[time-nuts] My Garmin 18x, Ver 3.50, currently 1 second slow to UTC
hmurray at megapathdsl.net
Wed Dec 29 09:16:07 UTC 2010
> It is possible that this has been reported as I do not see 3.50 available
> on garmin.com. 3.10 is the latest. Could not find anything in faq's or
> alerts though.
This page has comments for 3.20 and 3.50:
(But it's all in a Windows unpacker and I don't do windows.)
> It would certainly be useful to have a sentence transmission offset from
> UTC in the NMEA messages (or at least a new message heading/tailing the
> list with that in).
The problem isn't really the offset, it's the jitter. If the offset was a
constant, we could measure it.
I think it also depends upon the firmware version.
> You could scope it, (I am checking a MG1613S at the moment) but that is not
> that easy if you are selecting just one of the many messages being output.
You will have to watch it for a while to capture the range. There is roughly
150 ms of jitter, at least on an older unit.
> An easier method might be to just have NTP tell you what it thinks the
> offset is when measured against other references, then use that as your
> fudge factor.(use noselect directive for the NMEA server or set its stratum
> high so it doesn't get selected).
That's the way I would do it.
These are my opinions, not necessarily my employer's. I hate spam.
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