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Re: Satellites show up multiple times

From: Andreas B
Subject: Re: Satellites show up multiple times
Date: Wed, 5 Aug 2020 09:29:23 +0200


Thank you!


On Tue, Aug 4, 2020 at 5:53 PM Greg Troxel <> wrote:
> Andreas B <> writes:
> > I'm using a ublox ZED-F9P with default settings, which works great.
> >
> > Some satellites have two entries in the seen/used list in cgps. In
> > this case, a number is appended to the constellation abbreviation for
> > the second entry (see e.g. below). In xgps, no number is appended.
> > When the satellite shows up two (or more?) times in the list, does
> > this refer to the receiver using several frequencies from the
> > satellite (L1, L2,L5)?
> Probably.  And probably the entire scheme of passing this from receiving
> to display could use a good going over and some thought.  Dual-frequency
> receivers have only recently become affordable at the hobbyist level.
> > The SNR difference between the two entries of PRN 7 is 11, which
> > really seems to be alot. Why this big difference?
> could be differences in
>   tx antenna
>   tx power
>   propagation
>   rx antenna
>   rx local noise
>   rx preamp noise figure
>   rx preamp gain
>   rx cable loss
>   rx noise figure
> and surely other things I am not thinking of.  So I do not have an
> expectation that C/N0 will match, and I don't have an expectation that
> it will not.  Best to chase the signal path to make sure it all makes
> sense, first.
> Arguably a "where are the satelllites" list should not have multiple
> entries but a "how am I receiving it" list should.  I find "3" strange,
> vs something like L1/L2.  Keep in mind that Galileo has E5a and E5b.  So
> there really needs to be a "signal" field added.
> I think I am just talking about improvements that nobody has gotten
> around to, so far.

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