[ntp:questions] very confusing results though using pps and nmea

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Wed Aug 13 22:42:10 UTC 2008

>Note that serial port nmea is liable to be out by up to 1/2 sec and to have
>a lot ( 10s of msec) jitter on it, since the end of the string received by
>a slow serial port ( eg at 4800Bd, it takes an nmea sentence of about 60
>characters 1/8 of a second to be delivered and will have a jitter of few
>characters in length-- or about 10ms jitter).

That sort of jitter can easily be corrected.

Has anybody looked at a scope to see if the leading edge of a NMEA
string looks stable?

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