[time-nuts] I've been thinking about a GPS receiver experiment

Bob kb8tq kb8tq at n1k.org
Thu Oct 26 14:32:07 EDT 2017


You get into all sorts of issues trying to estimate tempco. You have time lags
and gradients that make it a very messy process. Toss in measurement based on
small range temperature swings (like from a HVAC system) …. it’s a mess. 

If the OCXO is a typical modern part and it’s been on power for a couple of weeks, 
why bother? The delta is small and it may not be quite the same yesterday as it is today. 
Guessing it based on the sort of data you have is worse than guessing tempco. 

This all *assumes* you are chasing the aging and tempco of the OCXO. If your
electronics contribute a lot of error (as some do), they may need the help. 


> On Oct 26, 2017, at 1:28 PM, Mark Sims <holrum at hotmail.com> wrote:
> Many years ago I  tried to add some code to Lady Heather to calculate the tempco and aging of the oscillator in a normally running Tbolt.   Although the equations would theoretically work (using SVD decomposition) it seldom worked properly.   Failure seemed to be caused by noise in the small numbers involved.   I wound up adding code that could do it by disabling disciplining to get aging and varying the temperature to get tempco.
> ----------------------
>> Separating this and that input to get a good value for a specific parameter is rarely done with good accuracy
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