Stereo generator
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A stereo generator is an electronic device designed to encode stereophonic information for transmission over radio or television. It generally only refers to analog audio.
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[edit] Radio
[edit] FM
FM stereo uses a double-sideband suppressed carrier (DSSC or DSB-SC) on a 38kHz subcarrier. This carries the "left minus right" (stereo difference) signal, while the baseband audio is the monophonic "left plus right" (stereo sum). It can be mathematically shown that time multiplexing the left and right audio channels (alternately switching between left and right) at a rate of 38 kHz and low-pass filtering at 54 kHz accomplishes the same effect. In both cases, the 19 kHz pilot is derived from the 38 kHz carrier and added to the result before the signal is passed to the FM modulator.
The old Soviet system uses polar modulation.
[edit] AM
There are several methods in AM, including Motorola's C-QUAM, and Leonard Kahn's independent sideband.
[edit] Television
[edit] NTSC
The main audio is on a separate carrier, but the stereo difference is a subcarrier of the video carrier. See multichannel television sound.
