[time-nuts] Update on Rb Performance
John Ackermann N8UR
jra at febo.com
Sun Feb 19 12:55:28 UTC 2012
Hi Warren -- for these tests, I wasn't capturing raw data, jut using the tables and graphs that come out of the TSC box.
On Feb 18, 2012, at 11:57 PM, "ws at Yahoo" <warrensjmail-one at yahoo.com> wrote:
> If you have the raw phase data, can you post a plot of what the well filtered freq offset looks like over that 10 day period?
> I've have found a properly filtered high resolution freq vs. time plot provides a lot more useful information than the couple of data numbers of a ADEV plot for evaluating long term performance of an Osc and helps separate all the many different possible causes of poor ADEV numbers.
> This is because then one can see the shape and magnitude of the Freq drift, therefore being able to see if the freq drift has a short term cycle due to temperature or if it is linear due to ageing or 2nd order due to still stabilizing or if it contains freq jumps due to 1/f flicker, or a single large jump due ...etc, etc.
> To be of any long term use, the freq data must be filtered over a long enough time period, such as a 1 hr running averaged, so the plot is more than just the 1 sec noise shown on most freq plots.
> The big avantage of using long term freq plot instead of a ADEV plot is the freq error is not noise but sytimatic errors which I have found to generally be the casse over longer time periods, then 10days worth of data can be use to prdict the what the future performance will be, compart that to what 10days of ADEV give, a lot of uncetaiy to even prdict what the one day drift will ber.if the Noise is not noise but due to Using a 10 day
> John Ackermann N8UR jra at febo.com
> This isn't the real long-term stability test I'm planning to do, but I
> did let the measurement continue on the last unit I was testing (an
> Efratrom FRS-type) out to 10+ days, which should give fairly reasonable
> data out to 100K seconds. An ADEV plot is attached. I would ignore the
> last two plot points as there isn't enough data for them to be very
> Bottom line is that Efratom specs the FRS units at <1e-10/day, and this
> one seems to do more than an order of magnitude better. But also looks
> like you need a lot more than 10 days data to draw any real conclusions;
> you can look at this plot and think that the ADEV is maybe heading back
> down after a peak near 1e-11.
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