BC66 poor connectivity depending on MCU


We designed a product based on a low-power MCU and a BC66 module and everything is working well.
But we recently had to use a new MCU and even though the design of our product remained the same (the only difference is the MCU), with this one, the connectivity of the BC66 is very poor.
For instance, at places where the network coverage is very good, we used to have a signal quality of 23-24 with the previous MCU, but now, at the same places, we get a signal quality of only 3-4 with the new MCU (according to the command “AT+CSQ”). Worse, where the network coverage is less good, our new product is not even able to connect to the network.

We don’t understand how the connectivity can be different as the communication module is the same. How can the MCU have an impact on the connectivity?

Thank you in advance for your insights,


Preliminary judgment may be due to the module access to the base station cell is different; Run AT+QENG=0 for query

Thank you for your answer.

We have just found the answer to our problem.
Actually there was a difference in the design even if it was hard to find. There was a capacitor near the antenna connection that should not have been there.