Two antennas on an Aironet 1310

[Richard-MARIE]

Hello,

When we add two antennas on the coaxial ports of a PA 1310, how to manage the power emitted by each antenna?
The two antennas transmit the same information from the interface Radio?

Thank you

[Rob Huffman]

Hi Richard,

You are most correct my friend, the Transmit Power setting is done

@ the radio interface and cannot bet set on the individual Antennas

http://www.cisco.com/en/US/docs/wireless/access_point/1300/12.2_15_JA/configuration/guide/o13rf.html#wpxref94126

Cheers!

Rob

[Richard-MARIE]

Ok thanks,

If i understand, Two antennas delivers the same signal but doesn't can not send a stronger signal from one antenna to another?

I know the command client power but a thinks that the config by default is the max from client power, no?

Thanks

[Nicolas Darchis]

Hi Richard,

your mistake comes from the fact that the 2 antennas are never used at the same time. When signal is received, the AP judges which antenna received the strongest of the signal and reads that one (same signal but received differently by the 2 antennas). When transmitting, it is using the same antenna that it received best signal just before.

So by default the right antenna is used to transmit except if the last frame from client was received through left antenna in a strongest way than through the right.

Since the antennas are not used at the same time, it would create major issues to allow to set differenet transmit power for each antenna.

I also fear that your question means you placed one antenna to cover an area and the second antenna to cover a second area which is very very wrong and creates collisions like there's no tomorrow.

Regards,

Nicolas

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[Richard-MARIE]

My case is as follows:
one antenna to cover 3 remote sites (omnidirectional antenna)
one antenna to cover 1 remote site (yagi antenna)
4 sites must communicate with each

I have to add an antenna because the site itself is not enough in view for the omnidirectional antenna.

All this with one AP 1310 (same radio interface, same SSID)

You things that is not possible with the problem of interface and power for the interface?

[Nicolas Darchis]

Hi Richard,

I assure 100% that you cannot change the power "per antenna".

But beyond that, from a design perspective, what you did is really bad. I think you will face a lot of collisions as soon as you will have traffic. The main reason is, as I mentioned, that antennas are not made to receive/transmit at the same time. So if a client is transmitting with the omni antenna, clients that are on the remote site don't hear anything, think it's good to transmit since they hear a silence and will transmit => creating collisions.

The good design in your case would simply involve 2 APs.

Hope this helps,

Nicolas

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[Kayle Miller]

Richard,

     As Nicolas stated this in not a proper design for the 1310, it may work at times but it will be extremely inefficent, as stated you will have a huge number of data errors and retries as well as collisions. The AP is designed for a single antenna and has no way of determining that there are 2 antennas; in terms of what Nicolas mentioned as the radio taking the strongest signal depending on your setup that could end up being the antenna with the highest gain. Because of the way it's all calculated.

     If you look at the attached picture you'll see in my example that 9 out of 10 times the AP will hear Building C only; because it will hear the strongest signal and pick that as Nicolas said.

Hope this helps..

Thanks,

Kayle

[Richard-MARIE]

Thank a lot for you help - This confirms what I thought: put two AP

Thanks