Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

RADar > 3D155 Volume 1 EOC > Flashcards

3D155 Volume 1 EOC Flashcards

1
Q

What is the purpose of AC&W radar?

A

To control friendly aircraft, detect hostile aircraft, and control interceptors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is used with proper receiving equipment to detect the presence of a distant object?

A

Reflect energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At what speed do radio waves travel?

A

The speed of light, or 162,000 nautical miles per second.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How long does it take for a radar pulse to travel one radar mile?

A

12.36us

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What radar assembly supplies timing signals to coordinate the operation of the complete system?

A

Synchronizer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What radar component permits the use of a single antenna for both transmitting and receiving?

A

Duplexer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the functions of the antenna on transmit?

A

To concentrate the energy in a predetermined beam shape and to point this beam in a predetermined direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the functions of the antenna on receive?

A

The antenna forms a beam in a particular direction to gather selectively transmitted energy that has been reflected from various targets.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does it mean if an antenna is said to be reciprocal?

A

The transmit and receive patterns of the antenna are usually identical.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which pattern is specified and measured for a reciprocal antenna?

A

Only one pattern, usually the transmit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why are reflector antennas extremely important and practical devices for use in radar systems?

A

They offer an economical method of distributing energy over a large aperture area and can produce shaped or pencil beams with high gain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What generally does the reflector do with its energy?

A

The reflector is used to redirect and reshape energy from one or more point sources located near the focal point into a desired far-field pattern.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the most common reflector shape?

A

paraboloid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the paraboloid formed?

A

The paraboloid is formed by rotating a two-dimensional parabola about its focal axis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why is the paraboloid shape useful?

A

All rays leaving the focal point and striking the reflector are reflected along a path parallel to the focal axis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is a paraboloid reciprocal?

A

It intercepts an electromagnetic plane wave traveling parallel to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens when you change the physical shape of the antenna?

A

It gives a fixed change to the radiated beam pattern.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How can you provide an amount of control over the received beam pattern?

A

use two feedhorns, one active(low beam) and one passive (high beam).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the purpose of the active feedhorn?

A

It is the horn normally used for transmitting and receiving

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the purpose of the passive feedhorn?

A

It is used only for receiving.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is an advantage of using MTI?

A

It reduces the clutter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is a disadvantage of using MTI?

A

It reduces system sensitivity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What could you expect if you’re using the clutter-reducing aspect of the dual-feedhorn system discussed on a mountain range reaching 3 degrees above the horizon?

A

the clutter would be reduced or eliminated because it is below 3.5degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What problem in the dual-feedhorn antenna can be eliminated by using a 12 feedhorn antenna?

A

Multipath reflections and holes caused by them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How is range gating adjusted in the 12 feedhorn system?

A

The range gating will be individually adjustable in each of four azimuth quadrants, relative to the north reference.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What do you call the use of contiguous beams stacked in elevation?

A

A stacked-beam radar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Why is stacked-beam a good technique?

A

It uses simultaneous pencil-beam radiation patterns from a single aperture to cover the elevation angles of interest.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is each beam considered?

A

A separate radar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How does the transmitter give the desired elevation coverage?

A

The transmitter radiates a fan beam from the summation of all overlapping pencil beams.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How many receivers are used for the pencil beam?

A

A separate receiver is provided each pencil beam.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How is sidelobe cancellation employed?

A

It must be used separately in each receiving channel.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is a disadvantage of using automatic detection, sidelobe cancellation, or MTI in the radar?

A

It adds to the cost and complexity of the radar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is an advantage of the individual pencil beams when handling rain clutter or chaff?

A

It limits the volume of space observed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How does the gain of the individual pencil beams compare to the fan-beam antenna?

A

The individual pencil beams have a higher gain than a fan-beam antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What phase-array ability is an important advantage if the required antenna is large?

A

Its inherent ability to steer a beam without the necessity of a large mechanical structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What are the attractive features of the phased-array antenna?

A

The capability to generate more than one beam with the same array and flexibility in the control of the aperture illumination.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Which array is particularly useful in radar applications?

A

The two-dimensional planar array

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

How does the two-dimensional planer array work in rectangular form; in circular aperture form?

A

It can generate fan beams. It can generate pencil beams.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What kinds of radiators have been used in phased arrays more than others?

