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Re: [gpsd-users] Garmin 18X-5Hz

From: Gary E. Miller
Subject: Re: [gpsd-users] Garmin 18X-5Hz
Date: Sun, 14 Aug 2016 10:42:21 -0700

Yo David!

On Sun, 14 Aug 2016 09:14:37 +0100
"David J Taylor" <address@hidden> wrote:

> I have tested using /just/ a GPS/PPS Uputronics module to provide an
> NTP server with no Internet connection and it works just as
> expected. 

Usually,  evey once in a wheil the GPS will go off into the weeds and the
time server will follow it.  Thus the need for the secondary time

> The serial support on the Raspberry Pi changed with model 3, and with
> the Jessie OS, and may still be changing so be prepared to fiddle
> around a little.

Yeah, or just go to Gentoo and get stability.

>  You need the "prefer" flag against the serial "time
> of day" source, not against the PPS source (as that had no
> time-of-day information).

Apples and oranges.  You are using the 22 driver, and I, and the
howto's, use the 28 driver.  Once again the 22 driver usually works, but
it lacks the fail safes in the 28 driver chain.

> # Coarse time reference-clock - nearest second
> server minpoll 4 maxpoll 4 iburst prefer
> fudge time1 +0.105 flag1 1 refid GPSD stratum 1

Putting prefer on NMEA time will lead to occasional serious problems.

Do you have long term graphs showing your approach is stable?  I have
graphs showing this will occasioanaly fail.

> The older Garmin GPS18 LVC needs to be outdoors as it has a
> relatively insensitive receivers,

Yeah, mine is outside, and still marginal.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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