Re: strat-1 gps

[Seth Mattinen <sethm () rollernet us>]

On 6/26/12 2:34 PM, Dave Hart wrote:
> On Tue, Jun 26, 2012 at 9:11 PM, Majdi S. Abbas <msa () latt net> wrote:
> > On Tue, Jun 26, 2012 at 04:33:35PM -0400, Robert E. Seastrom wrote:
> > > Word around the campfire is that the 18x is jittery compared to the 18.
> >
> >        The 18x is much worse than the 18LVC.  Thankfully I still have
> > 2 18LVCs... but that said, given the hockey puck design, and that Randy
> > already has an antenna, I wouldn't recommend this approach anyway.  It's
> > really only suitable next to a window, or in a short, wooden structure.
>
> I agree the Garmin GPS 18x LVC solution is only appropriate near a
> window, or in a short wooden structure.  David J. Taylor's experience
> was the older GPS 18 LVC had a substantially less sensitive receiver,
> so that his needed to be mounted outside, while his 18x LVC works
> inside.
>
> The area where 18x LVC underperforms the 18 LVC is the jitter of the
> timing of its NMEA output relative to the leading edge of the PPS.
> Configured correctly, this should matter very little, and only
> transiently at startup where ntpd first uses the NMEA end-of-line
> timestamp (possibly fudged to bring it closer to the top of second) to
> "number the seconds" before engaging the PPS.  I don't recommend
> attempting to use any NMEA source without PPS.  With it, I don't
> understand why Majdi finds the 18x LVC much worse.


Does anyone use or prefer the 5Hz version of the 18x LVC?

~Seth