3D155 Volume 1 URE Flashcards
Learn about V1
What is the required angle of incidence necessary to get a reflection back to a light source?
90 degrees
When a pulse of radio frequency energy is transmitted, it travels at
the speed of light.
Approximately how long does it take for radio frequency energy to travel 1 nautical mile to a target and return to the radar?
12.36us
You can identify the maximum detection range of a radar by dividing the time of one radar mile into the
pulse recurrence time.
What characteristic of frequency does a radar target moving towards the radar exhibit?
a higher frequency than the original broadcast.
Which radar subassembly ensures all circuits connected with the radar operate in a definite timed relationship?
synchronizer
What radar subassembly allows the radar system to transmit and receive from the same antenna?
Duplexer
An antenna is said to be reciprocal if
its transmit and receive patterns are identical.
Which feedhorn is used only for receiving?
Passive
One use for the beam-lobing switch of the multi-feedhorn system is to
Route the received signal from the number one feed horn to a dummy load.
What does the distribution of electromagnetic energy from the antenna over the aperture determine?
pattern of the antenna
The shape of the beam of radar energy and its antenna pattern depend on the radar’s
purpose.
The scanning method used by the radar system refers to the
motion of the antenna axis (of the beam) as the radar looks for an aircraft.
What scan is identified at the electronic countermeasure receiver by its regular intervals between illuminations?
Circular
What scan system uses a thin beam to cover a rectangular area by sweeping the area horizontally with the angle of elevation incrementally stepped up or down with each horizontal sweep of the sector?
raster
Which scan radar is also used in the acquisition phase by some airborne intercept radars?
raster
Which scan 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
In which scan radar does the antenna rotate on an azimuth sweep, while the elevation angle rises slowly from 0 to 90 degrees?
helical
What causes delayed, but separate, pulses?
near-simultaneous reception of pulse-type information.
attempts to reduce multipath effects on radar tracking accuracy include the use of
frequency agility
What type of radar system uses a B-scan indicator?
precision approach
What target information is provided by a plan position indicator?
range and azimuth
In a raster scan indicator, how many vertical scan periods does it take to produce one complete picture?
2
Which indicator component produces signals that determine the overall operation of what the indicator will do?
data processing circuits
In a typical indicator system, where is digital display data from the data processing circuits converted into analog drive signals?
deflection circuits
The vacuum in a cathode-ray tube (CRT)
prevents collisions between electrons in the beam and air molecules.
What frequency is used for identification friend or foe/selective identification feature (IFF/SIF) interrogations?
1030 MHz
An X pulse is present in a selective identification feature code train when
the aircraft is a pilotless drone or missile.
Which selective identification feature special response explains a 7500 reply?
hijacking
What is the AN/UPM-155 radar test set capable of testing?
interrogators and associated components.
What possible input voltages may be supplied to the AN/UPM-155 radar test set for operation?
115 Vac or 230 Vac
What element of modulation prevents interference when sharing the same communications path is necessary?
channel allocation
What factor determines the spacing of the sidebands in an amplitude modulated signal?
frequency of the modulating signal
What is the relationship of the bandwidth required for double-sideband emitted carrier (DSBEC) amplitude modulation (AM) to the bandwidth of the modulating signal of the AM bandwidth alone?
twice the modulating bandwidth
in frequency modulation, the amount of oscillator frequency change is
directly proportional to the amplitude of the modulating signal.
A 10KHz modulating signal has enough peak voltage to cause a deviation of 30kHz. What is the modulation index?
3
in phase modulation, the carrier’s
phase shifts at the rate of the modulating signal.
Information capacity is increased by how many times its normal rate if using 8-phase shift keying (PSK) instead of binary PSK?
3
What size bit combinations are allowed when using 16-phase shift keying?
4 bit
What part of the pulse code modulation process converts a continuous time signal into a discrete time signal?
sampling
By how much does non uniform quantizing and companding decreases the length of a code word?
11 to 7 bits
How is the parity bit used in asynchronous transmission?
by the receiving device to verify that the transmission was received correctly.
How does synchronous transmission reduce the overhead costs of data transmission?
blocks many characters together for transmission.
