How can I measure how well ClearBoost is working after updating my iPhone to 2.0?

The most accurate way to determine the signal strength on iPhone is to enter "Field Test Mode." To do this, go to the keypad in the Phone application, enter *3001#12345#*, and tap Call. This will place you in "Field Test Mode." (This code works on all current iPhone firmware versions.)

From the Field Test menu, you will see a number in the top left corner. This number represents the amount of signal your iPhone is receiving from a specific cell tower, measured in dBm. This is the number you should watch when comparing the reception benefit of the case. Since this number is a negative value, the closer you are to zero, the better. -111 would indicate that there is very weak reception, whereas a -60 would be very good reception. If a tower is showing a value at or below -106 dBm, you will most likely not be able to place a call using that tower.

To take a measurement without the case, hold the iPhone in your hand as if you where talking during a call (the iPhone doesn't need to be against your head). Wait about 45 seconds for the signal levels to stabilize, and take a reading of the RX value. As the towers are constantly shifting their power output, and the iPhone's reception can change at any moment, it may help to take a photo of the screen.

Then place the iPhone into ClearBoost, with both halves snapped shut, and repeat the test. Try to keep your hand in the same general area and orientation as in the previous test.

At this point, you should see an improvement in the signal (RX: value). Remember, an RX: -75 would be better reception than an RX: -80.

To put the RX measurements in perspective, a change of signal strength of just 3 dBm represents a doubling of the amount of RF energy reaching the iPhone's built-in antenna.

AT&T primarily uses the 850 MHz band in the US, and, as such, we designed ClearBoost to perform best at this frequency. However, if you are in a 1900 MHz service area, you should still see some benefit from using ClearBoost, though the amount of signal gain will be less than when compared to an 850 MHz area. This information doesn't apply to the newer, 3G iPhone, which will not correctly fit into the current ClearBoost case.