You probably have a controller deployment. In that case create an RF Management profile (first enable Advanced Profiles under your User Profile), and assign that to the AP Group:

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Herman Robers
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If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
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Original Message:
Sent: Oct 27, 2023 01:39 PM
From: Sar@_23
Subject: 8.10 settings after upgrade from 6.5
I can't find in 8.10 what you are showing in these images.
But I was able to find the 2.4 GHz and 5 GHz channels selection under AP Groups > Radio > Basic. I changed the channels for 5GHz and removed all 40 MHz , 80 MHz and 160 MHz channels and only kept 20 MHz channels. However I still see clients connected on 40 MHz and 80 MHz. Not sure if I am missing something.
Original Message:
Sent: Oct 27, 2023 10:46 AM
From: chulcher
Subject: 8.10 settings after upgrade from 6.5
Basic rates will follow the configured minimum transmit rates.

Channel width is configured under the RF section.

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Carson Hulcher, ACEX#110
Original Message:
Sent: Oct 27, 2023 02:23 AM
From: Sar@_23
Subject: 8.10 settings after upgrade from 6.5
Hi, I am unable to find some setting after upgrade from 6.5 to 8.10.
How do I enforce that I only use 20 MHz for all SSIDs and Clients. It was an option in 6.5 but I couldn't find it in 8.10?
How do I set 802.11a/g/x basic rates and transmit rates for my SSIDs?
Thanks
Sar@