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What your Phone Bars are Not Telling You

Cell Phone Bars and CEL-FI Smart Signal Booster

You have just installed your CEL-FI system. You have followed the directions and maybe even gone through some basic online troubleshooting steps… but you do not see any more bars on your mobile device. According to the bars on your handset you are not getting better signal after installing your CEL-FI Booster Device.

Even if your CEL-FI is installed correctly and the service you experience is substantially improved, your handset may not show these improvements with higher signal bars.

The easiest way to confirm that the CEL-FI is working is to remember what your initial need was. For example, if you had no coverage in this area before and now you do, or if you were experiencing dropped calls before and now you are able to hold calls without an issue, you can say without a doubt that your handset is getting a better signal thanks to your CEL-FI Smart Signal Booster!

The simple truth is that the number of bars might not always change. The bars on your handset or tablet can be confusing as they do not always show raw signal strength, as one might expect. Almost all mobile manufactures have their own algorithm to calculate things like signal strength, signal-to-noise ratio, and channel loading among other things. Here is a short video that explains what your phone bars are not telling you.

Check your RAW Signal Strength

Every mobile device has different algorithms for selecting bars and the method of putting your phone into Field Test Mode. Placing your phone into Field Test Mode will allow you to view raw signal strength, as demonstrated in the video above. Raw signal is the only way to get true signal strength readings from most smartphones. Below are updated instructions to the most popular mobile brands.

If you do not see a working code for your phone, please contact us.


iOS 10.3.1 and newer


  1. Dial *3001#12345#*
  2. Select “LTE”
  3. Select “Serving Cell Meas” signal strength will be displayed as “RSRP0”


  1. Dial *3001#12345#*
  2. Select “UMTS”
  3. Select “Serving Cell Meas” signal strenght will be displayed as “RSCP0”


iOS versions OLDER than 10.3.1

  1. Dial *3001#12345#*
  2. Hold the Power/Lock button until you see “Slide to power off”. Do not power off, but release the power button.
  3. Hold the Home button until the phone goes back to your home screen. At this time you should now see your raw signal strength instead of bars on the top left of your handset.
  4. To go back to bars, dial *3001#12345#* and tap the home button to Exit Field Test Mode.

Most Android Devices

  1. Go to Apps
  2. Settings
  3. General
  4. About Device
  5. Status
  6. You will find Signal Strength on this screen


  1. Dial *#0011#
  2. The Signal Indicator will be displayed as RI or RSRP.

Samsung RI RSSP

Deciphering what RAW Signal Strength means to you

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.

Improvement in handset’s signal value in dB (with Cel-Fi CU on) How much stronger the signal really is
Improved by… 03 2x Stronger
Improved by… 06 4x Stronger
Improved by… 10 10x Stronger
Improved by… 15 30x Stronger
Improved by… 20 100x Stronger
Improved by… 30 1,000x Stronger