Apple has confessed that it has discovered that every iPhone uses the wrong formula to calculate how strong a signal it is receiving – meaning that it seems to show good reception when the signal is weak. It has promised a software fix for the problem “within a few weeks” which will match that used in other phones.

The explanation, in which the company says it used “totally wrong” calculations to work out the strength of the signal, seems to explain why some people have complained to the company that they see a dramatic drop-off in the signal strength displayed when they hold the iPhone 4 in a particular way.
Within hours of the phone being delivered to customers last month, dozens had posted videos on YouTube showing that the number of “bars” indicating reception strength fell abruptly when they picked the phone up from a desk.
Apple says in a press release on its site that it was “surprised” after the launch of the phone to read reports of reception problems, especially those who reported that the signal strength dropped completely – from five “bars” (the strongest reception) to none when held in a way that covers the antenna on the bottom of the phone.
But after getting “hundreds of emails from users” and seeing articles about the problem, it took the phones back to its laboratories – and discovered, it says, that it has been measuring signal strength wrongly since the very first iPhone, in a development it calls “simple and surprising”.
The company explains: “Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays two more bars than it should for a given signal strength. For example, we sometimes display four bars when we should be displaying as few as two bars.
That would mean that the apparently strong reception that vanished when the phone was picked up was a mirage – and that the abrupt falloff was because the signal strength dipped below the normal levels for a lower range of bars.
The review site Anandtech investigated the iPhone 4's reception earlier this week, and found that there is comparatively little difference between the signal strength needed to get four “bars” and one: a difference of 12 decibels' signal strength is enough to boost the apparent reception from one to four bars. A difference of 10dB is equivalent to a tenfold difference in the power of the signal, and a 3dB difference equates to a factor of two in the signal power.
Other phones use different measures to indicate signal strength: different versions of RIM's BlackBerry, for example, will show only two bars out of five with a signal strength of -80dB – which would be enough on the iPhone to show five bars.
Apple says it intends to fix the problem with a software update which will mean that the displayed signal strength matches the formula recommended by AT&T, the sole phone provider for iPhones in the U.S.
(Source: Guardian.co.uk)