Custom STM32WLE5JB board transmits data but gateway can't decode it

[igor_b]

I'm working on a custom board based on STM32WLE5JB. First few prototypes worked without any issues, but in the last small batch (assembled by different assembly house) many boards have issues with data transmission: using HackRF I can see that the boards transmit something on the correct frequency (868.1, 868.3, 868.5MHz) but the gateway (RAK7258) doesn't detect it. Visually it looks like the transmitted signal on the bad boards is stronger so maybe it's somehow distorted (but it is slightly closer to the gateway so it's subjective).

So, two boards from the same batch, running the same firmware, do the transmission but the gateway can decode only one.

What would be the best way to debug this? Could this be the consequence of bad antenna matching (antenna was supposed be matched properly and boards are assembled in the same run so the components should be the same on them)?

signal from ok board:

signal from bad board:

 

[igor_b · Accepted solution]

It turns out the assembler put the wrong components to the RF part...