AIR-1250 antennas

[Rafael Jimenez]

I would like to know what type of external antennas can i use with the AIR-AP1252AG.

Can I use one 12dBi (AIR-ANT24120) antenna in the 2.4Ghz Radio and one 6dBi (AIR-ANT5160V-R) for the 5Ghz radio?.

thanks

[Rob Huffman]

Hi Rafael,

Hope all is well with you!

The use of a single 2.4GHz and single 5GHz Antenna is not recommended with the 1250 series and really defeats the benefits that can be gained with 802.11n (like MIMO).

The AIR-ANT24120 is not supported with the 1250. The AIR-ANT5160V-R is supported for use with the 1250.

From this doc;

http://www.cisco.com/en/US/docs/wireless/access_point/1250/installation/guide/125h_c1.html

Have a look at this recent thread which includes some good insight on Antenna options, from Dennis, who is very knowledgable about the Draft 11n;

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=General&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1ddfd891

Here are the new antennas being introduced with the Cisco Aironet 1250 Series.

AIR-ANT2430V-R=

2.4-GHz 3 dBi Triple Omni Antenna *3 RP-TNC

AIR-ANT5140V-R=

5-GHz 4 dBi Triple Omni Antenna *3 RP-TNC

From this good Q & A;

http://www.cisco.com/en/US/netsol/ns767/netqa0900aecd806b7c82.html

For a little more info on 802.11n and the use of Antennas have a look at the following;

802.11n Wireless Technology Overview

http://www.cisco.com/en/US/products/ps6973/prod_brochure0900aecd806b8a92.html

A nice description of why to use multiple Antennas is in this blog;

http://blogs.cisco.com/wireless/2007/09/whats_up_with_mimo.html

Hope this helps!

Rob

[Scott Fella]

Like Rob mentioned, it defeates the purpose if wanting to utilize MIMO. You can use one if you like, just make sure you configure diversity to right antenna which would be your primary.

[gagnona]

I see that the triple omni antennas cost something like 15 times as much as single dipoles. Is there a disadvantage to using three dipoles rather than a triple omni?

Thanks!

[Scott Fella]

Nope... 2.4ghz antenna is a 2.4ghz antenna just like the 5ghz. I have done it this way.

[access_it]

I have three 2.4ghz antennas.

In order to utilize MIMO, do i configure the center antenna to be the recieving and the other two to diversity transmitting??

Also, where would i place the antenna reletive to each other to achieve the max performance?

[Rob Huffman]

Hi James,

For question 1;

Radio antenna connector (A-Tx/Rx)

Radio antenna connector (B-Tx/Rx)

Radio antenna connector (C-Rx) "Middle"

Figure 1-2

http://www.cisco.com/en/US/docs/wireless/access_point/1250/installation/guide/125h_c1.html#wp1056874

For the second question you can't get better than this answer from Fred @ Cisco;

"So when it comes to antenna placement, you can look at multiples of a given wavelength but it's not nearly as critical as you might think. Basically you don't want the antennas so far apart that they cover different cell sizes - and they could (but shouldn't be) any closer then they are on the AP-1250 AP which is approximately 2 & 3/4 inches.

If you put them much closer then that, you run the risk that the Dipole elements will play off each other and perhaps take on additional directional properties."

Fred Niehaus N8CPI

TME Cisco WNBU.

From this recent discussion;

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=WLAN%20Radio%20Standards&topicID=.ee6e8c2&fromOutline=&CommCmd=MB?cmd=display_location&location=.2cc024a0

Hope this helps!

Rob