[time-nuts] Does adjusting ocxo's degrade adev / madev ?
kb8tq at n1k.org
Thu Nov 27 12:13:52 EST 2014
Any time you change the operating point of the sustaining circuit (limiter / amp) in an OCXO, there’s a chance that the drive level changes. For small changes in operating point, (and the absence of perturbations) you rarely will see any impact. For large changes (or tuning onto a perturbation), you can see impact on the ADEV. If it’s a drive level change, it probably will settle out.
> On Nov 26, 2014, at 9:04 PM, Mark Spencer <mark at alignedsolutions.com> wrote:
> I've long had a nagging suspicion that OCXO's that are not adjusted will in practice have lower ADEV than ones that are tweaked regularly. Several days ago I noticed that one of my 10811's was performing quite well (I believe this is the first time any of 10811's have delivered adev / madev numbers in the 13's) and this was sustained for approx 2 days. After trimming the frequency and letting it sit for a number of hours I noticed the adev was notably worse.
> I realize there could be a mechanical issue with the trimmer inside the ocxo that is causing this or simply touching the ocxo while adjusting it may have also caused this, but is changing the frequency of an OCXO in of it self likely to have an affect on ADEV / MADEV after a few hours ?
> Looking at the linear residual plot of the phase difference between the 10811 and the reference, I see a fairly large difference at first, then a somewhat smaller change, then a series of smaller changes. But I may be reading to much into this plot.
> I don't expect an absolute answer to this but I'm curious if anyone else has seen this.
> Sent from my iPad
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