69 lines
3.9 KiB
Markdown
69 lines
3.9 KiB
Markdown
E8B Modulation and demodulation: modulation methods; modulation index and deviation ratio; frequency- and time-division multiplexing; orthogonal frequency-division multiplexing (OFDM)
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- [[E8B01]] (A)
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What is the modulation index of an FM signal? #card
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- [[A.]] The ratio of frequency deviation to modulating signal frequency
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- [[B.]] The ratio of modulating signal amplitude to frequency deviation
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- [[C.]] The modulating signal frequency divided by the bandwidth of the transmitted signal
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- [[D.]] The bandwidth of the transmitted signal divided by the modulating signal frequency
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- [[E8B02]] (D)
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How does the modulation index of a phase-modulated emission vary with RF carrier frequency? #card
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- [[A.]] It increases as the RF carrier frequency increases
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- [[B.]] It decreases as the RF carrier frequency increases
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- [[C.]] It varies with the square root of the RF carrier frequency
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- [[D.]] It does not depend on the RF carrier frequency
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- [[E8B03]] (A)
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What is the modulation index of an FM phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency if the highest modulating frequency is 1000 Hz? #card
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- [[A.]] 3
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- [[B.]] 0.3
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- [[C.]] 6
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- [[D.]] 0.6
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- [[E8B04]] (B)
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What is the modulation index of an FM phone signal having a maximum carrier deviation of plus or minus 6 kHz if the highest modulating frequency is 2 kHz? #card
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- [[A.]] 0.3
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- [[B.]] 3
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- [[C.]] 0.6
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- [[D.]] 6
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- [[E8B05]] (D)
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What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 5 kHz if the highest modulation frequency is 3 kHz? #card
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- [[A.]] 6
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- [[B.]] 0.167
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- [[C.]] 0.6
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- [[D.]] 1.67
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- [[E8B06]] (A)
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What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz if the highest modulation frequency is 3.5 kHz? #card
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- [[A.]] 2.14
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- [[B.]] 0.214
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- [[C.]] 0.47
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- [[D.]] 47
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- [[E8B07]] (A)
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Orthogonal frequency-division multiplexing (OFDM) is a technique used for which types of amateur communication? #card
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- [[A.]] Digital modes
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- [[B.]] Extremely low-power contacts
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- [[C.]] EME
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- [[D.]] OFDM signals are not allowed on amateur bands
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- [[E8B08]] (D)
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What describes orthogonal frequency-division multiplexing (OFDM)? #card
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- [[A.]] A frequency modulation technique that uses non-harmonically related frequencies
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- [[B.]] A bandwidth compression technique using Fourier transforms
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- [[C.]] A digital mode for narrow-band, slow-speed transmissions
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- [[D.]] A digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference
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- [[E8B09]] (B)
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What is deviation ratio? #card
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- [[A.]] The ratio of the audio modulating frequency to the center carrier frequency
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- [[B.]] The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency
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- [[C.]] The ratio of the carrier center frequency to the audio modulating frequency
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- [[D.]] The ratio of the highest audio modulating frequency to the average audio modulating frequency
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- [[E8B10]] (B)
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What is frequency division multiplexing (FDM)? #card
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- [[A.]] The transmitted signal jumps from band to band at a predetermined rate
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- [[B.]] Dividing the transmitted signal into separate frequency bands that each carry a different data stream
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- [[C.]] The transmitted signal is divided into packets of information
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- [[D.]] Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter
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- [[E8B11]] (B)
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What is digital time division multiplexing? #card
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- [[A.]] Two or more data streams are assigned to discrete sub-carriers on an FM transmitter
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- [[B.]] Two or more signals are arranged to share discrete time slots of a data transmission
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- [[C.]] Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier
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- [[D.]] Two or more signals are quadrature modulated to increase bandwidth efficiency
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