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CDC 3D153 > Volume 1 URE > Flashcards

Volume 1 URE Flashcards

1
Q

What are the three general categories used to produce modulation in radio frequency (RF) transmission today?

A

Amplitude, frequency, phase

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2
Q

When the modulating signal and carrier signal are combined within a modulator, the output signal contains ______.

A

carrier, upper sideband, and lower sideband

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3
Q

If a carrier frequency of 1 MHz and a modulating tone of 10 kHz goes to the modulator, the output signal includes ________.

A

1.01 MHz, 1 MHz, and .99 MHz

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4
Q

The bandwidth of an amplitude modulated signal is _________.

A

two times the modulating signal

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5
Q

If an oscilloscope displays a modulation envelope having an Emax of 200 volts and an Emin of 20 volts, what is the modulation percentage?

A 
%mod = Emax-Emin/Emax+Emin • 100
%mod = 200-20/200+20
%mod = 180/220
%mod = 81.8
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6
Q

Which statement concerning bandwidth is true?

  • Overmodulating increases bandwidth because the distortion produces harmonics
  • Undermodulating increases bandwidth because the distortion produces harmonics
  • Overmodulating increases bandwidth because the output’s amplitude is increased
  • Undermodulating increases bandwidth because the output’s amplitude is decreased
A

Overmodulation increases bandwidth because the distortion produces harmonics.

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7
Q

The output of an oscillator in a frequency modulation (FM) modulator increases in frequency with each __________.

A

positive half cycle of the modulating signal

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8
Q

In frequency modulation, a significant sideband contains at least what percentage of the total transmitted power?

A

1%

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9
Q

What is the formula to find the modulating index?

A

Deviation divided by the frequency of modulating signal.

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10
Q

A 5 kHz modulating signal has enough peak voltage to cause a deviation of 15 kHz. What is the modulation index?

A

MI = Deviation/Modulating signal frequency

MI = 15/5

MI = 3

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11
Q

What is the name given to the narrow frequency band between adjacent stations which prevents frequency modulated sidebands from overlapping?

A

Guard band

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12
Q

In phase modulation, what part of the carrier signal is varied?

A

Phase

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13
Q

In phase modulation, the carrier’s __________.

A

phase is shifted at the rate of the modulating signal

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14
Q

What is the first step in the pulse code modulation process?

A

The analog signal is band limited.

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15
Q

What part of the pulse code modulation process converts a continuous time signal into a discrete time signal?

A

Sampling

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16
Q

In asynchronous transmissions, what bit is used by the receiving device to verify that the transmission was received correctly?

A

The parity bit

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17
Q

If an error should occur, what transmission is lost in a synchronous transmission?

A

An entire block of data

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18
Q

When using vertical redundancy check, what significance does the amount of ones have in a data bit pattern?

A

It determines parity

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19
Q

What error detection method is used for checking a data block greater than 512 and is about 99% effective in most applications?

A

Cyclic redundancy check

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20
Q

When using forward error control as a method of error correction, where does error correction take place?

A

Receiving end

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21
Q

Light sources that are applicable to fiber optic waveguides are light-emitting diodes and ________.

A

semiconductor laser diodes

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22
Q

What type of light is emitted from a laser?

A

Coherent

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23
Q

What are the two main types of photodetectors?

A

Positive intrinsic negative and avalanche photodiode

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24
Q

What photodetector converts one photon to one electron?

A

Positive intrinsic negative diode

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25
Q

Which repeater amplifies optical signal without converting to and from the electrical domain?

A

Optical amplifiers

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26
Q

A short section of single fiber cable that has a connector at each end is called a ________.

A

patch cord

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27
Q

Which fiber optic connector uses quick-release, keyed bayonet couplings that are preferred in situations where severe vibrations are not expected?

A

Straight tip (ST)

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28
Q

High altitude electromagnetic pulse is a wideband phenomenon that involves which frequency range?

A

1 Hz to 1GHz

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29
Q

High-altitude electromagnetic pulse environment protection is important for critical, time urgent mission systems because __________.

A

High altitude EMP is the only nuclear environment that may be imposed on many systems simultaneously with the expenditure of very few weapons.

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30
Q

A system-generated EMP is a problem for satellites and reentry vehicles that are _________.

