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

John Ackermann N8UR jra at febo.com
Thu Aug 2 15:59:00 EDT 2012


Magnus, this is very cool.  Can you describe your cross-correlation 
setup with the Time-Pod?  I'd like to play with it here and compare notes.

John
----

On 8/2/2012 12:36 PM, Magnus Danielson wrote:
> Fellow time-nuts,
>
> I have borrowed Björn's FTS1200 and OSA8600 and that complements my own
> OSA8600 and OSA8601.
>
> I use a HP5087A and one of the OSA8600 as references, such that I can
> cross-correlate out the reference oscillators. I'm still not quite
> satisfied just yet, so I may need to work some more to perfect this
> technique.
>
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_1.png
>
>
> Here you see the phase-noise of the four oscillators.
> It is distinct how the white noise floor of the FTS1200 is around -141
> dBc/Hz when the OSA8600s reach for -155 to -156 dBc/Hz.
>
> The spurs on the FTS1200 may trace back to the fact that the FTS1200 is
> -1.5 Hz of the references, but I like Johns comments on that.
>
> You can see that the older OSA8601 has better 1/f noise and that Björn's
> OSA8600 SN711 has higher 1/f^3 noise than any of the other three which
> seems comparable. The OSA8600 SN711 and SN817 has comparable 1/f noise.
>
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_2.png
>
>
> The ADEV plot of the oscillators.
> The noise on the FTS1200 dominates, it's inital response, but it is more
> clearly seen that the flat section is better and the OSAs.
>
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_3.png
>
> The Hadamard Deviation plot of the oscillators.
> The linear drift of the FTS1200 and OSA8601 is seen.
>
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_4.png
>
>
> The phase difference plot of the oscillators:
> The linear drift noticed from the ADEV plot and mostly removed in the
> Hadamard plot is seen more clearly in the phase plot as quadratic
> phase-shifts, a slot tendency on the other oscillatos can also be seen.
>
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_5.png
>
>
> The Frequency difference of the oscillators.
> The noise of the FTS1200 is visible. I haven't looked into it.
>
> As you may have noted, the measurement length varies, I haven't looked
> into it.
>
> My OSAs has been heated for a fairly long time, even if they had a short
> dip of voltage. Björns FTS1200 and OSA has been heated for almost 2
> weeks now.
>
> Measurement files:
> http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_HP5065A_OSA86000_20120802_1.tim
>
> http://rubidium.dyndns.org/~magnus/time/timelab/OSA8600SN711_HP5065A_OSA86000_20120802_1.tim
>
> http://rubidium.dyndns.org/~magnus/time/timelab/OSA8600SN817_HP5065A_OSA86000_20120802_1.tim
>
> http://rubidium.dyndns.org/~magnus/time/timelab/OSA8601SN1314_HP5065A_OSA86000_20120802_1.tim
>
>
> Comments welcome. I will spend some more quality time on this now that
> I've made a first stab at it.
>
> Got to locate a cable so I can toss a well-heated 10811A into the battle.
>
> Cheers,
> Magnus
>
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