Hi, I have the latest drivers. Interference could be indeed a cause for this. I will try running Iperf between two computers. Luckily I recently bought an apple mac mini which is also AC enabled. I did not understand though how to do this between A+ and the macbook. Can you elaborate?
A+ runs OpenWRT, so you should be able to SSH in as root.
Once in, iperf may be there, or you may have to use opkg to install it.
iperf is part of OpenWRT's trunk, so it should not require compiling, etc.
I don't have my A+ powered up right now to give details, but I found a lot of good links Googling.
But also, if you're getting such a low connection speed, that implies a lot of interference.
You can rule that out by testing device-to-device with all devices closer to the A+ first,
and/or in a different location.