Material selections, 160 loop

[kk7ue]

Greetings fellow sand-in-crack sters,

I think I have a spot where I can put up a loop for 160. While it is not perfect by any means, it should/has to suffice. IT would be suspended 25 - 35' agl in a four sided parallelogramishly laid out arrangement. I understand NVIS and that this height pretty much guarantees a cloud warmer on the lowest bands. This I can live with. :boohoo: Im on a low budget :boohoo: The IT and other stuff are what I want to banty about here with you.

IT - Have any of you used, succesfully, 10 or 12 ga THHN wire common to building centers for the main antenna wire? I wonder how it would stretch over time. Is it cost effective compared to using the real mc coy antenna wire?

Also, one of the four supports is a scaleable tree of immense proportions. I am considering the benefit of running some 10 ga thhn I have up the tree as a vertical, feeding ground off a radial network of some sorts. Unfortunately, the tree is on the property line so half the 'groundplane' could be potentially off limits. If so, then the ground radial network would be mainly pointing west and maybe that would not be so bad. As well it could mean that the eastward point of the loop could be raised significantly in elevation. A westward sloper has crossed my mind as well.

I have many other questions about this project, but one at a time for now. Today is the 'pros and cons of THHN wire as an antenna'. Thanks ahead of time

[ad4mg]

I found some interesting comments on using THHN wire for antennas at:

http://www.qth.com/ka9fox/thhn_wire_sum.txt

[N2RJ]

A lot of people who put up loops use CATV coax.

[M0GLO]

Interesting.

They must use the outer layer as the element, wonder how the braiding affects the signal?

[N2RJ]

I will tell you when I put mine up.

I got one of the pre-made Radiowavz ones.

Don't think braiding has much effect at all.

[n4aud]

I used plain old 12 awg stranded insulated wire from Lowe's. Works fine, it has stretched some over time. You've got a lot of weight with that much wire up, the copper's gonna stretch but if you are using a balanced feed line and tuner no big deal. I've trimmed mine a couple of times to make certain frequencies easier to tune.

[kk7ue]

Interesting info on the thhn. I suppose once the uv deteriorates the outer covering, you still have the undercoating remaining, which seems fine. Ive used #10thhn on a couple diploes strung up into tree limbs before at a previous qth with success but the wire was not under a load. This will of course be different. Im still leaning towards #10 for mechanical strength over lighter wires and the tuner will probably appreciate it more. Ice storms and freezing rain are not uncommon out here so I want to incorporate a letdown feature in the rope system for those times when a storm is predicted and can be dealt with ahead of time. An automatic slack feature is planned for as well.

Nylon rope is cheap but Im not sure I want to venture up to replace it once the uv has its way with it. Polyester seems like a good compromise for its uv rating but perhaps the fancy-dancy high dollar stuff would be wise money spent.

Any thoughts about using the mongo tree as a vertical suport from the azimuth perspective for dx on 160? Top band is a new experience for me and again, wanting the most bang for the buck the first time, is important especially on this one since I wont get a second chance stringing up another element.

Both antenas will be fed with 450 ladderline and a 4:1 balun at the shack. The thhn will be stranded versus solid for longevity. It seems Im on the right track here so far. Thanks for your expertise in this. When I get home from making the donuts today I should have another question to pose.

[ka4dpo]

I used the same wire to make an 80 meter loop about ten years ago. The wire stretch is no big deal but the insulation will oxidize in the sun over time and become hard and brittle. When that happens the wire will loose a good bit of it's strength which the insulation provides. At that point it's likely to start breaking in high winds. Even so, it's still cheaper than using the high buck antenna wire. The expensive stuff won't last much longer so I say go for it and good luck on 160..

[HUGH]

You have some good, practical suggestions already but here's mine.

My long antenna uses 4mm squared/12AWG, about 10 strands so it's neither solid nor flexible, and covered in grey PVC. At the ends, where it passes through egg insulators I added a 3 foot loop of 1.5mm galvanised fence wire (about 18AWG) also through the insulator and twisted round the conductor. This was wrapped in tape to deter any rusting.
Where the support ropes are likely to rub branches etc. I used stranded, steel rope with patent clamps at the ends.

