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ET1 SEP EXAM 2018 > NAVEDTRA 14184A, NAVY ELECTRICTY AND ELECTRONICS TRAINING SERIES, MODULE 12-MODULATION > Flashcards

NAVEDTRA 14184A, NAVY ELECTRICTY AND ELECTRONICS TRAINING SERIES, MODULE 12-MODULATION Flashcards

1
Q

Which year was the first practical telegraph established in London, England?

A

1838

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2
Q

Which year did Marconi demonstrate the first practical wireless transmitter?

A

1897

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3
Q

Which year was the first successful transatlantic transmissions achieved?

A

1902

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4
Q

What is the ability to impress intelligence upon a transmission media?

A

Modulation

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5
Q

What is the mixing two frequencies across a nonlinear impedance known as?

A

Heterodyning

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6
Q

What is the basic alternating waveform for all complex waveforms?

A

Sine wave

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7
Q

What is generated by rotating a coil in the magnetic field between two magnets?

A

Alternating current

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8
Q

What indicates how much of a cycle has been completed at any given instant?

A

Phase angle

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9
Q

Which cycle property is the elapsed time from the beginning of a cycle to its completion?

A

Period

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10
Q

Which sine wave property is determined by its physical length?

A

Wavelength

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11
Q

The frequencies involved in normal speech vary from a low of about 90 hertz for a deep bass to as high as what for a high soprano?

A

10 KHz

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12
Q

What is the ability known as to faithfully reproduce the input in the output?

A

Fidelity

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13
Q

What is the minimum frequency range that can be used for the transmission of speech?

A

500 to 2,000 hertz

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14
Q

In the modulation process, waves from the information source are impressed onto a radio-frequency sine wave called a what?

A

Carrier

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15
Q

What is an information wave normally referred to as?

A

Modulating wave

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16
Q

Output rises and falls directly with the input in which type of devices?

A

Linear

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17
Q

Which type of impedance is one in which the resulting current is not directionally proportional to the change in the applied voltage?

A

Nonlinear

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18
Q

What is the sum of two individual sine waves?

A

Complex waveform

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19
Q

What is the process of combining two or more frequencies in a nonlinear impedance which results in the production of new frequencies called?

A

Heterodyning

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20
Q

How can the heterodyning process be analyzed?

A

Spectrum analysis

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21
Q

What is the amound of the frequency spectrum that signals occupy known as?

A

Bandwidth

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22
Q

How many conditions must be met in a circuit for heterodyning to occur?

A

Two

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23
Q

What refers to any method of varying the amplitude of an electromagnetic carrier frequency in accordance with the intelligence to be transmitted by the carrier?

A

Amplitude modulation

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24
Q

What is a radio-frequency wave suitable for modulation by the intelligence to be transmitted?

A

Carrier frequency

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25
Q

What is on-off keying referred to as when applied to a continuously oscillating radio-frequency source?

A

CW signaling

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26
Q

What was the first type of modulation used?

A

Continuous wave

27
Q

What is a system of on-off keying developed for telegraph that is capable of passing intelligence over wire at an acceptable rate?

A

Morse code

28
Q

What is one of the best methods for keying amplifier stages in transmitters?

A

Blocked-grid keying

29
Q

Which type of transmission has a high degree of clarity under severe noise conditions, long-range operation, and narrow bandwidth?

A

Continuous-wave

30
Q

What is required when keying takes place in an intermediate or final amplifier operating at comparatively high power?

A

Buffer

31
Q

Oscillators are too unstable for direct frequency control in what type of transmitters?

A

VHF and UHF

32
Q

In practice, the multiplication factor (number of times the input frequency is multiplied) is seldom larger than what in any one stage?

A

Five

33
Q

Who developed the principles on which modern communications are built?

A

Alexander Graham Bell

34
Q

What is an energy converter that changes sound energy into electrical energy?

A

Microphone

35
Q

What has the largest voltage output for a given mechanical stress and is the most commonly used crystal in microphones?

A

Rochelle salt

36
Q

Crystal microphones are delicate and must be handled with care. Exposure to temperatures above what may permanently damage the crystal unit?

A

125 degrees F

37
Q

The dynamic microphone has a uniform response over a frequency range that extends from 40 to what?

A

15,000 hertz

38
Q

An AM transmitter can be divided into what two major sections according to the frequencies at which they operate?

A

RF and AF

39
Q

What are all of the sum frequencies above the carrier spoken of collectively as?

A

Upper sideband

40
Q

What is the resultant wave called when the carrier and sidebands are combined in a single impedance and viewed simultaneously with an oscilloscope?

A

Modulation envelope

41
Q

Which agency assigns carrier frequencies for radio stations in the standard broadcast band?

A

Federal Communications Commission (FCC)

42
Q

The standard AM broadcast band starts at 535 kilohertz and ends at what?

A

1,605 kilohertz

43
Q

How many sidebands accompany a carrier wave which has been modulated by voice or music signals?

A

Two

44
Q

What generates unwanted (SPURIOUS) sideband frequencies

A

Overmodulation

45
Q

To measure degrees of modulation less than 100 percent, what can you use to indicate the relative magnitudes of the rf carrier and the audio-modulating signal?

A

Modulation factor

46
Q

Which two categories are modulator circuits usually placed into?

A

High or Low

47
Q

What does the FCC define in the Code of Federal Regulations as “modulation produced in the plate circuit of the last radio stage of the system”?

A

High-Level modulation

48
Q

What is the simplest modulator available which is also the easiest to adjust for proper operation?

A

Plate modulation

49
Q

Which action in the plate modulator effectively changes an audio frequency to a different part of the frequency spectrum?

A

Heterodyning

50
Q

What is widely used in portable and mobile equipment to reduce size and power requirements?

A

Control-grid modulator

51
Q

What is generally employed when audio power is limited and distortion of the grid-modulated circuit cannot be allowed?

A

Cathode modulator

52
Q

What is the process of re-creating original modulating frequencies (intelligence) from the RF carrier referred to as?

A

Demodulation

53
Q

Which type of modulation consists of on-off keying of a carrier wave?

A

Continuous-Wave (CW)

54
Q

Which reception method is highly selective and allows little interference from adjacent cw stations?

A

Heterodyne

55
Q

What is used to receive short-wave code signals because it is easy to adjust and has high sensitivity and good selectivity?

A

Regenerative detector

56
Q

What refers to any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance with the message intelligence that is to be transmitted?

A

Amplitude modulation

57
Q

What is normally used where large input signals are supplied and linear output is required?

A

Series-diode detector

58
Q

What is often used in receivers to supply an amplified detected output?

A

Common-Emitter Detector

59
Q

What is essentially a tank circuit which is turned into a frequency either slightly above or below the FM carrier frequency?

A

Slope detector

60
Q

What uses a double-tuned RF transformer to convert frequency variations in the received FM signal to amplitude variations?

A

Phase-shift discriminator

61
Q

The output of the Foster-Seeley discriminator is affected not only by the input frequency, but also to a certain extent by what?

A

Input amplitude

62
Q

What occurs when an input frequency higher than the center frequency is applied to the discriminator circuit and the current and voltage phase relationships change?

A

Phase shift

63
Q

What uses the amplitude of a pulse-amplitude modulated (PAM) signal or the duration of a pulse-duration modulated (pdm) signal to charge a holding capacitor and restore the original waveform?

A

Peak detection

ET1 SEP EXAM 2018 (28 decks)

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