I just upgraded my iPhone 4 from JB 4.0.1 to 4.3.1. I had a lot of problems with the phone being in a restore mode loop and had to use fixrecovery from tinyumbrella sight to exit. At this point i'm not even jailbroken, however, my signal strength is only one bar on AT&T when it usually was 5 bars. I've seen some references to this on other threads but I don't understand why I have this since I haven't jailbroken after the upgrade. The one thing I do notice is my baseband is still at 1.59.00. I tried restoring again through iTunes and again was stuck in the retore loop and had to use tinyumbrella to exit. Any thoughts on why I'm having this problem and is this a signal problem or a firmware indicator problem? I tried the phone and the call quality seems ok, but I'm concerned since I use it for work. I went into field test mode and it showed my signal strength as -113db which from what I recall is not good. Thanks for your thoughts.