Hello friends
my iphone 5 works Only if i put the phone 10cm from the router i get 2 bars from total 3., or let's say everything works but only at very close distance ( with all routers and in different places same )
changing wifi antenna which i already did and restore the iphone didn't fix the problem
any hardware expert here can help?
8 months later
its a known issue for iphone 5 bad WIFI reception... but give this a shot :

Hard Reset (home button + lock/power button) and see if your signal changes to the better..
On the 4S it had a bug where the Wi-Fi disabled itself due to overheating (most of these issues are caused by the heat in summer) anw, when it gets overheated it disables itself to avoid damage, but it doesn't re-enable itself when it gets cooled again, so what's working for some people is that they're heating it up using a hair dryer until the phone shuts down, then putting it in a bag in a freezer to cool off. This solved the problem.

use this as a last resort
No no I had this issue easy fix, open the phone there's a screw in the back, in the top right corner or so, tighten it gently, you won't even need a restart, it will be instantly fixed.