First you need to understand that while you are sending data or browsing the web the connections done through 4G, otherwise it goes on 2G or, in certain cases, 3G (voice call). If the user is not talking continuously, the phone pause transmission.
The professional 4G mobile phone detector is designed to capture the spontaneous 4G signal and create a short beep to aware the user that there is a 4G link. But it can not be used to capture the caller unless who is making a voice call. Because 4G is sending packet data in short burst sporadically. So, you won’t expect a steady signal strength bar continuously. And the voice call is “jumping” through 2G or 3G depending on the local traffic.
The other problem related is: the signal strength is not a constant due to Fading”phenomena. The ideal testing condition is linear.
RFD-10 with the non-linear sensitivity adjustment software and it is for those users looking for maximum detection distance and catching instance signals. It is very effective in catching people sending short messages.