Archer c2600v1 - sysupgrade to 18.06.1 - no/intermitent 2.4GHz WiFi

[otnert]

Hi,

I've just sys-upgraded my Archer c2600 from Lede 17.01.5 ->OpenWrt 18.06.1, all is working except the 2.4GHz WiFi won't work (ie it is not displaying the SSID). It might show up, however very seldom and intermittent. If I do manage a connection, it won't remain connected, the SSID will dissappear again. Am at my wits end ATM.

I never had any trouble using 2,4GHz WiFi on 17.01.5, using the same WiFi settings, always working.

I'm starting to think the sysupgrade might have something to do with it!
Is there a way to reset 18.06.1 to default at least to test?

I've taken a look at the config, it seems OK, have tried changing wireless channels and widths, setting it to auto but still the same!

Here is the wireless config file... I hope someone can help?

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option path 'soc/1b500000.pci/pci0000:00/0000:00:00.0/0000:01:00.0'
	option country 'AU'
	option channel '149'
	option htmode 'VHT80'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option mode 'ap'
	option ssid 'LEDE_5GHz'
	option key 'xyz'
	option network 'lan'
	option encryption 'psk2+ccmp'

config wifi-device 'radio1'
	option type 'mac80211'
	option hwmode '11g'
	option path 'soc/1b700000.pci/pci0001:00/0001:00:00.0/0001:01:00.0'
	option country 'AU'
	option legacy_rates '1'
	option channel 'auto'
	option htmode 'HT20'

config wifi-iface 'default_radio1'
	option device 'radio1'
	option mode 'ap'
	option key 'xyz'
	option network 'lan'
	option encryption 'psk2+ccmp'
	option ssid 'LEDE'

config wifi-iface
	option device 'radio0'
	option mode 'ap'
	option network 'guest'
	option encryption 'psk2+ccmp'
	option key 'xyz'
	option ssid 'LEDE_5Ghz_G'

config wifi-iface
	option device 'radio1'
	option mode 'ap'
	option network 'guest'
	option encryption 'psk2+ccmp'
	option key 'xyz'
	option ssid 'LEDE_G'
	option disabled '1'

[otnert]

Further progress:

I clicked "Perform reset" under System >Backup >Flash operations, and did notice the default SSID showed up. I initially changed the 'ESSID', 'Wireless security' settings, and 'Country Code' to suit.
Made sure I could connect, fine
I then changed the default wireless 2.4GHz channel to 6, applied the change and could not reconnect, so tried trying another channel getting the same result!

Stumped, not sure what to do from here?

I'll try again tomorrow, pretty late here ATM, suppose I might need to put Lede 17.01.5 back on to be sure!

[otnert]

Touch Wood! All working now, so far so good!

All along it seems the culprit affecting the 2.4GHz WiFi ended up being the Kingston 16GB (DataTraveler 100 G3) USB3 stick! After removing it, WiFi started working as expected.

It would of been nice to know exactly why? Nevertheless have now swapped the Kingston USB stick with another.

Apart from this hiccup... the Archer c2600 Lede 17.01.5 => OpenWrt 18.06.1 sysupgrade is working!

EDIT surprisingly after using a different USB stick, then retrying the Kingston USB stick all has settled down to a fully working system. The only difference is that I moved the Kingston to front-most USB port. Maybe enough distance from the WiFi not to cause the interference as described by @slh in the next post.

[slh]

That's a known systemic issue, USB 3.x 'transmits' on the same frequencies as 2.4 GHz wlan and thereby produces interference.

There's only little you can do (the vendor could have improved shielding and located the USB port as far away from the antennas as possible), the only thing you could do is trying different USB 3.x devices (whose shielding might be slightly better) - or not using any.

[otnert]

Now that you mention it, I do recall reading about the interference issue!

TBH the thought would of never crossed my mind!... as I've been using the said USB stick with LEDE 17.01.5 since its release (ie on a daily basis) and didn't have any problems.

Live and learn I guess