[ntp:questions] NTP on local networks

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Wed Aug 1 09:15:54 UTC 2012

David Taylor wrote:
> I have information on my Web site on the easy-to-use Sure GPS, as well
> as the low-cost Garmin GPS 18x LVC.
>    http://www.satsignal.eu/ntp/Sure-GPS.htm
>    http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm
> Mine are using simple puck antennas, indoors, on the top floor of a
> two-storey building.  Be aware that USB-connected devices will give far
> less accuracy than serial-port connected ones, but may be adequate if
> "half-a second" is all you need.

This summer I received two more SURE boards, it took about an hour total 
to solder on the two required patch wires on each of them.

(I used David's pictures to remind me where to put the patch wires!)

Together with a pair of old laptops (with proper serial ports) this 
gives me another set of Stratum1 servers, for a total outlay of less 
than $100.

I've seen reports here that one of the timing nuts have measured the 
SURE board as giving a PPS signal that's in the 25-50 ns range?

According to the loopstats files my laptop is mostly in the 3-500 ns 
range, with excursions up to a us or two, obviously due to interrupt 
response time jitter and temperature variations.

- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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