At 6 feet, it won't matter to much about the coax.
LMR 400 is good for higher freqs because of it's low loss factors, but at 6 feet pretty much any 50 ohm cable will do.
Coax loss is rated at 100 feet lengths.
Example: (in theory of coarse)(also depends on the frequency the loss is calculated for)
coax loss at 100 feet = 6db
at 50 feet it would be 3db
at 25 feet it would be 1.5db
at 12 feet it would be 0.75 db
at 6 feet it would be 0.375db
see what I mean?