[time-nuts] Delay through GPS antenna splitter/amplifier -- an answer, and a question

[M. Warner Losh]

In message: <001501c764bd$eb38e740$0202a8c0 at quaddra>
            "Rob Kimberley" <rk at timing-consultants.com> writes:
: >From my experience, your position and hence derived time is based on the 
: antenna centre. Cable, splitter, connector, and antenna filter delays all 
: need to be taken into account when looking at  very accurate "nanosecond" 
: timing applications.

Getting cable delay wrong isn't the end of the world.  However, rather
than seeing a few ns of variance in pps data, you'll see something
more in the tens of ns variance.  The absolute offset isn't always a
good indication if you have the cable delay right.  The variance in
your data tends to be a better indication, at least for the systems
that I've worked on.

Of course, if you have an "on-time" pps to test against, things are a
lot easier than if you just have a stable PPS to test against.

: For most applications in the microsecond or tens of microsecond region it 
: isn't worth worrying about.

60m of cables + splitters, etc is only going to add 180-200ns to the
propigation time.  That's well below 1us or 10us :-).

Warner