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I have just bought Globsat BU353S4 GPS-receiver. Now I have a doubt: it is mandatory to mount it in an horizontal position (i.e. facing the sky) or it can be also tilted of some angle with no perceptible loss in precision?

I'm talking about an ideal situation: two antennas with zero obstacles around them. One is mounted horizontally, while the other has some angle with respect to the terrain.

As I know, usually this patch antennas have a ground plane. Maybe that metallic plane can obstruct the view of one or more satellites... but I'm not sure, this is just a personal speculation.

P.S. I'm struggling to mount it on a motorcycle, so there is not a big choice of places where the antenna can be mounted.

enter image description here

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    \$\begingroup\$ please perform an experiment and ask a question afterward, if you still have a question \$\endgroup\$ – jsotola Oct 13 '19 at 21:13
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    \$\begingroup\$ Google for a 3D image of a "patch antenna radiation pattern" and judge for yourself. \$\endgroup\$ – DKNguyen Oct 13 '19 at 21:42
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    \$\begingroup\$ You asked about "precision". That's not affected. The ability to see satellites and get a fix, is what's affected. \$\endgroup\$ – gbarry Oct 13 '19 at 23:02
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    \$\begingroup\$ @gbarry Precision can be affected. If the receiver can only see a subset of the satellites with less-than-ideal geometry, Dilution Of Precision will be increased. If it sees them through a lower-gain portion of the antenna beam pattern and picks up more terrestrial thermal noise and interference through the higher-gain portion of the pattern, then each pseudorange measurement will be noisier and this will also degrade the solution quality. \$\endgroup\$ – pericynthion Oct 14 '19 at 0:17
  • \$\begingroup\$ @jsotola - I have to build a special alu-bracket with a milling-machine in order to mount the receiver in the intended position on my motorbike. It would be nice to have some (even rough) indication before wasting money and time. \$\endgroup\$ – gimpo Oct 14 '19 at 9:18
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Short answer: yes.

If you look at the radiation pattern you can observe that the antenna "sees" the sky all around with the same "sensitivity" (ie. is omnidirectional). Horizontal mounting is ideal, because the satellites can be anywhere in the sky.

When such an antenna would be mounted at 90 degrees (extreme tilt), then half of the sky would be shielded by the ground plane, so the receiver could get signal from half of the satellites. Most of the time it should be enough to sustain a fix, so I think a small tilt can be accepted.

enter image description here

Picture from: https://www.semanticscholar.org/paper/Installed-Radiation-Pattern-of-Patch-Antennas%3A-on-a-Gao-Wang/2ffd12945b0588bf76fcd0408cc0d9c1c82737d8

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  • \$\begingroup\$ Thanks a lot for the answer. You've confirmed me my suspects. \$\endgroup\$ – gimpo Oct 14 '19 at 10:29

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