[LinuxPPS] Nmea driver and GPS18LVC

[tlhackque]

On 04-Aug-14 09:03, Paul wrote:
> I guess the configuration is in the title. I am using ntp 4.26p5, with
> NMEA compiled in. Hardware is a GPS18LVC, with no buffering.
>
> I`ll ask the questions as they occurred to me rather than at the end.
>
> First, how can I tell if ntp is locking to the NMEA sentences only,
> which I would expect to be rather inaccurate, or to the NMEA and the PPS?
>
> As soon as I powered up the GPS18 ntpq claimed that it was providing a
> stratum 1 time. (Hmm, so much for careful smoothing algorithms). It
> rapidly went to an offset of 0.011 with a jitter of 0.020. More
> significantly offsets to pool servers were of the order of -2 to -5.
> Believable?
>
> Unfortunately next morning things were much worse. While GPS claimed
> to be at an offset of 0.004, with an jitter of 0.013, the offset to
> the pool servers was in the order of 200.
>
> Do you think I am locked to the NMEA only?
>
> Regards
>
> Paul
>
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That sounds like you're using the wrong edge of the PPS signal.

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