Project Description

This web page is a journey through my efforts to build a low cost hex beam antenna for the 5 ham bands from 14 to 28 MHz. This construction project involved some scrounging, welding, 3D printing, 4nec2 simulations, some ebay purchases, and a lot of sifting through the junk box. It does not have step by step instructions, but provides information and ideas that one can use to create a working hexbeam antenna. The performance of this antenna design has been outstanding. It does not seem to need large antenna towers and in my design I aimed for getting the 20M element about 1/2 wavelength off the ground.

The hub that supports the spreaders was welded up from several pieces of scrap galvanized water pipe. This was placed over the mast section and bolted in place leaving enough of the mast below the hub to allow the mast to protrude through the thrust bearing on the top of the tower and be clamped into the rotor assembly. You can see in the picture below that the spreaders were adapted to fit into the 6 smaller pipes by using 3D printed sleeves (printed in PETG). The spreaders are a snug friction fit in the plastic sleeves and may be removed for replacement or moving/storing the antenna.


The second welded bracket is used to secure the spreader tension ropes near to top of the mast. This was built from some of the same pipe used in the lower bracket with 6 flatbar tabs welded around the perimeter. Stainless steel chain quick links were used to transition from holes in the flatbar to the UV resistant cord used for the spreader tension components. The assembly was bolted through the mast slightly below the top of the mast. My idea was to mount a small directional VHF/UHF antenna on top at a later date.

The spreaders were one of the hardest components to locate for the build. One needs 6 poles around 12 feet long. It is possible to buy replacement spreaders from some of the hexbeam manufactures, but a set of commercial spreaders run into the hundreds of dollars. I looked at using fishing rod blanks, PVC pipe, chimney cleaning rods and other sources of fibreglass tubing or rods. By far, the cheapest solution was 4' long fibreglass rods ($3 each or 2$ each if you catch them on sale!) used for marking driveway edges (thanks again to Princess Auto). The heavy duty rods are 10mm diameter and are joined by short sections of aluminum tubing found on ebay. The tubing is 10mm ID and 14mm OD and came in 1 foot lengths. I needed 12 joiners so I cut each piece of pipe into roughly 4" lengths. I cross drilled each joiner and put a short piece of aluminum welding wire through the center of each joiner. This acts as a stop for inserting each of the fibreglass rods and holds the joiner in position on the assembled spreader. I thought of glueing these connections, but for now they are just a friction fit which allows easy disassembly. The above picture also shows another 3D printed part that I used to secure a stabilizing cord around the perimeter of the antenna just above the second joint. This perimeter cord a holds the spreaders in position. I bought the UV resistant cord from a local fishing supply store. It is approximately 1/8" in diameter and came in a big spool thousands of feet long. It is my go to for hanging wire antennas.

The picture above shows the top end of one of the spreaders with details of the cord securing the spreader tip back to the central mast and the attachment of the 20 meter element using a small 3D printed part. The wire is stranded 16 gauge insulated hookup wire. You will need about 275' of wire for 20 through 10 meter elements. I used wire off a 500ft spool and have plenty left for more antenna projects.

The 3D printed wire supports were designed to use a nut and bolt to secure them on the spreader rods. The supports fit snuggly and I just used a wire tie to keep them closed on the rod. It is easy to slide the the supports up and down the rods to optimize the wire tension. The element wires do not need to be tight and a little sag is fine.

One of the key features in feeding a hex beam is the connections between the 5 antennas. Other hex beam designs I found on the net used the mast as a 50 ohm coaxial transmission line (lots of fiddly mechanics ) or used short 50 ohm sections of coax to jump between the 5 driven elements (way too many chances for water contamination). I elected to build a section of 50 ohm parallel transmission line using some aluminum square tubing (spindles from aluminum hand railing). Using the dimensions of the tubing, one can find the spacing needed to form a 50 ohm transmission line.
See https://hamwaves.com/zc.square/en/index.html
Again thanks to 3D printing, I designed standoffs that space the transmission line away from the mast to reduce coupling and to hold the 2 aluminum tubes at the correct distance apart to form a 50 ohm transmission line. The square aluminum tubing was drilled and tapped for attaching each of the 5 driven elements. Each driven element was terminated with a soldered on ring terminal and the junctions coated with dielectric grease to give some protection from the weather.

The top of the transmission line was fed with a choke balun consisting of 8 turns of RG-58 coax supported by 3D printed spacers.

