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New Member

Using two or four different antennas on a 1242AG

Hello I have a little doubt, I need to cover two diferentes areas with AG, is possible to use only one 1242 with:

1-A: AIR-ANT5160V-R (Patch)

2-A: AIR-ANT5160V-R (Patch)

3-G: AIR-ANT2410Y-R (YAGI)

4-G: AIR-ANT2410Y-R (YAGI)

Or

1-A: AIR-ANT5160V-R (Patch)

2-A: AIR-ANT5195P-R (Omnidireccional)

3-G: AIR-ANT5160V-R (Omnidireccional)

4-G: AIR-ANT2410Y-R (YAGI)

Thanks in advanced.

1 ACCEPTED SOLUTION

Accepted Solutions
Green

Re: Using two or four different antennas on a 1242AG

NO.

Dual antennas are for redundancy. They must be the same and "see" the same area of coverage.

Variation from this practice will get you (rightfully) fired, beaten up, ridiculed, and subject to continued scorn from your peers, because you must have failed to read and/or understand the documentation related to this topic.

There is no doubt, you cannot do this and have satisfied users (remember, your boss, and his boss, and his boss' boss are all users, they will point at YOU and say it's all your fault ... as you are walking out the door for the last time).

...not that I have any strong feelings one way or the other ...;)

Good Luck

Scott

11 REPLIES
Hall of Fame Super Gold

Re: Using two or four different antennas on a 1242AG

How many people are expected to use this AP?

Hall of Fame Super Silver

Re: Using two or four different antennas on a 1242AG

You need to have the same antennas on each radio no matter what. Do not mix and match! If diversity is enabled, the AP can use one to transmit and the other to receive or transmit and receive on one antenna.

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

-Scott
*** Please rate helpful posts ***
New Member

Re: Using two or four different antennas on a 1242AG

Thanks for the fast reply.One question is possible to shuntdown the diversity? And use option 1, two equal antennas in norma A and G?

New Member

Re: Using two or four different antennas on a 1242AG

Thanks for the help. If I use option 1: 1-A and 4-G is to the left side, 2-A and 3-G is for right side. The A is only for voice, G is for Data. Left Side is about 3 clients in G, right side is about 4 clients in G. The A have about 10 clients with phones 7921G.

Green

Re: Using two or four different antennas on a 1242AG

NO.

Dual antennas are for redundancy. They must be the same and "see" the same area of coverage.

Variation from this practice will get you (rightfully) fired, beaten up, ridiculed, and subject to continued scorn from your peers, because you must have failed to read and/or understand the documentation related to this topic.

There is no doubt, you cannot do this and have satisfied users (remember, your boss, and his boss, and his boss' boss are all users, they will point at YOU and say it's all your fault ... as you are walking out the door for the last time).

...not that I have any strong feelings one way or the other ...;)

Good Luck

Scott

New Member

Re: Using two or four different antennas on a 1242AG

Scott thanks for the help. I will solve the problem with two APs :). Maybe one to the right side another to the left side.

Hall of Fame Super Silver

Re: Using two or four different antennas on a 1242AG

That would be your best choice.

-Scott
*** Please rate helpful posts ***
New Member

Re: Using two or four different antennas on a 1242AG

I'm just curious as to exactly why it would not be a good idea to use two different types of antennas with diversity enabled on the same radio (1242). I thought the client made a decision on which antenna to connect to by RSSI. If that was the case, the client would see the signal and be able to communicate with both antennas ( assuming you mounted them correctly) and the client would not get disconnected. Is there a limitation on the AP for how it trades the clients off from primary and secondary antennas? I can understand if you went with an extreme like a yagi and an omni, but what about the attached image? I don't practice using different antennas, primarily because I know two of the same antennas on one radio will definitely work fine, but I don't see an obvious reason why it wouldn't work with some antenna combinations. Has anyone actually tried this to see if it causes problems? Does the client have to connect to both antennas at the same time for diversity to work? If that was the case then I can see how a directional antenna would cause a problem with an omni. Just curious...

New Member

Re: Using two or four different antennas on a 1242AG

Hi.

The reason that you can't cover two radio cell's using this setup is that each time the radio hears a preamble of a frame comming in, it chooses which antenna to use for receiving the frame using a special algorithm.

When it has made this choice, it uses only that antenna and the other one is effectively turned off until the next preamble.

So if Building 1 tries to communicate with building 2 when building 2 AP is servicing it's inside clients, the transmission will fail, and vice versa.

So as already pointed out, you should have same type antenna servicing the same area when using diversity.

If you turn diversity off, you only use one of the two antennas.

Cheers, Einar.

Re: Using two or four different antennas on a 1242AG

From the Cisco Aironet Antennas and Accessories Reference Guide:

One caution with diversity, it is not designed for using two antennas covering two different

coverage cells. The problem in using it this way is that, if antenna no. 1 is communicating to device

no. 1 while device no. 2 (which is in the antenna no. 2 cell) tries to communicate, antenna no. 2 is

not connected (due to the position of the switch), and the communication fails. Diversity antennas

should cover the same area from only a slightly different location.

New Member

Re: Using two or four different antennas on a 1242AG

Thanks for the more detailed answer guys. It makes sense to me now.

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