I have both a 130 foot dipole and a G5RV, I can switch between the two and
the reports are exactly the same on 75. With 100 watts on the G5RV I
have
worked well over 100 countries on SSB 75 meters. The day I received the
Olivia for my mix w, worked Russia on it with 5 watts on 20 meters.

I use it nightly on my Navy Mars nets in the 3 Mhz area.

Like the 130 foot dipole I vary the feed line length to tune.

Hummmmm.......... :/

Both feedlines are fed from the rig to the ladderline with coax covered
with
ferrite beads at the junction end.

Try the 130 ft dipole fed with straight coax and see if you don't
see a difference then. Sure, it won't be huge, but it should be
there, and be quite noticable too on a receiver. I think this why you
are seeing no difference. .
You are "clutter" feeding both antennas. :/ Seriously.
Coax to ladderline...yuk...:/
But saying that, it's obvious it works well nuff I suppose..
I just like to stir it. It's been too slow around here lately.
But...I am serious about what I say.. If you want the vurry
best 80m dipole, feed it with nuttin but coax.
MK

Tell me how to coax feed a dipole that works from 3.3 to 4.1 MHz and you
have my attention.

wrote in message
oups.com...
..
But...I am serious about what I say.. If you want the vurry
best 80m dipole, feed it with nuttin but coax.
MK

Tell me how to coax feed a dipole that works from 3.3 to 4.1 MHz and you
have my attention.

Probably wouldn't be practical for you.. Just offhand, I can think
of a way, but you'd have to run at least two set of dipoles, and
maybe even three, tied together in parallel. You would stagger
tune them one low, one middle, one high, and the SWR
plot should look about like a \/\/\/ . I've never tried using
three dipoles, but I've done it with two and having a W SWR
plot. That is one way you could have that range and use
coax feed. But like I say, probably would be a PIA with
it needing at least one center support and six tie off
points.
MK

wrote:
If you want the vurry
best 80m dipole, feed it with nuttin but coax.

Well, as a data point, Owen's transmission line loss
calculator says there's 0.362 dB loss in 100 ft. of
RG-213 feeding a 50 ohm antenna on 75m. The loss using
100 ft. of open-wire feedline feeding a 50 ohm antenna
on 75m is 0.169 dB, less than half the loss in the coax.
Even the Wireman #554 "450" ohm line is better than
the coax at 0.269 dB. Where are the losses in a Ladder-
Line fed system?
--
73, Cecil http://www.qsl.net/w5dxp

Where are the losses in a Ladder-
Line fed system? ....

The tuner that is usually used offsets the advantage
of the line itself. Sure, on paper you shouldn't really
be able to notice it. But I do when I test it. It's actually
measureable on an S meter when doing A/B comparisons.
Or at least it was for me when using a 989c tuner
and minimum inductance vs coax fed.
That tells me the tuner loss can often be a bit more
than it's cracked up to be. But I also found if you don't
use the minimum inductance when tuning the tuner,
you can lose quite a bit. I saw easy 20 % losses when
testing that one time. If I used the very least inductance,
I could get it down to an almost unmeasureable level.
If I get on 80m and want the very best efficiency I can get
feeding a dipole, I use coax.
Of course, the line is never more than 100 ft.
Usually more like 50 ft. I have a 50 ohm radio feeding a
low loss 50 ohm line, to a 50 ohm antenna feedpoint. You
have uncluttered perfection. :-) And in the real world
the most efficient that I've seen so far. If there was better,
I'd be using it. I could see using the ladder line on real
long distances. On the higher bands, it could be noticable.
But like I say, my run is about 50 ft. Considering efficiency
vs ease of use, wx resistance, ease of lightning protection,
coax is a no brainer for me. Of course, I ain't everyone.. :/
MK

wrote:
Where are the losses in a Ladder-
Line fed system? ....

The tuner that is usually used offsets the advantage
of the line itself.

Fred and I don't use a tuner.
--
73, Cecil http://www.qsl.net/w5dxp

Fred and I don't use a tuner.

