swap the two receivers and see which one is leading, if leading is
changing the delay difference is with the antenna signal distribution
73
KJ6UHN
Alex
On 12/21/2015 8:03 PM, paul swed wrote:
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
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