[time-nuts] Best GPS 1PPS Accuracy

Randy Warner Randy at synergy-gps.com
Thu Dec 14 18:18:17 EST 2006


I can't speak for all receivers, but the Motorola's decay gracefully for
about an hour. There will be a significant error (us level would be my
guess). I'll have to try one. Again, if you are a ns chaser this will
obviously be acceptable, but we have several customers that let the
receiver run outside and get all happy and then disconnect the antenna
before they take it inside to be used as a reference for some
(hopefully) short period of time. I wish I knew the application, but as
a patriot I'd probably have to kill myself if they told me..... 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Hal Murray
Sent: Thursday, December 14, 2006 2:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best GPS 1PPS Accuracy

> The beauty of a GPSDO is that you're only changing the DAC every few 
> minutes so there's plenty of time to look carefully at the quality of 
> your 1 Hz samples before you commit the DAC update.

I think this discussion started with somebody asking about the last few
PPS signals before the signal quality was declared to be no-good.

My guess is that they might be significantly in error.  That's a
systematic error rather than a glitch that's easy to filter out.

Has anybody measured this?  I'm thinking of something like setup a GPS
unit with a poor antenna and record the PPS times relative to a good
house standard as well as the RS-232 text that has the good/bad flag.
Then eyeball the samples around the time the flag changes.

These are my opinions, not necessarily my employer's.  I hate spam.

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