69 lines
3.8 KiB
Markdown
69 lines
3.8 KiB
Markdown
E8D Keying defects and overmodulation of digital signals; digital codes; spread spectrum
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- [[E8D01]] (A)
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Why are received spread spectrum signals resistant to interference? #card
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- [[A.]] Signals not using the spread spectrum algorithm are suppressed in the receiver
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- [[B.]] The high power used by a spread spectrum transmitter keeps its signal from being easily overpowered
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- [[C.]] Built-in error correction codes minimize interference
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- [[D.]] If the receiver detects interference, it will signal the transmitter to change frequencies
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- [[E8D02]] (B)
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What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier? #card
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- [[A.]] Frequency hopping
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- [[B.]] Direct sequence
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- [[C.]] Binary phase-shift keying
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- [[D.]] Phase compandored spread spectrum
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- [[E8D03]] (D)
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Which describes spread spectrum frequency hopping? #card
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- [[A.]] If interference is detected by the receiver, it will signal the transmitter to change frequencies
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- [[B.]] RF signals are clipped to generate a wide band of harmonics which provides redundancy to correct errors
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- [[C.]] A binary bit stream is used to shift the phase of an RF carrier very rapidly in a pseudorandom sequence
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- [[D.]] Rapidly varying the frequency of a transmitted signal according to a pseudorandom sequence
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- [[E8D04]] (C)
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What is the primary effect of extremely short rise or fall time on a CW signal? #card
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- [[A.]] More difficult to copy
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- [[B.]] The generation of RF harmonics
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- [[C.]] The generation of key clicks
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- [[D.]] More difficult to tune
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- [[E8D05]] (A)
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What is the most common method of reducing key clicks? #card
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- [[A.]] Increase keying waveform rise and fall times
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- [[B.]] Insert low-pass filters at the transmitter output
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- [[C.]] Reduce keying waveform rise and fall times
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- [[D.]] Insert high-pass filters at the transmitter output
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- [[E8D06]] (D)
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What is the advantage of including parity bits in ASCII characters? #card
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- [[A.]] Faster transmission rate
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- [[B.]] Signal-to-noise ratio is improved
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- [[C.]] A larger character set is available
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- [[D.]] Some types of errors can be detected
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- [[E8D07]] (D)
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What is a common cause of overmodulation of AFSK signals? #card
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- [[A.]] Excessive numbers of retries
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- [[B.]] Excessive frequency deviation
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- [[C.]] Bit errors in the modem
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- [[D.]] Excessive transmit audio levels
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- [[E8D08]] (D)
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What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels? #card
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- [[A.]] Signal-to-noise ratio
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- [[B.]] Baud error rate
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- [[C.]] Repeat Request Rate (RRR)
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- [[D.]] Intermodulation Distortion (IMD)
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- [[E8D09]] (D)
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What is considered an acceptable maximum IMD level for an idling PSK signal? #card
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- [[A.]] +5 dB
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- [[B.]] +10 dB
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- [[C.]] +15 dB
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- [[D.]] -30 dB
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- [[E8D10]] (B)
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What are some of the differences between the Baudot digital code and ASCII? #card
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- [[A.]] Baudot uses 4 data bits per character, ASCII uses 7 or 8; Baudot uses 1 character as a letters/figures shift code, ASCII has no letters/figures code
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- [[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
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- [[C.]] Baudot uses 6 data bits per character, ASCII uses 7 or 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes
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- [[D.]] Baudot uses 7 data bits per character, ASCII uses 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes
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- [[E8D11]] (C)
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What is one advantage of using ASCII code for data communications? #card
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- [[A.]] It includes built-in error correction features
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- [[B.]] It contains fewer information bits per character than any other code
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- [[C.]] It is possible to transmit both uppercase and lowercase text
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- [[D.]] It uses one character as a shift code to send numeric and special characters
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