Did you ever experience that your brand new wireless Access Point (AP) does not deliver as strong signal in your house as you expected? I did. Short investigations revealed details useful not only for fixing your home wireless network, but also for designing stable enterprise wireless environments. Putting configuration issues aside, one of the reasons for bad signal can be improper positioning of your wireless AP antennas.
The thing is that the coverage zone around your Access Point is not a sphere, but a donut. Wireless donut, so to say. And the orientation of this donut is dependent on the orientation of the antenna. If your access point has visible external antennas, they must be put in a vertical position. The “wireless donut” will be laying horizontally, providing maximum coverage in horizontal plane.
What happens to the wireless coverage field if the access point is not mounted like it is supposed to?
a) The wireless field is extended vertically. You will have much less coverage, and the neighbours above and below you – much more noise in wireless spectrum.
b) The wireless field is wrongly polarized: antenna position also defines the polarity of the emitted wave. If you want to have good reception, both sender and receiver’s antennas must be identically polarized.
There is one curious consequence. If your access point is more than, let’s say, 10 meters right above or below you, you may be in its blind spot. That’s why one AP might not be sufficient to cover the whole house.
Things get more complicated if your Access Point has internal antennas. They hardly ever mention in the manual what wireless field it has. Sometimes it is good for home use (the field looks almost like a ball), but sometimes not. Check few examples below.
So for access point with internal antenna, check the manual: it must be mounted like supposed to. If they say it should lay on the floor, never attach it to the wall: it will put its wireless donut on its side.
Alex Mavrin, CCIE #7846
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