I'm using Intel AC 7260 (built in my Toshiba laptop) connecting to an 1x1 AC access point.
When I try to test uplink throughput from 7260 to the AP in 5G channel, it goes well in the beginning with throughput around 80~90Mbps.
But after 1 or 2 minutes, the throughput drops to 40Mbps because 7260 starts to transmit in 20MHz bandwidth (from 80MHz to 20MHz),
and it just got stuck in 20MHz and never switch back to 80MHz.
Why would 7260 transmit in 20MHz? and can I turn this function off?. The driver is 18.33.02 2016/01/28.
You can set the channel width in the advanced WiFi adapter settings. For connectivity issues, we recommend to apply the configuration from the following advisory:
http://www.intel.com/content/www/us/en/support/network-and-i-o/wireless-networking/000005544.html Recommended Settings for 802.11n Connectivity
http://www.intel.com/content/www/us/en/support/network-and-i-o/wireless-networking/000005585.html Advanced Wi-Fi Adapter Settings
Also, make sure that this configuration matches the one from the your Access Point.
Another important thing is to verify with the Access point manufacturer that you are using their recommended/latest firmware.