updated 12:20 pm EDT, Wed June 30, 2010
Suggests odd criteria for iOS signal detection
Signal does indeed drop badly compared to other phones if an iPhone 4 is held in particular way, some more detailed tests suggest. Using modified iOS firmware, Anandtech says it was able to track a more precise signal rating than is possible with the bars an iPhone normally displays. When cupping an iPhone 4 with a tight grip reported to cause signal loss, the site says it noticed a 24.6dB drop in signal; this compared to 14.3dB for an iPhone 3GS, and 17.7dB for a Google Nexus One. More relaxed grips cut signals by 19.8, 1.9 and 10.7dB for each handset, respectively.
iOS is moreover said to show an uneven match between actual signal strength and the bars it displays. An iPhone will continue to display five bars between -51 and -99dB, or approximately 40 percent of the possible range. There is actually less distance in the gap between four bars and the bottom of the one-bar level, which is -113dB. This means that when close to the base of the five-bar level, a 24dB-plus drop can cause iOS to go from showing perfect signal to none at all. At four bars or fewer, only slight cupping is needed to cause an iPhone to apparently drop connection, since there is at most 14dB left in the scale.
Conversely, adding one of Apple's official bumper cases is said to eliminate the problem completely, and even result in smaller signal drop than when holding other phones. With this solved an iPhone 4 may actually get superior reception to the iPhone 3GS, holding onto calls and data in areas with weak or formerly non-existent connections.
"At the end of the day, Apple should add an insulative coating to the stainless steel band, or subsidize bumper cases," says Anandtech. Apple is so far refusing to offer free bumpers, though, and the expectation is that people will instead have to download an upcoming software fix. Given test results, the update could be meant to calibrate iOS 4 to more accurately reflect signal. Some iPhone 4 owners note that even when the device is showing absent reception, it may still be possible to make calls.