WT3121 EMF meter test at 900 - 2100 MHz

According to specification it should measure RF fields at frequency ranges 5Hz-3500 MHz, but it fails to measure RF radiation from cell phones, routers etc working at 900-2500 MHz range. I got some results in measuring low frequencies only, such as fields emitted from power lines (50Hz), TV&and monitors (60-250Hz). I decided to open WT3121 lid to check why it fails to measure high frequencies and I found, that signal path of WT3121 was designed to measure frequencies only up to 1.1 MHz, not to 3500 MHz. To get full claimed measurement range, both signal paths (electric and magnetic) are need to be redesigned, proper elements (especially operational amplifiers & detection diodes) are need to be changed and after this whole meter needs to be calibrated at the factory lab.