Extra-Study/pages/E8B.md

E8B Modulation and demodulation: modulation methods; modulation index and deviation ratio; frequency- and time-division multiplexing; orthogonal frequency-division multiplexing (OFDM)

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