[time-nuts] My Garmin 18x, Ver 3.50, currently 1 second slow to UTC

Kiwi Geoff geoff36 at gmail.com
Wed Dec 29 04:08:44 EST 2010

David Taylor wrote:
> I see the same effect on my GPS 18x LVC with the 3.50 firmware.
> Have you reported this to Garmin?

No I haven't reported this to Garmin, at first I just wanted to find
out if "my" GPS was at fault or was this common across any 18x.

The reason it caught me out, is that I had changed to version 3.30
(where it also delays NMEA) on the 27th Sep 2010, and it took a couple
of months to manifest as a problem. It was the "rising of the sap" in
my trees combined with windy weather - which pushed the NMEA into the
next second for my application.

Luckily I kept all the 18x firmware versions David, so I could simply
reload the firmware that completed the NMEA sentences well before the
next PPS.

> To me it's unacceptable that the NMEA output is delayed into the next PPS
> signal, making the unit much less useful.  I measure the NMEA output and
> it's not even a consistent distance delayed from the PPS, varying quite a
> bit.

Yes, that is why it got tricky for me David, because sometimes the GPS
gave the correct UTC time, and sometimes the UTC time was one second
slow - depending on how much the NMEA sentences were delayed from the

Regards, Kiwi Geoff (NZ).

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