WiFi Signal Strength and Computer Orientation

[Natanijel]

Hello everybody :)

This is my first post! I have a mystery about radio communication that I was wondering about for a long time:

If I have understood correctly, most computers have a single WiFi antenna in the shape of a rod, which is placed in a particular orientation. My question is this: why does the WiFi signal strength seem to be unaffected by the orientation of the antenna even though the voltage induced will depend on the direction and polarisation of the WiFi radio waves? For example, my laptop (as far as I know) has a single antenna in the plane of the keyboard, and if I rotate my computer through many angles, my signal strength is unaltered.

Could it be that there are multiple (maybe 3) radio receivers that are positioned perpendicular to each other for optimum radio wave capture? Or maybe the router has 3 perpendicular transmitters?

Thanks a lot for your help!
Nat :)

 

[mfb]

Signal strength does depend on the orientation, but the difference is small compared to other issues like walls.

 

[Natanijel]

Signal strength does depend on the orientation, but the difference is small compared to other issues like walls.

Thanks for the reply :)

 

[davenn]

Signal strength does depend on the orientation, but the difference is small compared to other issues like walls.

there is a huge difference in signal strength dependent on antenna orientation, the difference between horizontal and vertical polarisation is around 25 - 30 dB

Over the short distances that WiFi is used, several 10's of metres, it is as mfb said, not too much of an issue due to all the reflections of other objects
Over longer distances kilometres ++ it makes a major difference and matched antenna orientation is a must

Dave

PS ... nice to see you return after many months with a response
so many never bother to ever come back with a thanks
hope to see more of you on the Physics Forums

 

[TheDemx27]

there is a huge difference in signal strength dependent on antenna orientation, the difference between horizontal and vertical polarisation is around 25 - 30 dB

That may be true for some sort of dipole, but I believe there are other more complicated antenna designs available that can get closer to an ideal isotropic radiator, something I would guess computer manufacturers may take advantage of.

 

[Svein]

there is a huge difference in signal strength dependent on antenna orientation, the difference between horizontal and vertical polarisation is around 25 - 30 dB

One of the features of IEEE 802.11n is the optional use of multiple antennas in order to get a better signal strength.