In Depth Analysis of iPhone 4 Reception Issues

Anandtech has provided an in depth analysis of the iPhone 4's reception issue in their comprehensive review of the device.

The site was able to get the iPhone 4 to display signal strength numerically and mapped the bars to signal strength in the image below.

You can see just how little dynamic range iOS 4 has for reporting signal; over 40% of the range of possible signal levels (from -99 dBm to -51 dBm) is reported as 5 bars.


According to their tests, holding the iPhone 4 in your left hand and crossing the black strip can result in a worst case drop of 24 dBm in signal. This explains why some users report not having receptions issues. If you live in an area with high signal strength (-51 to -75) a 24 dBm drop won't even register on the display.

The site also reveals why some people say they can use their devices even when the bars have dropped all the way down. Typically at -113 dBm the iPhone would drop all calls and data. However, improvements to the baseband have made holding on to calls and data transfers at low signal levels massively better.

They conclude that 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. 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.

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