[time-nuts] Some results of PRS10 and Trimble Resolution T
hmurray at suespammers.org
Wed Jun 28 06:04:40 EDT 2006
> the M12+'s pps jitter has a strong frequency component at a repetion
> rate of 2 s. This component has a peak to peak value of 2-4 ns and is
> almost unseen in the raw pps values. It is, however, clearly to be
Where does that 2 seconds come from? Is that just one set of observations,
or does it hold for most M12+s and most of the time?
One of Said's graphs had a minor bump at roughly 2 seconds. I saw another
graph with a small spike at 2 seconds, but I don't remember where.
TVB's graphs show that the sawtooth period changes. I assume the sawtooth is
the beat of the local OSC with the 1 PPS from GPS. I'm assuming the sawtooth
graphs are derived from a greatly expanded temperature vs frequency graphs -
similar to a Fresnel lens.
The flat spots (suspension bridge) are not necessarily zero temperature vs
frequency. They might be where the temperature is changing by an integral
number of cycles per second per second. (It might be atmosphere or multipath
that is changing rather than temperature.)
So why does that cause a bump at 2 seconds? Why not 1 second or 5 seconds?
It seems reasonable to filter out the 5 seconds, but I can't see how to
filter out 1 second without also filtering out the 2 seconds. I think I'd
expect a shoulder rather than a bump. It would fall off above 2 seconds and
blend in below 2 seconds.
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