[ntp:questions] Re: Good GPS for attic?
brad at stop.mail-abuse.org
Sun Feb 13 17:41:56 UTC 2005
At 6:19 PM -0800 2005-02-12, David Schwartz wrote:
> I'm not suggesting doing this half-assed. I'm suggesting a well-designed
> solution. You can get a GPS receiver that has guaranteed timing
> specifications for less than $300. A low-end FreeBSD or Linux server to do
> the rest can be had for about $350 as well. This solution will give you +/-
> 3uS of UTC accuracy 99% of the time.
The acknowledged master in this field is Poul-Henning Kamp, who
has built various clocks using Soekris single-board computers and
Motorola Oncore 12+ GPS receivers, and has probably achieved the best
accuracy/cost ratio of anyone in the business. Certainly better than
almost all of the commercial GPS time server systems, at much less
than the price they charge.
Experience teaches that you do have to be pretty careful about
the components you put into these kinds of systems. See
for some tips.
All that said, sometimes a few hundred dollars for a local
refclock is still too much money for some. This is why we try to
make it easy for people to set up their own local time server, with a
reasonably robust configuration, making use of upstream time servers
that are more directly connected to Stratum 1 time sources.
Brad Knowles, <brad at stop.mail-abuse.org>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
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