On Mon, 25 Jun 2018 10:46:54 -0400
Bob kb8tq <[email protected]> wrote:
> Does UTC exist ( real time ) at the 1 ns level?
Currently, it does not. The clock comparison uncertainties are
still in the order of 1-3ns for short distances (several 100km)
and grow quite a bit once you go over something like 2000-3000km.
Unless you are using a dedicated fiber. But very few labs can
afford to have a fiber connecting them to another lab.
Also consider that, even within a lab, doing sub-ns accurate
time comparisons is challenging. All delays and their drifts
need to be precisely measured, characterized and factored in.
There is a reason why the SR-620 is still the main workhorse
in metrology labs, even though we have equipment available
that beats the SR-620 in terms of resolution and stability.
It's just not necessary to go below 20ps as the other factors
cannot be eliminated with that high precision/accuracy anyways.
If only precision time comparison is required, IIRC the current
limit is around 50-100fs. And even that requires a lot of work
and characterization.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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