Field Test Mode for the iPhone
So if you want to take a detailed look into your iphone signal then put it in field test mode. How to do this you ask well – Open the iPhone’s dialer keypad – Enter *3001#12345#* – Press the Call button. You can view a great deal of information in this mode. dBm is what most of you are after which reflects signal strength -80 to -70 dBm: Reasonably strong signal -107 to -90 dBm: Weak signal -113 dBM: No servicable signal. If you need more info on dBm If you want to exit the test mode, but retain the dbm display instead of bars, hold the home key about 3-5 seconds. You should then be able to toggle between bars and -dbm by tapping the bars or dbm numbers.
