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[KB6NU] 2016 Extra Class study guide: E8B - modulation and demodulation
KB6NU's Ham Radio Blog /////////////////////////////////////////// 2016 Extra Class study guide: E8B - modulation and demodulation Posted: 19 Feb 2016 11:50 AM PST http://feedproxy.google.com/~r/kb6nu...m_medium=email E8B Modulation and demodulation: modulation methods; modulation index and deviation ratio; frequency and time division multiplexing; Orthogonal Frequency Division Multiplexing In FM modulation, the two primary parameters of interest are deviation ratio and modulation index. Deviation ratio is the ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. (E8B09) 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 is 1.67. (E8B05)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 is 2.14. (E8B06) The term for the ratio between the frequency deviation of an RF carrier wave, and the modulating frequency of its corresponding FM-phone signal is modulation index. (E8B01) The modulation index is equal to the ratio of the frequency deviation to the modulating frequency. The modulation index of a phase-modulated emission does not depend on the RF carrier frequency. (E8B02) 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 is 3. (E8B03) 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 is 3. (E8B04) Some communications systems use multiplexing techniques to to combine several separate analog information streams into a single analog radio frequency signal. When a system uses frequency division multiplexing, two or more information streams are merged into a “baseband,” which then modulates the transmitter. (E8B10). When a system uses digital time division multiplexing, two or more signals are arranged to share discrete time slots of a data transmission. (E8B11) Orthogonal Frequency Division Multiplexing is a digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference. (E8B08) Orthogonal Frequency Division Multiplexing is a technique used for high speed digital modes. (E8B07) The post 2016 Extra Class study guide: E8B modulation and demodulation appeared first on KB6NUs Ham Radio Blog. |
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