The raw signal strength can determine if your handset is getting signal from the Coverage Unit. With the Coverage Unit plugged in, go to the location of your CU and dial the Field Test Mode Code for your phone, remember this number. Now unplug your Coverage Unit and watch your signal strength change, it make take a few minutes for your phone’s readings to update. Keep in mind, a smaller the negative number equals stronger signal. For example, if your signal strength jumps from -111 to -100 your signal is 10 times stronger with Cel-Fi than it was without Cel-Fi.
While the number changes might seem slight, even 3 numbers lower is 2 times stronger than before. The cellular scale is not 0 to 100, but the range of usable cellular LTE signal is -120 (just barely usable) to -60 (about the best you will find). Here is a simple chart to give you an idea of just how BIG the “little” improvement really is.