Hi!
After assembling the bluetooth-mod in my box, iād like to tell you guys about how i could solve the problems i encountered.
First thing was, that the speaker never turned on, with the KCX installed. Even not with the mentioned resistor between LINK and GND. I tried several MOFETs because at the first approach i had not used the mentioned Si2302. But even after buying, waiting and soldering that one, the speaker stayed mutet. I checked and double checked the pins an wires over and over but nothing helped. In the end i went from MOSFET to NPN resistor (S8050 in my case) and there you go, speaker comes to life again.
To prevent the KCX from interfering the WLAN i also use a mini latching switch to turn the module on and off. But because sometimes iād like to use the box for internet radio and than listening to the station with bluetooth headphones, i needed something else. So i removed the integrated antenna from the KCX (just broke it at the dotted line) and connected an external antenna to the onboard IPX1 plug. Because the external antenna also had influences to WiFi, i desoldered the pcb of the antenna and justed use the cable. The cable i put into the top under the ears besides the NFC antenna.
This way i can use WiFi an bluetooth simultanously and the bluetooth range is still acceptable with 4 to 5 meters.