My son was asking about some Ethernet cable (Cat 5 unshielded twisted pair), and since he recently passed his Technician exam and we both have "radio stuff" on our minds, I tried to make the analogy between coax transmission lines and the balanced pairs in the wire. I understand they both are used as RF transmission lines, essentially.
This got me thinking: why don't we use twisted pair for antenna feedlines?
As question T9B03 on the FCC exam covers:
Why is coaxial cable used more often than any other feedline for amateur radio antenna systems?
The correct answer being "It is easy to use and requires few special installation considerations" and not that "It has less loss than any other type of feedline" — the latter advantage going to balanced line, which is low-loss but does require special considerations particularly to avoid coupling to nearby metallic objects.
Would twisted pair offer something of best of both worlds? Could it provide lower loss than coax, and still without "special installation considerations"? (Looks like Category 5 cable specifically has a 100ohm characteristic impedance, but that seems easily enough dealt with since you'd need a unbalanced-to-balanced transformer off of most ham equipment anyway, right?)