A

The dipole, the open-ended waveguide, and the slotted waveguide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Which waveguide antenna is more suited for one dimensional scanning than scanning in two coordinates?

A

a slotted array antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Give four reasons why it is important that minor lobes of radar antennas be small compared to the main lobe.

A
  • Have an antenna with high directivity.
  • Reduce the susceptibility of the antenna to interfering signals.
  • Reduce the possibility of detecting a target in a minor lobe.
  • Reduce the probability of interference with other nearby systems.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What do we call the fictitious surface located on or near an antenna?

A

The antenna aperture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

How is the fictitious surface used?

A

It is often useful in computing the performance of the antenna.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

How is the pattern of the antenna determined?

A

The distribution of electromagnetic energy from the antenna over the aperture determines the pattern of the antenna.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

How can the antenna designer modify the shape of the pattern?

A

Altering the distribution of energy over the aperture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What are the 3 primary performance parameters for an antenna?

A

Gain, Beamwidth, Sidelobe level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Name two basic functions of the radar antenna.

A
  • To efficiently launch/receive electromagnetic energy into the atmosphere or space
  • To direct the energy into an appropriately shaped beam.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What determines the shape of the beam of radar energy and its antenna pattern?

A

The purpose of the radar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

In the search radar what do we need to measure?

A

Range and azimuth but not height

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What is a practical beamwidth and vertical height?

A

practical beamwidth: 1 to 2 degrees

average vertical beam height: 30 to 35 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

How doe we shape this beam?

A

Using a parabolic reflector.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What refers to the orientation of the electromagnetic wave as it travels through space?

A

Polarization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What refers to the motion of the antenna axis (of the beam) as the radar looks for an aircraft?

A

The scanning method used by the system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

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?

A

The conical scan.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is identified at the ECM receiver by its regular intervals between illuminations?

A

The circular scan.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

In what system does a thin beam cover 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?

A

The raster scan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Which radar gets its name from the fact that each echo pulse from the aircraft being tracked yields a new azimuth and elevation correction signal?

A

The monopulse scan.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

In what radar does the antenna rotate on an azimuth sweep, while the elevation angle rises slowly from 0 to 90 degrees?

A

The helical scan.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What happens to speed of electromagnetic energy traveling through air as the altitude increases?

A

signal speed increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What effects can ducting have on radar coverage?

A

Extend coverage or create holes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Name 4 types of propagation anomalies?

A

Ducting, subrefraction, superrefraction, and multipathing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What do we call propagation of a wave from one point to another by more than one path?

A

a multipath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

When multipath occurs in radar, of what does it consist?

A

It usually consists of a direct path and one or more indirect paths by reflection from the surface of the earth or sea or from large man made structures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

When may a multipath also include more than one path through the ionosphere?

A

At frequencies below about 40 MHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

What can near-simultaneous reception of ‘pulse-type’ information cause?

A

Delayed, but separate, pulses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

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?

A

A direct path from the target and an indirect path involving energy reflected from the surface of the earth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

What attempts are made to reduce multipath effects on radar tracking accuracy?

A

The use of frequency agility, polariation agility, high-resolution antennas, clutter fences, and complex indicated angle processing techniques.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

When would you use an electrostatic instead of an electromagnetic CRT?

A

When the requirements call for lightweight, compact equipment as used in aircraft.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

how is information presented on an A-scan indicator?

A

As a vertical deflection from the horizontal baseline.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

How is time represented on an A-scan indicator?

A

by the horizontal distance between the start trigger and the input signal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

How is the video presented on a B-scan indicator?

A

An intensity-modulated electron beam presents the target as bright spots.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What type of radar uses the B-scan indicator?

A

The PAR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

How would elevation and range be presented on a B-scan indicator?

A

The indicator uses a split screen configuration that presents azimuth and range on the lower portion of the indicator, while elevation and range are presented on the upper portion. In the azimuth presentation, the time base moves bottom-to-up the screen in synchronization with the azimuth antenna scan. In the elevation presentation, the time base moves bottom-to top up the screen in synchronization with the elevation antenna scan. Range is read form left-to-right across the screen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What target information does a PPI scan present?

A

it plots target range and azimuth information in polar coordinates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

What type of pattern does a Raster scan indicator use to scan the CRT?

