[time-nuts] Three-cornered hat on timelab?

Bob Stewart bob at evoria.net
Thu Apr 13 11:41:18 EDT 2017

Hi John,
Thanks!  With lesser equipment, such as the 5370A, would longer runs be better?  I used a set of 1 hr runs and the result wasn't quite what I had expected.  However, it may be that I had mislabeled the files, and thus got the sources confused.  Of course, it may be that the ionospheric effect was grossly different between the three tests.  So, with a 5370, Source A would be the START input and Source B would be the STOP input, right?  For my testing, the sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a GPSDO.


      From: John Miles <john at miles.io>
 To: 'Discussion of precise time and frequency measurement' <time-nuts at febo.com> 
 Sent: Thursday, April 13, 2017 1:07 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
> It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  Is
> this something that can only be done with multiple Timepods connected, or
> is there an option that I'm missing?  Or is there some other tool that needs
> to be used?  For the record, I want to create the 3c-hat from data that was
> run at different times, and I understand (at least somewhat) the
> shortcomings of doing that.  But, it would be interesting to see what would
> result.  And, not having three 5370s in good condition, it's the best I can do.

Hi, Bob --

N-cornered hat measurement is a beta feature, not in the docs yet.  A single TimePod can generate the required three plots simultaneously, but you can use individual plots from TICs and frequency counters as long as you start with highly-reproducible measurements and are careful with your interpretation of the results.  If your setup returns inconsistent results from one run to the next, then any attempt at a separated-variance plot will be GIGO.

You can see some examples at http://www.ke5fx.com/gpscomp.htm .  Various finicky conditions need to be met before the 3-cornered hat display will become available; check out https://www.febo.com/pipermail/time-nuts/2015-September/094039.html for some tips.  

-- john, KE5FX
Miles Design LLC

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