[ntp:questions] Installing more stable oscillator?

Steve Kostecke kostecke at ntp.org
Tue Jul 17 02:25:19 UTC 2007

On 2007-07-16, Wolfgang S. Rupprecht wrote:

> I don't think that the magnetically mounted GPS units are really meant
> to be kept mounted when the car is parked.  How long would they stay
> on the car?  Around here, I'd imagine it wouldn't last a month.

That would be an interesting test to undertake.

> It appears that their usage model is really is to only put the unit on
> the car roof when driving. I'm not sure where that leaves the magnetic
> car units like the Garmin 18 that have been pressed into PPS service.

The GPS-18 is an OEM unit that is intended for a variety of purposes.
Dismissing the LVC variant as merely a "magnetic car unit" gives short
shrift to it's capabilities and price/performance ratio.

A GPS that can produce the following peer summary through a non-metallic
shingled roof needn't be exposed to direct sun-light:

   ident     cnt   mean  rms   max   delay  dist  disp
GPS_NMEA(0)  5235  0.002 0.002 0.013 0.000  0.270 0.248

(from http://www.kostecke.net/ntp/index.html?date=20070101)

Anyone with a real need for better time will most likely have a
commensurately larger budget.

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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