AireOS Antenna Gain range is 0 - 12 - how to set gain value for AIR-ANT25137NP-R ?

[Arne Bier]

Hello

I have a bunch of Cisco external antenna AIR-ANT25137NP-R attached to 3602E APs - the antenna has a 2.4 GHz gain of 13 dBi but I am unable to set this high gain on a WLC 5508 running 8.5.151.0 - when I set the value to 26 (because 26 * 0.5 dBi = 13 dBi) then I get the error below - how does one set the gain for these high gain antennas?

Since the AP doesn't know what type of external antenna is connected, I always assumed that it was mandatory to set this gain value. Current value is the default '0' dBi. 

[patoberli]

Not sure if this is possible. This antenna is only approved for the 3502E, see:

https://www.cisco.com/c/dam/en/us/products/collateral/wireless/aironet-antennas-accessories/solution-overview-c22-734002.pdf

[Arne Bier]

Thanks - I noticed that as well and it's probably not working optimally. I don't have a 3502E AP around to see whether it would even allow me to enter 26 into the gain field? 

Further to the gain setting - I am starting to think that the gain value doesn't have any impact on the RF at all - if anything, it might only be there to inform Prime so that it can try to calculate the raidation pattern for the maps. Would that make sense?

[patoberli · Accepted solution]

I never used an external antenna with high power.
In any case, the radio must adapt to the antenna, otherwise you are in illegal power areas (besides of one-way communication issues) in most countries. So with your antenna, the AP must limit the power output to nearly the minimum in most countries.

[Arne Bier]

right I get it now. Of course, because EIRP is the radio radiated power + Antenna Gain.  So if the country limit for 2.4 GHz EIRP is 23 dBm, then the TPC Max should be configured as 10 dBm. Of course we don't want the AP to run that hot ... so realistically (ideally) the AP power should be around a few dBm only.

thanks for the clarification.