My 80m Full-Wave Loop Antenna in the Atacama Desert - Dean, CA1JDM

December, 2013
(Click on each image to see full size)

horizontal loop antenna During the 1990's in Paraguay as ZP6XD, I had imported and installed the best antenna I could buy at the time - a German designed Sommer XP-807 - a huge 7-band yagi that I enjoyed and worked countries all over the world in various modes, but most digital. It was mounted on an 18 meter tower and was a great performer. But in 2003, we decided to move to Chile for a number of reasons, but mostly because Chile is just a better place to live! I thought I had given up ham radio when we moved to Chile in order to pursue other things, but by 2010 the ham radio bug had bitten me again! I also figured with the way things are going in the world now that some form of "backup" communications would be a good thing to have, and as I'm writing this at the end of 2013, I believe this more than ever now. So after messing around with several wire dipoles, air choke baluns, and a 10m homebuilt 3-element yagi, I studied various types of wire antennas and decided that an 80 meter full-wave horizontal loop antenna, sometimes called a skyloop, might be best for me. I wanted to try it anyway since I have plenty of space here, no trees close by, etc. This antenna is reportedly capable of working all bands 80m through 10m with reasonably low SWR, but needing a tuner to be most efficient. So I set out to build one by first ordering the necessary 450 ohm ladder line and an automatic antenna tuner. I decided on the SGC MAC 200 tuner because it has some multiple antenna capabilities in case I decide to use those. As of Dec. 29, 2013, it still has not arrived yet but is in transit.

horizontal loop antenna I first measured and cut the wire for the actual antenna just a few inches longer than 80 meters. I bought a 100 meter roll of No. 14 stranded electrical wire type THHN. If I had it to do over again I would have used a slightly stronger No. 12 but the No. 14 is working fine so far. To support all four corners of my new skyloop, I positioned a No. 20 electrical elbow at exactly 20 meters plus 2 cm for each side and expoxied the wire into place so as to maintain the exact distance on all four sides and also keep the wire from possibly breaking fom a 90 degree sharp joint.

horizontal loop antenna I prepared each support pole using a 2 inch diameter steel tube, 6 meters long, for the bottom, and a 1 steel tube for the top section, telescoping into the bottom section by 60cm and using four x2 bolts and nuts as shown in one of the photos. My goal was to paint the poles a sky blue so they would not be too visible to passersby but I had to use the blue color that was available and it's darker than I wanted. All four poles are set 50cm deep with concrete poured around them, which results in the antenna level above ground being about 36 feet. At the top of each pole I installed 5/16 diameter zinc plated eye bolts to support each corner of the antenna wire using a nylon rope with about 150 pounds of breaking resistance. The distance between the poles and the corners of the antenna wire is 36 inches. And since I'm not the world's best knot-tyer, I applied a fast epoxy over the ends of the rope joints of all connections so they could not come undone.

horizontal loop antenna In the corner detail photo with the orange colored elbow, if you look carefully you can see a piece of 3/8 diameter steel reinforcing bar that I placed in the ground that I used to mark each of the four corners for where the antenna would be. And from each of these four corners, I made a post hole 45 degrees out from these corners and 36 inches away, so that when all four poles are raised up and put into the holes the antenna would be in the correct position - forming an almost perfect square with just over 20 meters or 65.68 feet on each side.

For the antenna feedpoint connection to the ladderline, I used a No. 32 (1 inch) PVC pipe tee and epoxied the wires both inside and outside the tee, through some drilled holes, so they could not slip out during all the movement from the high winds that are common every afternoon here in the desert. Our place is located in Grid Square FG59EP at 20.37170 S and 69.65029 W. It is not yet shown on Google Earth because it is all new construction since Google last updated the maps for this area. Then I torch soldered the ladderline to it and before I raised it up I added another plastic brace with epoxy over all joints. I wanted to insure the soldered joints did not break due to all the flexing it would receive. If a wire came loose up there I wouldn't have any practical way to repair it and I would have to take the antenna down would not be easy!

horizontal loop antenna

The work of raising up the antenna poles with the complete antenna wire and all guy ropes was made very easy and stable with the help of my old Komatsu PC-20 Excavator! Without it, the job would have required several people pulling on the guy ropes, guiding each pole into holes, holding each guy while someone else made sure the poles were vertical, etc, and all the while hoping the wind doesn't start blowing hard.

horizontal loop antenna Here you can see the contraption I rigged up, temporary of course, by welding some spare steel tubes onto the bottom of the bucket. Don't laugh! It worked! With the completed poles lying on the ground, I simply lowered the bucket over the tube and then manually positioned the tubular pole into the "contraption". I added a C-Clamp and ropes to make sure the pole doesn't fall out as I raised it. Oh, and I completely built this antenna and poles, all by myself in just in just a few hours, and raised each pole up and placed it in the hole using only one finger of pressure!

A view of one of the corners showing the guy connections which I mounted about 80 cm down from the top of the poles. Finally, because my new automatic tuner had not arrived yet, outside the shack I connected the ladder line to a Jetstream JTBAL41 which is a 4:1 balun. From the balun I used RG-213C into the shack to a MFJ-915 RF Isolator and from there to the radio antenna input of my Yaesu FT-857D. When the new tuner arrives, the ladderline connects directly to the tuner without the need for the 4:1 balun.

With the antenna ready, all except for the antenna tuner, I checked the SWR on all bands, 80m through 10m, and the bands with no SWR indication in the radio were 10m, 12m, 15m and 17m, with some SWR on all the other bands. So I decided to connect with an RMS Trimode station in Winmor 1600 mode in Australia. I was surprised and actually amazed when I connected on the first try! And I was using only 50 watts. I then connected with another station in Australia equally as easy. Later in the day, I tried connecting with a station in Switzerland, and again to my amazement connected on the first try! My 10m 3-element Yagi would not connect to any of those stations and I tried many times! Naturally, I'll be anxious to test the antenna once the new automatic tuner is installed! Just with these first few non-scientific tests, I am tempted to say this fll-wave loop antenna performs better than my old Sommer that I spent close to $3000. USD on, yet this wire antenna cost less than $200. to build!

My RMS Trimode Station is currently operating 24/7/365 in Winmor 1600 mode
on the following USB Dial frequencies:
28.137.500 and 21.113.000

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Updated December 2013