On May 28, 9:16 am, Sonny Hood wrote:
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?

If you switch from coax to ladder line and baluns or tuners, you are
going to lose a bit of efficiency I bet.
I always have when I've compared the two on that band.
You are converted from a pure and simple system which is a 50 ohm
radio, feeding 50 ohm line, which BTW at 75m is very low loss,
into an appx 50 ohm load. This "pure" system is probably 95%+
efficient on the 75m band as long as the coax is not junk.
In my opinion there is no better method of feeding a single band
dipole. Anything else is pretty much a step down as far as I'm
concerned. The *only* reason I would ever run that way is if I
wanted multi band use using ladder line and a tuner.
But in my case, I prefer multiple dipoles fed with a single coax.
The decrease in loss switching from coax to ladder line *on 75m*
is so small as to be nothing. But then you have baluns and tuners.
This is what is going to spoil the food. You will actually end up
with
a net loss at the end of the day. Maybe be a small loss, but I
bet it will be measurable on a meter if you used an A/B switch.
It was in my cases. Then you have the moisture issues, etc..
Do what you want, I prefer coax when feeding dipoles.
I usually use 213 on HF here at the house.
But at 3 mhz, even RG-58 is fairly low loss.
The mini 8 you are using should be a bit better than rg-58.
I think it's slightly larger and using foam if I remember right.