[ntp:hackers] u-blox reference clock driver

Gary E. Miller gem at rellim.com
Thu Aug 16 18:49:26 UTC 2018

Yo Achim!

On Thu, 16 Aug 2018 20:04:33 +0200
Achim Gratz via devel <devel at ntpsec.org> wrote:

> Gary E. Miller via devel writes:
> > u-blox has an app note:
> >
> > https://www.u-blox.com/sites/default/files/products/documents/GPS-Antenna_AppNote_%28GPS-X-08014%29.pdf
> >
> > In Section 5.1.1 they recommend a 50mmm to 70mm square ground plane
> > under a patch antenna.  They do not recommend anything larger then
> > 100mm (4").  
> That part of the app note is directed at passive antennas.

All antennas start out as are passive.  Some antennas have an added LNA
in the case, but the antenna is still the same.  The LNA just add gain.

>  The
> directionality should indeed change with the size of the ground plane

Yup.  The effect is to see fewer satellites on the horizon, and less
multipath.  This is seen in Fugure 17 of the app note.  The new polar
plot mode of gpsprof can be used to clearly see this effect.

> There is an immediate
> drop in performance without a ground plane

As clearly shown in Figure 18.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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