Diversity antennas on the same AP [AIR-ANT2465P-R on LAP1242AG]

[pcce5w2hlh]

I refer to the usage of Diversity antennas (AIR-ANT2465P-R) on a single LAP1242AG access point.

We are trying to cover two different cell locations. Can we use 2 physical different Diversity antennas (same model) on a single AP that is running on b/g radios only?

Will there be any degradation? If yes, then how should we go about covering these two different cell locations using a single AP?

[Leo Laohoo]

Are you trying to use two AIR-ANT2465P-R for one AP?  Does this mean that you will plug one set to the b/g radio and one set to the a/g radio?

[pcce5w2hlh]

Yes, of using two AIR-ANT2465P-R for one AP.

Nope, the AIR-ANT2465P-R is only a b/g radio antenna. Hence, it can only be plugged into the b/g radio of the AP.

The LAP1242AG has two connectors on the b/g radios. Hence, can we connect two different AIR-ANT2465P-R onto the same one AP?

To be exact, each AIR-ANT2465P-R antenna has 2 jumper connectors, hence, in this case, we will only use 1 connector at each antenna into the AP, the other jumper connector is unused and sealed up.

[Leo Laohoo]

Whaoooooooo!  I wouldn't consider using the AIR-ANT2465P for the "a" radio.  It just won't work.

As Jon, said, the AIR-ANT2465P is designed for APs with two radio antennaes like the 1230 or 1240.  Installing it on 1250 might work but you can kiss "diversity" good-bye.

I my humble opinion, and please don't get offended, it's either do-it-correctly or don't-do-it-at-all.

[Rob Huffman]

Hi Tan,

Just to add a note to the tips from my good friend Leo (+5 bud!)

Two Antennas in "Diversity" mode cannot be used to cover two different cell areas.

Have a look at the following clip/doc

When you use a pair of antennas with matching characteristics to  provide diversity for cell coverage in your facility, the guideline is  to put those matched antennas at a distance apart from each other that  is equal to a multiple of the wavelength of the frequency that is being  transmitted. The 2.4 GHz wavelength is approximately 4.92 inches.  Therefore, to support diversity on a 2.4 GHz radio with two separate  antennas, the antennas should be spaced approximately 5 inches apart.  The antenna pair could also be spaced at multiples of 5 inches, but the  distance between should not exceed 4 multiples: reflected waves farther  apart than that are likely to be so distorted and different in delay  spread that the radio could not work with them.Because each antenna is  selected by itself, both antennas must have the same radiation  characteristics and be positioned to provide similar cell coverage.  ***Two antennas connected to the same access point must not be used to  cover two different cells.***

From this good doc;

Multipath  and Diversity

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml

Hope  this helps!

Rob

Please support CSC Helps Haiti

https://supportforums.cisco.com/docs/DOC-8895

https://supportforums.cisco.com/docs/DOC-8727

[pcce5w2hlh]

Thanks Rob for the URL. The document did state "Two antennas connected to the same       access point must not be used to cover two different cells.".

Possible to clarify the following:

(1) How does that differ from deploying dipole antennas (e.g. AIR-ANT4941) onto the  same single LAP1242AG?

The antennas (AIR-ANT4941) are still 2 separate pieces of antennas of  the same model, one into each antenna connector of the AP.

(2) You have mentioned "The 2.4 GHz wavelength is approximately 4.92 inches.  Therefore, to support diversity on a 2.4 GHz radio with two separate  antennas, the antennas should be spaced approximately 5 inches apart.... "

Does that means that we can use two antennas connected to the same access point to serve two different cells, but by physically separate them apart by at least 5 inches apart?

[Rob Huffman]

Hey Tan,

No worries

1. The use of two Antennas (like the 4941) would be used in a "Diversity"

configuration model to overcome Multipath. This does not mean that they cover

two different cells but rather the same cell but from a slightly different angle. This

is to overcome problems caused by obsticles that may block the signal from

one Antenna but not the other. Don't forget that the 2465 is a "Diversity" patch

model (that means within the "Patch" enclosure there are actually two distinct

Antennas)

2.If the Antennas are 5 inches apart, they would not cover two different cells.

By design, they would cover the same cell or area but from a slightly different angle.

I hope this makes sense,

Cheers!

Rob