[time-nuts] Strange 100ns jumps on Motorola M12+T

[Stephan Sandenbergh]

Hi,

Bjorn, it is good to know such splitter devices exist. This is really neat.

I'm using the built-in offset function of the M12+, and not an offset
generator. I'm currently redoing the measurement to see if it has similar
issues. And yes, I was also interested to see what would happen at other
offsets. And, if all of them would do it. I'll post when I get the results.

At the moment, I don't have something stable to serve as reference for the
53131As so I use the 10MHz output of the one as reference for the other. At
least they are locked together.




On 21 November 2013 14:34, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> The counter and offset generator both should be quite accurate at a 1 us
> offset. That’s large enough that you are outside the range of most GPS
> jumps. If you are going to move things around, you might as well move out
> to that vicinity.
>
> Bob
>
> On Nov 21, 2013, at 6:20 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:
>
> >> Below is a plot so you could see exactly what I measured. What is
> peculiar
> >> is that the time jumps by exactly 100ns to 200ns. Almost as if the GPS
> >> receiver decides to offset the time by twice the amount I set it to.
> Which
> >> is why I initially thought it might be a firmware thing. I suppose
> >> multipath is a good explanation, it is just odd that the time error is
> >> exactly 100ns.
> >
> > Hi Stephan,
> >
> > A quick test you could perform is set the offset to 125 ns instead of
> 100 ns and see if the jumps still occur, still occur at 100 ns, or now
> occur at 125 ns.
> >
> > Since you have three M12's offset the third one by 150 ns and see if it
> experiences jumps too.
> >
> > Question -- are you using the external 10 MHz reference input or output
> for any of your 53131A counters?
> >
> > /tvb
> >
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