[time-nuts] Re: function generator

[Poul-Henning Kamp]

--------
Jeremy Elson writes:

> [...] I plugged an RbXO into the DG1022Z and simply asked the
> DG1022Z to divide it down to a 1pps signal. That is, I configured it to
> create a pulse with a small duty cycle and 1hz frequency using the external
> clock as a reference. To my surprise, it introduces a small but
> measurable error of one part in 1E11 in the dividing-down. You can read the
> full story of this in my post from earlier this year:

When you feed such instruments an external clock, you often have to change
one or more calibration constants for the internal (OC)XO's offset to zero.

Another problem is that if you use the square wave output of a DDS based
generator, they often produce the square from the sine output of
the DDS chip with a schmitt-trigger, which causes lousy jitter.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.