Folks at AnandTech have done a detailed analysis of iPhone 4’s new antenna system to investigate the reason for the reception issues reported by many users when they touch iPhone 4’s side antenna bands on the lower left corner.

Before starting the tests, AnandTech had to hack their iPhone 4 to get a numeric readout of the signal strength instead of the usual 5 bar signal strength scale.

AnandTech then ran many tests to find out the signal degradation by holding an iPhone 4, iPhone 3GS and Nexus One in their hand in 5 different positions. They observed the following:

Inside a case, the iPhone 4 performs slightly better than the Nexus One. However, attenuation gets measurably worse depending how you hold the phone. Squeezing it really tightly, you can drop as much as 24 dBm. Holding it naturally, I measured an average of 20 dBm.

The drop in signal from cupping the device with a case on is purely a function of us being "ugly bags of mostly water." A material which happens to be pretty good at attenuating RF – thus increasing path loss between the handset and cellular base station. There's nothing Apple nor anyone else can do to get around physics, plain and simple. It's something which demonstrably affects every phone's cellular reception.

Add in an external antenna you're essentially forced to touch and bridge to another adjacent antenna while holding, and the signal attenuation is even worse. The fact of the matter is that either the most sensitive region of the antenna should have an insulative coating, or everyone should use a case. For a company that uses style heavily as a selling point, the latter isn't an option. And the former would require an unprecedented admission of fault on Apple's part.

However, AnandTech goes on to add that they found that iPhone 4’s antenna performs much than iPhone 3GS:

I've determined that the iPhone 4 performs much better than the 3GS in situations where signal is very low, at -113 dBm (1 bar). Previously, dropping this low all but guaranteed that calls would drop, fail to be placed, and data would no longer be transacted at all. I can honestly say that I've never held onto so many calls and data simultaneously on 1 bar at -113 dBm as I have with the iPhone 4, so it's readily apparent that the new baseband hardware is much more sensitive compared to what was in the 3GS. The difference is that reception is massively better on the iPhone 4 in actual use.

With my bumper case on, I made it further into dead zones than ever before, and into marginal areas that would always drop calls without any problems at all. It's amazing really to experience the difference in sensitivity the iPhone 4 brings compared to the 3GS, and issues from holding the phone aside, reception is absolutely definitely improved. I felt like I was going places no iPhone had ever gone before. There's no doubt in my mind this iPhone gets the best cellular reception yet, even though measured signal is lower than the 3GS.

This is in-line with Apple’s claim that ‘iPhone 4’s overall antenna performance is better than iPhone 3GS’ in the leaked internal training document.

But holding iPhone 4 with the left hand remains a problem and they don’t expect an iPhone software update to fix the reception issues:

The drop in signal from holding the phone with your left hand arguably remains a problem. Changing the bars visualization may indeed help mask it, and to be fair the phone works fine all the way down to -113 dBm, but it will persist – software updates can change physics as much as they can change hardware design.

Based on their tests they have observed that bumper case is the best option to fix iPhone 4's reception issues:

If you add a bumper case to the iPhone 4, the signal strength drop from holding the device is on par if not better than other phones.

They go on to add:

At the end of the day, Apple should add an insulative coating to the stainless steel band, or subsidize bumper cases. It's that simple.

You can read AnandTech’s detailed review of iPhone 4 for more details.

It will be interesting to see how Apple addresses this highly publicized issue as these findings and customer complaints indicates that their stance that ‘nothing is wrong’ with iPhone 4’s new antenna system will end up hurting them in the long term. Though we’re still hoping that Apple can magically fix the issue with a software update. Interestingly, the simple trick to fix the reception issue seems to be working for some of our readers.

Let us know your thoughts in the comments section below.