Re: [gpsd-users] Acquiring a Navisys GR[67]01W (was: GR-301W)

[Gerry Creager - NOAA Affiliate]

On Wed, Nov 19, 2014 at 2:31 PM, Thomas P. <address@hidden> wrote:

Hi,


On Wednesday 19 November 2014 12:05:42 Gary E. Miller wrote:
> My experience says otherwise.  I find the uBlox6 and SiRF III have no
> trouble in most buildings I am in.  And not on the edge, quite strong.
> I do agree that steel and/or tall building are very hard on a GPS
> signal, but that is not something I often see.
Maybe a difference between Europe and US. Here you will hardly find any
buildings where it works and even trough modern windows its hard.

> > But I would not expect, 1dB more or less sensitivity such a chipset
> > version has more or less would make a difference. (And newer chipsets
> > typically have better sensitivity than olders)
>
> My experience says otherwise.  Many of the newest GPS chips have
> emphasized power saings over receiver sensitivity.  Way more than dB.
> For example, I find the SiRF IV to perform very poorly compared to the
> SiRF III.

What I quickly can find:
Sirfstar3 -159dBm sensitivity (http://www.globalsources.com/gsol/I/GPS-module/p/sm/1025755241.htm#1025755241)
Sirfstar4 -163dBm sensitivity (http://www.csr.com/products/35/sirfstariv-gsd4e)

Well, this numbers say at least, but should be in a theoretic scenario equal,
with a tendency the SS4 is a bit better.

However, such a difference could be easily overridden by poor antenna/PCB
design, choosing a cheaper LNA etc.

Also other effects like fading or spur tones might harm the one or other
receiver more or less. Could be again that e.g. somebody uses a cheaper filter
after the antenna.

System performance relies on the overall system gain and noise figures. You can't just look at preamp or antenna gain (or loss) and ignore noise sources. 

 -- 

Gerry Creager

NSSL/CIMMS

405.325.6371

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