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-requ...@lists.febo.com wrote:
Message: 3
Date: Fri, 04 Sep 2020 08:50:21 +0200
From: Matthias Welwarsky<time-n...@welwarsky.de>
To:time-nuts@lists.febo.com
Subject: [time-nuts] OCXO retrace, how long is reasonable?
Message-ID:<5901813.eksvcns...@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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