[ntp:questions] Re: difference between M12 & M12T GPS receiver

Hal Murray hmurray at suespammers.org
Tue Feb 3 00:29:42 UTC 2004

>If anyone can think of a way to test the RX vs. TX delays, I'm all

This is one of the great uses for good timekeeping.  :)

Setup another PC with GPS and connect it someplace where the
link speeds are known.  Close is better - just less noise
you have to filter out.  The idea is to have accurate clocks
on both ends so you can measure the one-way transmission times.

You might get enough info from peerstats.  Might work better
in burst mode.  At worst you have to write some simple code.

Do you have access to a "good" network connection?  Say
at work or through a friend?

Carry your PC and GPS there and then calibrate your setup using
nearby stratum1 clocks.  Compare the offsets with when you see
from home.  (I'm not sure that's good enough, but I think it would be
close.)  Again, the nearby isn't critical, it just means less
work to filter out the noise.  What you really need is links that
aren't too busy.  You want to find times when your packets will
go through with no queueing delays on any links.

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