A good source for good quality RG11 would be the cable TV repair guys... Everytime one comes around here I will flag them down and see if they have any cut off lengths.
They usually have a hugh spool on their trucks and most don't mind sharing it especially if you are customer. This is that orange cable they bury in the ground from the pole to the house.
We get 6-36 digital channels just about every we go on free CLEAR TV ... Alot of our camping is in the Blue Ridge Parkway and high country in the northern parts of AL-GA-NC-SC and TN areas. There we get sometime a hundred digital HDTV channels but of course most are duplicated Broadcast network channels...
Roy Ken