Originally Posted by amirTor
did you try AOSP roms? check the 4.4.2 ver if the problem is still there, just for curiosity
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No problem with AOSP roms (no slams at the first call) but I have a worst quality : voice during calls is bad (isn't catastrophic). Others people have not this problem with AOSP (I think)... My Galaxy S3 is recent (made, I believe in October, hardware is different?)
Roms 100 % custom (AOSP, CM...): no slams but voice calls quality is bad
Roms stock: 4.1 -> perfect (no slam and good quality during calls).
4.3 -> Slams at the first call and good quality during calls.
I think the problem is android 4.3 (but what???), not the modem and not the kernel (I tried a custom kernel with official samsung ROM)