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Occasional Contributor II

Relationship between Min/Max Tx power in ARM profile and actual EIRP

I have an ARM profile with single-band assignment, min Tx 24 dBm, max Tx 33 dBm, applied to 11a radios only. When viewing the output of show ap active, the EIRP and Max EIRP are both always 22 for all 11a radios across the entire campus.

 

I would have thought that:

1) The EIRP shown by show ap active would not be lower than the Min Tx in the ARM profile

2) The Max EIRP would reflect the Max Tx in the ARM profile

3) There would be some variation in the transmit power between the APs

 

Clearly these assumptions are incorrect and/or I’m not using the right commands to view the actual radio status. What is the correct method to set and then monitor the actual radio power? Thanks in advance.

 

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

What APs do you have?  The regulatory regulations limit the output based on domain.  In addition, the most indoor APs have a limit of 23dBm per the datasheets

Seth R. Fiermonti
Consulting Systems Engineer - ACCX, ACDX, ACMX
Email: seth@hpe.com
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Occasional Contributor II

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

Thanks for your reply Seth. They're 225s. So, for example, I have run "show ap allowed-max-EIRP ap-name [ap-name] country-code au" on an AP whose 5 GHz radio is transmitting on channel 161. The max allowed EIRP for channel 161 shows as 33 (or 32 for HT 40).

 

But, as you point out, the specs for the 220 series list +23 dBm as the max. transmit power. So it would make sense if, regardless of the ARM and other settings, the radio maxxed out at 23, but they're all at 22. Small difference, I know, but I'd still like to understand why this is.

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

Fero, what regulatory region are you in? US, EU, etc? For this example AP can you log in and capture the the 'show ap active | incluede ap-name <apname>'?

 

If you are running HT40, you will max at 22dBm. The reason is that with HT40 you are using two streams/chains. You need all three chains to hit the 23dBm (and actually that's rounding up). 2x2 MRC is +3dBm, 3x3 MRC is +4.5dBm. So my question is why is it saying 22dBm when it SHOULD be 21dBm for HT40. Show AP active would help though.

Jerrod Howard
Sr. Techical Marketing Engineer
Occasional Contributor II

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

Hi Jerrod,

 

Region is Australia. Output for an AP on channel 161:

PNSWWOM-WAP38  default  10.100.0.58  0            AP:HT:7+/18/21       0            AP:HT:161/22/22      225      A2da   6d:22h:43m:53s  N/A

 

On the 802.11a radio profile HT is enabled, VHT is disabled.

 

Thanks for your input.

 

 

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

How about this

 

show ap debug driver-log ap-name PNSWWOM-WAP38 | include EIRP

 

Should show you the 'logic' behind the power selection.

Jerrod Howard
Sr. Techical Marketing Engineer
Occasional Contributor II

Re: Relationship between Min/Max Tx power in ARM profile and actual EIRP

The 5 most recent entries in that log are all identical:

394 530706.892282 wifi1: EIRP (Config: 18.0dBm, Set: 18.0dBm, AP Max: 21.50dBm, Reg Max: 32.0dBm), Conducted Power Set: 14.50dBm, Gain: 3.50

Prior to that, there is an entry where the power appears different:

390    525018.553272 wifi1: EIRP (Config: 21.0dBm, Set: 21.0dBm, AP Max: 21.50dBm, Reg Max: 32.0dBm), Conducted Power Set: 17.50dBm, Gain: 3.50

 

This presumably means that the power changed (lowered) recently?

 

Also, I assume the 2nd number in each line is a timestamp? How do I convert that to a human-readable date/time, please?

 

Thanks for your assistance.

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