[time-nuts] KS problem

Bob Stewart bob at evoria.net
Wed Dec 10 17:56:50 EST 2014


The issue for me is that if it couldn't get a good timing solution, why did if fail quietly?  I would expect it to at least go into holdover and turn on an alarm or something.  It was giving me fits at least 4 times a day, so I should have some idea whether using a different port on the splitter fixed it pretty soon.

Bob

      From: Charles Steinmetz <csteinmetz at yandex.com>
 To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Wednesday, December 10, 2014 4:42 PM
 Subject: Re: [time-nuts] KS problem
   
Bob wrote:

>No, I do not have a 360 degree view of the sky  *  *  *  I have 
>the southerly 180 degrees from about 20 degrees elevation and up.  I 
>bought this KS as an example reference for my homegrown.  It may be 
>that it's just not up to the job under my conditions.

This will affect the ultimate performance of your GPSDO, too.  GPS 
engines are able to generate the best "solution" and, therefore, to 
produce the most stable PPS, when the available satellite 
constellation includes a geometric diversity of good signals (i.e., 
good signals from satellites everywhere in the skyward 
hemisphere).  A limited view of the sky causes a less stable PPS, 
which in turn causes a less stable GPSDO output.  Probably not a big 
factor at xDEV ~ e-10, but increasingly important if you push toward e-12.

Best regards,

Charles



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