How to test if TX Power setting is working

Hi, I am running the GL-AR750S (slate) on 3.210 beta 6. Setting the TX power setting for both 2.4ghz and 5ghz to low I can detect no notable difference in signal strength on my laptop or phone even two rooms away. What is the best way to measure the impact of the TX Power setting?

You need to look at the RSSI with a WiFi analyser app for your phone or pc. When you increase the power, the RSSI should increase (-55 for good signal, -80 for bad signal)

For me on Mudi, the difference is quite big between low and max signal strength.