That would suggest your interference was coming in via the RFX antenna itself. Getting the antenna away from whatever is emitting all the RF noise was your only choice, other than eliminating the noisy equipment. What you did was improve the S/N ratio; your interference was reduced in strength to a greater degree than your remote RF signal. Adding the CAT5 to connect the RFX unit added another measure of additional safety; it safeguarded your RFX cable from picking up the same noise.

I only have an MRF unit; the antenna is not detachable, so the only cabling I have is the power and IR emitter cables.