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

From: Gary E. Miller
Subject: Re: [gpsd-users] Garmin 18X-5Hz
Date: Tue, 16 Aug 2016 13:05:36 -0700

Yo Robin!

On Tue, 16 Aug 2016 21:40:47 +0200
Robin Schwab <address@hidden> wrote:

> Am 16.08.2016 um 20:44 schrieb Gary E. Miller:
> > The cool thing about the Trimbles, and similar, is the grat hold-up
> > time for PPS.  Some specify an accurate PPS for a day after signal
> > loss.  A modern PPS, like a Venus 828F will perform as well as a
> > Trimble as long as it has a good lock.  And good lock is easy with
> > the super sensitivity these have.  
> Better than having a good oscillator in the gps would be to have one
> in the computer itself. A raspberrypi with a oxco would be an
> interesting platform for a timeserver.

Yes.  Uputronics takes one of the GPSDO boxes and uses it to driver
the RasPi clock.  A $200 OSC for a $35 board.  :-)

> NTPd would have less work to
> correct system time.

I disagree there.  On my Pi's the instability is in the interrupt
latencies.  So the clock is not bad, but the jumpy PPS timestamps
convince ntpd to keep slewing the clock back and forth.  I mitigate
that a bit by setting min_poll larger, and ntpd averages the one second
timestamps within the poll period.  Except for the timestamps it

> But this SMD stuff on todays computers is too
> small for my eyes and soldering capabilities.

Yeah...  But I like the new prices.  $35 for quad core CPU over @ GHz!

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

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