Antenna Display Fine Engineering, Poor Usability
Apple's engineers took an innovative approach to creating antennas with good access to free space, appropriate physical and electrical length for the frequencies required, and a robust physical design. It's much better in many ways from the little wire pull-up antennas that used to plague cell phones. It's also a more efficient design than those zig-zag antennas buried in the innards of most other devices. But it is subject to user interaction. But user interaction is a factor in every phone, regardless of maker or design. One way or another, users can find a way to interfere with radio reception regardless of the phone. With the iPhone 4, you can do it by putting your hand on that little black strip. With the Nokia 100 (this goes way back), you could do it by touching that little wire antenna that stuck up from the top.From an engineering viewpoint, the iPhone 4 has a seriously good antenna design. From a usability viewpoint, not so much. Perhaps the inclusion of a thin layer of clear plastic might have helped, or even a sticker with an arrow pointing to the gap and the words, "Don't hold phone here" might have been enough. But once you know that when your hand covers that gap you will get poor reception, then you will know not to do it. Given the location of the iPhone 4's antenna, it was a sure thing that the reception would have been affected by being held, if only because the user's hand can change the overall capacitance of the system, and that in turn can affect the efficiency of the antenna. Given the fact that the design overall will result in better reception than if it had been placed internally, it's a net gain. There's really nothing wrong with the iPhone 4's antenna that a little knowledge about antennas won't fix.
At this point, I'm going to totally ruin the day for those iPhone partisans who are just waiting for an excuse to yell at me. When I looked at the interior of the iPhone 4, I was struck by the elegance of the device's antenna design. It was clear from the first glance that there would be an issue with people touching the antenna, but it seemed to me at the time that that risk was worth it given the efficient radiators that those outside strips of metal had become.