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Author Topic: Full Wave Loops?  (Read 1634 times)
AI0F
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Posts: 40




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« on: December 24, 2006, 02:46:34 PM »

I am getting ready to build my first full-wave loop antenna. I know pretty much what I need.. about 268 ft. of wire, about 67 ft/side I believe is pretty close to correct(for an 80M loop). Question is, I have enough land, but it's all trees....how "altered" can the antenna be and still function as one would want it to? Regardless of how I do it, it's going to be in the trees...how much effect with the trees have, how can the configuration be and still be effective, etc.?

Tnx in advance to all you antenna "guru's" for any insight...
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KE6VG
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Posts: 298




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« Reply #1 on: December 25, 2006, 04:29:35 PM »

At 80 meters the trees won't bother you. Get the loop as open as possible. Circle is actually better than a square. The more open the loop the better the capture area will be and the less cancelation you will have. If you get it at a decent height, you will be amazed. Either feed it with ladderline or use a remote tuner.
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K8AC
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Posts: 1464




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« Reply #2 on: December 26, 2006, 05:28:45 AM »

The answer is the loop can be VERY different from a square or circular loop and still work very well.  See www.cebik.com and read all about the SCV group of antennas, in which he includes all forms of the loop.  He gives modeled gain figures for the various types and configurations so that you can see the differences as the shapes are changed.  You'll see that the delta or triangular full wave loop is very effective and for the lowest bands the height of the single support can be compressed quite a bit and the antenna will still work well.  Information is given on how to feed the antennas for vertical or horizontal polarization as well as impedance matching.  The loop shape can be chosen based on the height and number of supports you have available.  You didn't say whether you primarily chase DX or ragchew on 80, but choose the appropriate polarization for you primary activity.
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N3BIF
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« Reply #3 on: December 26, 2006, 09:49:12 PM »

You best use insulated wire, mine runs over under and through the canopy in my yard with only about 75 out of the 270 feet in the clear. It remains my best antenna.
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AL7II
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Posts: 8




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« Reply #4 on: December 27, 2006, 08:47:10 AM »

I have my loop in the shape of a sloppy pentagon.  I feed it with ladder line, and tune it with Icoms AH4 Auto Tuner.  Right now it's only 25 feet high but it still usually out performs my vertical and G5RV.  I can see as much as 3-4 S-units difference between the loop and vertical.  Plus my S/N noise ratio dramaticly improves.  I use the loop on all bands 80-10 and on occasion for DX do I see a noticible difference in favor of either the G5RV or vertical.  Depends on the angle that signals are coming in.  During the 10m contest a few weekends ago for a while the vertical was working better than the loop but  as propagation changed the loop ended up being better than the vertical.  If I could only put up one antenna, I think I'd perfer the loop.  I plan on getting my loop up higher in the tops of the trees about 60' and see what happens.  I suspect a lower angle of radiation so it should improve as a DX antenna.  
73
Scott, AK9I
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N4KZ
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Posts: 592




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« Reply #5 on: December 29, 2006, 08:47:18 AM »

The horizontal loop is the best wire antenna I have used in more than 30 years of hamming. It's very forgiving as to its configuration. Three sides or four sides -- both will work although four is better.

I use 280 feet of No. 16 insulated stranded wire. Nothing magical about my choice -- it was just available cheap at a local electrical supply house. I have used No. 18 bare copper-clad steel wire. It's very light and very strong but will rust quickly and has a terrible memory if dropped on the ground during installation -- which means you will have a bad tangle quickly.

I feed mine with 450-ohm twinlead in the middle of one side and run the twinlead all the way to the rear of my transmatch. My transmatch has an internal balun. Others prefer an external balun and then run coax into the house. Either way works fine.

This has been a very successful DX antenna for me on 80, 40 and 30 meters. I have even used it all the way up to six meters with success. On 160, I load one side of the feedline as a random wire. I laid down some radials and it performs as an inverted L, of sorts, on 160, with some decent reports from Europe on CW.

You will find the loop to be versatile and frequency agile. But make sure to disconnect when storms approach because that big capture area is prone to static discharge.

Good luck.
73, Dave, N4KZ
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W7TEA
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Posts: 16




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« Reply #6 on: December 31, 2006, 07:30:40 AM »

I've used loops at this location for 17 years and have been surprisingly pleased.  We live in an antenna restricted area and I finally settled on a 80m slanting delta loop with the apex about 50 ft up a fir tree.  The base runs along a cedar fence and is fed in a bottom corner with a 4:1 current balun, then coax to the shack some 30 ft away.  Since I'm not to have outisde antennas at all, it is made of #16 copperweld and has held up well over the years.  It is nearly invisible.   The CCandR's expire in two years and then I can try something more visible.  

Gary W7TEA
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WW5AA
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Posts: 2088




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« Reply #7 on: December 31, 2006, 08:44:47 AM »

The shape of a 80 meter loop (within reason) does not matter unless it can be mounted at least 1/2 wavelength high at the operating frequency. Not practical for most of us.  

73, de Lindy
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K3JVB
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Posts: 837


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« Reply #8 on: January 01, 2007, 06:54:05 AM »

I to would like to build one..

I am in a position that I can only go vertical, with the apex up at 70 feet ( delta). Although , All I have read...it seems that the horizontal would be the best for most bands covered. Cebik seems to favor the horizontal over the "apex" up delta as well.

Anybody have any thoughts on either?
73, happy new year

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KF5KWO
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Posts: 52




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« Reply #9 on: January 01, 2007, 08:49:35 AM »

You'll have great fun with your loop.  Mine is 12 feet off the ground, attached under the eaves of the roof of my one-story house.  I've worked all over the US on 80 on mine.

73 and good luck de Jeff, KF5KWO
Helotes, TX
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W7TEA
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Posts: 16




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« Reply #10 on: January 01, 2007, 11:14:20 AM »

I have only one high support and a small city sized lot.  Picked up the idea for the slanting delta from an article Lew McCoy wrote in QST in the mid 80's.  Now I can't compete in pileups with guys with beams, but I work a lot of DX.  Picked up Christmas Is. this year on 30m where the antenna is hardly resonant, so the slanting delta can get out.  

Gary W7TEA
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