A

The electron beam scans a phosphor-coated screen on the CRT in a pattern that goes from left to right and in incremental vertical steps from top to bottom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What components do all indicators have regardless of type?

A

Power supplies, data processing circuits, video circuits, deflection circuits, a CRT, and front panel controls.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

What furnishes the operating voltages for the CRT?

A

The high voltage power supply

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

list the three functions performed by the data processing circuits.

A
  • Control operations and data calculations.
  • Interface.
  • The data distribution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

How doe the video circuits protect the CRT during certain malfunctions?

A

By disabling the CRT high-voltage power supply.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

How do the data processing circuits specify beam position?

A

By using x and y coordinates with the origin at the center of the CRT screen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

List the two types of CRTs

A

electrostatic or electromagnetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

what part of a CRT shields the electron beam from unwanted electric fields?

A

The aqaudag-the tapered portion of the CRT that is lined with a conductive graphite coating.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

What is the primary hazard involved with high-vacuum CRTs?

A

The high vacuum and large surface area of the tube make the tube especially vulnerable to dangerous implosions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

What do front panel controls allow the operator to do?

A

To select input signals and messages, enter operating parameters, and adjust indicator format.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

What are the SIF modes used to interrogate an aircraft?

A

Mode 1, Mode 2, Mode 3/A, and Mode C.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

What is the spacing between P1 and P3 pulses for the four SIF modes?

A

Mode 1=3μsec
Mode 2 = 5μsec
Mode 3/A = 8μsec
Mode C = 21μsec.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

What is the pulse width of P1, P2, P3 pulses?

A

.8 μsec wide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

What is the Mode 4, four-pulse spacing?

A

The mode 4 preamble contains four pulses and a blank space. Each pulse is .5μsec wide, and the pulses are spaced 2μsec apart.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What is the transmitted frequency of the interrogation pulses?

A

1030MHz.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

What is the purpose of transmitting a P2 pulse?

A

To eliminate side lobe reception.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

What the D4, D1, C2, B4, B2, B1, A4, A1 pulses are in a SIF reply code, what is the code?

A

The code will be 5725.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

What pulses must be in the code train to decode a Mode 2 reply of 3752?

A

A1, A2, B1, B2, B4, C1, C4, D2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

What type of code and what are the increments of the altitude information received in Mode C?

A

Mode C utilizes the Gray Code and has 100 feet increments.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

What terms are used for the first and last pulse present in an SIF?

A

Bracket or framing.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

What is the bracket pulse spacing on a normal SIF code train?

A

Bracket or framing pulses are spaced 20.3 μsec apart.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

What signifies that the SIF reply ahs been transmitted by a missile or drone?

A

The presence of an X pulse in the reply code train.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

What is the purpose of a reply pulse that is a 4.35μsec after the last bracket pulse of a SIF code train?

A

It signifies an I/P response has been generated by the aircraft pilot at the request of the operator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

What is the only IFF/SIF mode that can decode civilian emergencies?

A

Mode 3/A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

How is a communications failure emergency received by the ground station?

A

A 7600 emergency reply signifies a communications failure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

Which modes will decode military emergencies?

A

It can be received in any SIF mode, including Mode C.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

Describe a Mode 4 IFF reply.

A

The actual Mode 4 reply received by the ground station consists of three .5μsec pulses, spaced 1.8μsec apart.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

What are the seven functions within the an/upm-155 test set?

A

control and interface, iff simulator, measurement system, interface, front panel, oscilloscope, and power distribution.

104
Q

an/upm-155 Control and Interface

A

provides overall control

105
Q

an/upm-155 IFF Simulator

A

provides calibrated RF output

106
Q

an/upm-155 Measurement

A

measure VSWR

107
Q

an/upm-155 Interface

A

used for automatic testing

108
Q

an/upm-155 Front Panel

A

contains keyboard and display

109
Q

an/upm-155 Oscilloscope

A

used to view signals under test

110
Q

an/upm-155 Power Distribution

A

provides all required voltages

111
Q

Name the part of the AM carrier that varies according to the modulating signal

A

Amplitude

112
Q

What frequencies are present at the output of an AM modulator?

A

Carrier frequency, Carrier plus the Moduling frequency, and Carrier minus the modulating frequency

113
Q

What would be the frequencies at the output of the modulator when you modulate a 500 kHz carrier with a 2 kHz tone?

