[time-nuts] fts 4050 performance

[Tom Van Baak]

Thanks for posting the plot. At first glance it looks
close to OK. Remember what you are plotting is
the RMS sum of stability and noise of three things:
your FTS4050, your Z3801A, and your 53132A.
Each of these three instruments will contribute for
good or for bad at different ranges of tau.

What did the datasheet show for the 4050?

In the short-term the resolution of the 53132 will
limit the results. In the mid-term your 4050 will
expose the limitations of the 3801. And in the
very long-term the 3801 will expose the limitations
of the 4050. Make sense?

For example, note that the ADEV is around 2e-10
at tau 1 s, which is just what you would expect for
a counter with ~150 ps TI resolution. The 4050 and
3801 are much better but the counter limits your
short-term measurements.

The plot then follows a nice -1 slope for a couple of
decades, as expected, until the averaged resolution
of the counter "catches up" with the 4050 or 3801.

By the time you hit tau 1000 s the counter is better
than either the 4050 or 3801 and so what you are
seeing is the true stability of the two standards
compared together, no longer limited by the 53132.
I hope you plan to keep the experiment running so
you can plot out to larger tau.


There are some FTS 4050 cesium plots here:
http://www.leapsecond.com/museum/fts4050/
see log23031v.gif and log22421v.gif

Also some HP Z3801A GPSDO plots here:
http://www.leapsecond.com/museum/z3801a/
see log8286v.gif or log8550v.gif

/tvb


----- Original Message ----- 
From: "Christopher Hoover" <ch at murgatroid.com>
To: <time-nuts at febo.com>
Sent: Sunday, July 30, 2006 12:09
Subject: [time-nuts] fts 4050 performance


> 
> Attached is what I'm seeing in terms of adev and mdev on my "new" FTS
> 4050.  
>  
> The performance is worse than I had expected, as compared to the
> datasheet.
>  
> I'm not 100% confident in my test setup, but I'm not seeing any obvious
> outliers in the data.
> 
> Test setup is as follows:
>  
> Counter: HP 53132A
> Timebase: external, 10MHz from Z3801A
> Start: 1 PPS from Z3801A, DC, 50Z, 2v5 trigger level
> Stop: 1 MHz from FTS 4050, AC, 50Z, auto trigger
> 
> -ch
>