On Monday, September 2, 2019 at 10:39:51 PM UTC-7, boB wrote:
(snip regarding analog television vestigial sideband modulation)
Very interesting point ! I wonder if they make use of that extra bit
of information ? I would think that if they needed to use the
vestigial part that the main sideband would be messed up enough that
it would be unusable ?
Never even asked why that sideband was there at all before... Maybe
because it's easier than filtering or cancelling out all the way ?
In the case of NTSC VSB, the lower sideband is filtered out with
a specific frequency range. The result, then, of demodulating the
signal as a normal AM signal is that the frequency response isn't
flat. The lower sideband is cut off at about (I don't know the exact
shape) 1MHz. The result is that the demodulated signal is reduced
by half past 1MHz. The IF amplifiers, then, are designed to compensate
for this.
Getting the frequency response in audio may seem more obvious, but
it is still considered important in video.
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