Image from Anandtech
The short answer…it does, you just don’t see it in “the bars”.
I first thought this could be the answer way back on the June 24th during my bumper testing:
I then tested in another room with less electronics. In this room I started with a strong signal of 5 bars. This time around, with or without the bumper, the signal held pretty much at 5 bars. This may explain why some people don’t seem to notice this issue. If you have really great AT&T service where you live, the in hand signal drop may not be as noticeable.
I think the problem is “the bars”. They serve their purpose for the most part, but when trying to do a test involving signal strength we need more detail. I would argue that 5 bars in one area is not necessarily equal to 5 bars in another. Start with a “weak 5 bars” and you can see the signal loss represented by the bars dropping. Start with a “strong 5 bars” and the signal may be getting weaker, but never below the 5 bar threshold. In this case it appears to the user that they still have the same signal strength and it goes unnoticed.
Turns out the “not all 5 bars are created equal” was dead on. It was hard to prove this before because the old field test app that showed these numbers was removed from iOS 4. That didn’t stop Anandtech though, with a neat hack job they were able to get the numeric signal number back on iOS 4 instead of the bars:
However, 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 dB to -51 dB) is reported as 5 bars.
They go on to test the drop in signal by how it’s held:
Tight grip in hand: 24.6 dB
Holding naturally in hand: 19.8 dB
Holding naturally with case: 7.2 dB
Open palm: 9.2 dB
Now let’s revisit my bars and bumper test with the dB numbers provided by Anandtech:
Strong 5 bars (Naturally held)
You start with the strong 5 bars at -60 dB (-51 dB would be strongest 5 bars), then you hold it in your left hand, lowering the signal to -79.8 dB (-51 dB – 19.8 dB). Even though you have a significant drop in signal, it’s still above the -99 dB threshold for 5 bars, so it goes unnoticed in the bars. If you did a speed test before and after, you would be able to see the difference…try it.
Weak 5 bars (Naturally held)
You start with the weak 5 bars at -90 dB (-99 dB would be weakest 5 bars), then you hold it in your left hand, lowering the signal to -109.8 dB (-90 dB – 19.8 dB). This now takes you past the 1 bar threshold of -107 dB. With 1 bar you can still make calls, but have a better chance of a drop. The bigger issue, at least for me, is the 3G data speeds drop dramatically.
Bumper (Naturally held with case)
I know I was starting with a signal that was on the lower end of 5 bars because every once in a while it would drop down to 4 bars. For this example let’s assume it was -95 dB. Holding naturally with the bumper it would drop down to -102.2 dB (-95 dB – 7.2 dB) putting it in the 3 bar range, exactly what I got during my test.
Another way to think about it in terms of bars would be to add 5 more bars on top of the 5 that already exist. Not as an average, but just adding more detail to the high end. The user that claim they don’t have an issue are really starting out with 9-10 bars in this 10 bar and dropping to 5-6, but those that start with 5 are dropping to 1.
So those of you that were counting yourself lucky are just starting off better, but when you aren’t holding your phone you still have a stronger signal.
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