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Author Topic: Good distance for supports of a loop?  (Read 1324 times)
KD8Z
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Posts: 169




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« on: January 17, 2013, 05:17:27 PM »

What is a reasonable distance for supports of a loop, mine is a 160 loop but I guess all loop supports are same as another.  That will get some static.

ty to all that participated.
73
KD8Z
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ZENKI
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Posts: 980




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« Reply #1 on: January 17, 2013, 06:56:40 PM »

Depends on how much sag you have in your wire. You need to look at the wire gauge and determine how much the wire  will sag between poles based on the span length.
 If you look in this months QST there is  full details on how you can calculate and allow for wire sag. The article is written by Joe Hallas.
There are some online wire sag calculators floating around.

You will also need to allow for movement and the weights used to allow for wire movement also needs to be worked out based on the span and the weight. If you dont use moving weights the wire will snap.
There is full details in the ARRL Antenna Handbook.

If you want a simple answer, you need to give the distances between supports and the  wire diameter, I am sure someone will give you answer.

What is a reasonable distance for supports of a loop, mine is a 160 loop but I guess all loop supports are same as another.  That will get some static.

ty to all that participated.
73
KD8Z
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KD8Z
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Posts: 169




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« Reply #2 on: January 17, 2013, 10:04:21 PM »

AWG # 12 stranded on 160 mtrs.
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W3HKK
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Posts: 602




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« Reply #3 on: January 18, 2013, 06:15:48 AM »

Part of  the fun ismaking do with what you have.  With a bow and arrow or  bait casting with a small sinker, or other method, hang some twine, tie it to stronger rope, and haul up a corner of your  loop.  Keep it as symmetrical s possible, although Ive had some pretty wierd shapes in the air and they all work well. 

Let enough sag  in the wire to let the trees sway.   If it  snaps and comes down, do it again with a stronger line or a little more snag.  Dont be Hercules when hoisting the wire. When it feels hard to move and its mostly up where you want it, accept it and start operating.

Our club uses horizontal loops as terrific antennas on 160-80-40m,  often erected just for FD, the Ohio QSO Party, etc.  Ive used them  for 20+ years and rarely had one come down.  But nothing is really lost if one does.  SO no need to sweat the details or seek perfection.

Ive used #14 solid copper on 160-40m loops ( an assortment of 4 sided and 3 sided shapes depending on tree availability) with some stretching but nothing I couldnt live with.  The tighter you hoist it the more stretching you get. So dont be a perfectionist. Being a slacker is ok! Smiley
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KU3X
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Posts: 144




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« Reply #4 on: January 18, 2013, 08:26:12 AM »

What is a reasonable distance for supports of a loop, mine is a 160 loop but I guess all loop supports are same as another.  That will get some static.

ty to all that participated.
73
KD8Z

Is it a delta loop or a quad loop? Is it mounted vertically or a horizontal loop? You don't give enough information.
Barry
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WB6BYU
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Posts: 13474




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« Reply #5 on: January 18, 2013, 08:46:13 AM »

If you are talking about installing supports for the corners of a horizontal loop, and how
far out from the wire itself they should be, my recommendation would be at least 5 to 10
feet if possible.  That gives you some room for adjustment in case the wire stretches, and
a bit more flexibility in stringing it up.

If you tie the wire directly to the support post it doesn't allow you to vary the wire length
for tuning, and limits the options for strain control in the wind.  But sometimes this is the
best you can do, especially when using existing supports.

If you put the supports too far back then you can run into problems with sag, but with
130+ feet of distance between posts to start with (for a square 160m loop) another 10
or 20 feet won't make a lot of difference.

The best approach I've found is to put a pulley and halyard on each support, attach the
halyard to an insulator around the wire (the "egg" types sold for electric fences don't need
to be threaded onto the wire) then hoist it into place.  A counterweight on the bottom of
the halyard limits the stress on the loop when the wind blows - this is particularly important
when using trees as supports.
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N6AJR
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Posts: 9921




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« Reply #6 on: January 18, 2013, 10:45:36 AM »

You can also run a rope  between two supports as a carrier to support the  wire. I use 3 section push up masts. This gets my wire up 30 feet. pound a pipe into the ground  and leave it sticking up a couple of feet. slide your push up mast over this to hold the bottom and run 2 guys at the back to counter the pull from the antenna. cheap and easy.  Remember too, that no matter how tight you make the wire, it will always have some droop. no way around that.
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N7WR
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Posts: 45


WWW

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« Reply #7 on: January 20, 2013, 04:38:07 PM »

The best approach I've found is to put a pulley and halyard on each support, attach the
halyard to an insulator around the wire (the "egg" types sold for electric fences don't need
to be threaded onto the wire) then hoist it into place.  A counterweight on the bottom of
the halyard limits the stress on the loop when the wind blows - this is particularly important
when using trees as supports.

The above is BYU's advice and that is exactly what I did with my 80 meter horizontal loop...which had 2 of my 4 vertical support posts snap in a 102 MPH wind gust on 12/17/12.  When I re-build it this spring I will be guying the support poles Cry
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KD8GEH
Member

Posts: 476




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« Reply #8 on: January 22, 2013, 10:05:16 AM »

The right answer is enough, depending on your loop configuration and rope weight limits. I use a sling shot and exsisting trees for my 160 meter loop and feed it with a home brew stub feeder of ladder line with a ugly balun. Love the darn thing, works well on all bands and is pretty quiet compared to my dipoles.

Hot tip, I use plastic clothes line pulleys to feed the wire through on mine and carbon rope for support. My wire "floats" in the pulleys and can be moved as needed at the feedpoint. This seems to help quite a bit keeping keeping it from breaking from my old method platic insulators. Been up for about 4 years now. Last tip, get as high as you can, where you can.

Best of luck and feel free to contact me if you need any further help.

73, 
De Dave  KD8GEH 
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N4JTE
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Posts: 1158




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« Reply #9 on: January 22, 2013, 09:00:48 PM »

Assuming a horizontal loop, think this way, the optimum shape for a loop is a circle for the best results but usualy impossible.
Bob
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