2016-E8B: Modulation and demodulation: modulation methods; modulation index and deviation ratio; frequency and time division multiplexing; Orthogonal Frequency Division Multiplexing
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?
Percentage of modulation
How does the modulation index of a phase-modulated emission vary with RF carrier frequency (the modulated frequency)?
It does not depend on the RF carrier frequency
It increases as the RF carrier frequency increases
It decreases as the RF carrier frequency increases
It varies with the square root of the RF carrier frequency
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?
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?
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?
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?
Orthogonal Frequency Division Multiplexing is a technique used for which type of amateur communication?
High speed digital modes
Extremely low-power contacts
OFDM signals are not allowed on amateur bands
What describes Orthogonal Frequency Division Multiplexing?
A digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference
A frequency modulation technique which uses non-harmonically related frequencies
A bandwidth compression technique using Fourier transforms
A digital mode for narrow band, slow speed transmissions
What is meant by deviation ratio?
The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency
The ratio of the audio modulating frequency to the center carrier frequency
The ratio of the carrier center frequency to the audio modulating frequency
The ratio of the highest audio modulating frequency to the average audio modulating frequency
What describes frequency division multiplexing?
Two or more information streams are merged into a baseband, which then modulates the transmitter
The transmitted signal jumps from band to band at a predetermined rate
The transmitted signal is divided into packets of information
Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter
What is digital time division multiplexing?
Two or more signals are arranged to share discrete time slots of a data transmission
Two or more data streams are assigned to discrete sub-carriers on an FM transmitter
Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier
Two or more signals are quadrature modulated to increase bandwidth efficiency
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