wifi 5Ghz connection gone

[v7peer]

I just updated from 18.04 to 18.10
On my router I have a 2.4 GHz connection and a separate 5 Ghz connection with different names.
In kubuntu 18.04 I could use both connections. I used the 5 Ghz connection.
After updating to kubuntu 18.10 only the 2.4 GHz connection is avaliable. The 5Ghz connection is no longer shown in the network manager.

The command "iwlist chan" in the terminal shows that the 5 Ghz channels are there:

enp3s0 no frequency information.

wlp2s0 26 channels in total; available frequencies :
Channel 01 : 2.412 GHz
Channel 02 : 2.417 GHz
Channel 03 : 2.422 GHz
Channel 04 : 2.427 GHz
Channel 05 : 2.432 GHz
Channel 06 : 2.437 GHz
Channel 07 : 2.442 GHz
Channel 08 : 2.447 GHz
Channel 09 : 2.452 GHz
Channel 10 : 2.457 GHz
Channel 11 : 2.462 GHz
Channel 12 : 2.467 GHz
Channel 13 : 2.472 GHz
Channel 36 : 5.18 GHz
Channel 40 : 5.2 GHz
Channel 44 : 5.22 GHz
Channel 48 : 5.24 GHz
Channel 52 : 5.26 GHz
Channel 56 : 5.28 GHz
Channel 60 : 5.3 GHz
Channel 64 : 5.32 GHz
Channel 149 : 5.745 GHz
Channel 153 : 5.765 GHz
Channel 157 : 5.785 GHz
Channel 161 : 5.805 GHz
Channel 165 : 5.825 GHz
Current Frequency=2.437 GHz (Channel 6)

lo no frequency information.

The command " sudo lshw -C network" in the terminal shows (only the wifi part):

*-network
description: Wireless interface
product: AR93xx Wireless Network Adapter
vendor: Qualcomm Atheros
physical id: 0
bus info: pci@0000:02:00.0
logical name: wlp2s0
version: 01
serial: 14:cc:20:10:c3:ec
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical wireless
configuration: broadcast=yes driver=ath9k driverversion=4.18.0-10-generic firmware=N/A ip=192.168.178.10 latency=0 link=yes multicast=yes wireless=IEEE 802.11
resources: irq:16 memory:f7d00000-f7d1ffff memory:f7d20000-f7d2ffff


What could be the reason that the 5 Ghz connection disappeared in the update from 18.04 to 18.10? An how can I get it back?

[GreyGeek]

I'd wager it is a kernel issue. My Bionic installation is using
$ uname -a
Linux GreyGeek 4.15.0-34-generic #37-Ubuntu SMP Mon Aug 27 15:21:48 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Yesterday a neighbor told me of his Win10 woes and how he hadn't been able to use his computer for several reasons. I offered to replace Win10 with Kubuntu BIonic and he agreed. My first installation attempt failed because his HP used efi and when it got to the point of installing grub it failed. So, I recreated the partition with a small front end partition and gave it to the efi what ever. The installation completed. It booted up nicely, ran well, even for a lowend HP laptop which makes a good browser and emailer but not much else. A visit to the Brothers printer website and using their installer took connected with the USB Brothers MCF-J870DW printer. Printed nicely.

Then I noticed that his WiFi (rtl8723be) was not staying up. One worm in the apple.
It turns out that when the 4.15.0.32 kernel was upgraded to 4.15.0.33 it lost the ability to communicate well with the rtl8723be chip.
https://bugs.launchpad.net/ubuntu/+s...x/+bug/1788997

People are having varied success with reverting to the .32 kernel, but it didn't work for me. And, setting ant_sel to 1 or 2 helped others, but didn't help me. All the combinations of the .32 & .33 and .36 kernel, with ant_sel, lps and fwlps variations never helped. I strung an ethernet cable from his cable modem to his laptop next to his recliner. His wife re-routed the cable behind funiture and underneath throw rugs all the way to his recliner. So, he has a potential 100Mb speed. Unfortunately, his Spectrum service gives him 40Mb down and 8Mb up, so his browsing crawls compared to my fiber optic 300Mb/s up and down.

I told him that given the fact that the devs were working feverently on a solution (the last post was two days ago) I suspect that within a month or two the fix will come down the pipe automatically.

[v7peer]

Yes, you were right. It is a kernel issue
I went back to the last kernel on my pc : 4.15.0-36 and my 5 gHz connection is back.