Yo Paride! On Mon, 22 Jan 2018 16:38:01 +0100 Paride Legovini via time-nuts <time-nuts@febo.com> wrote:
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
Before you bother looking at any GPS, you need to look at your server.
Hardly any Intel CPU can give you time resolution much better than
200 nS on a PPS in. Raspberry Pi's actually have slightly better
clock resolution than Intel parts, just under 190 nS.
That resolution os worse than what you get out of any good modern
GPS.
By 'local resolution' I mean the shortest time interval you can
read by repeatedly doing clock_systime() calls. clock_system() is
is many key ntpd paths.
The accuracy of your NTP server will be strongly affected by your server
choice, and the cheap RasPi is often one of the best for the job. Fot
$70 you can get a RasPi and a u-blox-8 hat. Add a few bits here and
there and you have a nifty stratum 1. You'll find its harder than it
looks to make a better NTP than that combo.
Then, once you have a strong baseline, you can see what tricks you
can do to improve on that.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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