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?
There is so little loss at 3.5 mHz for RG8X you would have a hard time
telling any difference.

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

"Sonny Hood" wrote in message
...
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 all likelihood, no one on the other end will ever be able to tell the
difference after you make the changes. Neither will you.

Ed, NM2K

On May 30, 6:46 pm, "Ed Cregger" wrote:


----------

In all likelihood, no one on the other end will ever be able to tell the
difference after you make the changes. Neither will you.

Ed, NM2K

Maybe not from any practical standpoint, but I could see the
difference on a meter when I fed both a coax dipole, and a
ladder line dipole using the same tuner, which has antenna
switch, and meter built in.
So I could A/B real fast. I could see a slight difference on
receive switching between the two. And if it's enough to see
on a meter, I consider it a noticeable amount.
Most of the signals were in the 20-40 over 9 range being 75m,
and I'd see about 5 db worth of difference between the two
antenna/feed lines.
Course, I make no claim as to the exact DB amount of difference,
but I could see it on a meter.
After many years of 75 and 40 m operating using mostly NVIS
paths, I've come to the conclusion nothing will beat a dipole/loop/
turnstile fed with good coax for sheer system efficiency unless
say you had a run of several hundred feet or something...
Which of those three doesn't really matter much, although I
prefer the turnstile over the other two if I had a choice.
Nothing wrong with a loop, but in my cases, some sections
end up sagging closer to the ground, and you are often a
bit more prone to ground losses, and also overall performance
if sections of heavy current are low to the ground.
With a dipole or turnstile, max current is at the feed point, so
the ends of the wires height above the ground is often not quite
as critical.
As far as I can think of, only Cecil's no tuner/no choke system
would let a ladder line fed dipole equal or slightly beat a coax
fed. And in that case, I'm not sure how noticeable it would be,
being as the 213 I use is quite low loss at 3-4 mhz.
But like you say, for on the air, many would probably not
notice much. #1, you would have to do quick A/B transmit
tests for them to notice any difference, and also make sure
fading doesn't skew the results. It would be best to test with a
stable ground or space wave signal.
But... I still prefer coax.. I want every drop out I can get, and
I also much prefer the convenience of coax. IE: with most
antennas, no tuner required. And really not even a "balun"
required if you roll a choke out of the feed line itself and tie
wrap it. Weather is no issue with coax. I can have it sitting
in standing water with no problems.
The only time I use ladder line is mostly experimental
antennas where the feed point impedance is not the usual
50 ohms. If the mismatch to coax is high, ladder and the
tuner makes sense.

wrote in message
...
On May 30, 6:46 pm, "Ed Cregger" wrote:


----------

In all likelihood, no one on the other end will ever be able to tell the
difference after you make the changes. Neither will you.

Ed, NM2K

Maybe not from any practical standpoint, but I could see the
difference on a meter when I fed both a coax dipole, and a
ladder line dipole using the same tuner, which has antenna
switch, and meter built in.
So I could A/B real fast. I could see a slight difference on
receive switching between the two. And if it's enough to see
on a meter, I consider it a noticeable amount.
Most of the signals were in the 20-40 over 9 range being 75m,
and I'd see about 5 db worth of difference between the two
antenna/feed lines.
Course, I make no claim as to the exact DB amount of difference,
but I could see it on a meter.

Most of it had to be the antennas. Going from almost no loss open wire to
much higher loss rg58 would be only 1 db at the most on 75 meters.
You still need a magnifing glass to see the smeter move this much on a ham
receiver.

On May 31, 8:17 pm, "Ralph Mowery" wrote:


Most of it had to be the antennas. Going from almost no loss open wire to
much higher loss rg58 would be only 1 db at the most on 75 meters.
You still need a magnifing glass to see the smeter move this much on a ham
receiver.

What about the tuner loss? And.. I was using the least amount
of inductance needed to tune.. The difference was noticeable on a
meter.
So that would tend to indicate the difference was more than 1 db.
The 213 I use at the house would be even lower loss than the 58,
but I do use rg-58 sometimes when portable, etc..
Doesn't do any good to use a slightly lower loss feed line, if the
tuner
needed to match causes more loss than the feed line saves vs coax.
And tuners will vary also. Also setting the tuner itself can lose even
more power if the minimum inductance is not use. It's not too hard
to lose up to 20% of your power if the inductance settings are wrong.
I'll still stick with coax and no tuner.