[time-nuts] Re: Trimble GSPDO - ISSUE

[Dana Whitlow]

Most general purpose passive splitters for the L-band regime are
essentially variations
on the Watkinson splitter, which provides good isolation between the output
ports, if
(and only if) the input port is driven from a matched source.

So if your GPS antenna, whether active or passive, has a good output match
then
the Samsung's input impedance will not affect operation of the Trimble.
But, again,
this is true only if the antenna's output impedance is matched to the
splitter's
characteristic impedance (including consideration of any impedance
transformation
in the transmission line between the antenna and the splitter).

I cringe at the cavalier treatment given to line impedances used in GPS
systems.
AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of such
equipment is provided with 'F' connectors, which invite the use of
inexpensive RG-6
line, which is 75 ohm cable.  In addition to problems with impedances and
loading,
It's a built-in source of multipath, all at no extra charge!

Dana   K8YUM


On Tue, Jul 27, 2021 at 3:01 PM Don Cross <cosinekitty at gmail.com> wrote:

> On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts <
> time-nuts at lists.febo.com> wrote:
>
> >
> > Any guess? Do I have to throw the unit from the window? For your
> > reference, I have a samsung unit connected to same antenna via a
> > splitter. The GPSDO is performing very well.
> >
> >
> Hi Ordnit,
>
> I'm hardly an expert, but I wonder about the splitter. Is this a passive or
> active splitter? If passive, it could be the input impedance of your
> Samsung is much lower than for your new Trimble and it is making the signal
> seen by the Trimble too weak. If you are willing to disconnect the Samsung
> temporarily, perhaps you could try connecting your antenna to the Trimble
> only and see what happens.
>
> Don
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send
> an email to time-nuts-leave at lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>