Although not strictly required, it is recommended to remove C91/C92 for better performance in USB mode.
C91/C92 used to be required for the analog VFO. You can safely remove them when the Raduino is used instead of the original analog VFO.
In USB mode, the VFO operates at 19 MHz instead of 5 MHz in LSB mode. At 19 MHz, the two capacitors attenuate the VFO signal too much. It is possible, to some extend, to compensate for this by increasing the VFO drive level (in the SETTINGS menu). But removing the capacitors gives better results.
73 Allard PE1NWL
Allard PE1NWL