Verizon IPhone Can Suffer Signal Loss If Held in 'Death Grip'
An online report says that the Verizon iPhone 4 can experience the same kind of weakened signal when the antenna is gripped as some AT&T users experienced last year. The alleged "death grip" detunes and reduces (or attenuates) the signal, potentially dropping a call or slows a data download.
It's not clear how common or serious either problem is. Detuning and signal attenuation are common to all smartphones to varying degrees, and don't always result in a dropped connection or a notably slow data download. A report on iLounge.com claims there is also now some evidence of what's now being dubbed a "death hug" for the phone's Wi-Fi link.
[FAQ: iPhone 4 antenna issue]
(Word of the possible antenna issues comes as Verizon is making the iPhone 4 available for ordering by the public this week.)
After viewing the iLounge video of the death grip in action on a Verizon iPhone, antenna design expert Spencer Webb was not surprised. He's president of consulting firm AntennaSys, and blogged extensively last year about the original iPhone 4 antenna issues, and devised some tests to document the affect of different grips on signal reception.
"Yep, the antenna is still in the exterior band," he says. "So if you cover them up with your hands, if you deathgrip it, hug it, full-bodyhug it, deathhug it, it will affect the signal."
But Webb's own very preliminary assessment is that Apple may have made a key change in the Verizon model's antenna: moving the Wi-Fi and GPS antennas to the interior, and creating two cellular antennas, one at the top and one at the bottom of the phone. If so, this change will actually make weakened signals ever rarer, he says.
His recommendations for Verizon users are the same as for AT&T users: buy a rubber bumper for the phone and practice what he dubs the "Vulcan iPhone Pinch," holding the phone between thumb and first finger.
The new round of speculation and in some cases outrage was triggered in part by a video posted by iLounge, a Web site focusing on iOS devices, showing a signal loss with the Verizon iPhone. The video shows an initial 3G download with acceptable signal strength. When the phone is then held in a more cupped grip, reloading the same Web page is much slower, showing a drop in signal strength.
The same video shows the phone switched to a Wi-Fi connection, and loading a Web page. Changing to the "death grip" doesn't affect the load time. Then, the phone is shifted to a snug, two-handed horizontal (or landscape) grip, now being dubbed the "death hug," and the page reloaded over Wi-Fi: it becomes "very labored and very slow" according to the video's reviewer.
In the accompanying iLounge story, author Charles Starrett concludes "Once again, use of a protective case appears to fix the antenna issue, and attenuation may not be noticeable in areas with stronger signal strength." A speed test by iLounge found that a "normal grip" on the phone, caused download throughput to drop from 1.1Mbps to 0.1Mbps, and upload throughput from 0.5Mbps to 0.
The Verizon model lacks the SIM card slot for a GSM phone (for AT&T, for example), which frees up more space on the "PC board," Antennasys' Webb noted.
Based on Apple's FCC filing, Webb recently speculated that Apple moved the Wi-Fi antenna and possibly the GPS antenna to the interior board, under the rear glass. Based on earlier photos posted by Ars Technica, he notes that the Verizon iPhone model eliminates the gap in the exterior frame at the top (where the Wi-Fi and GPS antenna was located on the AT&T model), and creates new gaps on the sides.
"Is the new iPhone using antenna diversity (two antennas in the frame with switching between them) to compensate for hand effects? Possibly," Webb writes in his blog, concluding with a pun that perhaps only antenna engineers could love, "Stay tuned." (See "Antenna guru: 'Get a bumper and learn the Vulcan iPhone Pinch'".)
Antenna diversity is a "magnificent thing," Webb says. Using two or more receive antennas and separating them far enough apart means the phone can compensate for the effect of multipath – the time delay of received radio signals bouncing off objects between the transmit and receive antennas. At its worst, multipath can create destructive interference, dubbed a "null," where there's not a signal. Multiple antennas means "you have a high probability of not entering a null," Webb says.
But in the case of the Verizon iPhone, it may be something more basic: a grip that covers the top antenna will not cover the bottom one, or vice versa. "If I hamper one antenna but not the other, the system will survive that," Webb says. "If they're doing this, I think it will be a big improvement."
Webb happily uses an iPhone 4, with a bumper,on AT&T.
The iLounge story has triggered a new round of invective. The Inquirer's Lawrence Latif led off his story this way: "Just how long does it take for Apple to fix an antenna? That is the question Verizon Iphone 4 users must be asking after finding that the problems that plagued the device at launch over six months ago still persist." The headline: "Apple fails to fix Iphone 4 antenna for Verizon."
TheITnerd.com, referencing the iLounge report, concluded, "Steve [Jobs], you've got some explaining to do."
For others, the report is a non-issue. "In the height of the madness last year surrounding this, Apple held a press conference and handed out free bumpers," recalls Stephen Hackett at Macgasm.com. "After that, I think most people understand this to be an issue that happens to some people, with some devices, some times. I really don't think there's much to see here."
Hackett added, "I am unable to reproduce the issue on my new iPhone, but if this is similar to the issues with the AT&T model, it may be spotty."
John Cox covers wireless networking and mobile computing for Network World.
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