A

directly exposed to nuclear radiation from high-altitude bursts

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31
Q

Which distinct region of the source region electromagnetic pulse is produced by the interactions between the weapon products and the earth’s atmosphere?

A

Source

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32
Q

Atmospheric disturbances from initial nuclear radiation on higher frequencies affect communications with ________.

A

scintillation effects

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33
Q

Currents and voltages induced on power lines, cable links, and pipelines by EMP are called _________.

A

long-line effects

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34
Q

Which type of filters are always used in combination with surge arrestors?

A

Linear

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35
Q

If the interference can be eliminated by disconnecting the receiving antenna, the source of the disturbance is most likely ___________.

A

external to the radio

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36
Q

Little or no variation in the strength of the interfering signal when moving the antenna for short distances normally indicates _____________.

A

enemy jamming

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37
Q

What type of electromagnetic interference occurs when a receiver responds to off-frequency signals?

A

Spurious responses

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38
Q

Which type of intermodulation interference varies with temperature and weather conditions?

A

Rusty bolt

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39
Q

What man-made noise results from voltage surges, arcing, or corona discharges?

A

Power line

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40
Q

How can you normally eliminate electromagnetic interference noise bursts causes by sodium and mercury vapor lights that have stopped working while power is still applied?

A

Change the bulb

41
Q

What Air Force program is used to resolve an electromagnetic interference incident?

A

Spectrum interference resolution

42
Q

At what level does the Air Force want electromagnetic interference problems resolved?

A

Affected Unit

43
Q

What do you do when you are reasonably sure electromagnetic interference exists?

A

Systematically gather data for analysis

44
Q

Who is initially responsible for reporting electromagnetic interference?

A

The operator

45
Q

Who is tasked to provide interference resolution to the unified commanders?

A

Joint spectrum center

46
Q

Which feature of the Fluke 8025A multimeter is used to select various measurement functions?

A

Rotary switch

47
Q

Which part of the Fluke 8025A’a display section indicates the absolute value of the input?

A

Analog bar graph

48
Q

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?

A

The touch-hold button

49
Q

When you use the Fluke 8025A, which voltage range do you select to measure 50 volts DC?

A

Volts DC

50
Q

When testing a diode with the 8025A, the leads across a “good” diode produces an “OL” on the display in one direction while reversing the leads produces __________________.

A

A continuous audible tone

51
Q

How are voltage, time, and depth represented on the oscilloscope display?

A

Voltage on the vertical axis

Time on the horizontal axis

Depth as a variation if the intensity

52
Q

Which oscilloscope’s input coupling position allows one to view both AC and DC components of the input signal?

A

DC

53
Q

Which oscilloscope probe is essentially just a shielded piece of wire?

A

Passive 1:1

54
Q

Which probe lets you use the oscilloscope to measure higher voltage levels, raises the input impedance, does not require a bias voltage, and attenuates noise?

A

Passive divider, 10:1

55
Q

Which probe does not need to actually make contact with the circuit under test?

A

Current

56
Q

Sampled data points are stored in the memory of a digital storage oscilloscope as ______________.

A

waveform points

57
Q

What area of a digital storage oscilloscope takes digitized samples and performs numerous manipulations on the data including measuring the rise and fall times, periods, time intervals, and math computations?

A

Microprocessors

58
Q

What type of sampling does a digital storage oscilloscope normally use on single-shot or seldom-occurring signals?

A

Real-time

59
Q

In real-time sampling, what type of interpolation is used when measuring pulse waves?

A

Linear

60
Q

In acquiring a 4K record length on a digital storage oscilloscope, how many samples can you view at one time?

A

1000

61
Q

What pattern simulator section of the bit error rate test set accepts a 48-bit parallel word and generates a serial pattern?

  • 48 bit transmitter only
  • 48 bit register and 8-bit word display
  • Psuedo random noise generator
  • Psuedo random noise comparator
A

48-bit transmitter only

62
Q

Which pattern simulator section of a bit error rate test set controls the clock selector and selects either the external clock or the internal clock for processing?

A

Data/clock select encoder

63
Q

Which is the primary means of measuring the quality of transmitted digital information, and how is this means derived?

A
  • Bit error rate (BER)

* BER is derived from the ratio of the number of bits in error to the total bits transmitted

64
Q

Which bit rate is used for a bit error rate test on a 64 kbps data circuit?

