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1704Re: "FTL" experiments for dummies

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  • Ed Minchau
    Feb 19 12:17 AM
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      --- In nanotech@y..., Mark Gubrud <mgubrud@s...> wrote:
      > If we are interested
      > in detecting the signal as soon as possible, the answer is not
      necessarily
      > the center of the pulse. We could set some threshold, say, half
      way up
      > the slope, and have our detector tell us the signal has arrived
      when that
      > threshold is reached. If we set the threshold lower, we'll get the
      > signal sooner. But we also have to consider the presence of
      noise. We
      > can always reach our threshold of detection sooner if we just
      amplify the
      > signal, but we'll be amplifying noise along with it. That's the
      problem
      > with these schemes. You can amplify the leading edge, attenuate the
      > trailing edge, or do both, but you never reach a given signal-to-
      noise
      > ratio at any velocity greater than c. That's what the people who
      try to
      > pass this off as "FTL" never bother to tell you.

      Furthermore, according to the Nyquist sampling criteria, you need to
      receive two "pulses" to be certain that you have received one at the
      desired wavelength; again, slower than c.

      :) ed
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