Ian Jackson wrote:
The question is, "Do you use a quarterwave of 75 ohm cable to get
something like a 50 ohm impedance at the TX end - even if this means
using more coax than you really need or, to minimise losses, do you
simply use the shortest length of coax - either 50 or 75 ohm?"

Usually not a problem since 1/4WL of RG-11
at 4 MHz is only ~40 feet - hopefully less
than the height of the antenna. 1/4WL at any
higher HF frequency would be shorter than that.
Excess coax can usually be coiled into a choke.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com