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Comms > Comm 2-3 - Modulation Systems > Flashcards

Comm 2-3 - Modulation Systems Flashcards

1
Q

Review Questions

What are the 3 main components of a basic radio system?

A

Transmitter, receiver and antenna

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2
Q

Review Questions

What are the two main sections in a transmitter?

A

RF section and modulator section

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3
Q

Review Questions

What is modulation?

A

The process of varying a carrier signal so that it can convey a message

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4
Q

What are the different forms of modulation?

A

AM, FM and digital (pulse, phase and frequency shift keying)

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5
Q

Describe amplitude modulation

A

Amplitude of carrier wave is increased/ decreased IAW changes in the audio signal to be conveyed

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6
Q

Where is power concentrated in the AM method?

A

Carrier frequency and in two adjacent sidebands

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7
Q

Sum frequency or upper side band (USB) =

A

carrier wave + audio frequency

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8
Q

Sum frequency or lower side band (LSB) =

A

carrier wave - audio frequency

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9
Q

Describe SSB modulation and it’s redundant feature.

A

Form of AM where only one side band is used to convey info.

Since USB and LSB are mirror images, it is redundant to send both sidebands.

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10
Q

What are the 3 SSB advantages?

A

Less power required for transmission (carrier wave takes 2/3 of antenna power)

Approx 1/2 of bandwidth required

Intercepted signal is better quality

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11
Q

Describe Frequency Modulation

A

Frequency of carrier wave is modified to reflect changes in the audio signal to be conveyed.

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12
Q

What determines the frequency change to the resting carrier frequency for FM modulation?

A

The loudness or amplitude

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13
Q

True or false

The pitch or frequency of the audio signal determines the rate at which the carrier frequency is affected.

A

True

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14
Q

What are some advantages of FM Vs AM?

A

FM signal-to-voice ratio is better than AM

FM has better fidelity at reception

FM allows for transmission of signal at constant power (because amplitude does not change)

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15
Q

What are some disadvantages of FM Vs AM?

A

FM needs more complex equipment

FM requires more bandwidth

Restricted to LOS due to high frequencies (29.999 and above)

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16
Q

What are some examples of digital modulation?

A

Phase

Pulse

Frequency Shift Keying

17
Q

What sort of data can you send with digital modulation?

A

Text, picture/ videos and tactical information

18
Q

What are the advantages of digital modulation?

A

Send more types
Encryption
Higher fidelity
Better signal to noise ratio

19
Q

What are some disadvantages of digital modulation?

A

More complex equipment

More complex transmission protocols

Requires Error Correction codes

20
Q

Describe Phase Modulation

A

A form of modulation where the phase of the carrier wave is varied by the intelligence signal

Normally used to transmit digital signals

21
Q

What is Pulse Modulation?

A

The carrier wave is not a continuous alternating wave, but a train of discrete pulses.

22
Q

What is Frequency Shift Keying

A

A form of modulation where a carrier signal of constant amplitude is frequency modulated to 0 and 1.

23
Q

What are some examples of digital modulation in aviation?

A

Tactial common data link
SATCOM
Link 16 / Link 22
Future Air Nav System (FANS)

24
Q

Review Questions

What is a sub-form of AM?

A

SSB Modulation

25
Q

Review Questions

What are three advantages of SSB Modulation?

A

More effective use of avail EM spectrum
Better quality of intercepted signal
Higher % of power can be used to tx the intelligence

26
Q

Review Questions

Why does the SSB modulation provide a better quality of sound at reception?

A

Intercepted signal is of better quality

better signal-to-noise ratio compared to full sideband modulation

27
Q

Review Questions

What is the main operational disadvantage of FM?

A

Restricted to LOS due to its use of higher frequencies.

28
Q

Review Questions

What are the three digital forms of modulation?

A

Phase, Pulse and Frequency Shift Keying

Comms (9 decks)

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