[time-nuts] GPSDO - Does it work?

[Bob Stewart]

In this case, I was using the 10MHz output from the GPSDO as the reference and measuring the 5MHz output from the GPSDO.  So, even if the GPSDO is off in frequency, the relationship between the 10MHz reference and the 5MHz signal are mathematically fixed.  It just seemed strange to me that under such a circumstance the final count would wander only in the minus direction.  I expected either to see a solid 5.0000000, or to see it wandering between 4.9999999 and 5.0000001.

Bob





>________________________________
> From: Azelio Boriani <azelio.boriani at screen.it>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>Sent: Monday, July 15, 2013 4:47 AM
>Subject: Re: [time-nuts] GPSDO - Does it work?
> 
>
>It is normal for a counter to have a +/- 1 count of wander. Then you
>have to consider the reference for that counter. When you connect a
>GPSDO on the input of a counter with its internal reference used as a
>timing source, you are measuring that internal reference accuracy and
>stability, not the GPSDO's one. To verify a new GPSDO it is necessary
>to have another (know good) GPSDO or a Cs reference. Missing that, you
>can use the PPS output of the GPS receiver but then an average process
>is needed: say, a digital 'scope with the display persistence function
>and... wait a lot of time (or use a high resolution TI counter and the
>TimeLab software).
>
>
>