Ubiquity Wireless Cards

[blak111]

You can improve performance quite a bit with better omni directional antennas. Like Gruens said, you wont get gain, but you can greatly reduce the loss so it's worth looking into.

[GruensFroeschli]

blak111: there is not such a thing as an omnidirection antenne.
Advertising generally refers to rod antennas as omnidirectional even if they arent.

The 11dBi antenna has most probably an emission profile similar to the attached diagram:
As you can see the antenna has a very bad gain in direction of the top of the antenna
If you have a building with multiple floors such an antenna can only serve one floor.

[thekod]

so…how do i do multiple floors? Impossible?

[GruensFroeschli]

Well this can be tricky.
First find out from where you need to have access to the WLAN.
Then find out where it's possible to set accesspoints.

Generally i'd set one accesspoint per floor. (depending on how big the floor is more)
Usually you can connect two antennas to one accesspoint.

Now you connect the apropriate antenna: There is a very wide array of different types.
Use one with an emission-profile fitting the area you need to server with WLAN.
For indoor office applications you usually use patchantennas:
http://www.germes-online.com/catalog/88/1350/page3/136413/wall_patch_antenna.html

In this link you can see the emissionprofile of a patch antenna.
http://www.feko.info/knowledge-base/application-notes/patch-antenna-with-capactive-feed-probe/
As you can see it's only in one direction, but with a relatively high gain.

[thekod]

Thanks for the info.

[blak111]

Yeah, sorry I should have specified. I meant what is referred to as omnidirectional antenna by manufacturers (equal radiation in all directions across a plane). So if you're shopping for an omnidirectional antenna, your coverage will either be mostly vertical or horizontal depending on how you orient it.

Another option to cover multiple floors is to install a couple access points in the floor/ceiling right between them. You don't get the range of a directional antenna, but it's generally less cable to run; and, if an access point goes down, people will probably still get a signal from the other access points so they don't completely lose service. This option can also reduce the number of clients per access point which will greatly increase throughput.
More access points gets you the flexibility and throughput, but it can get expensive fast. It all depends on how much throughput the actual clients require. If it's really simple things like email, the extra access points probably aren't worth the money.

[lsf]

Remeber that most antennas with 360 deg. radiation patterns also has sidelobes (look at a co-linear type antenna) so even if the main radiation pattern has a narrow horisontal plane you will still get pretty good coverage both over and under the antenna due to the sidelobes (cheap designs = more/large/high sidelobes).

To make a simple co-linear take a look at this:
http://martybugs.net/wireless/collinear.cgi

[blak111]

Yeah, if they didn't have a vertical angle of radiation, you could only get signal if you were exactly on the same plane as the antenna.

[lsf]

What I mean is that if you are close to the antenna you would get a radiation pattern that would be spherical due to all the sidelobes. Most cheap designs would give you this if you had a co-linear design.
A typical 14dBi co-linear would give a spherical 100% cover with R around 150 ft.

[blak111]

Sorry, I meant to say if they didn't have a verticle angle…

[blak111]

lol, I think this thread needs to be put out of it's misery. I don't think anyone is getting anything out of this. ;)