Transmitters

Got some good pdfs on transmitters from Surge.. doing a little research first on how they work and then how to build them

frequency modulation (FM) and phase modulation (PM) can be received my an FM receiver

FM transmission

carrier frequency and audio frequency

when audio energy (audio tone in kHz displayed in a sine wave) is applied to RF carrier the carrier fq increases during the during positive half of audio and decreases during negative. Deviation is the shift in the RF carrier fq. Deviation is proportional to amplitude of the modulation signal (lower audio level smaller amount of deviation). unlike AM, the output amplitude of a FM transmitter is consistent during modulation.

fq modulation occurs during oscillation

phase modulation occurs after oscillation

FM much wider bandwidth than AM or SSB

commercial FM have peak deviation of 75 kHz amateur + land-mobile FM have 5 kHz deviation aka wide band and narrow band FM

amp modulation has sidebands above and blow the carrier fq

the # of the sideband pairs that occur during FM and PM operation depends on the ratio between the audio modulation fq and the carrier fq deviation ratio is called modulation index

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Transmitters

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