It's lasted 4 years with no deterioration and little stretching. What has deteriorated slowly is the 10mm blue polypropylene rope. It seems to lose bulk and then become slightly hairy but the blue colouring does reduce UV decay. Polyester rope is better but I thinks ship's chandlers are the only place to obtain it. The wire comes from the local electrical wholesaler and all the other stuff, including insulators, from agricultural suppliers.

I have a 40m vertical hanging from a tree. For monoband use it's handy, fed directly with 75 ohm coax but I can't claim brilliant results. This is brown PVC coated and the grey wire is perfect against the skyline.

[n4aud]

I would add that using pulleys makes putting up a very large loop much easier. Attach your support lines to the pulleys and allow the antenna wire to run through the pulleys. I found some strong plastic pulleys at Lowe's.

[kk7ue]

Wonderful input, very much appreciated by all. Cool! Thanks for your time.

Lets see if I can articulate my vision for the hanging hardware in an accurate fashion...


I planned on using a cord of sorts; dacron, polyester, or whatever is lightweight, as well as being moisture and uv resistant to attach to the trees and to the metal fitting on the unused power pole on the property. This cord will extend a couple feet from the tree/pole and have a pulley attached to it like the metal ones (brass?) I have laying around for a 1/4" cord. This is a solid connection. The cord going through the pulley will attach to the insulator and come back to a lanyard on the support at or near ground level with enough extra rope so I can let the insulator down to ground level for maintenance and attachment of the wire, while allowing the antenna to be clear of the 'branch plane' when its up in place. Two opposing corners will allow the wire to 'float' through the insulator allowing for wind driven adjustments horizontally and at least one of the ropes will have some sort of counterweight device attached to allow up and down movement of the antenna in the wind. So far so good.

Not sure about a secondary support for the ladderline, beyond attaching it to the antenna a few feet offset from the power pole attachment point. It may or may not need extra support at the antenna side of things. I dunno; Ive never had the pleasure of using ladderline yet. I know to put a casual twist in it to avoid wind loading issues, from what Ive read and heard. At least I should be able to let it down for service if necessary easily enough.

Did that paint a good mental picture of my intentions? I hope so and thanks for your input. At least it sounds like Im thinking in the right direction, based on your feedback.


Now, to just find a climber and get it done before the leaves return......... :pray

[kk7ue]

Not sure what to do exactly about using the humongeous tree as a vertical. Maybe its not worth it, however if I get a climber out here maybe I should try to get that done on a secondary basis while the person is on site. Who knows, maybe a vertical for 160 would be FUN.

[ad4mg]

Wonderful input, very much appreciated by all. Cool! Thanks for your time.

Lets see if I can articulate my vision for the hanging hardware in an accurate fashion...


I planned on using a cord of sorts; dacron, polyester, or whatever is lightweight, as well as being moisture and uv resistant to attach to the trees and to the metal fitting on the unused power pole on the property. This cord will extend a couple feet from the tree/pole and have a pulley attached to it like the metal ones (brass?) I have laying around for a 1/4" cord. This is a solid connection. The cord going through the pulley will attach to the insulator and come back to a lanyard on the support at or near ground level with enough extra rope so I can let the insulator down to ground level for maintenance and attachment of the wire, while allowing the antenna to be clear of the 'branch plane' when its up in place. Two opposing corners will allow the wire to 'float' through the insulator allowing for wind driven adjustments horizontally and at least one of the ropes will have some sort of counterweight device attached to allow up and down movement of the antenna in the wind. So far so good.

Not sure about a secondary support for the ladderline, beyond attaching it to the antenna a few feet offset from the power pole attachment point. It may or may not need extra support at the antenna side of things. I dunno; Ive never had the pleasure of using ladderline yet. I know to put a casual twist in it to avoid wind loading issues, from what Ive read and heard. At least I should be able to let it down for service if necessary easily enough.

