I have a ~7m unshielded CAT5 cable between the UIRT2 PCB and the receiver/transmitters and it has worked perfectly for the last few months. I haven't had any problems due to interference. The only difference that I see between what you're planning to do and what I have done is that I have the LC filter at the receiver end of the cable.
There are two 3.5mm stereo audio plugs on each end of the cable. One end of the cable plugs into the UIRT2B the other end plugs into a box that houses the receiver and transmitter. I think I had each data line twisted with a ground - so data from the receiver was twisted with ground from the receiver, etc. Using a shielded cable would work even better (or even a fiber optic cable :lol: ).
in PC \____Transmitters