[time-nuts] Is possible precise 1pps?

Bob Camp lists at rtty.us
Thu Mar 14 10:09:12 EDT 2013


Are we talking about steps between adjacent pps outputs or the relation of
the pps output to correct GPS time? They are two very different things. I
can put out twenty pulses that are each 50 ns to fast and be 1 us off
relative to the correct time. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David J Taylor
Sent: Thursday, March 14, 2013 2:57 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Is possible precise 1pps?

From: David
This brings up something that I have wondered about for a while.

The Garmin GPS18x (and many other receivers) specify the PPS output as
within 1uS but does that mean it wanders around over say 12 or 24
hours within 1uS of GPS Time or does it mean something else?  I can
easily see the granularity of the PPS output but that is obviously not
what the specification refers to.

I guess I need to pickup a real timing receiver or good oscillator to
run a comparison with to see what is going on.


I haven't looked often, or in great detail, or logged results, but my 18x 
and 18x LVC seem to be very similar in its offset from the rest such as 
U-blox 6M, 6T, Sure, Adafruit etc.  I.e. well within 100 ns.  Causal test, 
others may have measured more accurately.  I've not seen any 1 microsecond 

SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 

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