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Ham Extra 2016-2020 > E8 Signals and Emissions > Flashcards

E8 Signals and Emissions Flashcards

1
Q

E8A01 (A)

What is the name of the process that shows that a square wave is made up of a sine wave plus all of its odd harmonics?

A

A. Fourier analysis

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2
Q

E8A02 (C)

What type of wave has a rise time significantly faster than its fall time (or vice versa)?

A

C. A sawtooth wave

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3
Q

E8A03 (A)
What type of wave does a Fourier analysis show to be made up of sine waves of a given fundamental frequency plus all of its harmonics?

A

A. A sawtooth wave

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4
Q

E8A04 (B)

What is “dither” with respect to analog to digital converters?

A

B. A small amount of noise added to the input signal to allow more precise representation of a signal over time

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5
Q

E8A05 (D)

What would be the most accurate way of measuring the RMS voltage of a complex waveform?

A

D. By measuring the heating effect in a known resistor

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6
Q

E8A06 (A)

What is the approximate ratio of PEP-to-average power in a typical single-sideband phone signal?

A

A. 2.5 to 1

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7
Q

E8A07 (B)

What determines the PEP-to-average power ratio of a single-sideband phone signal?

A

B. The characteristics of the modulating signal

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8
Q

E8A08 (C)

Why would a direct or flash conversion analog-to-digital converter be useful for a software defined radio?

A

C. Very high speed allows digitizing high frequencies

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9
Q

E8A09 (D)

How many levels can an analog-to-digital converter with 8 bit resolution encode?

A

D. 256

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10
Q

E8A10 (C)

What is the purpose of a low pass filter used in conjunction with a digital-to-analog converter?

A

C. Remove harmonics from the output caused by the discrete analog levels generated

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11
Q

E8A11 (D)

What type of information can be conveyed using digital waveforms?

A

A. Human speech
B. Video signals
C. Data
D. All of these choices are correct

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12
Q

E8A12 (C)

What is an advantage of using digital signals instead of analog signals to convey the same information?

A

C. Digital signals can be regenerated multiple times without error

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13
Q

E8A13 (A)

Which of these methods is commonly used to convert analog signals to digital signals?

A

A. Sequential sampling

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14
Q

E8B01 (D)
What is the term for the ratio between the frequency deviation of an RF carrier wave and the modulating frequency of its corresponding FM-phone signal?

A

D. Modulation index

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15
Q

E8B02 (D)

How does the modulation index of a phase-modulated emission vary with RF carrier frequency (the modulated frequency)?

A

D. It does not depend on the RF carrier frequency

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16
Q

E8B03 (A)
What is the modulation index of an FM-phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency when the modulating frequency is 1000 Hz?

A

A. 3

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17
Q

E8B04 (B)
What is the modulation index of an FM-phone signal having a maximum carrier deviation of plus or minus 6 kHz when modulated with a 2 kHz modulating frequency?

A

B. 3

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18
Q

E8B05 (D)
What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz when the maximum modulation frequency is 3 kHz?

A

D. 1.67

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19
Q

E8B06 (A)
What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz when the maximum modulation frequency is 3.5 kHz?

A

A. 2.14

20
Q

E8B07 (A)

Orthogonal Frequency Division Multiplexing is a technique used for which type of amateur communication?

A

A. High speed digital modes

21
Q

E8B08 (D)

What describes Orthogonal Frequency Division Multiplexing?

A

D. A digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference

22
Q

E8B09 (B)

What is meant by deviation ratio?

A

B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency

23
Q

E8B10 (B)

What describes frequency division multiplexing?

A

B. Two or more information streams are merged into a baseband, which then modulates the transmitter

24
Q

E8B11 (B)

What is digital time division multiplexing?

A

B. Two or more signals are arranged to share discrete time slots of a data transmission

25
Q

E8C01 (C)

How is Forward Error Correction implemented?

A

C. By transmitting extra data that may be used to detect and correct transmission errors

26
Q

E8C02 (C)

What is the definition of symbol rate in a digital transmission?

A

C. The rate at which the waveform of a transmitted signal changes to convey information

27
Q

E8C03 (A)
When performing phase shift keying, why is it advantageous to shift phase precisely at the zero crossing of the RF carrier?

A

A. This results in the least possible transmitted bandwidth for the particular mode

28
Q

E8C04 (C)

What technique is used to minimize the bandwidth requirements of a PSK31 signal?

A

C. Use of sinusoidal data pulses

29
Q

E8C05 (C)

What is the necessary bandwidth of a 13-WPM international Morse code transmission?

A

C. Approximately 52 Hz

30
Q

E8C06 (C)

What is the necessary bandwidth of a 170-hertz shift, 300-baud ASCII transmission?

A

C. 0.5 kHz

31
Q

E8C07 (A)

What is the necessary bandwidth of a 4800-Hz frequency shift, 9600-baud ASCII FM transmission?

A

A. 15.36 kHz

32
Q

E8C08 (D)

How does ARQ accomplish error correction?

A

D. If errors are detected, a retransmission is requested

33
Q

E8C09 (D)

Which is the name of a digital code where each preceding or following character changes by only one bit?

A

D. Gray code

34
Q

E8C10 (D)

What is an advantage of Gray code in digital communications where symbols are transmitted as multiple bits

A

D. It facilitates error detection

35
Q

E8C11 (A)

What is the relationship between symbol rate and baud?

A

A. They are the same

36
Q

E8D01 (A)

Why are received spread spectrum signals resistant to interference?

A

A. Signals not using the spread spectrum algorithm are suppressed in the receiver

37
Q

E8D02 (B)

What spread spectrum communications technique uses a high speed binary bit stream to shift the phase of an RF carrier?

A

B. Direct sequence

38
Q

E8D03 (D)

How does the spread spectrum technique of frequency hopping work?

A

D. The frequency of the transmitted signal is changed very rapidly according to a particular sequence also used by the receiving station

39
Q

E8D04 (C)

What is the primary effect of extremely short rise or fall time on a CW signal?

A

C. The generation of key clicks

40
Q

E8D05 (A)

What is the most common method of reducing key clicks?

A

A. Increase keying waveform rise and fall times

41
Q

E8D06 (B)

Which of the following indicates likely overmodulation of an AFSK signal such as PSK or MFSK?

A

B. Strong ALC action

42
Q

E8D07 (D)

What is a common cause of overmodulation of AFSK signals?

A

D. Excessive transmit audio levels

43
Q

E8D08 (D)

What parameter might indicate that excessively high input levels are causing distortion in an AFSK signal?

A

D. Intermodulation Distortion (IMD)

44
Q

E8D09 (D)

What is considered a good minimum IMD level for an idling PSK signal?

A

D. -30 dB

45
Q

E8D10 (B)

What are some of the differences between the Baudot digital code and ASCII?

A

B. Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 characters as letters/figures shift codes, ASCII has no letters/figures shift code

46
Q

E8D11 (C)

What is one advantage of using ASCII code for data communications?

A

C. It is possible to transmit both upper and lower case text

47
Q

E8D12 (D)

What is the advantage of including a parity bit with an ASCII character stream?

A

D. Some types of errors can be detected

Ham Extra 2016-2020 (10 decks)

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