Anyone has same issue?? I cannot set 40MHz channel in Wlan in 4.13 ver and 5.0rc3 version
In specs, this card shows supports i.e. MSC7@40MHz 
with R52N card I have the same issue.
What happens???
On ‘HT’ tab find ‘HT Extension Channel’ and set it to ‘above control’ or ‘below control’.
Your channel will be 40MHz wide.
Regards, Grzegorz.
solved but with below control, and htchains marked only 0. with 0&1 don’t connect my laptop atheros 9285 and with 0rx and 1tx works with packet drop…
But solved…
Atheros 9285 is single-stream chip, so max throughput is 150Mbps, and HT tx/rx chain must be ‘0’ only.
Regards, Grzegorz.
I have changed on ‘HT’ tab ‘HT Extension Channel’ and set it to ‘above control’ or ‘below control’. But I don’t see a 40MHz in the ‘Channel width’ list. (R52HN)
i still never get 40Mhz option
what i have is wireless tab
Band: 5Ghz A/N
and then
in HT tab:selected all the chains (so 4 checkboxes) (also tried only selected chain 0)
and HT Extension channel : above control (i also tried below)
But i never have an option for the 40Mhz Channel Width
Must i reboot after setting some setting?
This is a RB600A (5.0) with a R52Hn wifi
40mhz “Channel Width” field is available only if you have non-N chispet card, for example, R52 (AR5414 chipset).
For N chipset cards like R52N you need to use “HT Extension Channel” option.
From the Wiki manual
ht-extension-channel - whether to use additional 20MHz extension channel and if it should be located below or above control (main) channel. Extension channel allows 11n device to use 40MHz of spectrum in total thus increasing max throughput.
We will try to improve those fields in future RouterOS versions so it would not be so confusing.
So it is more or less the same if you would hide the “ht-extension-channel” setting all together
and just place a 40Mhz option in it and if you select that you set the right properties?
Because now you just have 2 things that do the same thing and sort of contradict each other?
Correct. But there could be one problem - customer might think that N card supports Turbo mode, but only Non-N cards supports turbo channel (40mhz). N cards supports only Extension channel option (2x20Mhz).
We will try to make an option in the current “channel-width” field so could select the extension channel also from there.