I will be sending you some photos of my final installation. I did a number
of tests comparing how tight you can wind the loops. I was amazed at how non
critical it was, considering all the dire warnings one receives from the old
wife's tales.

Aside from all the ham bands, I have the need to get down to 3.347 MHz as
well. My setup with the thumbwheel digital rotary switches lets me look at
my chart, see 3.5 MHz needs 39 additional feet and set 39 in the switches,
I built a box outside the house with 4 dowel rods to wind the loops around.
It worked out great both mechanically and electrically.

After I inserted the relay box, I cut additional feedline off the 90 foot
feedline so the output side at the end of the coax agreed with the original
readings. Once that was accomplished all the plots were in agreement with
the predicted except on 40 meters. Predicted should have been 7.3, actual
was 6.8 MHz. Easy enough to correct for, but have not yet figured out what
causes it. All other freqs were spot on.

Worst SWR is 1.8:1 I am a happy camper. On 75 an A/B test shows no
difference was noted between it and a 75 meter dipole.

I need to A/B it on the other bands yet.

My method of 1,2,4,8 and 10,20,and 40 feet uses extra feed line, but is made
up for in the ability to enter feet directly on the switches.


Three other folks here are constructing a duplicate.

"Cecil Moore" wrote in message
...
Fred W4JLE wrote:
All my feedlines have a 9:1 SWR by design.

Heh, heh, I understand perfectly. Don't know
how many others do. :-) All my feedlines have
an SWR between 5:1 and 13:1 by design.
--
73, Cecil http://www.qsl.net/w5dxp

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Of Course you are, all horror stories aside.

Don't confuse the angels dancing on the pinheads around here with practical
world experiences. The best solution is to increase the length of your
dipole to 130 feet and feed it with 100 foot of 450 Ohm ladderline. Connect
a piece of coax with a ferrite bead choke to the 450 Ohm line. Your tuner
will love you and you can use all bands from 80 on up.

The electrical plug on your rig has losses that are about as meaningful real
world..

"Buck" wrote in message
...
On Sun, 05 Jun 2005 19:21:27 -0500, Cecil Moore
wrote:

Chuck Olson wrote:
The tuner doesn't reduce efficiency - -

There's no such thing as a 100% efficient tuner.


I realize that a tuner is not 100% efficient, but when I hook up my 80
meter dipole and listen on 20 meters (the wire is fed with coax), the
signals are stronger when tuned thru the tuner rather than direct from
the antenna. Not to mention that when I transmit, the radio is
operating on reduced power with the dipole direct. I realize that
there is considerable loss in my coax (I am using garbage and know it)
and that I am taking a loss thru the tuner, but it is a better option
than direct thru the coax alone.




--
73 for now
Buck
N4PGW

My 132 foot dipole is fed by lengths of 450 Ohm line of lengths depending on
frequency. The first part acts as a matching section to achieve 50 Ohms.
This feeds an electrical 1/2 wavelength 450 Ohm section the 50 ohm
impeadence is seen by the rig, while maintaning a 9:1 swr on the 1/2 wave
section. 450/50=9:1

"Wes Stewart" wrote in message
news
On Tue, 7 Jun 2005 12:19:23 -0400, "Fred W4JLE"
wrote:

All my feedlines have a 9:1 SWR by design.

Really, and how is that?

Fred W4JLE wrote:
Once that was accomplished all the plots were in agreement with
the predicted except on 40 meters. Predicted should have been 7.3, actual
was 6.8 MHz. Easy enough to correct for, but have not yet figured out what
causes it. All other freqs were spot on.

What causes it is the feedpoint impedance of a one wavelength
dipole is very high and therefore easily upset by the surroundings.
A low impedance feedpoint impedance is not easily upset by the
surroundings. It's the same concept as using a 20k ohms/volt
voltmeter to measure the cathode voltage or the screen voltage
of a tube. One will give correct results and one won't.
--
73, Cecil http://www.qsl.net/w5dxp


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Wes Stewart wrote:

Cecil Moore wrote:

Fred W4JLE wrote:
All my feedlines have a 9:1 SWR by design.

Heh, heh, I understand perfectly.

You do?

Of course! The feedline Z0 equals 450 ohms. 450/9=50
Fred is using my design from:
http://www.qsl.net/w5dxp/notuner.htm
--
73, Cecil http://www.qsl.net/w5dxp


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On Tue, 7 Jun 2005 15:01:23 -0400, "Fred W4JLE"
wrote:

My 132 foot dipole is fed by lengths of 450 Ohm line of lengths depending on
frequency. The first part acts as a matching section to achieve 50 Ohms.
This feeds an electrical 1/2 wavelength 450 Ohm section the 50 ohm
impeadence is seen by the rig, while maintaning a 9:1 swr on the 1/2 wave
section. 450/50=9:1


Because you see 50 ohm (more or less) at the input of your "450 ohm"
(more like 400 ohm) line with an arbitrary impedance at the other end,
you incorrectly conclude the 450 ohm, variable length line is
operating at 9:1.

