The testing involved three of iPhone 4s (purchased at three separate retailers in the New York area) in the controlled environment of a radio frequency (RF) isolation chamber impervious to outside radio signals, where test engineers connected the phones to the base-station emulator, a device that simulates carrier cell towers (see video ).
Consumer Reports also tested several other AT&T phones the same way, including the iPhone 3G S and the Palm Pre. None of those phones had the signal-loss problems of the iPhone 4.
Findings call into question the recent Apple claims that the iPhone 4's signal-strength issues were largely an optical illusion, caused by faulty software that "mistakenly displays 2 more bars than it should for a given signal strength." Tests also indicate that AT&T's network might not be the primary suspect in the iPhone 4's much-reported signal woes.
One solution to the antenna problem is to cover the lower left corner with duct tape or another thick, non-conductive material. It may not be pretty, but it works. The engineers expect that using a case would remedy the problem and will test a few cases this week and report back.
A high scoring problem device
The signal problem is the reason that the iPhone 4 is not a "recommended" model, even though its score in other tests places it atop the latest ratings of smart phones released.
The iPhone scored high, in part because it sports the sharpest display and best video camera seen on any phone, and outshines its high-scoring predecessors with improved battery life and such new features as a front-facing camera for video chats and built-in gyroscope that turns the phone into a super-responsive game controller.
But Apple needs to come up with a permanent—and free—fix for the iPhone 4. antenna problem before it can be recommended.