MacRumors reports that removing/reinsertion the SIM card may improve the reception of the iPhone 4

I went on my merry way, but realized something now. No matter what position I held my iPhone 4 in, the signal never decreased. I held it the many ways I know the signal issue pops and nothing. No bar loss, no signal loss, no call drop. NOTHING. So there you have it.

I am theorizing that moving the SIM card had something to do with the signal issue, because the only thing I have done to my iPhone 4 differently is take out and reinsert the SIM card. Other than that no other changes to it. No setting change, no software change no nothing. Just reinsertion of the SIM card.

  One Possible iPhone 4 Antenna Fix With Mixed Results