Default Trying to figure out poor signal strength issue

Hey guys!

Since I got my Nexus 5 a week ago, I'm experiencing a very poor performance of the signal reception at my office. At the same spot, Nexus' signal is around -103 dBm whereas a Neo or Arc S is around -93 dBm. Translated to bars, Nexus has 2 bars using EDGE and the others have 3-4 using HSPA.

I've tried to disable 4G, even for testing purposes I disabled 3G, but the signal strength is the same. I have read that many people have issues with the signal, either this same issue or other, and I got two Nexus with the same behavior, so I don't think it's due to defective devices.

I have noticed that the wifi drops some times and that the Nexus makes more noise on the speakers of my computer. Hence, I think it's a problem of some sort of interference produced by the Nexus.

Checking the testing menu (*#*#4636#*#*), on "Select radio band" at the "Phone information" field I only see "USA Band". I live in Spain, do you think this may be the source of the problem? If it is, how can I fix it?

The version 4.4.2 neither improve nor worsen the signal strength.