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Author Topic: delta loop for horizontal and vertical orientation  (Read 2142 times)
W4PAH
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« on: July 15, 2009, 12:18:18 PM »

After having so much good luck with the delta loop I used at the beach, I am considering putting one up at home.

I live in a duplex townhouse that would accommodate a full-wave 20m delta loop in my small back yard.

When the loop is horizontal, I'm considering using two 32 foot high poles to anchor two sides of the loop and the other side to the house (where I have an eye bolt at about 20 feet up).

When it is vertical, I'm considering just having the flat portion of the loop at the top (inverted delta) between the two poles. It could easily be set up with the apex at one of the poles and the feed point at one of the bottom corners.

A few questions...

How would the radiation pattern be affected if the horizontal loop is more of a right triangle (90 degrees, 45 degrees, 45 degrees) versus an equilateral triangle?

I'm interested in using it on other bands (1/2 wave loop for 40m, all HF bands above 20m) and am wondering if I should feed it with a 1:1 balun at the feed point or with ladder line. If ladder line, should I use 450 ohm or 300 ohm?

What radiation patterns would I expect if I used the vertical loop in the inverted position versus the apex-up position? Which would be better for DX or local?

Are there any other considerations I'm not mentioning? Please let me know. Thanks for all your help!
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KQ6Q
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« Reply #1 on: July 15, 2009, 12:40:16 PM »

It's just rope and wire, try the various configurations and see what differences you notice! That's the joy of hamming and the simplicity of antennas....
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W5WSS
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« Reply #2 on: July 15, 2009, 01:11:56 PM »

Check out Antennex they have many articles written by LB Cebik SK. He did a complete modeling excercise demonstrating the variables you mentioned. The loops offer utility for the ham. Their patterns are really very reliable and repititious throughout the bands. Height is vary important with horizontal varieties. feed location anywhere around the perimeter is convenient and available. For a better understanding of what is happening and why check out MR.Cebiks writs 73
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WX7G
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« Reply #3 on: July 15, 2009, 04:11:08 PM »

For your delta loop with the horizontal wire at the top:

For horizontal radiation feed at the bottom. For vertical radiation feed on one side 25% from the top. That's about 6'.

This 72' perimeter loop exhibits an input impedance like so:

7 MHz  >12000 ohms
14 MHz    100 ohms
21 MHz   3000 ohms
28 MHz    230 ohms

450 ohm ladder line will work well on 10 - 30 MHz. 7 MHz not so well. I've used the same kind of antenna and was able to tune it on 40 meters but it didn't compare well at all to a vertical.

If you want to run this antenna on 40 meters it can be fed at the bottom with the top wire open in the center. It is now a 40 meter dipole that is bent into a triangle. It will present a tunable impedance on 40-10 meters similar to a 40 meter center fed wire.
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N1LO
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« Reply #4 on: July 15, 2009, 04:32:07 PM »

See the patterns for yourself using the free demo antenna modeler at www.eznec.com

--...MARK_N1LO...--
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WA3SKN
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« Reply #5 on: July 16, 2009, 05:34:44 AM »

Preferences...
Horizontal is slightly better than vertical. (Even though mine is vertical).
450 Ohm ladder line and a tuner.
Make the loop as open and as high as you can, and the larger the better... no need to cut to frequency.
You can load down to 1/3 wavelength... and it will work well from 2/3 wavelength on up.
Great multi-band antenna!
73s.

-Mike
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W4PAH
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« Reply #6 on: July 16, 2009, 05:44:20 AM »

Thanks for all your insight. My 32 foot poles come in next week and I hope to get an antenna together at some point in the near future. Once I do, I will post results of my tests.
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N5LRZ
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« Reply #7 on: July 16, 2009, 07:22:07 AM »

The radiation pattern is perpendicular to the plane of the loop.  So if you put your loop in a horizontal configuration it will radiate most of its signal up and down.  If you put your loop in a vertical configuration it will radiate on its own in in a bi directional pattern just like you were looking thru the loop itself.

The radiation orientation will be the half of the loop opposite the feed point half.

Keep the loop of wire as open and as circular as is possible.
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WB6BYU
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« Reply #8 on: July 16, 2009, 12:15:33 PM »

Radiation is perpendicular to the loop when the length
is less than 1.5 wavelengths.  As the loop gets longer
in terms of wavelengths (that is, you use the same length
on higher frequencies) the radiation shifts to where it
is more in the plane of the loop.  That is why large
horizontal loops are popular:  they give good NVIS coverage
on the lower bands and lower angle radiation on the higher
ones.

But on 20m you don't want high angle radiation, so a
horizontal loop isn't a good choice for that band.  It
might be useful on 10m, but on all the lower bands you
will be better off with the loop in a vertical plane.
(The situation is very different for an 80m loop.) You
may, however, find that changing between vertical and
horizontal POLARISATION of a vertical loop may give an
improvement on some bands - you'll just have to try it
and see.  (If you put pulleys on the corners of the
loop you can slide the feedpoint around and try it out.)

In your case there will be little difference in performance
between an equilateral triangle and a right triangle.
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W4VR
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« Reply #9 on: July 16, 2009, 02:18:17 PM »

If you have the supports try a horizontally-mounted loop fed with open wire line.  They seem to work quite well on all bands.
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