[time-nuts] OCXO retrace, how long is reasonable?

[Dan Kemppainen]

Matthias,

How about a 'quick and dirty, hand wavey' graph?

This is a known 'kinda good' OCXO, that was off for about a year. The 
DAC values are just that, DAC counts.  The black line should represent 
about 8e-12 per day drift. (Sorry, I don't have better numbers than that 
easily on hand). I think it's about 4uHz per count, or so.

Note 1: The first 13700 seconds of data were thrown away. That drift was 
astronomic. (Basically vertical on this scale!)

Note 2: Also, note that this only one retrace, of one trimble OCXO.

Note 3: Notice the dates on the bottom of the graph. This is around 6 
months of worth of drift. Small tics are 7 days apart, major tics 3 weeks...

Hopefully this helps!

Dan



On 9/4/2020 12:00 PM, time-nuts-request at lists.febo.com wrote:
> Message: 3
> Date: Fri, 04 Sep 2020 08:50:21 +0200
> From: Matthias Welwarsky<time-nuts at welwarsky.de>
> To:time-nuts at lists.febo.com
> Subject: [time-nuts] OCXO retrace, how long is reasonable?
> Message-ID:<5901813.EksvcnS80i at linux-5fgm.suse>
> Content-Type: text/plain; charset="us-ascii"
> 
> Hi,
> 
> I mentioned in a previous email that I seem to have picked a particularly bad
> (broken?) OCXO for GPSDO testing. It drifts at a very high rate, from the DAC
> graph I calculate it is around -4e-4 Hz/hour. It's been on for about 1 week
> now and the drift doesn't seem to come down, or maybe just marginally.
> 
> Of course, this being a surplus OCXO with unknown history, odd startup
> behavior is somewhat expected but so far I haven't seen anything this drastic.
> 
> Could this be OCXO retrace? How long can that phase last? I'm trying to decide
> if I should give it another week or just scrap it and move on.
> 
> Regards,
> Matthias
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