iPhone 4 Signal Strength Indicator Issue Alleviated by Use of Bumper or Case
Quite a few users have reported experiencing an issue with cellular signals appearing to degrade when holding the lower left portion of their iPhone 4s. While not all users have been able to reproduce the problem, it does seem to be fairly widespread, and can be easily visualized as users watch their bars indicating signal strength drop all the way down over a period of a few seconds while the lower left portion of the device is cupped in the hand.
In his iPhone 4 review for The Wall Street Journal, Walt Mossberg did note the device's tendency to show a lower number of signal strength bars than the iPhone 3GS, but that calls did continue to go through and Apple reported that the issue is simply a software issue with the display of the bars rather than an actual signal strength issue.
The cupping issue, however, may be more significant than just a software presentation issue, as several users have reported dropping calls as they place their hand over the lower left portion of the phone.
One user has posted a YouTube video demonstrating the issue and the use of a slide-on iPhone 3GS case to eliminate it.
We have confirmed that Apple's bumper case also appears to effectively prevent the issue from occurring. It remains to be seen, however, what Apple's official response to the issue will be.