A

500 kHz, 498 kHz, and 502 kHz

114
Q

In convention AM (DBSEC), what is the relation between the bandwidth required to transmit the signal and the bandwidth of the modulating signal?

A

the bandwidth required is twice the modulating signal.

115
Q

What part of the bandwidth of a DSBEC signal carrier the information signals?

A

the sidebands.

116
Q

State a disadvantage of DSBEC AM

A

It wastes power.

117
Q

What determines the amount of deviation of a FM carrier?

A

The amplitude of the modulating signal.

118
Q

How does the rate of deviation relate to the frequency of the modulating signal?

A

They are directional proportional.

119
Q

Who determines the maximum amount of deviation in FM?

A

The FCC establishes the maximum amount of deviation.

120
Q

How do you determine the modulation index in FM?

A

By dividing the amount of frequency deviation by the frequency of the modulating signal.

121
Q

What is a significant sideband?

A

A sideband that contains at least 1 percent of the total transmitted power.

122
Q

Where do FM sidebands get their power?

A

From the unmodulated carrier.

123
Q

What is the relationship between modulation index and sideband power?

A

A higher modulation index means more power in the sidebands. It is even possible to have all the power in the sidebands and none in the carrier. At this point, any further increase in modulation would start taking power from the sidebands and placing it back in the carrier resulting in a redistribution of power.

124
Q

In PM, what effect does the change in carrier frequency have?

A

None. The frequency change in PM is incidental.

125
Q

Describe the effect the positive and negative alterations of a modulating signal have on the phase of the carrier in PM.

A

During the positive alternation of the modulating signal, the phase of the carrier lags behind the unmodulated carrier. During the negative alternation it leads the unmodulated carrier.

126
Q

When is the carrier at its rest frequency in PM

A

During the constant amplitude part of the modulating frequency.

127
Q

What part of the modulating signal controls the amount of phase shift in PM?

A

Amplitude

128
Q

What part of the modulating signal controls the rate of phase shift?

A

Frequency

129
Q

How can you increase efficiency in digital modulation?

A

By using multilevel encoding.

130
Q

Describe the QPSK process.

A

The input NRZ signal is split into two direction (I-rail and Q-rail), each at half the data rate. The Q-rail signal is phase shifted 90deg and both are modulated in bi-phase modulators. The signals are recombined to form the QPSK signal.

131
Q

What are the two reasons for using higher levels of PSK?

A

To increase capacity or decrease modulation rate.

132
Q

How many bits are grouponed in 8 PSK? 16PSK?

A

3 bit combination; 4 bit combination.

133
Q

What is the main disadvantage of higher level PSK?

A

You need a higher S/N ratio.

134
Q

Define the term ‘digitzation’.

A

The process of converting analog signals into digital signals.

135
Q

Name the four steps of PCM.

A

Band limiting, sampling, quantizing, and encoding.

136
Q

State the main purpose of the band-limiting filter.

A

It ensures the input to the sampler never exceeds a maximum frequency.

137
Q

Define sampling

A

Converting a continuous time signal into a discrete time signal.

138
Q

What part of the pulse train is varied using PAM, PWM, and PPM?

A

PAM=amplitude
PWM=width/duration
PPM=position

139
Q

What is the Nyquist sampling rate?

A

Sampling the input at twice its highest frequency.

140
Q

Which step of PCM assigns discrete amplitude values to the sampled amplitude values?

A

Quantization

141
Q

Name the two methods of quantization.

A

uniform and non-uniform

142
Q

Which method assigns amplitude values based on an equal amplitude range?

A

uniform quantizing

143
Q

With ATM, what is the length of each transmission unit?

A

one character in length.

144
Q

What part of an ATM transmission tells the receiving device that a character is coming and that the character has been sent/

A

The start and stop bits.

145
Q

How does the receiving device determine whether it has received a correct character?

A

By summing the 1 bits.

146
Q

Why do some networks elect to send synchronous transmissions?

A

To reduce the overhead costs of data transmission.

147
Q

How does synchronous transmission handle characters?

A

Synchronous transmission blocks many characters together for transmission.

148
Q

What does VRC check each incoming character for?

A

odd or even parity.

149
Q

What is even parity?

