[time-nuts] ADEV vs MDEV
magnus at rubidium.dyndns.org
Sun Feb 7 08:50:16 UTC 2010
Bob Camp wrote:
> I believe the statement:
> "Both systems are equally limited by the reference oscillator"
> was part of the same paragraph as the comment on 10811 short term stability.
> Neither system, no matter how well set up will get below the stability of the reference oscillator.
For DMTD systems the transfer oscillator noise can be partially
cancelled. You do have two inputs, but you then play three-cornered hat
tricks. However, for a DMTD system to be able to cancel noise, good
time-correlation between channels is needed to make the
noise-integration time-periods of both channels to match up. The more
they are apart, the bigger difference in noise it is between the
channels and thus it will fail to cancel. Thus, phase-alignment prior to
ZCDs could be a treatment. Using the audio channel approach avoids the
issue as the full-wave signal is being used and time correlation between
samples is high, an approach not available when DMTD was developed.
Magnus - while visiting fellow time-nut
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