[ntp:questions] GPS clock for Linux

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Sat Sep 13 09:02:08 UTC 2008

>> I assume it's a software bug/feature.  The problem is drift/wander
>> in the offset.  The offset changes too slowly for normal
>> jitter filters to work on it.
>>   http://www.megapathdsl.net/~hmurray/ntp/GPSSiRF-off.gif

>connected via serial/nmea or pps?

Direct USB.

I have another one (using the SiRF chips)  that is serial
via a serial-USB adapter.  Same thing.

>that looks like some beat frequency effect.
>But it is much too slow/time too big
>  to be sender and/or receiver uart clocking.

Yes.  But I don't think it's a USB problem.  I get much better
results with a Garmin GPS 18 USB.  (Of course, what I don't know
about USB could fill ...)

These are my opinions, not necessarily my employer's.  I hate spam.

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