OK, now questions.
Obviously, now I'm obsessed with accuracy and precision. So I did the typical dual trace oscilloscope measurement. Channel A gets 10MHz for GPSDO that has been running for months. Set a trigger on it. Channel B has 10MHz output from FTS4040a. It has been warming up for like 4 hours. (I know, it's not long enough). Scope is set for 20ns/div.
In 10 hours, it looks like it moved 1.5 division. So by extrapolation, to move full cycle (5 division), it'll take approximately 33 hours: which is 118,800 sec, or for ease of calculations 1x10^5 Period is 1x10-5.
10MHz is 10^7. So movement is 10^-5 / 10^7 = 10^-12. 1 part per billion.
Is this calculations right? This is within spec but warm up time was insufficient. So it isn't the final result.
If I want to do this continuously to say get a daily report, how do I automate this? Since sine wave is a periodic function, there is no way to tell a peak from another peak. Moving to the right 180 degrees looks exactly like moving to the left 180 degrees.
I have a chart recorder. I have counters like HP53131A and HP5335A. My GPSDO has 1 pps output and 10MHz output, but Datum only has 10MHz, 5MHz, and 1MHz out. No pps. The ideal result will be a continuous recording on chart recorder with 1 day worth of change in 10cm of paper.
There is no GPIB and there is no serial communication on Datum either.