I'm just curious though, what's the point of the 300 ohm wire? is it a matter of connectors and terminations or is it a characteristic of the signal that would require the 300 ohm wire?
Now Hal may be able to give a better explanation than me, but 300 ohms was the input impedance of a centre-fed dipole antenna, when TV first started.
Hence the use of twin-lead feed lines (Ribbon lead) for TV's at the time.
TV sets that use antennae, to recieve a signal now are still 300 ohms but we use a 75 ohm coaxial cable to feed the TV Set.
Between the antenna and the co-axial cable, you need to have a "matching device" so that the two things "agree" with each other.
We use a Balun to do this, which is a 1:4 RF Transformer.
This is an impedance only, not a true resistance.
Anyone else care to put thier spoke in?.
Let's face it, these days if you're not young, you're old - Red Green