Then you and Fred aren't running the same G5RV that
most people buy and throw up. And then feed with a tuner. :/
That's why I say I'm not really talking about your antenna.
I know you will modify it to make it more usable. This is a
given. You are Cecil. But all those 1000's of users who don't
have the time or the clue to modify? Like Lurch would say
on the Addams Family...Gruggggghhhhhhhhhhhhhhh... :/
MK

On 11 Jan 2006 01:09:41 -0800, wrote:

Where are the losses in a Ladder-
Line fed system? ....

The tuner that is usually used offsets the advantage
of the line itself. Sure, on paper you shouldn't really
be able to notice it. But I do when I test it. It's actually
measureable on an S meter when doing A/B comparisons.
Or at least it was for me when using a 989c tuner
and minimum inductance vs coax fed.

You are telling us that you have evaluated the loss of a MFJ-989C
antenna tuner + open wire line vs coax by on air A/B tests using the
S-meter as your indicator.

Presumably you used exactly the same antenna, how are you sure that
the feedline wasn't an active part of the antenna, was the measurement
made over an ionospheric path, was the A/B comparison made at
different times when other things may have changed?

What would be your confidence limits on such a experiment?

If you recorded your results, the variance would be revealing.

I suggest that the noise in your experiment would probably swamp the
true difference between your A and B configuration, and therefore your
conclusion might not be sound.

Your observation is (as you note) different to "on paper"
expectations, that might be reason to re examine the experimental
setup in search of an explanation.

Owen
--

You are telling us that you have evaluated the loss of a MFJ-989C
antenna tuner + open wire line vs coax by on air A/B tests using the
S-meter as your indicator.

Sure.

Presumably you used exactly the same antenna, how are you sure that
the feedline wasn't an active part of the antenna, was the measurement
made over an ionospheric path, was the A/B comparison made at
different times when other things may have changed?

The A/B testing is instant. All comparisons were done in the
usual up/down NVIS envionment. Mostly close in stations, and the
noise floor as another opinion. Just comparing any difference
in noise floor is a fairly accurate indication of efficiency in a
case like that. I didn't worry about the feedline being part
of the antenna, as I never would in the real world. I'm
running ladder line the whole way from the tuner to the antenna.
If the line is radiating, there would not be too much to do about
it at that point, without going to further measures. . I noticed
no obvious problems in tuning, or a "hot" line, rig, etc..

What would be your confidence limits on such a experiment?

Very high overall.

If you recorded your results, the variance would be revealing.

No. Not that time. It was just for my personal amusement.
In fact, I was out camping when I did that test.

I suggest that the noise in your experiment would probably swamp the
true difference between your A and B configuration, and therefore your
conclusion might not be sound.

What noise? I'm just using a switch to compare both antennas.
In that particular case, when switching to the coax fed, the noise
floor rose a bit, and strong signals that were way over S 9 rose
about 5 db worth on that particular meter. Easily repeatable
over and over. I'm not giving any numerical value to this
increase, I just know the coax fed system was the most
efficient. All signals increased when using coax. Noise floor,
desired signals, the whole deal. Switching to the tuner/LL fed
was like adding a small bit of attenuation. The way I see it,
the loss had to be at the tuner. And I was very careful in
tuning, using the least inductance to get a usable match.

Your observation is (as you note) different to "on paper"
expectations, that might be reason to re examine the experimental
setup in search of an explanation.

Why is it different? Actually, I found about what I was expecting.
I was expecting the coax fed to win. And it did.
Now, I realize this is a fairly sloppy test, and could be
improved greatly for accuracy, but there was no doubt
which system was better at that particular time.
The "on paper" expectations of the ladder line winning
would depend greatly on the losses of the tuner involved.
Sure, ladder line on it's own is very low loss, but add a
tuner, and things can change quite a bit as far as
system loss.
Now, granted the difference is small in general, but
I could see it. And if I can see it on a meter, it's not as
small as it's oft cracked up to be, or I wouldn't be able to
see it.
MK

ORIGINAL MESSAGE:


"Owen Duffy" wrote in message
...
snip

You are telling us that you have evaluated the loss of a MFJ-989C
antenna tuner + open wire line vs coax by on air A/B tests using the
S-meter as your indicator.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can do a pretty good evaluation of a tuner's loss by putting your hand
on the cabinet after running a few minutes. Just imagine a 25, 50 or
whatever watt resistor in there dissipating the same heat.

One needs to calibrate one's hand, of course. :-)

Bill, W6WRT