Apple's iPhone Signal Strength Placebo

Apple's iPhone Signal Strength Placebo

Ben Wilson
2 min read

As previously noted, users continue to report poor 3G signal strength under iPhone OS 2.1. To be clear, iPhone OS 2.1 does not purport to actually boost signal strength. Instead, it provides "more accurate" signal strength display, which, in most cases, means more bar bars, but not necessarily better reception or ability to make/receive calls. However, it appears that "more accurate" may mean "unreasonably generous."

Noted in our previous report, the most reliable indicator of actual signal strength is the iPhones dB meter, which can be accessed in field test mode. Dial *3001#12345#* then press "Call." A dB reading below 50 generally indicates good strength.

iPhone Atlas reader Michael did some testing, and found that widely varying dB readings resulted in the same five-bar signal indicator on his iPhone. He writes:

"After I upgraded to 2.1, I did indeed notice a consistent indication of '5 bars' of signal strength. Then I learned how to put my iPhone in field test mode so the phone displays an absolute signal strength indication of dBm rather than a relative signal strength indication of 'bars.' You can then tap the signal strength to switch between the two. I have done an informal survey and observed the following:

  1. -50 dBm = 5 signal bars
  2. -75 dBm = 5 signal bars
  3. -80 dBm = 5 signal bars
  4. -95 dBm = 5 signal bars
  5. -113 dBm = 5 signal bars

Michael's results beg the question -- does iPhone OS 2.1 really provide more accurate signal strength indication? Or does it simply inflate the signal strength reading?

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