Issues with apple products connect to Asus EA-N66

[fuzon1337]

Okey, so the Asus adapter is /and always has been on 2.4ghz

Maybe I have asked the question a bit wrong...
I told him to buy that product since it could be used as more than just an access point.

He choosed to use the setup "range extender" so he could get better signals from his router into his room.

And now out of nowhere he got full signal strenght on the iphone, but still have low signal strenght on his ipad.
When he is choosing which wifi network to connect, the signal strenght on his network says
Before he bought this product he could access the router without any problems, but had very low internet signals in his room.