The Dell Wireless 1397 WLAN Half Mini Card is a single band wireless card that works on 2.4GHz ONLY, so speeds will be limited. Not sure what adapter you have installed on the Mac. Is it a wireless N? Use 5.0GHz or 2.4GHz? If 2.4GHz, does it use dual streaming?
If you run Network Interface it will show you the speeds of your adapter. Not sure if this can be run on a Mac.
Original poster, If you have solved your problem, can you please mark the correct thread(s) with your solution. Thanks
Welcome to Dell Community!
#MicrosoftMVP - Windows Expert-Consumer April 1, 2012 to March 31, 2015
The Dell 1397 Mini-Card is a b/g rated wireless adapter. However, your router is N rated, thus the N600 name. G ratings max out at 54mb download, however, I had the same issue with performance. I have 65MB down when hardlined and 21 running wirelessly.
Your best bet is to buy a Dell DW1515N rated wireless mini-card and swap out your current one. I just bought one on Amazon and it cost me only $25. Here's a link to that item if you're interested.
It's very simple and can be done in about 2 minutes. Here's a tutorial video to help.