[time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi



> On Nov 18, 2016, at 1:31 PM, Lars Walenius <lars.walenius at hotmail.com> wrote:
> 
> Hi Bob (and all others),
>  
> I agree to all your points but am curious to your comment: ”that OCXO is aging a lot for one that has been on that long”.
> As I have only done this test and seen no other test of OCXO´s powered over at least ten years, I have no idea what is reasonable. I also guess I will not do another test of an OCXO powered and measured over ten years again.
>  
> Could you give some examples what is reasonable for aging after ten years? Maybe others have data? I have searched internet and it isn´t easy to find long-term data on OCXO’s (at least for me).

The only people I know of that have the gear and the interest to run a number of OCXO’s are oscillator manufacturers. They also track parts
in the field by various methods. The data takes real effort to collect and thus is “part of our IP”.

Bob

>  
> This oscillator drifted about 60ppm between 1month on to ten years on . Do others have figures what is reasonable over this time span?
>  
> For point 1: Is it possible from the aging curve to have some ideas what is going on??
>  
> Lars
>  
> >Från: Bob Camp
> >Skickat: den 17 november 2016 01:03
> >Hi
>  
> >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).
>  
> >Bob
>  
> >> 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