5ghz Wifi Slowness with 7800DXL

[swakefield]

I just bought the 7800DXL and on the whole I'm happy with it apart from the 5ghz network. It states its connected at 300Mbps but when running a speedtest on speedtest.net on any device while connected to this network the results won't GK above 10/6Mbps when I'm on a 40/10 fibre connection from Sky

If I connect to the 2.4ghz network the rests are in excess of 33/8 everytime.

Does anyone have any suggestions or tips to resolve the issue?

[billion_fan]

I assume you have tried changing the 'Control Sideband' to 'Higher' and then pick a wireless channel??

Do you have any other devices running on a 5ghz band eg network streaming devices, cordless phones etc?

Seems like a interference issue