C/No drops around elevation angle of 15 degree

I collected 24-hour data with NovTel OEMV-3 GNSS receiver, and I found
there was a dip at the elevation angle of about 15 degree for all
satellite . Does anybody have an explanation for it?

Thanks in advance.

What was the elevation cut off selected ?

By default on that kind of card this one seems to be about 15=B0

Utilsea
http://utilsea.free.fr
.

On Nov 13, 3:40 pm, util...@aol.com wrote:

It is unlikely caused by the cut-off angle. Since when looks closely,
the dip happens at slightly different elevation angles for every
satellite which is ranging from about 10 degress to 19 degress.
Moreover, the cut-off angle for this test was set to 0 degress.

Have you looked around at the horizon from where your antenna is located?
Its it obstructed by buildings or hills?

Jeff

On Nov 13, 6:24 pm, gpsab...@gmail.com wrote:

What shape is the radiation/reception pattern of the antenna that you
are using? What sort of ground plane is there near the antenna?
Manufacturers generally try to get a uniform radiation pattern for
their antennae but those pesky laws of physics generally get in the
way causing the gain to drop off at lower elevations.

There will also quite likely be obstructions on the horizon (trees,
buildings, hills, trucks...) that upset the signal path from the
satellite to antenna.

Ian