It appears that you've copied Cecil's design (ingenious BTW) but even
he admits to anywhere from 6:1 to 13:1 on his line.

For discussion purposes let's say that a 132 foot dipole, 50' above
average ground operated on 3.5 MHz has a feedpoint Z of about 61 -j63.
That's about SWR = 7.5 using 450 ohm as a normalizing factor.

Except for the effects of loss, the SWR *everywhere* on the line is
7.5:1. You don't get to say that 1/2 wavelength of it is operating at
9:1 and some other part is operating at something else.

Change the frequency to 7 MHz and the SWR is ~10:1 and so forth.

On Sun, 05 Jun 2005 16:57:03 GMT, GeorgeF
wrote:

I put up an 80 meter full wave loop using about 280’ of #14 wire in
almost a square. Each end of the loop was soldered to an SO-239
connector. I’m feeding the loop via RG-8 coax, about a 30’ run.

I have a 400 foot loop that is more triangular than square but it
still seems to work pretty well. The biggest difference between our
antennas is how they are fed. I use 450 ohm ladder-line to a balanced
tuner (Johnson Matchbox) to my FT-897D. According the Yaesu's display
a suitable match can be obtained on all bands except 30 and 60 meters.

I can also use the antenna on six meters with a homebrew matchbox for
that band. A two meter matchbox is in the works.

Using an MFJ Antenna Analyzer I can’t find a nice low SWR point. The
lowest I can find is at 2.5 MHz, the SWR at that point is still high at
3.4:1. In the 80 mtr band its 8:1 and in the 40 mtr band its 7:1.

The impedance, is that the right word?, of a loop can be several
hundred to several thousand ohms. As you have found, the antenna is
not a fifty ohm load.

My installation is far from ideal. First, the antenna for about ½ the
loop is at about 20’ high and the second half is about 15’ high. Next,
in the center of the loop is the metal frame work for a screen-room over
the swimming pool (50’ x 30’) which I’m sure interacts with the loop
antenna to some degree. The screening is not metal however the frame
work is.
The antenna is what it is. Although a little more elevation would be
FB I wouldn't be too concerned with what is in the middle of the loop.


Of course I can use my MFJ-949 tuner to get a low SWR on any band but by
doing so am I loosing efficiency? I also notice that trying to tune the
loop the tuner seems to be very touchy! I have noticed on 20 meters
the loop received on average about 2 S-Units better than my 20 meter
dipole. On 40 meters it receives almost 1 S-unit better than a 160’
randomwire. On 80 meters just slightly better than a 160’ randomwire.
(all antennas I’m comparing are all at about 20’ high).

I would have started making the loop shorter to bring up the resonate
frequency to 80 meters however I’m concerned as to why the lowest SWR I
can find anywhere on the HF band is still over 3:1. Is it because the
loop low to the ground (20’)? Or do I need a balum? 1:1 balum? 4:1
balum? Looking for any suggestions.

Ack, do not shrink the loop!!!!! The tuner you have can be used with
a balanced feeder, the built-in balun should be satisfactory. Try
feeding your loop with 450 ohm ladder-line from the tuner and things
should improve significantly.

73 de n4jvp
Fritz

Nonsense Wes, take the case of an antenna that is of sufficient length,
height, or what ever so that at the antenna is exactly R 50 J0.

I feed it with an electrical 1/2 wave length of exactly 450 Ohm feedline.
The 50 Ohms from my antenna is repeated at the other end of the feedline. An
SWR bridge calibrated for 50 Ohms and my rig see 1:1.

Would you deny that the SWR on the feedline is 9:1? What is my SWR?

Can I say I have 1:1 at the ends and 9:1 anywhere on the feedline? I do get
to say it!

Now if you want to argue that it will never be exactly 9:1 because the
feedline is never exactly 450 Ohms, or the antenna has a reactive portion,
you will have to change the subject. No generalization is valid, including
mine that I have a 9:1 by design. But I suspect you already new that and
decided to increase the quantity of fly crap in the pepper.

"Wes Stewart" wrote in message
...
On Tue, 7 Jun 2005 15:01:23 -0400, "Fred W4JLE"
wrote:
You don't get to say that 1/2 wavelength of it is operating at
9:1 and some other part is operating at something else.

On Tue, 7 Jun 2005 18:02:43 -0400, "Fred W4JLE"
wrote:


You started with this (mis)statement:

All my feedlines have a 9:1 SWR by design.

I challenged this crap and showed that, using your own example, this
was not the case.

You called my challenge "nonsense" and then go on to agree with my
original point:

No generalization is valid, including
mine that I have a 9:1 by design.

Simply amazing.

You win Wes, pick up the marbles.

"Wes Stewart" wrote in message
news
On Tue, 7 Jun 2005 18:02:43 -0400, "Fred W4JLE"
wrote:


You started with this (mis)statement:

All my feedlines have a 9:1 SWR by design.

I challenged this crap and showed that, using your own example, this
was not the case.

You called my challenge "nonsense" and then go on to agree with my
original point:

No generalization is valid, including
mine that I have a 9:1 by design.

Simply amazing.