Hi Carsten,
It must be different for powerbox products; thanks for clarification. I found this reference in the robbe pss2018 instructions which is what had stuck in my mind:
"S-BUS receivers are connected to the PSS2018 by patch cables (Part Nr. 4090,4093 or 4096 – depending on length). See print RX1 and RX2 on housing. Patchcables can be up to 50 cm / 20". This allows for long distances in-between themand therefore for optimal positioning of the antennas. "