I have for almost 2 years a SVF14N13CXB laptop. Since then I experienced all of the time slow wifi signal. Over the years I changed a lot of mini pcie wifi adaptapters. Finally, one day, after trying all kind of solutions, I tried to put another antenna from another old laptop. But I didn't put the antenna in the right place (behind the touchscreen) but just hold it my hand. The results were amazing: networks that I never seen right now just showed their SSID. So finally I concluded that something that has to do with antenna is the problem. I pulled and put the wifi card into another laptop and I had the same results: great signal. What? Yes, it's not the adapter fault, it's antenna fault! I tried to find another place inside the laptop to mount this new antenna, but didn't fit anywhere. Finally, I told myself: what if I unplug one antenna connector? Nothing happened! What if I schitch the connectors of antenna? WOWWWWW! A miracle!!! My signal increased from -77dB to -62dB. What if I unplung the black antenna cable and let only the gray cable pulled in the socket marked with "Main"? The results were amazing: -53dB instead of -75 .. -77 dB with the original configuration! After putting back the backcase of the laptop the signal (in the same place, with the same router) is -57 dB. So, after all this years I have one mici PCIe card with a single antenna cable put in place of "main" and the signal in as normal as other laptops!
If anyone can test and confirm will save many people from selling this amazings VAIO laptops just because of wifi!
PS: Sorry for my English