some pictures of my ic880a / Pi hardware, I placed the connectors close to each other, antenna as far as possible away from the “noisy” Pi. Very short interconnect, 100E series resistors in every signal wire. Scope picture is the SPI clock, running at 8MHz. Please note that any wire will act as antenna, if you have the strong signal e.g. from GSM telephone it could transfer energy to those “long” wires, disturbing the signals…
measured on the ic880a connector between closest GND and pin 14 (SPI-CLK)