[time-nuts] GPS for Nixie Clock

Hal Murray hmurray at megapathdsl.net
Fri Jul 15 16:50:06 EDT 2016

kb8tq at n1k.org said:
> Well, if you actually sit down and measure the serial timing on a modern GPS
> module, you will find that it is very consistent. That degrades quickly if
> you  enable a few dozen sentences. Sub 10 ms accuracy is not a tough target
> to  hit when standing still.  

Do you have brand names/models for units that give good serial timing?  (or 
even reasonable?)

All the ones I've tried have ballpark of 100 ms of wander.  The short term 
jitter is in the ms range but the long term wander is more like 100 ms 
peak-peak.  I assume it's a firmware screwup, probably because it didn't get 
into the requirements sheet.

The last time I looked carefully was quite a few years ago.  Maybe one of the 
newer brands is reasonably good.

The Garmin 18 was reasonably good.  The 18x is crap.  I assume they 
outsourced some of the work rather than updating their old firmware.

In case anybody is concerned about the PC end of serial timing, I have good 
data from a Z3801A feeding Linux.  With ntpd's filtering, it's well under a 

These are my opinions.  I hate spam.

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