First of all, you need to determine the strength of the mobile signal outside the building. The best way to check it is in decibels, as bars are not as accurate as dbs. On most Android phones you simply need to navigate to Settings-About Phone. Your signal strength in decibels (dB) will be displayed under ‘Status’ – ‘SIM Status’.

Next, estimate the area in square meters that you want to cover.

Note: Update for iOS 11 does not allow for iPhones to be placed in the Field Test mode.