strat-1 gps

Seth Mattinen sethm at rollernet.us
Wed Jun 27 03:58:13 UTC 2012


On 6/26/12 2:34 PM, Dave Hart wrote:
> On Tue, Jun 26, 2012 at 9:11 PM, Majdi S. Abbas <msa at 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






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