5GHz not working on Archer C7 v5 - tried many fixes

Hi everyone,

Been using OpenWRT for a long time, but this is the first time I need a little help if anyone has some ideas how I can diagnose this problem.

I've used linux for 20+ years so I'm hoping with a little help I can get the 5Ghz working....

I have an TP-Link Archer c7 v5 and I'm using latest 19.07.4 OpenWRT

Here is a screenshot of the 5Ghz.. its there, but not visible when scanning WIFI:

I tried replacing drivers, messing with different settings, I tried flashing back to factory, bricked the router, then restored back to factory with TFTP, 5ghz is working, but not in Open WRT. I re-flashed OpenWRT and now I have it setup repeating 2.4Ghz to wwan and lan, works pretty well like this, but tbh I was really hoping to get the 5Ghz working.

The 5Ghz radio will scan and show nearby 5Ghz access points, but it won't transmit ...

I searched may forum posts and tried everything I can find, nothing works, or at least I haven't found the right combination of things to get it working...

Interestingly I also have an Archer c50 v4 and it is exactly the same problem.... but first things first, if I can get the Archer c7 working I will try to duplicate on the C50 and of course I will post the exact fix, with steps to the community also.

thanks

fwiw, have you tried using lower channel number, such as 36?

Have you changed the country code?

you cannot use channel 161 with contry code FR.

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@adamess here the wifi channel list with country/region list

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Great, thanks...

I looked at the wifi chart, very useful!

I tried with US as the country also, same results... if I add a 5GHz Client then it connects as a client to the 5GHz net of the main router, like this:

Then I add a master to the radio, like this:

Then I save and apply, and I see this:

Both are enabled still, great! this is the furthest I got and I now understand a little more about 5Ghz that i didn't before, since all of my equipment was only 2.4Ghz before I upgraded ...

Now I can see that the wireless is working and not disabled according to the router... but as I scan the SSIDs the LF50 (5GHz channel) is not present / being broadcast.

I also then I check the connectability of the router, and it can't connect:

Once I diable the Master for 5Ghz, then the router can again connect to the internet (via 2.4GHz and/or 5GHz), verified with ping:

Any more ideas would be very appreciated?

you cannot use width 80 mhz on that channel
if you want use 161 as channel try 40 mhz

Yep I tried 40 and 20 .. unfortunately its same result...

I assume that I can repeat 2.4 and 5GHz radio without a problem ?

I also changed channels according to the list: (thanks @faser )

Which allowed the radio to stay enables after I clicked 'save&apply' but then the router wouldn't connect to the internet at all, until I disabled or deleted the 5Ghz Master...

I’m also having the same or similar problem. I have an Archer A7 using it in WISP mode and the 2.4 connects fine and repeats the signal perfectly but when I try to do it with the 5ghz it connects but doesn’t give me any internet access.

This could work while testing, but I guess as part of 802.11d the driver will detect it's not actually there and disable the radio. Just set the radio to where it's used and use legal channels only.

Another thing I found out the hard way is that channels are usually configured by their first channel, even though it will report back with the correct channel. So to explain using this picture, you'd set the channel to 36 for a 20, 40 and 80 MHz channel. Even though they like to call it 38 or 42 and it might report back on this channel. (OpenWRT does this reasonably well, unlike Mikrotik or UI AirOS)

Hi, I had similar issues after messing around with my settings one time.
I also have Archer C7, with the following version of OpenWrt installed:

Firmware Version - OpenWrt 19.07.2 r10947-65030d81f3 / LuCI openwrt-19.07 branch git-20.131.47987-bcdb9fd|

Kernel Version - 4.14.171

I found there's a bug, if you set the channel of the 2.4Ghz network to be "auto", it creates the problems you describe. I had the same thing happen to me when I set the channel on the 2.4Ghz network to "auto", and the 5Ghz network started working again when I reverted to some random numbered channel.

Hope this helps!

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This worked for me on stock firmware. Thanks, ghostcow!

Eh, only temporary relief.