A

there is an even number of 1’s in the bit pattern for each character.

150
Q

What is the difference between VRC and LRC?

A

VRC checks each character for odd parity; LRC checks an entire horizontal line within a block for odd or even parity.

151
Q

What transmitted character does the receiver use to determine if a transmission was error-free?

A

BCC

152
Q

When using the checksum method of error detection, what binary number is used to divide the sum of all the characters in order to derive the checksum?

A

255

153
Q

How does the CRC method of error detection determine the dividend when computing the BCC?

A

CRC treats the binary ones and zeros in the frame address, control, and information fields as one long binary number.

154
Q

How effective is CRC at detecting errors in most applications?

A

99%

155
Q

How does ARQ work?

A

The receiver automatically sends a retransmittal request to the sender if it finds an error in a received frame.

156
Q

What is the most common method of error correction?

A

ARQ

157
Q

On what type of circuits is forward error control most useful?

A

On circuits with extremely high error rates or on 1-way broadcast circuits

158
Q

Using forward error control, at which end of the transmission link are errors corrected?

A

receiving end

159
Q

using forward error control, what is the transmitter’s function in error correction?

A

To transmit multiple copies of the same message to the distant end.

160
Q

Using forward error control, what is the receiver’s function in error correction?

A

to compare all copies of transmitted message, then reconstruct the message using the good portions of the message copies received.

161
Q

how doe we define fiber optics?

A

a technology in which light is transmitted along the inside of a thin, flexible glass or plastic fiber.

162
Q

What is the most common use of fiber optics?

A

a transmission link connecting two electronic devices or circuits.

163
Q

One of the advantages of fiber optics is high bandwidth. What is bandwidth?

A

high bandwidth, the information-carrying capacity of a carrier wave.

164
Q

Compare attenuation in fiber optics to attenuation in metallic cables.

A

optical fibers have less attenuation (power loss) than metallic cables.

165
Q

Optic fibers are made of dielectric materials. How are fiber optic cables affected by electromagnetic interference?

A

Fiber optic cable does not radiate or absorb energy through its outer jacket, it is immune to this type of interference.

166
Q

Why are communications over fiber optic cables highly secure?

A

it is virtually impossible to tap a fiber optic cable unnoticed because the light-carrying part of the core is so affected by the tap that it is easily detected. Since fiber does not radiate energy, other eavesdropping techniques are useless.

167
Q

Why do we use the metric system to measure fiber optics?

A

because fiber optic dimensions, weights, and frequencies are generally very small or very large.

168
Q

micron

A

one millionth of a meter

169
Q

nanometer

A

one billion of a meter

170
Q

millimeter

A

one thousandth of a meter

171
Q

micrometer

A

one millionth of a meter

172
Q

Gigahertz

A

One million Hertz

173
Q

What are the components of a typical fiber optic cable?

A

core, cladding, and protecting coating (buffer)

174
Q

Describe the fiber core

A

It is often made from a solid section of ultra pure, ultra transparent silicon dioxide or fused quartz(glass), but may also be made of plastic.

175
Q

What is the purpose of the fiber cladding around the core? what material is it made of?

A

provide the reflective surface that allows light to propagate along the core to the distant end. it is a solid section of transparent glass or plastic with a much lower density than the core.

176
Q

List the three major types of buffering designs.

A

tight buffer tube
loose tube
ribbon

177
Q

How is a loose-tube buffer formed?

A

optical fibers are usually coated with a thin layer of acrelate (250um diameter) and then several fibers are placed in a hard plastic tube with an inside diameter several times larger than the diameter of the fiber.

178
Q

What characteristic of the carrier wave does the energy possessed by the photon determine?

A

the frequency.

179
Q

Photon particles are a part of what spectrum?

A

electromagnetic spectrum

180
Q

What is the frequency range of infrared light?

A

750 to 1500 nm

181
Q

describe the refractive index

A

it’s the ratio of the speed of light in a vacuum to its speed in a given medium.

182
Q

what do we call the phenomenon that occurs when light bends while passing through material of different density?

A

refraction

183
Q

describe reflection

A

reflection is the bouncing back of light from an object.

184
Q

what happens to light when it passes from a higher index material to a lower one?

A

it’s bent away from the normal.

185
Q

Describe the critical angle.

