This is deprecated feature and not available in app after 5.1.4.
Feature not working after Android 7+. Use native Cell ID API to get band data.
Cellmapper Field Test Reader is new feature on Cellmapper app. You can with this feature read Band and Bandwith data without root. This feature is available Cellmapper 4.1.5 16.3.2016 to 5.1.4.
Tested NSG method (Method working if NSG working on your phone):
More phones here: Tested_Phones
1. Enable Cellmapper Field Test Reader under Android Settings:
Android Settings -> Accessibility -> Cellmapper Field Test Reader
2. Open Cellmapper App and enable recording
3. Open Service Mode calling *#0011#. Wait few seconds...
4. Switch back to Cellmapper App (Don't close Service Mode) and watch if you see Band and Bandwith data.
Network Signal Guru (Working 1.1.4 version): You can use Network Signal Guru also. First change on NSG Settings all to Decimal and then restart NSG.
Then open Network Signal Guru and CellMapper. Keep Network Signal Guru Foreground so when you switch back to CellMapper you should see example LTE MIMO, LTE Bandwith, LTE Band data.
Please ask/report everything to Google Plus community or email: support (at) cellmapper.net.