Rectangular sky loop

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Marco EVANGELISTA

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Jul 1, 2018, 3:30:15 PM7/1/18
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Dear all,
I would like to install a loop skywire around the perimeter of the terrace of the building where I live.
The terrace is about 35' x 70'. Therefore the loop will be rectangular. 
The loop is supported at the corners by four 35' fiberglass poles.
About 70' of 600 ohm open wire ladder line connect the loop to the balanced input of a MFJ-993B tuner.
Will this setup work well? I am concerned about the rectangular shape of the wire.
Your opinions are welcome.

73 Marco IU8HXM


Ronald Johnson

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Jul 1, 2018, 6:01:35 PM7/1/18
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It should work well. The shape not much to do with how well it works. The total length will tell the freqs. that u can use on it. Ron KC4EQR

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kc koellein

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Jul 2, 2018, 12:28:08 AM7/2/18
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That will work beautifully! Especially when fed with balanced open-wire line.

Let us know how you do! Jealous!

73 de K9SPY

Marco EVANGELISTA

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Jul 2, 2018, 2:18:59 PM7/2/18
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Thank you for your answers.
I have heard that the loop should be one wave long. However, my loop will have a total length of about 210'. Will this loop work well on 80m?
As for now, I am collecting materials. I plan to start building the loop in September (in July and August it is too hot here in Italy!).
I will post some pictures and details if anyone is interested.
73 Marco IU8HXM


Il giorno lunedì 2 luglio 2018 00:01:35 UTC+2, Ronald Johnson ha scritto:
It should work well. The shape not much to do with how well it works. The total length will tell the freqs. that u can use on it. Ron KC4EQR
On Sun, Jul 1, 2018 at 3:30 PM, Marco EVANGELISTA <marco...@gmail.com> wrote:
Dear all,
I would like to install a loop skywire around the perimeter of the terrace of the building where I live.
The terrace is about 35' x 70'. Therefore the loop will be rectangular. 
The loop is supported at the corners by four 35' fiberglass poles.
About 70' of 600 ohm open wire ladder line connect the loop to the balanced input of a MFJ-993B tuner.
Will this setup work well? I am concerned about the rectangular shape of the wire.
Your opinions are welcome.

73 Marco IU8HXM


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Marco EVANGELISTA

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Jul 2, 2018, 2:19:14 PM7/2/18
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Ronald Johnson

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Jul 2, 2018, 5:58:50 PM7/2/18
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For 80 meters it will be to short (about 60 feet) but anything above 80  meters should work well with a good tuner...Ron KC4EQR

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kc koellein

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Jul 2, 2018, 6:31:22 PM7/2/18
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With your tuner it might be tough, but you have the correct feedline for making it work!  You need a roller inductor tuner like the MFJ-962 to add some more options to your particular compromise. I have had a series of skyloops and not having the ideal 280 feet for 80M is not the last word. You can get some fair tune-up and "SHOULD" be able to get a good signal on 210 feet, with some loss and RF-on-the-feedline. Its hard to say if the negatives would be minimal enough to still be usable for YOU in YOUR shack. 

My 250 feet skyloop was good on 80M until around 50 watts. Made plenty of contacts. Over 50 watts though, and my rig would reboot, or other RF-in-the-shack behaviors. QRP was usually just great though. 5-10 watts of JT-65 on 80M would get QSOs all day on a 250 foot skyloop. I made at least a dozen 160M contacts on the same loop... again... low watts, JT-65/FT-8 stuff.

Antennas have so many variables though... its WITCHCRAFT sometimes! Try it!

Good luck!
 
73 de K9SPY


kc
K9SPY

“God” is known to many different peoples by many different names… when he plays cards with his buddies, they just call him Murphy!

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Andy

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Jul 2, 2018, 11:58:34 PM7/2/18
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I don't think there is any reason for RF-on-the-feedline, not just because it's less than a wavelength in circumference.

Being too small means the feedpoint impedance isn't resistive, and might be harder for the antenna tuner to tame.

Regards,
Andy


kc koellein

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Jul 3, 2018, 1:28:42 AM7/3/18
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Could be. Only thing I could guess to explain the RF in my shack that only manifests at 80M and 160M... when using my 250ft skyloop.

40, 30, and below does fine with 100W.

\_O_/

Witchcraft, I tell ya!


73 de K9SPY

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Ronald Johnson

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Jul 3, 2018, 10:38:43 AM7/3/18
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You can increase the length of the ant wire but not its size(area) and your tunner will love it.using an MFJ-915 RF isolator. Feed ant with coax to get out of the house about 20 to 40 feet then connect it to the ladder line by using  a MFJ-16E01 (coax to ladder line connector). U should not have any RF in your radio room.I will tell U how to do it U want by calling me at 1-828-632-2981 ...Ron 

On Tue, Jul 3, 2018 at 1:28 AM, kc koellein <kc.ko...@gmail.com> wrote:
Could be. Only thing I could guess to explain the RF in my shack that only manifests at 80M and 160M... when using my 250ft skyloop.

