[ntp:questions] lots of GPS modules and info at SparkFun

Chris Albertson albertson.chris at gmail.com
Thu Feb 9 17:43:11 UTC 2012

On Thu, Feb 9, 2012 at 1:08 AM, Ron Frazier (NTP)
<timekeepingntplist at c3energy.com> wrote:
> OK, so I'm replying to my own message, what's strange about that?  8-)
> VERY preliminary data, after running an hour with my USB GPS without PPS
> outputting only GPZDA sentences, I'm getting ~ +/- 5ms peak offsets of the
> computer clock vs GPS.  I'm liking it so far.  It initially looks more
> stable than when I was using GPGGA sentences.

Warning: This is addictive.   After you get some improvement then you
try for more and so on and so on.   Before your most recent change you
were about three orders of magnitude from the state of the art so you
have room for a great number of those "and so on and so on" cycles.

Before long you'll take seriously the old joke that a man with a watch
knows what time it is, but a man with two watches is never sure of the
time.  So you end up with three or five GPS systems and a couple
rubidium standards as well.  Then you'll be measuring cables to
account for propagation delays and placing your equipment in
temperature controlled enclosures,..... The spiral  does not have an
end.    Now your emails have many uses of "ms" but later we will be
reading "us" and even later "ns" and "ps"   This is the normal
progression for most addicts.

Chris Albertson
Redondo Beach, California

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