The far ends of each of the driven elements is connected to a short spacer of cord that connects to the reflector element on each band. I looked at using small fibreglass rods as the insulators but decided simple was better. I formed an eye at each end of the elements as shown above and used the fishing cord with bowline knots to form the spacer. It was easy to form the eye around a screwdriver shaft and twist the connection. I quick coating of solder gives the joint some strength and stops water from wicking up the wire strands. I did add some dielectric grease to help waterproof the wire end.

The table above lists the lengths of each of the band elements used for the initial construction. I built each band element (combination of the driven elements, 2 spacers and the reflector) and mounted it on the support structures.

The graph above shows an SWR sweep from 13.5 to 33.5 MHz. The yellow sections show the position and width of each of the ham bands. As can be seen, each band has the best match just below the ham band. The frequency being low makes it much easier to shorten the driven elements than to lengthen them. The insulation on the wire likely caused the several percent error in resonant frequency. If you use bare wire or different gauge wire you will have to experiment with the lengths as well.

I did a quick spreadsheet shown above and intend to adjust the driven elements by a few inches shown in column E. This should center the antenna more in the frequency range of my preferred operation. Stand bye for final results! I dont think I will have to adjust any reflector lengths.

Building The Foldover Tower

This part of the antenna system started with making a solid base for the tower. The location selected is centrally located on my lot which happens to be covered with a concrete driveway. The first job was to punch a hole through the driveway to gain access to the bedrock which was known to be close to the surface at this location. I drilled holes with a hammer drill and used a diamond blade on the skill saw to cut partially through the driveway. Next chore... bring on a chisel and sledge hammer!

The picture above shows the four 3/4" stainless rods used to bolt to the baseplate. Also shown is four pieces of rebar grouted into the bedrock at an angle. A collar tie of rebar was used to reinforce around the 4 base plate bolts. A wooden form was constructed for the concrete and placed around the hole. The resulting concrete base is about 24"x24" and covers the hole cut in the driveway.

To transition from the four anchor bolts to the plate on the bottom of the tower section I used a 1/2" plate drilled with 3/4" and 5/8" holes as shown above. The plate is coated with metal primer to help with keeping corrosion under control in this seaside location.

The base plate is bolted to the concrete base and the lower fixed tower section is bolted to the base plate. The lower tower section is about 12.5' high. I needed to use a fixed section of tower to raise the hinge point above the retaining wall and to provide a somewhat centralized balance point for the moving section of tower. Note that it took some head scratching to get the tower orientation correct so that the moving section of tower would clear the car port and garden shed.

To further support the base section of tower, I added two outrigger legs that tie the fixed tower section from near the hinge point to a couple of anchors points poured in the grass area. This resulted in a very rigid fixed tower section in the form of an asymmetrical tripod.

The tower hinge section was constructed from two pipe collars welded to legs of the tower. The hinge pin was made from 1" mild steel bar stock. The pipe located in the center of the picture above was welded to a tower bridle which can be seen in the very upper portion of the picture.

Two of the above bridle assemblies were constructed from 2"x1/4" flat bar. One of them bolts to the moving section of tower at the hinge point and the other bolts to the base of the moving section of the tower and is used to secure the moving tower section to the fixed tower section. These bridle sections have holes spaced to match the bolt pattern used to connect the moving tower sections together. To insure a good supportive fit to the tower, the tower sections were bolted together with the drilled flat bar in place. Then the longer sections of flatbar were cut to length and tacked in place. The bridle at the hinge point serves two purposes. It supports the entire weight of the antenna/tower/rotor and it stops the tower deforming (buckling) due to the forces on the tower during foldover operations.

Here we see the completed base assembly showing how the base plate is secured to the threaded rod anchors ( nuts above and below the plate to allow adjusting for plumb ) and the fixed tower base plate bolted on with 5/8" galvanized bolts. The moving section of tower is shown bolted to the fixed tower with two 5/8" bolts in the center of the photograph. These bolts are removed when folding over the tower. Because of the geometry of the hinge point, the tower wants to stand vertically once you get it close to vertical. To raise and lower the tower, I tie the rope shown dangling in the top of the picture to the lower bridle. I thought of mounting a boat winch for raising and lowering the tower, but the balance is good enough that one person on the rope can easily control the tower movement as it rotates on the hinge assembly.

Source Code

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