40, 30, and below does fine with 100W.

\_O_/

Witchcraft, I tell ya!


73 de K9SPY

On Mon, Jul 2, 2018, 10:58 PM Andy <andy....@gmail.com> wrote:
I don't think there is any reason for RF-on-the-feedline, not just because it's less than a wavelength in circumference.

Being too small means the feedpoint impedance isn't resistive, and might be harder for the antenna tuner to tame.

Regards,
Andy


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John Dennison

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Aug 26, 2019, 6:38:18 AM8/26/19
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John Dennison, KW4OI
500’ open loop 40’ tall. Plan to use LL feed point at a corner closest to the building. LL to drop straight down to 4x4 post with it’s own ground rod and spark plug lightning arrestor. Post ground rod connected to service and several additional rods around building. LL continues backup at a 45 degree angle to 2nd floor eve, outside 1:1 current balun, 12 foot RG8 to IT-100 tuner RG8 jumper to ICOM 7300.
What can be done to help this plan?

George Riedel

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Aug 26, 2019, 6:56:23 AM8/26/19
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I have two loops , my SKYWIRE Loop is a total of 1,500 foot

long suspended 60 foot up in our Oak Trees, I use an ARRAY SOLUTIONS 4:1
tuner balun

(AS 200-T), and my DELTA LOOP is approximately 200 foot and is suspended
up 60 foot and the

DELTA also using an ARRAY SOLUTIONS 4:1 AS 200-T tuner balun. Both with
great success .

The SKYWIRE can tune from 1.5 mhz to the top of 10 meters with no problem.

I do not know of your 1:1 balun is going to do well in tuning.

If you have time, call DX Engineering or PALISTAR Engineering and ask if
a 1: balun will work ??


73

George N1EZZ

John Dennison

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Aug 26, 2019, 8:01:25 AM8/26/19
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Will swap out baluns as needed. Worried more about LL Straight down from corner feed point to lightning arrestors. Shack is upstairs in the loft inside a barn like building some 25’ from the post with the ground rod. Need to bring the LL up under this eve to the balun then coax.
Does this make sense? |/ ? What about LL through the entry into the shack? I have put down a grounded wire mesh on the floor of this upstairs shack.

George Riedel

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Aug 26, 2019, 10:12:24 AM8/26/19
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Hey John

As far as L.L. into the shack, I keep my balun out side on the

wall, I hook the L.L.  from the antenna T - directly to the balun and
through a hole

I drilled into the house, I ran LMR400 from the balun into the house

and connected LMR400 directly to the radio equipment

LADDER LINE has to be kept at least 4 inches away from any metal

objects. The LMR400 feed is about 20 foot long

kc koellein

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Aug 26, 2019, 11:36:04 AM8/26/19
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For what it's worth, my 385 ft loop was fed at my tower with 450 line. Each side of the 14ga stranded THHN copper wire was soldered directly to my 450 Ohm "window line". No balun at the actual feedpoint. I had PVC pipes clamped to the tower to act as stand-offs and they made great "stays" as well. Every 5 ft, I had one. Cut two little slices, top and bottom, an inch from the end of each pipe and threaded my ladder line through on the way down. Kept it from blowing in the wind. At the 15-20ft mark, I let it free swing arc over to my window about 10ft laterally from the tower. My "window" is a piece of 1/8" Lexan from Depot. I cut a rectangle in my wall and framed out an opening and then installed a fixed pane of Lexan in it. I drill a hole in the Lexan for each of my feedlines. I leave the hole a little large for wire motion. My ladder line is going through two holes with a soldering-iron plastic-blade slot melted between them. It feeds into an MFJ-934 with built in 4:1 balun. This is the best antenna I have ever known. Worked Ukraine and Antarctica and New Zealand and Finland from my house in San Antonio on a 100 Watt TS-2000. To be fair, EACH of those stations had enormous ears... but I was able to get a signal out as well as HEAR each of them to make the QSOs!

The skywire came down with a tree a couple years ago and I have been chasing the dream with other antennas ever since. One day I'll have my skywire again!

73 de K9SPY

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John Dennison

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Aug 26, 2019, 1:05:09 PM8/26/19
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George and KC

still trying to figure out how groups works.

Lightning into the shack is my main concern. I know arrestors will not protect against a direct strike there for disconnect.

544’ loop. Direct 450 ohm window line feed. Here’s the problems.
1. Set a post directly under the feed point, drop window onto he top of post
Drive ground rod next to post run #4 wire from rod to top of post
Place arrestors on top of post then suspend window line to balun under 2nd floor eve
Balun ground to its own rod with #4 down the side of building
Separate ground rod 8’ from balun rod withdrew #4 up the side of building into the shack.
For shack ground for Bench and wire mesh on floor of shack.
All rods are connected at ground level to the service rod and perimeter rods
The balun ground path down the side of the building does not come into the shack.
Run 15’ coax to IT-100 tuner then to ICOM 7300 or ICOM 720A
2. Should window line at post go all the why down the post to the rod and arrestors
Then back up the post with stand offs?
3. Forget the post, string window line from feed point direct to eve, place arrestors
Under eve along with balun and let the balun ground serve as the strike path?

