I think you are doing the right test to see if the splitter delay is the issue 21 ns is mighty small and a real possibility. Regards Paul WB8TSL
On Mon, Dec 21, 2015 at 8:24 PM, <[email protected]> wrote: > Hi All, > > So I've been playing with some timing hardware here, and have noticed > something rather curious. I have two otherwise identical Lea-6T GPS > modules, configured exactly the same. These units are tied to the same > antenna, with a splitter with the same length cables running to each unit. > They were given the same survey coordinates. Initially there was not any > appreciable difference between the PPS outputs. The outputs were on average > within about one nS of each other. However after a day or two they started > to display a difference of about 21nS between the PPS outputs. This is also > evident in the GPSDO output, as the phase of the 10Mhz is also skewed by > 21nS or so. > > A few days ago I started a 48 hour survey. The came up virtually identical > coordinates at the end of that survey. After the survey the phase is still > 21nS different. > > At this point, my only thought is the GPS splitter. It's DC coupled to one > unit, and AC coupled to the other. It is possible there are some delays on > one output vs. the other due to the blocking caps and bypass inductor in > the splitter. I've tried swapping the GPSDO units on the splitter, so we'll > see what happens there. > Can anyone offer any insight as to why the two units may have a different > PPS output timing? It's not really a problem, more of a curiosity and > mildly academic exercise. > Thanks, > Dan > > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