Did that paint a good mental picture of my intentions? I hope so and thanks for your input. At least it sounds like Im thinking in the right direction, based on your feedback.


Now, to just find a climber and get it done before the leaves return......... :pray

Just a suggestion as an alternate to the counterweight ... those can be unsightly and dangerous if installed too high. I attach the ends of my support ropes with 4' bungee cords fastened at the base of the tree. The bungee allows enough "give" for wind related movement, and is nearly invisible. Also, whetever you use, leave an extra 10' or so of rope, and tie it off solid to the tree at the end, in the event your counterweight or bungee becomes detached ... you sure don't want to be forced to rehang the whole thing should the rope pull completely out of the tree!

[N3ATS]

I can offer some advice on how to hang the antenna. This is how I do mine (not a 160 loop, but nevertheless), and they have withstood ice loading and 45 MPH winds.

I use braided dacron/nylon. The standard black antenna rope everyone sells. DX Engineering has some of the best prices on this stuff, BTW. I use 1/8" rope personally, it is a lot stronger than it looks.

1. Screw a 1/4" eye screw into your tree at chest height. Put a screw driver through the eye and turn it in. Don't worry tree-huggers you won't hurt anything. :mrgreen:

2. Tie the end of your antenna rope to an extension spring (tension when pulled), and leave about 12-14" of tag end of rope end on it.

3. Using one of those hardware store grade carabeeners (the things that snap open and closed, NOT a dog leash thingy), clip it through the loop on the end of the spring and through the eye of the eye screw.

4. With the 12-14" left over tag end, tie a bowline knot in the end of the rope and clip it inside the carabeener as well. This way if the spring breaks, the antenna will not fall. Make sure the bowline is large enough to allow the spring to pull and be bound by the rope.

5. On the other end of the wire, do the same thing, except pull the rope and antenna as tight as you can, and then tie the rope to the spring.

The springs will keep tension on the antennas (you have to pull it tight to start with as in #5), and relieve tension on the rope and wire when the wind blows. Like I said, ice and wind here in the NE over the last week or so, and ZERO problems.

No pulleys to deal with either!

[N8WWM]

I would go to a farm supply store and get some aluminum fence wire...its 17 gauge and comes in 1/4 mile spools for under 20 bucks. what I do is roll out 2 equal lengths and chuck one set of ends into my drill, tie the other set of ends to my fence, and then twist em into a 2 strand cable. I made 4 strand cable outta this stuff and use it to hold up shelves in the garage, too. Handy stuff, cheap, easy to work with. My HF antenna is that stuff and PVC pipe insulators...it rocks.

Doug


Greetings fellow sand-in-crack sters,

I think I have a spot where I can put up a loop for 160. While it is not perfect by any means, it should/has to suffice. IT would be suspended 25 - 35' agl in a four sided parallelogramishly laid out arrangement. I understand NVIS and that this height pretty much guarantees a cloud warmer on the lowest bands. This I can live with. :boohoo: Im on a low budget :boohoo: The IT and other stuff are what I want to banty about here with you.

IT - Have any of you used, succesfully, 10 or 12 ga THHN wire common to building centers for the main antenna wire? I wonder how it would stretch over time. Is it cost effective compared to using the real mc coy antenna wire?

Also, one of the four supports is a scaleable tree of immense proportions. I am considering the benefit of running some 10 ga thhn I have up the tree as a vertical, feeding ground off a radial network of some sorts. Unfortunately, the tree is on the property line so half the 'groundplane' could be potentially off limits. If so, then the ground radial network would be mainly pointing west and maybe that would not be so bad. As well it could mean that the eastward point of the loop could be raised significantly in elevation. A westward sloper has crossed my mind as well.

I have many other questions about this project, but one at a time for now. Today is the 'pros and cons of THHN wire as an antenna'. Thanks ahead of time

[kk7ue]

Another thought: I am considering using one continuous strand of wire as antenna and feedline. Anybody have suggestions for homemade ladderline insulators? Gap is important as well; what is the dimension to imitate 450 ohm line? just noodlin....