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Old September 12th 05, 08:45 PM
Steven Fritts
 
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Default Full Wave Loop Question

Hi all,

I am thinking of building a full wave loop for 17 meter ham band. What
I plan to do is to build a cross shaped form...then run wire approx
12.7 ft on each side....then hang the antenna vertically from a tree
or mount it on a support 30-40 ft up with the V point of the antenna
straight up with the other "V" point straight down. In other words the
antenna will look like a diamond hanging vertically in the air. If I
feed the antenna at the bottom V with ladder line, one lead on each
leg, how will this antenna perform? The antenna wire wil be seperated
at the bottom point-not tied together. Will it have any gain? I am
sure there will be directivity broadside to the antenna.Thanks for any
help.

Steve W4SEF

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Old September 12th 05, 09:29 PM
Cecil Moore
 
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Steven Fritts wrote:
Will it have any gain?


Not over a dipole at the same maximum height.
Lots of gain over a 1/4WL vertical. :-)
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73, Cecil http://www.qsl.net/w5dxp

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Old September 13th 05, 01:09 AM
Hal Rosser
 
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Hang a closed loop 5% longer in back of it and one 5% shorter in front, and
you'll hava a quad.

"Steven Fritts" wrote in message
...
Hi all,

I am thinking of building a full wave loop for 17 meter ham band. What
I plan to do is to build a cross shaped form...then run wire approx
12.7 ft on each side....then hang the antenna vertically from a tree
or mount it on a support 30-40 ft up with the V point of the antenna
straight up with the other "V" point straight down. In other words the
antenna will look like a diamond hanging vertically in the air. If I
feed the antenna at the bottom V with ladder line, one lead on each
leg, how will this antenna perform? The antenna wire wil be seperated
at the bottom point-not tied together. Will it have any gain? I am
sure there will be directivity broadside to the antenna.Thanks for any
help.

Steve W4SEF



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Old September 13th 05, 11:56 AM
KC1DI
 
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On Mon, 12 Sep 2005 15:45:45 -0400, Steven Fritts
wrote:

Hi all,

I am thinking of building a full wave loop for 17 meter ham band. What
I plan to do is to build a cross shaped form...then run wire approx
12.7 ft on each side....then hang the antenna vertically from a tree
or mount it on a support 30-40 ft up with the V point of the antenna
straight up with the other "V" point straight down. In other words the
antenna will look like a diamond hanging vertically in the air. If I
feed the antenna at the bottom V with ladder line, one lead on each
leg, how will this antenna perform? The antenna wire wil be seperated
at the bottom point-not tied together. Will it have any gain? I am
sure there will be directivity broadside to the antenna.Thanks for any
help.

Steve W4SEF


Hi Steve,

The clssic Quad loop is a good single band antenna , you could feed it
with coax as well. (75 ohm) The impeadence is about 125 ohoms. It will
have on the order of about 1 to 3 db of gain over a dipole
bi-directional. but that is not much and you won't notice a lot of
difference , some claim the loop is much quiter on Rx and that has been
the experience here. If your thought is to use it on multiple bands the
vertical loop is a poor choice for that application.. but it's a good
single band antenna.
you may want to look over the material on Cebik web page at
http://www.cebik.com/fdim/fdim5.html

In any event have fun and experiment.
73 Dave KC1DI



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Old September 13th 05, 03:04 PM
Cecil Moore
 
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KC1DI wrote:
The clssic Quad loop is a good single band antenna , you could feed it
with coax as well. (75 ohm) The impeadence is about 125 ohoms. It will
have on the order of about 1 to 3 db of gain over a dipole
bi-directional.


Hi Dave, I'm interested in knowing how you get the gain of a
quad loop to equal the gain of an Extended Double Zepp dipole?
--
73, Cecil http://www.qsl.net/w5dxp

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Old September 13th 05, 06:42 PM
KC1DI
 
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On Tue, 13 Sep 2005 10:04:26 -0400, Cecil Moore wrote:

KC1DI wrote:
The clssic Quad loop is a good single band antenna , you could feed it
with coax as well. (75 ohm) The impeadence is about 125 ohoms. It
will have on the order of about 1 to 3 db of gain over a dipole
bi-directional.


Hi Dave, I'm interested in knowing how you get the gain of a
quad loop to equal the gain of an Extended Double Zepp dipole?


Hi Cecil,

Good Question.. I should have been more specific.. the gain of a fullwave
vertical loop over a 1/2 wave dipole is approximatel 1.2 db-- if you use
the same antenna on the 2nd harmonic you will get about 3 db gain , but
with that said we must realize that this gain is not necessarily at good
angles for DX. The dipole may actually have a better pattern that a 2
wave vertical loop. and thus any gain achieved will be negated by the
fact that this gain is at angles that are not conducive to good Dx
propagation.

Cebik places the gain of a full wave vertical loop at about 5.9 dbi that
rises to about 7.6 dbi on the 2nd harmonic and about 8 dbi on the 4th
harmonic.

But the T.O. Angels are as follows-- Fundamental Frequency- 35 deg. 2nd
harmonic 48 degrees 4 harmonic 45 degrees This is for a square loop.
these are not great figures for DX but useable none the less. A Dipole
would though I have not researched it do better in the angle department.
thus any gain received by the loop would be negated but a stornger signal
at the right angle by the dipole.

73 Dave


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