Testing the latest LEDE build I run into the following issue. When I change the channel of the 5Ghz of my wndr4300 higher then channel 48 the 5Ghz stops working and gets disabled. Changing the region to US or World doesn't make any difference.
This is completely normal behavior. At channel 50 the DFS channels start. These channels can be used for wifi, but unfortunately these frequencies are also used for radar equipment at for example airports. This made it mandatory by regulations for wifi equipment to first scan for interfering radar signals. During this scanning phase, the accesspoint appears to be offline.
If these signals are detected, the accesspoint will automatically revert to a non-DFS channel (usually 36) as to not disturb these radar signals, as this could be dangerous for the planes relying on there signals. If these are not detected, the accesspoint will come online at the selected DFS channel.
I'm not entirely sure how long this scanning phase takes, but AFAIK it is at least 1 minute, although it might be even longer. I recommend waiting for at least 5-10 minutes after selecting the desired channel to see if it comes online at that channel or a non-DFS one. This will tell you whether it detected any radar signals on those frequencies.
Note that this mechanism is logged in the system logs. After having waited for 5-10 mins after selecting a DFS channel, check the logs (or post them if you want me to have a look) and it will give you more details about the scanning procedure that took place.
Good luck!
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Does it not come up after a while either?
Since on DFS channels, the radio first needs to scan for interference, it might take a minute or so before you see it pop up again.
Rather than returning to a non-DFS channel, check logread output from a wired violent when you restart WiFi, that should give you some clues.
Thank you both for the explaination about the DFS channels, I was not aware of that. The 5Ghz didn't came up after a while but maybe I was not waiting long enough. In the weekend I will to test again since it's my main router and I need to switch between OpenWRT CC en LEDE.
I tried it with 17.01.0 RC1, the DFS channel is working now.
I made the changes (channel, width and dBm) after that I reboot the router and few minutes later it was picking it up.
Hope this helps for others also