had the iphone a fluid damage or was it dropped ?

the problem is most likely a connection problem

i would first look at the golden spring and the whole lower quarter of the logic board (everything whats on the left side of the picture)

Hi everyone,i thinck that maybe help http://img189.imageshack.us/img189/4586/...

Where is the squere you must fractute line.

The other way is maybe this http://www.reperatorium.pl/Alle/frct.jpg

I try the second way and it works.Wish succes

Wow! Ive had this issue for 3 weeks since replacing my lcd and screen, all i did was removed the "do not remove" stick and screw, pushed the little copper piece up a bit. Turned the phone back on and boom full signal and working fine!

The WIFI antenna is in the upper part of the phone - the Cellular antenna is at the back of the dock connector assembly! They have nothing to do with each other.

I found a great tutorial on the net. Maybe it will help you!

"How I recovered my iPhone's lost GSM signal!"

http://www.mauron.net/iphonerepair/

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And I found that suggestion on CNET:

"ok here we go the problem is with a small piece of copper sticking out from the mainboard of the iphone 3g believe it or not, not the antenna not a blown chip a small lick of copper which has to rest snugly on the metal bezel ring surrounding the phone, that's it!! i know what you're thinking that is not possible right your do no remove screw is still in place your phone was never open before, put away all your cynicism, look carefully at the small piece of copper if just a quarter is on the metal bezel that is not enough a full half has to rest snugly to the bezel you can either solder an extension or remove the do not remove screw altogether (i had to remove mine) it now has full 5 bars no intermittent hide and seek with the signal, lol."

http://reviews.cnet.com/8618-19512_7-101...

replace the sim reader in the board.