What is the accuracy of the Flex 6700's GPSDO?

Roy Laufer

I have been looking at the documentation for the improved accuracy with the Flex 6700's GSDO.  In places I have seen "<5.0 x 10^-12, but in other places I have seen the accuracy estimated as "0.005 ppm" (which would be 5x10^-9 NOT 10^-12).  Am I losing my ability to do simple math, or are one of these published specs a typo??

At these accuracies it's almost just academic, but I'm still curious!

73,
Roy, AC2GS

Martin AA6E

The current FRS spec says the stability of the GPSDO is 5 x 10**-12 over 24 hours. They do not specify any level of accuracy, which can be quite a different thing.  To my mind, the stability spec means that the frequency (averaged over some short time period) will not vary by more than the given number over a 24 hour period.  There will be a constant offset from the nominal frequency -- that's the accuracy.  You can take that out by entering the offset in SSDR -- if you can measure it!

Characterizing high performance oscillators is not simple, and I wish FRS gave more information. In my astronomical work, we commonly used the Allan Variance, which tells you what frequency / phase performance you can expect over a wide range of time intervals. See www.rohde-schwarz.de/file/1EF69_E3.pdf, for example.

73 Martin AA6E