A

The angle of incidence that causes the angle of refraction to equal 90 degrees.

186
Q

What does snell’s law state?

A

if a ray of light enters a junction of two media of different refractive indices beyond the critical angle, the light is totally internally reflected.

187
Q

what is numerical aperture?

A

it’s a fiber’s inherent light-gathering capability.

188
Q

How is light affected in a cable that has a large numerical aperture?

A

dispersement is increased.

189
Q

how does a fiber reach equilibrium-mode distribution?

A

over distance

190
Q

How do we express the amount of power in a fiber optic link/

A

in microwatts or milliwatts

191
Q

To what can we attribute fiber-to-fiber connection power losses

A

Acceptance con/ejection cone mismatches, fiber core diameter mismatches, connector insertion loss, and intrinsic fiber loss.

192
Q

What unit of measurement do we use to express fiber optic attenuation?

A

decibels per kilometer (dB/km)

193
Q

list the two main causes of attenuation in optical fibers

A

absorption

Rayleigh scattering

194
Q

what is spectral attenuation

A

it is related to light wavelengths and requires careful balancing of light sources and fibers.

195
Q

How can we reduce Fresnel losses in a fiber?

A

by using index-matching fluids.

196
Q

What effect does nuclear radiation have on fiber optic cables?

A

Increased attenuation caused by absorption and scattering

197
Q

what happens when a fiber’s bending radius is exceeded

A

it experiences macrobends or microbends

198
Q

What is dispersion in a fiber optic cable?

A

the spreading out of the light in a fiber.

199
Q

How does dispersion affect the bandwidth?

A

it limits it

200
Q

what causes each of the two main types of dispersion?

A

Modal dispersion is caused by the different paths of light in various modes. Material dispersion is caused from differ velocities of different wavelengths.

201
Q

How de we measure dispersion?

A

in nanoseconds per kilometer (ns/Km).

202
Q

Optical fibers are normally composed of what materials?

A

entirely of glass or silica, plastic-clad silica, or all plastic.

203
Q

How are optical fibers generally classified?

A

By the number of modes and the core’s refractive index profile.

204
Q

What is a mode?

A

a mathematical and physical concept describing the propagation of electromagnetic waves, but for our purpose it’s simply a path that light can take in traveling down a fiber.

205
Q

The refractive index is a relationship between what elements of a fiber?

A

the core’s refractive index and the cladding’s refractive index.

206
Q

Which fiber classification has the highest dispersion factor?

A

multimode step-index

207
Q

Which fiber type is very efficient for long distance and very high speed applications, but is hard to work with?

A

single mode step-index

208
Q

Which control do you use to select the 8025A meter’s different measurement functions?

A

the rotary switch

209
Q

What two ranges of DC voltages can you measure using the 8025A multimeter?

A

-1000 to +1000 vDC and -320 to +320 mVDC

210
Q

How can you electrically isolate a resistor from its circuit when measuring resistance?

A

by disconnecting one of the resistor’s soldered connections.

211
Q

How do you determine if you’re testing a ‘good’ diode with the 8025A?

A

Placing the leads across a good diode produce ‘OL’ in the display while reversing the leads produces a continuous audible tone.

212
Q

what does low-insulation resistance cause?

A

high attenuation, crosstalk, and noise on the circuit

213
Q

define insulation resistance

A

opposition to the passage of electrical current through the insulation.

214
Q

What terms do we use to measure insulation resistance?

A

ohms or megohms

215
Q

How is insulation resistance affected as the thickness of the insulating material increases and how is it affected as the area of the conductor is increased (respectively)?

A

increases as thickness increase; decreases as area of conductor increases.

216
Q

What is the minimum distance between earth ground test probes?

A

25 feet

217
Q

how many probes are used in a normal earth ground test?

A

3

218
Q

What is the required earth ground reading for communications facilities?

A

10 ohms or less

219
Q

What is normally used as an earth ground at deployed locations?

A

8 ft copper rod

220
Q

What are some ways to lower earth resistance?

A

Deeper ground rod, parallel ground rods, or electrolytic salt solution

221
Q

What type of display does the oscilloscope present?

A

amplitude versus time

222
Q

One which axes of an oxcillosocope are voltage, time, and depth information presented?

