Hi Warren -- for these tests, I wasn't capturing raw data, jut using the tables and graphs that come out of the TSC box.
John On Feb 18, 2012, at 11:57 PM, "ws at Yahoo" <warrensjmail-...@yahoo.com> wrote: > John > > 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 > ws > **************** > > 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 > meaningful. > > 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. > > John > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
