RF Module PCB design & supply decoupling

[glynhudson]

For the RF Module footprint, I see you have connected in the secondary GND on P14. This is quite important for EMI - you can improve further by "stitching" the top and bottom floods in this area with "random" vias. If you make changes in this area, I suggest altering the top silk also - confusing the crystal position then flipping the RF module around has been a common construction error.

I'd also find space for pads for a series L just before C8 in the module Vcc feed - it is supplied after the ESP-12 so the supply decoupling may need improving. C8 is probably too large, it will be inductive in the RF range of interest. You can get a handle on this by checking the background RSSI with ANT shorted locally to GND (BTW, if you juggle R2,C8 around, putting C8 closest to the Vcc pin, there is probably enough room for an explicit GND pad right next to ANT - very useful for an external rubber duck pigtail