[time-nuts] GPS Locked and Unlocked Performance Comparison

Tom Van Baak tvb at LeapSecond.com
Tue Feb 12 19:54:46 EST 2008


Hi Said,

Yes, it was quite a bit of work. Thanks for noticing.

My goal is to extend the plots out well past a day but as you
know to get good statistics out there takes a week or two of
data for each run. Or I can switch measurement systems
and try to do several in parallel.

Theoretically just 3 or 4 days of data is sufficient to compute
the ADEV(tau 1 day) but the error bars are too wide that way.
When comparing different GPSDO, one needs to keep the
error bars pretty small in order to be fair. That's why the plot
stops at tau 40k.

Anyway, once I collect enough data, yes, adding a holdover
test is the next thing. Several of these GPSDO have such low
drift as it is that it could take a week to accurately measure it.

/tvb
  ----- Original Message ----- 
  From: SAIDJACK at aol.com 
  To: tvb at leapsecond.com ; time-nuts at febo.com 
  Sent: Tuesday, February 12, 2008 4:13 PM
  Subject: Re: [time-nuts] GPS Locked and Unlocked Performance Comparison


  Hello Tom,

  excellent web-page! That looks like a lot of work was done.

  Would you have data for 24 hour hold-over performance (86400s ADEV) for these units?

  thanks,
  bye,
  Said

  In a message dated 2/11/2008 21:17:49 Pacific Standard Time, tvb at LeapSecond.com writes:
    Sifting through old data, in addition to recent measurements
    made in the past few months, I have 4 very interesting plots
    of GPSDO performance.

    The goal was to see real-life plots of disciplining in action by
    contrasting free (unlocked) vs. GPS-locked performance as
    compared with my 10 MHz house reference. The four GPSDO
    measured so far are: Z3801A, Fury, Thunderbolt, and Miller.

    http://www.leapsecond.com/pages/gpsdo/

    Comments & questions welcome.

    I hope to measure quite a few more this year. Contact me
    offline if you want your favorite one included in the list. Note
    that I'm not necessarily looking for the best GPSDO; instead,
    for this page at least, the more variety the better.

    /tvb




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