[time-nuts] Precision Time Protocol – Windows 10 implementation

[Adam Kumiszcza]

On Sun, Aug 11, 2019 at 8:01 PM Achim Gratz <Stromeko at nexgo.de> wrote:

> Adam Kumiszcza writes:
> >> The key here is to have some conducting magnetic material under the
> >> antenna, not just sitting on its own.
> >
> > My GPS antenna hangs on the window handle and still gives the good
> result.
> > It's on the south facing window. Unfortunately, in the new location I
> will
> > have access only to west facing window.
>
> You should orient it correctly so that it is facing up, not simply
> dangling it from the cable.  GPS antennas are directional.
>
> > Why is it good to have some conducting magnetic material under the
> antenna?
> > Is it to reduce multipath?
>
> The GPS dielectric patch antennas are designed to perform best with a
> ground plane.  The optimum size varies a bit, but between 10…14cm in
> diameter is about right. [...]
>

Thanks for all the info!
I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and put
it under my gps antenna. It does not hang now, but lays on the window sill,
facing up.

I cannot see any difference between these positions. I've made 10
measurement for each position, getting 12 SNR values for satellites for
each measurement and then calculated the average of these.
Hanging antenna had 25.18 SNR average (2.21 standard deviation). Antenna on
a ground plane had 26.10 SNR average (2.08 standard deviation).
https://docs.google.com/spreadsheets/d/1lvGFTQS62MqiQALjHmWFZRY3hb5O1OqANFGBhnCaEUo/edit?usp=sharing

2 example screenshots from gpsmon included (before and after the change of
position)

If I take into account single high elevation satellite with good SNR
(satellite 26 in the examples), the new placement and ground plane even
lowered it :(
I guess the real benefit of the ground plane would be if the antenna was
outside, or my measurement method was wrong?

Best regards,
Adam
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