Sonny Hood wrote in
:

I have an efficiency question concerning feed lines. My present
system is RG-8X to my 75 meter inverted vee which is about 85 feet
away from the shack. I propose to replace some 88 feet of coax with
300 ohm window ladder line that is inserted into the coax run with 4:1
baluns to match the coax on each end. Also at the feed point of the
antenna switch from a voltage balun to a current balun (ferrite chock
type). By my calculations with a 98 watt generator I will increase
the power to the load by about 11-20 watts and with a 985 watt
generator, 117-210 more watts will reach the load. Figuring
theoretical total system (A) against total System (B) or by just the
difference in the 88 feet of ladder line versus coax. What do you
think the increase will be?

One of the numbers that is hard to come up with is the loss through a
balun. The only number I could find for a voltage balun is a matched loss
of 0.075db, this would be times 2 in your setup. So there is loss, and it's
well known that the loss goes up with miss match. I think you are
neglecting the loss through the baluns and the miss match loss. Remember
your antenna will not be 50 ohms over a very wide frequency range.
Going open wire line all the way or changing to RG8 size coax will likely
work just as well and be simpler to do.

John W3JXP