AIR-ANT2430V-R & AIR-ANT5140V-R height limitation

[mcaoile]

Hi,

Can anybody provide me any information regarding height limitation for installing the above ceiling mounted antennas.  And is there a separation between the 2 antennas when mounted in the ceiling.

Regards,

[maldehne · Accepted solution]

please check the following links:

http://www.cisco.com/en/US/docs/wireless/antenna/installation/guide/ant2430v.html

http://www.cisco.com/en/US/docs/wireless/antenna/installation/guide/ant5140v.html

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[Amjad Abdullah]

If you look into the antenna guides maldehne posted you'll find that:

AIR-ANT2430V-R has E-plane beamwidth = 60 degrees. This means (not exactly, but approximate definition) the signal goes 30 degress above and 30 degrees below the antenna.

AIR-ANT5140V-R has E-plane beamwidth = 45 degrees. This means (again, not exactly, but approximate definition) the signal goes 22.5 degress above and 22.5 degrees below the antenna.

Based on that you can calculate the distance from which you want to connect and find the proper height at which the antenna can be put.

Regards,

Amjad

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[mcaoile]

Hi Amjad,

Is there any formula that I can use to compute the height limitation?

Regards,

[Amjad Abdullah · Accepted solution]

mcaoile: we value you rate useful replies.

You can use triangle laws.

You have to keep in your mind that as the beamwidth is only 60 degrees, and depending on the height of the AP, the users standing directly under the AP or close to the point directly under the AP may not get proper signal. The reason why is the AP is not senidng the signal directly below it.

Triangle laws can tell you for specific AP height, at what horizontal distance (approximate) the users can get proper signal.

One relationship between the AP height and horizontal distance can be

tan (VBW/2) = H/L

where

VBW: vertical beam width.

H = AP height.

L = horitontal length of the AP signal.

suppose we put the AP at height 7 meters with vertical beamwidth of 60 degrees and we want to know what horizontal distance the users will start getting good coverage. Now the equation will be:

tan (60/2) = 7/L

L = 7/tan(30)

L =~ 7/0.577

L =~ 12 meters.

Now, if the AP is at 7 meter height you know users at 12 meters distance from the AP will get proper signal. (7 - 11 meters from the AP may probably still get adequate signal. (practically, real distance may be 1/3 or 1/2 closer to the AP. If AP height is close enough to the calculated L that may indicate you can get good signal just under the AP).

This is optimal claclulation but in practice you'll surely find closer users are getting also good signal. However, 12 meters guarantees good signal. moving closer to the AP than 12 meters will cause signal degradation gradually until (possibly) you reach a point where signal is not that good. Depending on the antenna and the height you may reach blind area closer to the AP with no RF signal.

Using same equaiton with 60 degrees VBM, we'll find that:

If AP put at

3 meters height then L =~ 5.2 m.

2 meters height then L =~ 3.5 m.

10 meters height then L =~ 17.3 m.

With 3 meters height you may get adequate signal starting

Hope this is useful to you.

Regards,

Amjad

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[mcaoile]

Hi Amjad,

Is there any Cisco recommendation for the up to what height an indoor AP can be installed?

Regards,

[Scott Fella · Accepted solution]

It depends... 25-30' max but that is not set in stone. A site survey can determine if you have adequate signal even if the AP is 40' up.

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