[time-nuts] Best GPS 1PPS Accuracy

bg at lysator.liu.se bg at lysator.liu.se
Thu Dec 14 18:37:47 EST 2006


By unplugging the wrong cable on leaving my lab, I found out that my
Jupiter (nav) receiver drifted 180ms in 36h. A Meinberg GPS167, with a
standard OCXO drifted 1.8ms in the same time.

-- 

  Björn

On Fri, December 15, 2006 0:18, Randy Warner said:
> Hal,
>
> 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.....
>
>
> Randy
> ________________________________________________________________________
> ________________________________________________________
>
> -----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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