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I am testing a new 5GHz 6db patch antenna with an 80 degree spread in the horizontal direction and a 30 degree spread in the vertical direction. The antenna has a marking with 'top' on it.

My company has some very long rooms (40 meters long and 10 meters wide) that are full of tall machinery. I want to mount the antenna over the door that faces the long dimension and point the antenna down to shine over the machinery. I am thinking about rotating the antenna so the 80 degree spread covers the 40 meter span, but that means I'm rotating the antenna on the side by 90 degrees.

Some people endorse rotating antennas. However, I also see talk that rotating the antenna like this is very inefficient.

in a linearly polarized system, a misalignment of polarization of 45 degrees can degrade the signal up to 3dB and if misaligned and 90 degrees the attenuation can be more than 20dB.

I want the 80 degree cone aligned with the room's long dimension. Is it a bad idea to mount the 'top' of the antenna on it's side?

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I want the 80 degree cone aligned with the room's long dimension. Is it a bad idea to mount the 'top' of the antenna on it's side?

Misaligned antenna polarization will affect the received signal strength. You need to consider how your clients' antennas are aligned and shoot for matching that as closely as possible.

Antenna alignment gets kindof complicated because mobile clients like hand-held barcode scanners don't always keep their antennas aligned the same way; people often rotate the scanner to get a good barcode scan, and in the process change the scan gun's antenna plane. Tablets / iPads have similar problems.

You should also to check the manufacturer's specs for how the antenna is polarized. We are using a dual polarized antenna that is both vertically and horizontally polarized, so you can mount it either way; however, that same manufacturer makes a single polarized antenna that would suffer if you rotated it.

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