[time-nuts] GPS splitter measurements

Azelio Boriani azelio.boriani at screen.it
Fri Oct 12 03:38:52 EDT 2012


I test GPS antennae for warranty purposes: customers want to know if really
defective or not.

On Fri, Oct 12, 2012 at 7:45 AM, <bg at lysator.liu.se> wrote:

> Paul,
>
> > Azelio,
> > Not at all the satellite splitters can be smart or passive. I use a
> > passive
> > so it has 1 dc path. But all of the other ports have dc blocks built in.
> > The smarter units will direct the highest DC to the antenna. Its really
> > diodes and I stay clear of those. To smart for there own good.
>
> The S14WI chose the lowest port with a DC present. (smarter than diods...
> ;-))
>
> > Plus with 3.3v and 5 v... it gets messy. I actually use the whole thing
> as
> > a passive. Have a line amp ahead of the splitter to make up for splitter
> > loss. Feed it with its own supply that also feeds the antenna.
>
> > On some gps units you do have to add a dc load to trick them into
> > believing
> > an antenna is connected.
>
> This is included in (all) decent splitters. The load is usually 200ohms.
> The S14WI will actually remove the load towards the receivers when it
> detects a short/open condition towards the antenna.
>
> > Regards
> > Paul
> > WB8TSL
> >
> > On Thu, Oct 11, 2012 at 7:15 PM, Azelio Boriani
> > <azelio.boriani at screen.it>wrote:
> >
> >> To test this kind of items, you have to play with DC-blocks and
> >> bias-tees.
> >> Rather tedious but necessary. I know as at times I have to test
> >> questionable GPS antennae that return after lightning strikes.
> >>
> >> On Fri, Oct 12, 2012 at 1:09 AM, paul swed <paulswedb at gmail.com> wrote:
> >>
> >> > Magnus what would the possibility be of measuring an 8 way satellite
> >> > splitter? The $7 wonders with dc pass through. That looks like a very
> >> nice
> >> > network analyzer you have.
> >> > Regards
> >> > Paul
> >> > WB8TSL
> >> >
> >> > On Thu, Oct 11, 2012 at 7:05 PM, Magnus Danielson <
> >> > magnus at rubidium.dyndns.org> wrote:
> >> >
> >> > > On 10/12/2012 12:16 AM, Azelio Boriani wrote:
> >> > >
> >> > >> Please take care that the S14WI is "smart": if it doesn't sense a
> >> DC
> >> > >> current on the antenna port then it reports that to the user ports
> >> and I
> >> > >> think it can even power off the internal amplifier, this can
> >> account
> >> for
> >> > >> the observed loss instead of the gain.
> >> > >>
> >> > >
> >> > > I did consider this. but did not have the time and energy to follow
> >> that
> >> > > up at the time. It was only when I got home that I could dig up the
> >> > > datasheet and manual of the S14WI. Didn't want to fry it in the lab.
> >> > >
> >> > > I rather do an incomplete lab quick and safe. I reports warts and
> >> all.
> >> > >
> >> > > I'll see if I get time to re-do it tomorrow.
> >> > >
> >> > > Regardless, I want to get things going. More people than me should
> >> be
> >> > able
> >> > > to do this.
> >> > >
> >> > >
> >> > > Cheers,
> >> > > Magnus
> >> > >
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