Please help identify the positive and ground for adding an external BLE antenna, after the chip antenna was removed. I am connecting an external antenna (not the removed one) to this Nrf51822 BLE module made by Raytac, Model MDBT40. There is a small blue SMT component right before the removed antenna was soldered, but cannot make out what it is. It seems to have a grey dot on it towards one end.
Cannot find the PCB circuit either for inside the metal shield. The module is mounted on the Adafruit Bluefruit 32u4 BLE Feather. I do not have access to the bottom of the module. There is a tiny hole in the motherboard holding the module about where the circle is which I suspect is the positive of the antenna. I thought initially that the trace coming out from the metal enclosure/shield is the positive, but I measured GROUND.
I also enclosed the photo of a MBTB42 module that has a factory external antenna connector. That one has another version of the BLE chip.