or buit-in test equipment (BITE)
192
What radar unit displays corresponding radar information on a cathode ray tube (CRT)?
Indicator
193
What type of cathode ray tube (CRT) is mostly used in ground radar equipment?
Electromagnetic (EM)
194
The most basic type of scanning indicator is the
A-scan
195
The scanning indicator that plots target range and azimuth information in polar coordinates is the
plan-position indicator (PPI)
196
What type of scanning indicator do surveillance radars primarily use?
plan-position indicator (PPI)
197
What type of scanning indicator completes two vertical scan periods to produce one complete picture called a frame?
Raster
198
Which indicator power supply furnishes the cathode ray tube (CRT) operating voltages?
high voltage
199
Along with determining the overall operation of the indicator, the data processing circuits
provide data distribution and interface with the radar
200
What indicator circuit converts digital display data from the data processing circuits into analog drive signals?
Deflection
201
What part of the cathode ray tube (CRT) is tapered and lined with a conductive graphite coating?
Aquadag
202
The high vacuum and large surface area of the cathode ray tube (CRT) make it especially vulnerable to
implosions
203
Which is not an advantage of identification friend or foe/selective identification feature (IFF/SIF) equipment?
Only one mode is used for simplicity
204
An aircraft transponder answers an interrogation by transmitting a reply pulse train signal back to the ground station at a frequency of
1090 MHz
205
To eliminate interrogator side-lobe suppression (ISLS), the ground radar site transmits the P2 signal in what type of radiating pattern?
omnidirectional
206
What selective identification feature (SIF) mode has a limit of 32 codes?
Mode 1
207
What generates an identification of position (I/P) response?
aircraft pilot
208
A 7600 emergency reply signifies an aircraft
communications failure
209
What is the only type of aircraft that can present a single-arc identification friend or foe (IFF) reply on a scope?
Military
210
What function of the AN/UPM–155 test set provides overall control of the other functions?
Control and interface
211
What function of the AN/UPM–155 test set provides signal conditioning required for testing transponders and interrogators?
Interface
212
What are used to couple waveguide components and sections to prevent radio frequency (RF) leakage?
Choke joints
213
What do most radars use in their waveguide system to prevent arcing?
Air compressors
214
What waveguide compressor subsystem controls operation of airflow and indicates normal or malfunction conditions?
Electrical
215
What duplexer sub-component accepts radio frequency (RF) transmit power from the transmitter and directs it through the waveguide to the antenna assembly?
circulator
216
What waveguide component has a mechanical stop mounted on its base to limit movement to each extremity of travel?
Radio frequency (RF) switch
217
What antenna device reduces precipitation display to nearly zero on an indicator?
polarizer
218
The two most often used radar remoting configurations are
cable/land lines and radio microwave links
219
Due to high signal loss, about how many feet are coaxial cable remoting systems limited to?
12,000
