I’m looking for advice whether a wire connection between RP-SMA antenna connector of the 868x modem to freshwater would act as a suitable ground plane for small size 2dB RFD rubber ducky antennas. I’m runnig a sub with the rfd TX modem system and space inside the pressure hull is in very short supply. A larger dipole antenna just wouldnt fit in… placing a 3db dipole antenna outside might be another option - whats your opinion and advice?