Apple released an official comment on the issue this week, suggesting that users either adjust their hand position on the phone, or buy a case (such as Apple's $29 bumpers) that prevents one's hand from touching the exterior of the device.
"Gripping any mobile phone will result in some attenuation of its antenna performance, with certain places being worse than others depending on the placement of the antennas," the company said in a statement to Engadget. "This is a fact of life for every wireless phone. If you ever experience this on your iPhone 4, avoid gripping it in the lower left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases."
Some users have said they can recreate the issue by holding the iPhone 4 in their left hand, making their palm cover the seam that separates the device's two perimeter radio antennas. The metal band around the outside of Apple's new handset has breaks in it that allow the antennas inside the device, including cellular, Wi-Fi and Bluetooth, to establish connections.
For some, covering -- or even just touching -- the point where the two antennas meet can result in signal degradation, or cause a dropped call. It is believed that a person's skin can act as a conductive agent, bridging the gap between the two separate antennas.
The issue can be avoided when using Apple's official "bumper protective case, which covers the metal band around the outside of the device.
Supporting Apple's claims that the positioning of one's hand plays a part in cell phone reception, Engadget also posted a video from 2008 in which a user demonstrated loss of signal when adjusting an iPhone 3G.