Appreciate any comments or suggestions on this grounding scheme.

John Dennison

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Aug 26, 2019, 1:40:14 PM8/26/19
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George and KC

still trying to figure out how groups works. was trying to use Groups on my iPhone.  The editor does not work very well.

Lightning into the shack is my main concern. I know arrestors will not protect against a direct strike therefore disconnect panel for equipment.

I am planning a 544’ loop at my new QTH. Plan to use a directly coupled 450 ohm window line feed. Here’s what I see as my lighting problems/solutions.

1. Set a post directly under the feed point, drop the window line directly down onto he top of post.
    Drive a ground rod next to post and run #4 wire from rod up to the top of the post
    Place arrestors on top of post then suspend the window line to the balun under 2nd floor eve of my shack which is kind of a hay loft in a barn type structure with its own service. 
    use a dedicated balun ground wire down to its own dedicated rod with #4 down the side of building
     use a separate shack ground rod 8’ from the balun rod with #4 up the side of building into the shack for the shack bench ground and the wire mesh on floor of shack.
    All rods are connected at ground level to the service rod and all perimeter rods and to the post rod
    The balun ground path down the side of the building does not come into the shack but should serve as the second most  likely direct path to ground. 
    Run 15’ coax through the wall to IT-100 tuner then to ICOM 7300 or ICOM 720A 

2.  Should window line at post go all the why down the post to the rod and arrestors then back up the post with stand offs, then suspended to the balun and its ground? 

3.  Forget the post, string window line from feed point direct to eve, about 25 feet, place arrestors under the eve along with balun and let the balun ground serve as the only direct strike path?

Appreciate any comments or suggestions on this grounding scheme.   

Maybe should of put this at the bottom?

John Dennison KW4OI 73

kc koellein

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Aug 26, 2019, 2:05:21 PM8/26/19
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John,

I would move that lightning ground point.

So you have a really good which I recklessly disregarded when MY loop was up. Yes, I had static dissipated at my tuner by always having the loop grounded, but a lightning strike would have devastated my rack of equipment. I'll just call that luck and I currently have a better system for that!

So!

I would not run the Ladder Line to lightning arresters unless they were some gadget specifically designed to lightning-arrest your specific 450 ohm ladder line (or whichever type you have). Reason being, approaching the metal objects of your lightning arrestor is gonna cause an impedance "squeeze" or "void" (my made-up terms) based on the exact mathe-magic of how RF in a ladder line interacts with metal.

I would get you a Cantex box from Depot. Big enough to fit your BALUN. And ground the whole thing at the output of the balun box. This way you end up with only one RF/Impedance disturbance point right by the BALUN. 

The trade-off is "do you put the BALUN by the tower or by the house?" Coax has losses, but so does half a dozen reflection points and impedance squeezes in a total run! 

So, it sounds like you probably wanna mount a Cantex box on the outside of your house, at the eave somewhere... ideally even OVER the hole you already drilled to get your feedline into the house. But then you can put your arrestor right on the output side of the balun and run your lightning ground down the wall of your house to a serious ground rod below.

HA!!!  Now that I finished reading your post! I say Option 3!

:-)

kc
K9SPY

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John Dennison

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Aug 26, 2019, 6:36:51 PM8/26/19
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George and KC,

Your idea sounds good to me for those times I am on travel.  It makes the antenna the only thing at risk.
During the build I will arrange the pulley system to allow lowering of the feed point so it can be grounded.

I have decided to also take KC's advice and forget the post directly under the loop feed point. I will put a rod there
for the times I need to travel and ground the antenna.

Luck is with me that it is easy to keep the window line at 90 degrees coming away from the side of the loop that the feed point is on.
KC's approach eliminates several design flaws I had in my original plans with a down back up type of path. By stringing the window line directly
to the eve. Connecting it directly to the 1:1 current balun, out of the balun to a coax ICE type arrestor, out of the arrestor into the shack.

Grounding the box, balun, arrestor and coax all to a #4 wire going down the outside of the building to a dedicated rod that's part of the perimeter ground system.
This makes the antenna, window line, box, balun, arrestor, and #4 wire the most likely direct path. This path grounds the coax shield to the balun ground rod,
but even  though the coax comes into the shack, I plan to let it float from the shack ground rod ground. When it is storming, disconnect the coax and let it float.
I don't believe I will have a ground loop problem when operating as the balun ground and the shack ground are both tied to the perimeter which is also tied to the service ground.

A strike gets the balun box, balun, and arrestor with a good path to ground rather than coming into the shack.  I have tried to also eliminate high RFI voltages from a
strike by installing a metal ground grid on the floor of the loft with the shack bench and floor all going down a separate #4 path eight feed from the balun rod and 
closer to the service box.

I really have benefited from both of your suggestions, hope to be on the air soon.  73

John Dennison KW4OI
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