BLE receiver poor sensitivity, external antenna possible?

robjordan

I read the above thread but it's pretty old.

Adding my wish to this topic. I hoped to use M5StickC plus as a BLE scanner, using Arduino/ESP32. I need to detect a small battery-powered beacon which transmits at 2.5dBm. I've run my BLE scanner on M5stickC, a bare Esp32-Pico board with 3D antenna, and a bare Esp-Wroom32 board with PCB antenna. The RSSI measured with the receiver about 3 metres from the beacon is:
M5StickC ~ -75
Esp32-Pico ~ -69
Esp-Wroom32 ~ -66

M5Stick is worst by 6-9 dB. I suspect this will make the M5StickC useless for my project, which is a great shame because the combination of features is great. Any ideas on improving sensitivity or adapting it to take an external antenna?