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?

In one short word: imperceptible.

Using twinlead or ladder line is a good idea if you're feeding an antenna
that has a high SWR at the feedpoint on some of the frequencies you're
going to use it with, but at 75 meters, RG8X vs. ladder line will only
make a small difference if the SWR is at all close to 1. Less than half
a decibel, or a tenth of an S-unit!

Sure, it might make enough difference on very weak paths, but most of the
time nobody would be able to tell the difference on a direct on-air A-B
test!

And even that advantage almost disappears when the ladder line is wet.

Like I said, the picture is quite different at high SWR.


--
Dave Oldridge+
ICQ 1800667