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

Didier Juges didier at cox.net
Wed Oct 25 08:30:20 EDT 2006

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

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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