I've got almost 5 days uptime using channel 108, which is a DFS channel in Sweden with reg domain SE with a DFS patch.
I'm running my own custom build.
OpenWrt Chaos Calmer r45561 / LuCI Master (git-15.110.30908-6a13d73)
And no, Luci won't show DFS channels due to a bug/feature in Luci. They know about it and they will probably fix it at some point.
If you want to use DFS channels, do the following:
1) Set everything up in Luci the way you want it and set a channel (36 or whatever).
2) Set 80MHz width if you want to run that (why wouldn't you?).
3) Notice how it actually uses 5210MHz on channel 40 and not 5180MHz (which is channel 36)?
40MHz HT uses two sets of channels (20MHz each) with a primary channel and a secondary channel beneath (HT-) or above it (HT+). 5180MHz = Channel 36. 5200MHz = Channel 40. 5220MHz = Channel 44.
VHT at 80MHz however works differently, you define a center channel and then it goes the same amount in both directions.
So 5210MHz center channel becomes 80MHz between 5180 and 5260 (not including 5260), ie spanning all of channels 36, 40, 44 and 48.
4) "Save and Apply" all settings.
5) Figure out which DFS band you want to run on. Let's for the sake of discussion say you want to run on the H-Band which is channels 100-140. Lower frequencies as we all know have better wall penetration, etc so the lower the better, really. Now here's a gotcha that I ran into and couldn't figure out right away:
I set up 80MHz on channel 100 and wireless didn't go up. On the lower bands (36-48), it will auto-adjust the center channel so that all frequencies in the 80MHz spectrum are within the channel limits, ie lowest frequency is right at channel 36, etc.
Over on the H-band it doesn't do that, so if you put in channel 100 and 80MHz it would try to put the center channel right on channel 100 and since it can't run on frequencies below channel 100 it barfs. Move the center channel up to for instance channel 108 and you have the lowest frequency within the limits (and obviously the highest frequency as well since the H-band is more than 200MHz wide).
6) SSH to the router and modify /etc/config/wireless:
config wifi-device 'radio1'
option type 'mac80211'
option hwmode '11a'
option path 'platform/soc/soc:pcie-controller/pci0000:00/0000:00:03.0/0000:03:00.0'
option htmode 'VHT80'
option country 'SE'
option txpower '27' <--
option channel '108' <--
That's from my Kernel 4.0 running 1900AC. What you need to modify is basically the channel right at the bottom to whatever you want. Check out regulations where you live and if they allow you to boost the transmit power (like ETSI does in Europe as long as you run DFS with TPC), set it to the value that's allowed, in my case regulations here allow me to run 1W but the driver won't let me set above 500mW which is 27dBm.
(Last edited by stesmi on 28 Apr 2015, 15:23)