I had the same problem after replacing the digitiser on my ipad 2 and got here after searching relentlessly. I trashed the WiFi antenna when I opened it up and had to fit a new one. New antenna had really poor signal so I had to open it up again. I found out that with the antenna unscrewed from the chassis the signal was strong all over the house, but died whenever the antenna made contact with the chassis. I covered the "free" end of the antenna with electrical tape (and where it connects to the WiFi board to avoid shorting as someone mentioned previously). Without screwing it down at all, I tucked it between the screen and the battery! Tested it all with the ipad in bits and all was good. Still good on re-assembly. Hope this helps!