[time-nuts] Allan deviation -> finally some data!!!

[Dr Bruce Griffiths]

Didier Juges wrote:
> I have downloaded and installed Plotter, and found it easy to setup and use, at least for basic functionality. The menu threw me off a little bit (no simple File->Open dialog), but I am sure I will get used to it.
>
> I have ran my spare HP10811 overnight (twice), against the HP5370A's own timebase, and the plots are at
>
> http://www.ko4bb.com/Test_Equipment
> under HP10811xxx.png
>
> It turns out I simply fed Plotter with a flat file containing a single record per line, which is the formatted output from the 5370. Yesterday's file is Counter_TI.dat in the same directory as the pictures, for the curious (it is almost 1 MB).
>
> The large variations in the raw data are due to the house heating, which I turned on briefly before going to bed, and again when I woke up, causing the delay to drop slightly.
>
> Other than those variations, the DUT and the HP5370's own timebase were in pretty good sync, considering that I compared the 10 MHz outputs directly, and they were not phase locked.
>
> There are two sets of plots, those with -2 were taken yesterday with no averaging in the 5370, the others were taken the day before had 1k averaging, so they show considerably more noise, as expected. The -2 data was collected at 2 seconds interval instead of 0.4 second for the other set.
>
> Interesting to note that the variations in the first raw plot are due to house heating, which I turned on briefly before going to bed and again in the morning, before shutting down the equipment. There should have been the same variation in the second set of data, but it is buried under the noise because of the lack of averaging.
>
> Other than that, the oscillators remained within 50-60 nS of each other over night without being phase locked, not bad for 2 free running OCXOs I believe.
>
> Obviously, I need to refine my setup and procedures before the data is meaningful, but so far, it is working.
>
> Didier KO4BB
>
>
>
>
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>   
The apparent behaviour of your 10811's is far too good!!
Over a period of 15,000 seconds the allan deviation should have reached 
a minimum and then increased as the effects of ageing manifest themselves.
Either the oscillators are injection locked or your analysis is suspect.

If the analysis were correct the performance approaches or even exceeds 
that of the most stable crystal oscillators ever built.
This is extremely unlikely something has to be wrong.

Bruce