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Author Topic: Skyloop Antennas  (Read 1845 times)
KD7KXT
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Posts: 12




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« on: August 05, 2006, 12:29:34 PM »

I have been thinking about putting up a Skyloop antenna on my property but, as is the case with most residential lots, there are some limitations. Because of the location of trees and poles I have 3 possible loops:
1. Is a loop with 160’, 146’, 92’, and 98’ foot sides for a total length of 496 feet, the closest to the ideal length for 160M.
2. Is 113’, 188’, and 160’ feet a total of 451 feet.
3. 211’, 188’, 146’, 92’ for a big loop of 637 feet.
None of the loops are of a size to be resonate on any single band but to help offset that I have a MFJ 993B automatic tuner. Given my conditions I would appreciate your thought about the best path forward, allowing use on 160M through 10M. Before anyone asks, I have read past QST articles and Elmer posts but that doesn't mean I understood everything.
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KZ1X
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« Reply #1 on: August 05, 2006, 01:52:21 PM »

I'd just put something up, whatever works best mechanically, and idealize the coupling to the tuner, like use window line, and remote the autotuner at the ground end of the feed ... if that isn't where the radio will be.  That will make far more of a performance difference from my experience.  The loop lengths you mention are plenty long enough, I think.  Maybe too long!
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KZ1X
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« Reply #2 on: August 05, 2006, 01:53:02 PM »

Oh, I should have asked ... how high up?
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WB0M
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« Reply #3 on: August 05, 2006, 02:02:15 PM »

A full-wave 160-meter loops measures out a 560 feet at the low end of the band, 530 feet at 1.9 MHz. So your tuner should handle any of the lengths, although the closer the better. I used 500' for a loop with an MFJ 949E manual tuner and had great success - of course it was pretty low to the ground and had a NVIS effect, but it was quiet. You might want to think about the shape and height in your choice of antennas. The more "uniform" and higher the wire might be best. I don't really qualify as an "elmer", but just my $.02 from experience. Oh, KZ1X is right on track about feeding the loop with ladder line. Plus it should work on most other bands. GL & 73, Jeff/wb0m
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KD7KXT
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Posts: 12




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« Reply #4 on: August 05, 2006, 03:22:51 PM »

The height is somewhat limited but will very between 30 and 40 feet.
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RobertKoernerExAE7G
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« Reply #5 on: August 05, 2006, 03:24:04 PM »

You'll probably have more fun with a simple multiband inverted Vee for 15, 17, 20, 30 and 40 meters.

Low antennas for 160, 80, and 40 send your signal almost straight up to the reflecting layers, and then almost straight back down.  As a result, you are limited to talking with people very close to you.  Also, the low bands are mainly used during our winter months.  We are currently at the bottom of the sun spot cycle; so, the higher bands like 6, 10, 12 and 15 aren't open that often.

73
Bob
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K3AN
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« Reply #6 on: August 05, 2006, 03:54:32 PM »

The W4RNL web site has a good treatise on loops. Check out www.cebik.com, then click on Tales and Technicals. You'll find several articles about loops.

Per Cebik, at 30 to 40 feet off the ground, a large horizontal loop like you propose will radiate much of its 30M and up energy at relatively low angles. It should perform far better than an inverted V.
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WB0M
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« Reply #7 on: August 05, 2006, 05:46:08 PM »

Are you looking to work just 160 or other bands too and what would be the length of your feedline?
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KD7KXT
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« Reply #8 on: August 05, 2006, 08:46:19 PM »

I would hope to be able to work all bands with the help of an antenna tuner. Loops 1 and 2 would have a feed line lenght of 50' while the third would be approx. 100'.
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KD7KXT
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« Reply #9 on: August 05, 2006, 09:29:15 PM »

Thanks for the link that's a great web site and resource for antenna information.
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N3BIF
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« Reply #10 on: August 05, 2006, 10:55:37 PM »

Any  decent feedline will have a negligible losses at those lengths on hf. The height is also a wash as it seems to be the same regardless of the supports. The closest you can get to a circle would be the better way to go, so 4 sides should be better than 3 . I would go with number 1 for the following reasons
     4 more equal sides than choice 3
     shorter feed line
     can be made with a single 500 foot roll of wire
     closer to the full wave length than the other        choices.

 In reality though being you are so relatively close to the ground it probably wouldn't make much difference which one you go with. They all will work very well.


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WB6BYU
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« Reply #11 on: August 07, 2006, 12:13:03 PM »

I'd go with the third option, because you can always
install the loop smaller than the space between the supports.

Go down to the local farm supply store and get a bag of
plastic electric fence insulators.  I like the type that
look like an egg insulator with slots rather than holes,
but any insulator that will clip around the wire rather
than passing the end of the wire through a hole should work.

Lay the desired length of wire out on the ground in the
middle of the supports.  Toss a rope over each of the
supports, bring one end out to the wire, slip an insulator
around the wire and tie the rope to it.  Then pull up on
the various ropes to hoist the antenna into the air.  The
insulators will slide along the wires a bit to adjust
the shape.  This also allows you to lower the antenna
for maintenance - even easier if each loop is a continuous
halyard, which makes it easier to pull the insulators
down from the trees if the wire breaks.

Cutting the loop to resonance on the low end of 160m
and feeding it with a 4 : 1 balun should give you an
antenna with a reasonably low SWR on most bands - mine
worked well with a limited-range autotuner.  If you are
going to use open wire line the exact wire length is
much less critical.
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NE5C
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« Reply #12 on: August 07, 2006, 03:52:07 PM »

Man, I ENJOY MY SKY LOOP or SKY-BURNER as we call em...I believe the age old Formula was; 1005 (Divided by the Frequency in Mhz) = The feet of wire... you would want to use for that desired Frequency. Then - if you desire it to be Square divide by 4 or if you desire a DELTA LOOP - divide by THREE = the length of Feet - of each side. BUT...I will say that we have found the sides DO NOT have to Be Equal and it still works, as one of my Mentors say's "Like a Hose" yeah Man the "SKY-BURNER" is one of the Best antennas I've ever used. GOD BLESS De N5JFJ ... -.-  
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WB0M
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Posts: 15




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« Reply #13 on: August 08, 2006, 02:38:49 PM »

You can't go wrong with Mr. Cebik's antenna info. Line loss should be minimal using ladder line (I use the 450 Ohm version) and you want to keep it in the multiples of 25-feet, so that sounds okay (you want to avoid harmonics as your feedline will radiate also). But I don't know whether having a shorter feed line (using ladder line) outweighs the overall antenna length. Maybe someone else could give some input. It would seem the overall shape and dimensions of the antenna be more important than feedline length. Of course, as with all antennas, sometimes you don't know until you actually get it up and try it. GL & 73, Jeff/wb0m
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