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Some Advice for iPhone 4 Owners with Antenna "Issues"

Shortly after the iPhone 4 went on sale yesterday, complaints began to circulate that just holding the device a certain way can interfere with calls.

iPhone 4 antenna system
James Martin

In its redesign, Apple replaced the unit's sloping edges with a stainless steel band that wraps around the more squared-off sides. The metal band, which acts like a sturdy skeleton for the delicate phone, also does double duty as the device's antenna.

But Apple has since been swamped with calls about intermittent problems. The common complaint - which has received an extraordinary amount of attention - is that gripping the gadget in ways that cover the small black lines in the steel band will reduce the number of "bars" - the indicator of call signal strength.

In an email to Ars Technica, Steve Jobs counseled, "Just avoid holding it in this way."

Which reminded me of the old show business bit:

Patient: "Doctor, doctor, I hurts when I do this.

Doctor: Then don't do this.

So what's an iPhone lover to do. Spencer Webb of AntennaSys, Inc., who considers himself one, offers a good good explanation of the antenna issue.

In the first generation iPhone (which I am currently using), the antennas were on the back of the phone, near the bottom. There was a piece of plastic on the bottom covering the antennas, so you knew where they were. I developed a way to hold the phone which avoided covering this area with my hand, similar to the Gizmodo article linked above. It is worth stepping back a moment and asking the question, "Why are the antennas placed where my hand is MOST likely to cover it?" It's a fair question.

The FCC puts strict limits on the amount of energy from a handheld device that may be absorbed by the body. We call this Specific Absorbtion Rate, or SAR. In the olden days, when I walked ten miles to school in three feet of snow, uphill in both directions, cell phones had pull-up antennas.

This allowed the designer to use a half-wave antenna variant, and put the point of maximum radiation somewhat away from the users cranium. Of course, most people did not think it was necessary and kept the antenna stowed. Motorola's flip phone acutally had a second helical antenna that was switched into place when this was the case. But, more importantly, SAR rules were not yet in effect.

Flip phones became yesterday's style, and phones were becoming more monolithic. Some phones, like the early Treo, kept the antenna in the traditional location at the top of the phone, near one edge, but reduced it to a short stub. Whips became stubs, stubs became bumps, and finally antennas were embedded into the rectangular volume of the phone. The trouble was SAR; if you left the antenna at the top, the user was now pressing it into their head, insuring lots of tissue heating. Enter the bottom-located cellphone antenna.

Just about every cell phone in current production has the antenna located at the bottom. This insures that the radiating portion of the antenna is furthest from the head. Apple was not the first to locate the antenna on the bottom, and certainly won't be the last. The problem is that humans have their hands below their ears, so the most natural position for the hand is covering the antenna. This can't be a good design decision, can it? How can we be stuck with this conundrum? It's the FCC's fault.

Returning to the iPhone 4, Webb noted that when you cover the units two symmetrical slots in the stainless frame, there's likely going to be a performance hit. Just as bad, he says, there are no quick fixes.In fact, he argues that this is a "design compromise"  forced by the requirements of the FCC, AT&T, Apple's marketing department and Apple's industrial designers," among others.

A possible work-around, he suggests, is to put the iPhone in your pocket and make sure the screen faces toward your body with the antennas facing out. But even that is not a guaranteed.

However, if you put your iPhone in your left back pocket, and your earpiece in your right ear, you may have issues. This is a failing of the Bluetooth system in dealing with severe body losses at 2.4GHz, not the cellphone's problem.) The iPhone 4, however, moved the antenna action from the back of the phone to the sides. This probably improves the isotropy of the radiation pattern, but only when the phone is suspended magically in air. Not too helpful. Putting this iPhone 4 in your pocket will likely couple more energy into your body (you bag of salt water, you) than did the first generation model. Yep, I predict it will be worse.

Such is the joy of being an early technology adoptor.

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