During a vertical redundancy check, what significance does the amount of 1’s have in a data bit pattern?
determines parity.
using the longitudinal redundancy check method of error correction, what does the receiver compare with the transmitter to ensure an accurate transmission of data?
block check character
When used together, what two error detection methods are 98 percent effective in detecting errors?
vertical redundancy check and longitudinal redundancy check
What error detection method is used for checking a data block greater than 512 and is about 99 percent effective in most applications?
cyclic redundancy
when using forward error control as a method of error correction, where does error correction take place?
receiving end.
which statement describes an advantage of using fiber optic cable?
electromagnetic fields do not affect fiber optic cables.
which statement describes a security feature of using fiber optic cable?
virtually impossible to tap a fiber optic cable unnoticed.
what type of buffer allows the fiber optic cable to be twisted or pulled with little stress on the fiber?
loose tube
most fiber optic links use infrared light and consist of what frequency range?
750 to 1500 nm
When considering light wave propagation, what is the name of the angle between the normal in the first material and the ray that is bounced back in the first material?
angle of reflection
what is the principle on which fiber optics work?
total internal reflection
what occurs because of imperfections in an optical fiber’s basic structure?
scattering
what is reduced through the use of index matching fluids on fiber optic connectors?
fresnal reflection
what is the most useful way to classify fiber optic cable?
refractive index profile and number of modes.
what type of fiber is the least efficient, with the highest dispersion and has a core diameter range of 30um to over 800um?
multimode step-index
what type of fiber has a core diameter of 50-125 micrometers (um) and consists of numerous concentric layers of glass, something like the annular rings of a tree configured to reduce dispersion?
multimode graded-index
which feature of the fluke 8025A multimeter do you use to select various measurement functions?
rotary switch
which feature of the fluke 8025A locks the measurement into the display for viewing and automatically updates the display when you take a new measurement?
touch-hold pushbutton
which current range on the fluke 8025A do you select to measure 250 milliamps alternating current (AC)?
Milliamps/amp AC
When you make a resistance measurement, how do you electrically isolate a resistor from the circuit?
desolder one side of the resistor?
what is caused by low insulation resistance between conductors?
high-attenuation, crosstalk, and noise.
when will insulation resistance increase?
thickness of the insulating material increases.
when using the AN/PSM-2 megger, how do you apply the correct regulated output voltage?
turn the hand-crank at a rate to keep the indicator lights at a steady glow.
what type of megohmmeter do you use on paper insulated conductor cable?
500 volt
How many probes are normally used for an earth ground tester?
3
what is the earth ground standard for communications facilities?
10 ohms or less
Which mode of triggering an oscilloscope causes a trace to be drawn on the screen at all times, whether there is an input signal or not?
auto
which input coupling switch position allows you to view both alternating current (AC) and direction current (DC) components of the input signal?
DC
which probe lets you use the oscilloscope to measure higher voltage levels, raises the input impedance, and attenuates noise?
passive divider, 10:1 probe
which probe does not need to actually make contact with the circuit under test?
current probe
what digital storage oscilloscope circuit compensates for high sampling rates of high-frequency signals?
charged coupled device
sampled data points are stored in the memory of a digital storage oscilloscope as
waveform points
what area of a digital storage oscilloscope takes digitized samples and performs numerous manipulations on the data including measuring rise and fall times, periods, time intervals, and math computations?
microprocessors
what type of sampling does a digital storage oscilloscope normally use on single shot or seldom-occurring signals?
real-time
what is the frequency range of an audio signal generator?
20 Hz to 20kHz
Which one of these is not an application of a radio frequency generator?
aligning galvanometers
how is a radio frequency generator used?
align telemetry receivers
the 10:1 power ratio represented by 1 bel can also be represented by how many decibels (dB)?
10dB
what does a power reading that uses the abbreviation dBm indicate?
ratio of decibels relative to a 1-milliwatt standard.
If someone says, ‘we doubled our transmitter power;’ how much is the gain in dB?
3 dB
the measurable frequency and power ranges of the HP 436A power meter system are determined by the
selected sensor
during what operation is the radio frequency blanking output used on the HP 436A power meter
during automatic zeroing
which measurement is not made with a spectrum analyzer?
peak-peak voltage
which electronic counter measurement represents the average bit to bit time of an input signal?
period
which electronic counter measurement counts the number of bits in a pulse train?
totalize
which are the correct four classes of electronic counters?
frequency, universal, microwave, and reciprocal
