[time-nuts] Crystal aging

John Green wpxs472 at gmail.com
Wed Sep 2 19:31:20 UTC 2009

I realize that making measurements over a day or two says very little about
long term aging. Most of my crystal oscillator experience has been with
TCXOs in the communications industry. We are talking about orders of
magnitude difference with regard to just about everything. In my experience,
a good TCXO will age in a given direction if set and left alone. They
generally do get better with time. I have seen a TCXO be within 100 Hz after
15 years of on off operation and temperature cycling. For a TCXO, that's
outstanding.I hooked the Z3801 and Tbolt up to the same antenna and after
the Tbolt had completed a 4K point self survey, I was amazed to find that
the difference between the two is actually very easy to see. A 50 nsec.
drift over 30 minutes. Funny thing is it slowly swings back and forth. I
suppose it is due to the different disciplining algorithms of the two units.
It is easier to see on the oscope than the 1992. I don't think it is due to
temperature. I have a thermometer a couple of feet from both units and it
hasn't moved more than maybe a degree. I am going to leave them this way a
while to see what develops. I also want to see how much difference there is
in the reported position between the two units.

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