Mike, I have RG-213U feeding an OCF Dipole up about 25-Ft.  The feed line goes into a lighting arrestor then to my LDG YT-1200 Automatic Antenna Tuner.  From the tuner I feed a one-meter piece of RG-8X to the QCX for 20M.  I have the same set up for my QCX-mini on 40M and there is no issues with harsh side tone.