[time-nuts] Thermal impact on OCXO

Bob Camp kb8tq at n1k.org
Wed Nov 16 18:00:52 EST 2016


Your data demonstrates a couple of things:

1) There are a number of different things going on with that OCXO and some things are a lot less predictable than others.
2) Oscillators do drop rate while on power.
3) Oscillators that age a lot are easier to model (yes, that OCXO is aging a lot for one that has been on that long).


> On Nov 16, 2016, at 2:41 PM, Lars Walenius <lars.walenius at hotmail.com> wrote:
> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch type without EFC marked OFC MC834X4-009W with date code 97. Probably it was from some base station testing and it had been sitting in my shelf since 98. The OCXO were battery backed but at two occasions (2004 and 2007) we had power fails that drained the battery as can be seen in the graph.
> Just out of curiosity I yesterday put just the first thirty days (like in the pdf mentioned below) and let Excel calculate the logarithmic function. If I extrapolate that to 10 years it seems that the drift would be 6E-13/day but as can be seen in the aging graph it was more like ten times higher.
> Some days ago I started the OCXO again after it had been on the shelf for more than 4 years. Enclosed is a graph for the first 7 days. After six and half days it seems to be a jump of about 1.5E-10 and as I have no indication of anything else I believe it is from the OCXO.
> /Lars
>> On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe <scott.j.stobbe at gmail.com>
>> wrote:
>> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
>> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>>         Year   Aging [PPB]  dF/dt [PPT/Day]
>>            1       180.51       63.884
>>            2       196.65        31.93
>>            5          218       12.769
>>            9       231.69       7.0934
>>           10       234.15        6.384
>>           25        255.5       2.5535
>> If you have a set of coefficients you believe to be representative of your
>> OCXO, we can give those a go.
> <Aging per day OFC x834 2001-2011.PNG><Drift OCXO OFC x834 2001 30 first days.PNG><Drift OCXO OFC x834 2001-2011.PNG><Drift OCXO OFC x834 2016.PNG>_______________________________________________
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