[Elecraft] Another feedline question

[Parker Buckley]

I know this probably belongs on Antennex, but while you guys
are all fired up over transmission lines, I'll ask my
question.  When one makes parallel transmission line from
two pieces of coax, say 50 ohm, shields connected, using the
inner wire as the transmission line to get 100 ohm line,
what is the theoretical loss of this line?  Is it twice the
loss of a single piece of coax, half the loss, or something
entirely different?  I've measured velocity factors of these
lines and get exactly the same velocity factor for the pair
that I do for a single piece of the same coax.  I have not
attempted loss measurements, however.  Maybe loss is related
to vf, and I've answered my own question and don't realize
it.

Parker WD8JOL  K2 #2636