I agree,
Luciano
timeok
Il 2012-10-09 10:41 Azelio Boriani ha scritto:
Is there any difference between what a GPS receiver can receve via
crosstalk or receive directly from the antenna? In my opinion
crosstalk is
absolutely less than the last argument about GPS antenna splitters.
On Tue, Oct 9, 2012 at 9:58 AM, Timeok <[email protected]> wrote:
Hi all,
In my shack I have a single antenna with two power splitter in
series
because I need several ports for the four GPSDO and spare port for
occasional testing.
1.1 They argued that cross talk could happen among ports. I
doubt
it
with the newer models. I have experience with HP and Symmetricom
units
and they state their products cancel cross talk.
any cross talk depends on the circuit and layout of the splitter.
Some
crosstalk can happen with two close antenna cable.
I suppose the first question have to be : What is my time stability
target?
Important is a stable electrical and mechanical configuration and
port
connection.
1.2 They argued that there could be problems from the power
feeding
of the antenna and mismatches at the receiver antenna port
voltages.
Again I doubt it if one uses receivers in the same voltage range
I have the same dubt and for this reason I have powered my Agilent
splitter not from the GPS but from separate port is present (ac and
backup
du power).This also for the smart splitter.
2. I have been experimenting with GPS constellation coverage with
different brands of antennas. I have found different gains,
different
radiation patterns and as a result different satellites in view for
identical GPS receivers.
2.1 I have found that using a single antenna and a two port
HP
splitter I get the same radiation pattern, gain and identical
satellites in view for a set of identical receivers. For comparison
purposes I feel this is an adequate scenario.
I agree, the new receivers have comparable performance.Some more
difference are in PLL OCXO and firmware.
It is easier for me to take care of the transmission line
length
and
errors caused by phase differences, attenuation and delays.
2.2 Two identical GPS receivers each one with it's own
antenna,
could eventually cause spatial diversity reception for a system of
two
receivers conceptually set as one for comparison purposes.
Different
satellites being tracked on
each receiver if not connected to a common antenna. Even if
antennas
and transmission lines are identical.
Question is: Am I wrong doing the above mentioned assumptions while
considering the use of GPS transmission line splitters? I which
scenarios are the splitters recommended? In which cases they are
rather not to be considered?
I think a standard calibration lab have to setting up with two
antenna
system and two receivers as recovery plan in case of fault. One
system can
be single antenna plus GPSDO (recovery reference). The other can use
a
splitter connected to second receiver and several more ports for
testing.
All my ports are with a blocking capacitors in series to avoid any
antenna
or active splitter interaction.
Luciano
timeok
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