Apple open letter on antenna reception issues

Apple has posted an open letter addressing the widely reported issues surrounding iPhone 4 antenna reception -- how it drops or loses signal when held in such a way that the lower left side is covered.

Short version is, Apple's claiming they are, and historically have been, miscalculating how they display signal strength as bars on iPhone. They repeat that all phones will drop some signal when held in certain place, Nokia, Android, BlackBerry, and iPhone alike, but because of the way Apple was displaying signal strength, the drop appeared far more dramatic on iPhone 4.

For example, if the signal drops two bars when you hold it, and you only really have two bars, you'd see no signal and understand the drop. If you have two bars but Apple is showing you 5 bars, and weighting the calculation far too heavily towards high bars, you could drop 2 bars and really have 0, but iPhone is still showing you 3, 4, or even 5 bars. There in lies epic frustrati

A software update, to be issues within a few weeks, will change the calculation to AT&T's recommended method, and Apple will make the lower signal bars easier to see at the same time. So, in other words, your signal will still drop but it won't look to be as good before it does so.

Apple also reiterates that both they and their customers continue to report that iPhone 4 has better than any previous model, and remind everyone that anyone unsatisfied can return an undamaged iPhone 4 for a refund within 30 days.

While this does seem to address the miss-reporting of signal strength Anandtech found in their tests, and acknowledging that iPhone 4 does get better reception and does drop fewer calls -- when it works -- it doesn't seem to address the higher levels of attenuation seen in raw signals, or some reports that the baseband software wasn't properly adjusting when that attenuation occurred.

A few weeks seems like a long time to push out an iOS 4.0.1 update just to fix signal bar strength reporting, so either Apple is just waiting until their usual late July window for their first update or are working on other bug fixes -- related to the antenna or other issues like the proximity sensor -- we'll have to wait and see.

Full letter after the break.

Dear iPhone 4 Users,

The iPhone 4 has been the most successful product launch in Apple’s history. It has been judged by reviewers around the world to be the best smartphone ever, and users have told us that they love it. So we were surprised when we read reports of reception problems, and we immediately began investigating them. Here is what we have learned.

To start with, gripping almost any mobile phone in certain ways will reduce its reception by 1 or more bars. This is true of iPhone 4, iPhone 3GS, as well as many Droid, Nokia and RIM phones. But some users have reported that iPhone 4 can drop 4 or 5 bars when tightly held in a way which covers the black strip in the lower left corner of the metal band. This is a far bigger drop than normal, and as a result some have accused the iPhone 4 of having a faulty antenna design.

At the same time, we continue to read articles and receive hundreds of emails from users saying that iPhone 4 reception is better than the iPhone 3GS. They are delighted. This matches our own experience and testing. What can explain all of this?

We have discovered the cause of this dramatic drop in bars, and it is both simple and surprising.

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.

To fix this, we are adopting AT&T’s recently recommended formula for calculating how many bars to display for a given signal strength. The real signal strength remains the same, but the iPhone’s bars will report it far more accurately, providing users a much better indication of the reception they will get in a given area. We are also making bars 1, 2 and 3 a bit taller so they will be easier to see.

We will issue a free software update within a few weeks that incorporates the corrected formula. Since this mistake has been present since the original iPhone, this software update will also be available for the iPhone 3GS and iPhone 3G.

We have gone back to our labs and retested everything, and the results are the same— the iPhone 4’s wireless performance is the best we have ever shipped. For the vast majority of users who have not been troubled by this issue, this software update will only make your bars more accurate. For those who have had concerns, we apologize for any anxiety we may have caused.

As a reminder, if you are not fully satisfied, you can return your undamaged iPhone to any Apple Retail Store or the online Apple Store within 30 days of purchase for a full refund.

We hope you love the iPhone 4 as much as we do.

Thank you for your patience and support.