Apple on Friday published a long letter to iPhone 4 customers in an attempt to explain why they are seeing reception problems. The culprit, said Apple, is a bad formula used to calculate the signal strength.

A bad formula? Really? That's what Apple said is the foundation for all the iPhone's reception problems. Apple said it has been incorrectly calculating signal strength from day one, and the issue actually affects all iPhones shipped since the iPhone 3G in 2008.

In the letter published today, Apple said that it was pleased with the mostly glowing reviews of the iPhone 4, but was confused when complaints about its signal strength started pouring in. Apple set out to determine the root of the problem, as its labs insist that the iPhone 4 has the best reception of any iPhone made.

Apple said, "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 2 more bars than it should for a given signal strength. For example, we sometimes display 4 bars when we should be displaying as few as 2 bars. Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don't know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars were never real in the first place." (...)

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