A 
voltage = vertical
time = horizontal
depth = intensity
223
Q

What is the purpose of the delay line at the input of the vertical amplifier?

A

it allows the sweep generator circuitry time to start a sweep before the signal reaches the cathode ray tube vertical deflection plates. This enables you to view the leading edge of the signal waveform.

224
Q

What position of the input coupling switch do we use to view digital-type or square wave signals?

A

dc coupling

225
Q

What is the basic purpose of the oscilloscope probe?

A

to provide isolation for scope inputs and prevent circuit loading.

226
Q

list four types of probes

A

high resistance
passive divider/x1 probes
active
current probes

227
Q

What is the typical input impedance of most oscilloscopes?

A

one megohm shunted by 20 pF of capacitance

228
Q

When making an amplitude measurement with the oscilloscope and the source impedance is unknown, when can you achieve greatest accuracy?

A

when the Z in of the probe is maximum

229
Q

What is the biggest difference between digital storage oscopes and analog scopes?

A

digital storage oscopes digitize the input signal for storage or display.

230
Q

What is the function of charged coupled devices in the digital storage oscilloscope’s signal sampling process?

A

charged coupled devices accept fast-changing data and send it to the analog-to-digital converter at a slower rate for more accurate data collection.

231
Q

List two digital storage oscope sampling techniques

A

real time

repetitive sampling

232
Q

Define interpolation

A

This is a process that estimates what the signal will look like between samples and ‘fills in the blanks’ between data points.

233
Q

What are the two types of interpolation?

A

linear and sine

234
Q

What is the difference between sequential and random sampling?

A

sequential sampling takes a sample at a predetermined time after the trigger in a progressive order until there are enough data points to reconstruct several periods of the signal. Random sampling takes samples at an undetermined point on a signal and stores them.

235
Q

What is a common cause of aliasing?

A

Undersampling due to having the time base turned down too low, thus reducing the sample rate for a frequency that is too high for a given setting.

236
Q

Describe the three types of acquisition modes.

A

Sample mode
Peak detect mode
Averaging mode

237
Q

What is the function of the acquisition controls?

A

to set the digital storage oscope’s sampling rate, determine what type of processing is to occur and how many record points can be shown.

238
Q

A signal generator is primarily used to troubleshoot what type of circuit?

A

frequency sensitive or tuned circuit

239
Q

What range of frequencies does the audio signal generator provide?

A

20Hz to 20kHz

240
Q

What range of frequencies does the radio frequency signal generator provide?

A

10kHz to 10GHz

241
Q

What do you use to match the input impedance of a circuit under test?

A

an attenuator

242
Q

What are the major components of a basic signal generator?

A

power supply, oscillator, amplifier, an output control

243
Q

Why are voltage regulation circuits necessary?

A

to ensure stability of the oscillator in generators deriving power from 115v AC sources.

244
Q

What element of a resistance-capacitance oscillator in a commercial signal generator is used as a variable element?

A

capacitance

245
Q

What types of modulated signals are possible with the radio frequency generator?

A

either sine waves, square waves, or pulses of varying duration.

246
Q

List some applications of the radio frequency generator.

A
  • verify transmission w/in designated frequency ranges by comparing tx outputs with known radio frequencies.
  • align a receiver by injecting the system with range-standard modulated radio frequency.
  • check transmission lines and antenna systems for proper operation.
247
Q

The decibel is part of what larger unit of measure?

A

Bel

248
Q

A power ratio of 10000:1 can be represented by how many bels?

A

four

249
Q

What’s the most commonly used industry standard power reference level?

A

The 1 milliwatt standard

250
Q

How is the 1 milliwatt standard expressed

A

dBm

251
Q

What does every 3 dB increase in gain do to the power level?

A

roughly doubles it

252
Q

How much more power is available at 6 dBm than at 3 dBm?

A

Twice as much.

253
Q

List at least three of the units that can displayed by th eHP 436A power meter

A

watts, milliwatts, microwatts, nanowatts, dBm, and relative dB

254
Q

What is a major difference between the oscope and the spectrum analyzer?

A

the oscope displays frequency information in the time domain, whereas the spectrum analyzer displays frequency information in the frequency domain

255
Q

What provides the time reference for the precise timing and where does this function take place?

A

a quartz-crystal oscillator inside the counter.

RADar (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions