Full Wave Loop Antenna - Skywave

[JohnyMac]

I am in the process of planning a full wave skywave antenna. Once the leaves drop around the first week of November, I will start this project. So far I am looking at,

> 574' 14 gauge insulated wire,
> 8, 3" Harken blocks (pulleys for you landlubbers),
> 1,000' 3/16 three strand nylon line,
> 100' 450 ohm ladder line,
> 8, 1" pvc elbows, and
> Other assorted nuts and bolts.

Using  http://www.n1su.com/loop.html and another article for guidance.

Thoughts?

[FeedingFreedom]

Been my main HF antenna for at least 15 years now, I've built quite a few and often joke that I'm a "loop evangelist".

Couple observations over the years:

> I never use ladder line. All my loops have been fed with coax, never had a single issue.

> I've also never used a balun or choke. I tried one once to fix some issues I was having, the balun didn't help, I fixed the actual issue and removed it. Never had RF issues.

> I hang the antenna with 2 fixed and 2 free corners, diagonal from each other. This gives plenty of flexibility to the antenna when the trees move. I hang them with paracord right in the tree. I've only ever had one piece fail, and that was at a point where it was tied off to a metal post. I use electric fence "egg" insulators in the corners, I just use a zip tie to lock the corner if I want it fixed.

> I've been using a "commercial" dipole feed point with crimped and soldered ring terminals on the end. Add a little dab of anti-corrosion schmutz. Seal the coax properly at the feed point. I could probably do a class on just sealing coax properly. My coax connections have survived a minimum of 10 years on top of our area's highest peak with no issue.

> I usually use 14 AWG stranded wire, just the normal stuff you can buy in a 500' spool at the building supply store. I prefer black, I don't want to see my wire, or have anyone else see it. Almost as a joke, the last time I replaced the wire with 10 AWG stranded- a friend gave me a spool. I weighed the two wires (14 and 10), and the overall weight difference was a couple pounds. Haven't noticed any improvements or detriments, so I'll call it a wash.

> Hang it as close to square as you can, but no need to obsess. Mine is currently in a sort of diamond/parallelogram now, still works the same.

> In order to have it tune easily on every harmonic, the 80 meter tune point needs to be in the CW portion of the band. As with most 80 meter antennas, the bandwidth is pretty narrow and the SWR dip is very sharp. The tuner in my radio will not match in the upper portions of the band, I use an LDG tuner which has no issues, but it bothers me to be so inefficient.  The loop tunes fine from 40 on up, with great bandwidth on most of the bands, including WARC.

> Overall, I think you can't beat it as a fixed-location, multi-band, omnidirectional antenna. Great receive characteristics, useable on every harmonic and more, and once you get up around 20 meters, the angle of radiation is low, and you are starting to actually get some gain. Definitely not a beam, and you do need 4 or 5 supports to hang it (depending on if you put the feed in the corner or in the middle of a side, I've not noticed a difference with either, depends on your layout more than anything).

These are just my experiences, YMMV. I am an antenna fanatic, probably my favorite part of the hobby is building and trying antennas.

[FeedingFreedom]

For reference, this is an SWR plot of my loop as it is now.

[JohnyMac]

Thanks FF for your writeup. Do you remember how many feet you have in the air? Also, about high is your antenna over terra firma? 

[pkveazey]

I've made a couple of full wave loops for 440 and 2 meters and they worked pretty well but they were mounted vertically and were pretty much bi-directional. I've also made a couple of full wave VHF and UHF Cubical Quad beams that worked fine. Now, I have a Ham buddy about 7 miles up the road who put up a 160 meter full wave horizontal loop, mounted at 40 up from tree to tree, fed with coax and I can only repeat what he said. He said it worked great and it was quieter than his other antennas. I don't think it was more sensitive than his other antennas but since it was a lot less noisy, he could hear the weak signals pretty good. If I was going to build a 160 meter full wave loop, I would try to make it as square as possible, 130 feet per leg, and feed it with either 75 or 52 Ohm coax and let the antenna tuner clean up the slight impedance mismatch. The whole antenna would be about +-520 feet. If you use ladder line and then coax to bring it into the house, its going to turn into a nightmare to get the coax length and the ladder line length perfect. Now, I'm not knocking Ladder line. Ladder line is the best feedline on the planet but it is length critical and stray Capacitance is critical. A little too close to metal shed, Snow or Ice or even rain will bugger things up until the ice melts and the line dries out. I don't know if all this helps or hurts but its all I can come up with.

[JohnyMac]

Thx PKv. 

Heck I have 35-acres mostly of tree's. Might as well use 'em. 

[FeedingFreedom]

Thanks FF for your writeup. Do you remember how many feet you have in the air? Also, about high is your antenna over terra firma? 

I started with ~280 feet of 10 AWG stranded THHN (1,005/3.5); I did end up trimming quite a bit, maybe 6' or a little more. One of the hidden bonuses of a loop is that you only need to lower and raise the feedpoint to trim. Right now, the loop is only up around 40 feet, I'm going to have to lower it anyway to drop some dead ash trees, so it will go back up as high as I can get it, around 60' or so. It is fed with 75' of RG-214, which is gross overkill for HF, but I got a lot of it for free, so...

[FeedingFreedom]

Another point I was thinking of was that if you had a 160-meter loop, you will have great performance on 60, 40, and 30 meters, but it will diminish somewhat going up from there. My 80 meter loop doesn't do real great at 10 or 6 meters, although it does work. The sweet spot for mine is 20, which for some reason is a favorite band of mine. If you had the time, inclination, and supplies, I'd also put up a 40 meter loop with the 160 to give you great performance anywhere you want to work.