Are you asking about using it as feed line, or building a receive station for DX short wave listening ocer multibands?
As far as using it for feed line, while I'm not a SWL enthusiast, I've used it on CB and some Amateur bands.
For receiving you can using anything you want and it is not going to make much, if any detectable difference, at all. RG-6 is cheap and actually quite good coax. use it all you want. I know hams that use it instead of 50 ohm coax in a lot of long runs out to various antennas.
RG 6 works fine for.\ antennas.
I use it on many of my antennas here at the QTH, cheap, easy to work with, and lower loss than many of the expensive 50 ohm coax.
Adapters available on Ebay for SO239 or PL259.
That RG-6 is pretty good stuff. It isn't going to be a 'perfect' match, but no coax ever is. If you're observant, watch the cable TV guys and you can get miles of it!