[ntp:questions] How exact are the PPS pulses of common GPSses?

Gabs Ricalde gsricalde at gmail.com
Wed Feb 13 15:21:44 UTC 2013


I asked something similar on the time-nuts list as I have a cheap
navigation receiver that seems to have a 2 us offset compared to a
timing receiver:
http://www.febo.com/pipermail/time-nuts/2012-December/072358.html

I just got a GPS board with a LEA-6T mdule, I'm using the time mark
feature to compare external PPS sources to its internal timebase.
Results:

Trimble Acutime Gold: ~80 ns early
Symmetricom 58534A: ~100 ns late

Comparing to a realization of UTC is another thing, see
http://www.cnssys.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf
http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf


On Wed, Feb 13, 2013 at 9:29 PM, Ralph Aichinger <ralph at pangea.at> wrote:
>
> Has anybody checked the PPS output for constant shift against
> UTC? Is it possible that the pulses are off with a constant offset,
> even if they have very little jitter? Or is this unlikely from what
> happens inside the receiver?
>
> /ralph -- I am waiting for the first tutorial how to build a
>           rubidium-disciplined Raspberry Pi ;)
>
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