[ntp:questions] Re: Good GPS for attic?

Brad Knowles 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 
<http://lists.ntp.isc.org/pipermail/hackers/2005-January/001405.html> 
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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