So I made some measurements with WIFI Analyzer, and it goes from -35db to -80db depending on my position compared to the CP5, but the problem is that when I turn on the computer with the USB3 connected and the antenna raised , the GTOCP5 hotspot disappears, so no measure possible of course. When I put the aluminum foil back on the antenna the hotspot reappears. I also made another test with a small USB2 extension cable (50cm) on the connection to my computer and there with the antenna raised and without aluminum foil the hotspot also reappears !!! This suggests that the "USB3" stream creates interference via the antenna which goes as far as "hiding" the hotspot, because if I move the CP5 away from the USB3 cable it works again.
You should be able to reproduce this situation I think.