Topband: Question on common mode chokes

[James Rodenkirch]

I seem to recall, while reading up on common mode chokes, where I wouldn't need one if I employ an autotuner at the base of the antenna...is that true/factual?
 
I have an LDG Z11ProII autotuner right at the base of my vertical - I did add a common choke at the input to the autotuner (21' of my LMR-400 coax wound around a piece of 4.5" PVC for the low bands) but wonder if that is really necessary.  
 
72, Jim Rodenkirch K9JWV