[time-nuts] FTS1200, OSA8600, OSA8601 phase noise and ADEV measures

bg at lysator.liu.se bg at lysator.liu.se
Thu Aug 2 23:48:04 EDT 2012


> Bottom line, the large low-frequency spurs in the FTS plot at 1.4 and 2.9
> Hz
> will be caused by one of these conditions:
>
> 1) A problem with the reference source(s)
>
> 2) A problem with the FTS oscillator itself
>
> 3) A normal characteristic of the FTS oscillator (maybe its spur specs
> weren't very good to begin with?)

It seems the FTS1200 is only slightly out of spec compared to

 http://www.ece.gatech.edu/academic/courses/ece4007/08fall/ece4007l01/al4/datasheets/symmetricon_oscillator_instructionsheet.pdf

  http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_1.png
>
> 4) An RF crosstalk or leakage problem with the cables/adapters used
>
> 5) A power-supply regulation issue
>
> 6) Coupling between inadequately-bypassed power leads.  This is a big
> problem with some OCXOs where they apparently forgot to use bypass
> capacitors inside the can.  I usually solder a 0.1 uF ceramic chip cap
> right
> at the point of entry, if in doubt.
>
> 7) Some as-yet-unexplored effect related to beatnotes in dual-reference
> measurements.
>
> It may be possible to rule out cases (2) and (3), and definitely case (7),
> by temporarily switching back to the normal single-reference
> configuration.
>
> -- john, KE5FX
> www.miles.io
>

--

    Björn





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