[time-nuts] A question about GPS pps quality.

Robert Sexton robert at kudra.com
Thu Jul 26 11:38:53 EDT 2007

Greetings, all.

I've been a time-nut for years, and now I have a mailing list.

I've wanted a personal Stratum-1 server for a long time, and I'm still 
trying to figure how to get there.  I've got three GPS devices around, 
all of which promise 1us pulse accuracy.  I thought the simplest thing 
would be to use the TAPR fatpps gadget to interface with a FreeBSD 
machine.   I've got three Garmin devices to choose from: A GPS-20, a 
GPS-25, and an 18LVC.  The 20 and 25 are old and otherwise useless, so 
they are the first choices.

I don't have much of a budget, as I'm a grad student (EE).

So the question is:

1.  If I interface one of these to my closet-based server, do I really 
have a Stratum-1 source? 1us accuracy doesn't sound all that great, but 
I'm nut so sure that the server can take advantage of a pulse with 
greater accuracy.

2.  Would I get significantly better performance if I shelled out $75 
for one of the new trimble timing GPS modules, or found an old oncore 
timing module on ebay?

I know that the oscillator on my old AMD based UNIX machine isn't all 
that great, but I'll leave that question for another time.

Robert Sexton - robert at kudra.com, Cincinnati OH, USA
You should never wear your best trousers when you go out to fight for
freedom and liberty.  -- Henrik Ibsen

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