The folks at AnandTech just published their review of the iPhone 4 and took a close look at the antenna issue that is plaguing the handset. In true geek style, they mapped the bar representation of the signal strength from -51dB (perfect signal strength) to -131dB (bare minimum to maintain a connection) and measured the iPhone 4 signal strength attenuation in terms of decibels. The result of the mapping show that over 40% of the signal strength range is represented by 5 bars which means your signal has to drop significantly (over 40dB) to go from 4 to 5 bars and only 10db to go from 4 bars to 3. Pretty big difference. They also found that the iPhone 4 on average loses 24.6dB when tightly held in your hand and 19.8 when held naturally due to the positioning of the antenna and the fact that it lacks insulative coating. These two above factors combined explain why those in strong coverage areas do not see any perceptible drop in bars while those in marginal areas do. If you are sitting pretty at -60dB you can easily absorb a 24dB loss to -84dB and not see any change in bars. But if you are at -91dB and lose 25dB, you will drop from four bars to almost none in a heartbeat. Interestingly enough, they find that the iPhone 4 antenna is significantly improved over the 3GS but is hampered by Apple’s choice not to shield the now famous metal band.