phaedrus wrote:
Hi again,

Well I have read your informative replies on the problems with making
a low Zo twin feed with much interest. Clearly it's not really a
practical proposition. Shame.

So the obvious question is: why are transmitters normalised to 50 ohms
when clearly 450 ohms would enable us to enjoy cheaper, do-it-
yourself, lower loss feeders? Was this some oversight at the time, or
good practice for some obscure reason that I simply cannot think of?

Twinlead transmission lines have to be kept away from other conductors,
can't be taped to a tower leg, run through a metallic trough, or be
buried. If there's a substantial amount of solid insulation between the
conductors, it can get very lossy when wet. Even when properly balanced
(often not easy to do), some field escapes so it can be subject to
undesired radiation and signal pickup.

Coaxial cable has none of these limitations. It's a good trade for most
people.

Roy Lewallen, W7EL