A

64 kbps

65
Q

On the bit error rate test set, the 25-pin connectors are designed to operate with data modems to _____________.

A

simplify connection of test equipment to the modem under test and to carry the necessary signaling and handshake signals for modem operations

66
Q

How often must system grounds be tested?

A

Periodically

67
Q

What type of equipment helps resolve intermittent electrical problems because of poor grounding?

A

Earth ground tester

68
Q

Resistance reading on the ground under test is plotted on a graph of _____________.

A

Resistance versus distance

69
Q

A known current is generated by the earth ground tester between the earth ground electrode and the ____________.

A

Auxiliary current probe

70
Q

What component of a protocol analyzer discards frames based on its definition or activates a trigger based on the trigger definition?

A

Filter

71
Q

What protocol analyzer test window provides information concerning the network utilization and frame error that are related to a specific protocol?

A

Protocol statistics

72
Q

What protocol analyzer test window automatically runs in the background when the protocol analyzer application is activated?

A

Node discovery

73
Q

What protocol analyzer test window provides information concerning the bandwidth utilization and number of connections that are related to specific nodes?

A

Connection statistics

74
Q 
Which of these is not an application of a radio frequency generator?
• Verifying transmitter frequency
• Troubleshooting receivers
• Checking antenna systems 
• Aligning galvanometers
A

Aligning galvanometers

75
Q

A power reading that uses the abbreviation dBm indicates the _____________.

A

ratio of decibels relative to a 1-milliwatt standard

76
Q

The measurable frequency and power ranges of the HP 436A power meter are determined by the ___________.

A

power sensor

77
Q

During what operation is the radio frequency blanking output used on the HP 436A power meter?

A

During the automatic zeroing operation

78
Q

The two switches on the front panel of the wattmeter correspond to the _____________.

A

power range of the forward element

79
Q

What feature is useful for making adjustments to optimize any of the parameters which the wattmeter produces?

A

Peaking aid

80
Q

Which measurement is not made with a spectrum analyzer?

  • Frequency stability
  • Peak-peak voltage
  • Amplitude modulation
  • Subcarrier oscillator outputs
A

Peak-peak voltage

81
Q

Which electronic counter measurement represents the average bit-to-bit time of an input signal?

A

Period

82
Q

What are the four classes of electronic counters?

A
  • Frequency counters
  • Universal counters
  • Microwave counters
  • Reciprocal counters
83
Q

What function is not part of the communication service monitor?

  • Radio frequency generator
  • Analog multimeter
  • Oscilloscope
  • Receiver
A

Analog multimeter

84
Q

What is one reason for modulation of low frequency signals for transmission over long distances?

A

Ease of radiation

84
Q

What operational capability of the communication service monitor receives amplitude and frequency modulated signals?

A

Receiver

86
Q

What operational capability of the communication service monitor produces sine, square, and triangle waveforms?

A

Function generator

87
Q

Why should the number of splices be controlled during fiber optic installation?

A

To minimize transmission loss

88
Q

What is a function of Air Force Communications Special Instructions?

A

Issuance of optional equipment modifications

89
Q

What are the three main functions of grounding?

A
  • Personnel safety
  • Equipment protection
  • Noise reduction
90
Q

What facility ground subsystem uses surge arrestors?

A

Lightning protection

91
Q

What facility ground subsystem is also called the safety ground?

A

Fault protection

92
Q

Bonds in the earth electrode subsystem normally are direct permanent bonds and do not exceed a resistance of _____________.

A

1 milliohm

93
Q

What kind of bond is a signal reference bond, usually?

A

Mechanical

94
Q

What are the two basic functions of shielding?

A
  1. Prevent interference between multiple emanating systems

2. Minimize compromising emanations

95
Q

What equipment should be designated as RED?

A

Equipment processing clear-text classified information

96
Q 
Which of these is considered a primary cell?
• Nickel cadmium
• Carbon zinc
• Lead-acid
• Lithium
A

Carbon zinc

97
Q

What power line fault category is more typically referred to as Electro-Magnetic Interference and Radio Frequency Interference?

A

Noise

98
Q

What type of uninterruptible power supply (UPS) has traditionally been referred to as offline by technicians?

A

Passive standby

99
Q

How many phases of generator power are usually required for industrial and commercial applications?

A

Three

CDC 3D153 (5 decks)

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