WiFi 802.11n on T520 and T530

[JBUK]

My T520 and two T530s have the Intel N 6205 adapter fitted. When I look at the connected speed using 5GHz they show connected at 300Mbps. However when I connect using 2.4GHz band connection speed is only 54Mbps. Signal strength is strong as the Router is 5 ft away.
If I connect my T61 with an Atheros5008 then connection speed on 2.4GHz is 130Mbps. So it seems that the Intel 6205 does not want to connect to my router, a Netgear DGND3700 at the full speed and performs at 802.11g speeds.

On my 50Mbps Broadband, speed tests show 50Mbps on 5GHz and 20Mbps on 2.4GHz. So it is not just that they are reporting the speed wrongly, they are underperforming.
Firing up a spare 3700 router shows the same result making the issue look like a compatibility problem between the adapters and the routers.

I have the most recent Intel wifi drivers from Lenovo and as all the machines are connecting at the same slow speed I am wondering if fitting the alternative Intel adapters - 6250 or 6300 would be any more successful.

[JBUK]

Can anyone help me with this wifi issue?

[axur-delmeria]

I have an X220 with the same Intel 6205 WiFI, and remember forcing the driver to enable 40MHz channel width (instead of the default auto or 20MHz) in order to get a connection speed of 300Mbps @ 2.4GHz.

More thoughts

I don't know if the Intel 6300N will give improved performance. I think it's not really a compatibility issue, but more like Intel's WiFi chip isn't as good as Atheros'.

Atheros usually has better WiFi chips TBH.

BTW, that Netgear router is dual-band right? IMO it's best to connect WiFi 802.11n devices on the 5GHz band. That way you can get 300Mbps connection speed without messing around with driver or router settings.