Design

Despite that the concept of a hexagonal beam (in particular the G3TXQ hexbeam) is well known and home-brew hexbeams are around for some time, it is a different story designing a hexagonal beam commercially, in particular having Australian conditions in mind.

UV resistance and the aim to design a solid product has its challenges. Not only from a technical perspective, but also from a supply chain point of view and to be competitive.

We started with the modelling of the mechanical parts in CAD software. The CAD software provided the 2D drawings which were used to CNC waterjet-cut the StarHub (aka Centre Hub) and CNC machine the components for the Centre Post. During the design more components such as the flanges and mounting tubes have been also CNC machined to allow accurate fitting of all components.

Figure 1: Rendered CAD Model of the star hub

All major components are made of corrosion resistant aluminium which have been anodised to provide a longer life time and to reduce the risk of galvanic corrosion. All fasteners are made of stainless steel. The fibreglass spreaders are also specifically made for us. The spreaders already include an UV stabiliser, however after further analysis we determined that further protection was required to be safe for Aussie conditions. (Here in QLD we have a rating of UV 6 in winter and up to UV11+ in summer)
We apply not one but two layers of an UV resistant coating with a brush by hand to have a solid and matte finish which provides good protection against the strong Australian sun.

All plastic components have been selected to be UV and weather resistant too including 3D printed parts.

The PTFE (also known as Telfon (R)) insulators on the Centre Post are also our own design and have been specifically made for us. PTFE has excellent dielectric and UV resistant properties.

All SO-239 and PL-259 plus / connector are made by Amphenol and NOT by an unknown Chinese manufacturer. The SO-239 are designed for 3kW.

The electrical (RF) component was calculated and simulated with modelling software. We have also modeled different heights above the ground.

The wire has been selected with a local supplier who confirmed that the insulation is compliant with Australian Standards and is UV resistant (the wire is also locally made in Australia).

Other manufacturers have this as option, not us. The support chords are made of genuine Kevlar(R) and have a polyester coating which is very UV resistant. Kevlar(R) has non-strech properties and is very strong. The breaking strength is greater than 400kg (4kN, 800 pounds).

StarHub

CNC waterjet cut and anodised aluminium StarHub

StarHub of the Hexagonal Beam – all aluminium parts are anodised (black and clear), plastic components are UV resistant and fasteners are marine grade stainless steel
Close-Up of the Star Hub. Arrow shows the direction of radiation and provides help during assembly.

Centre Post

Spreaders

Painted Fibreglass Tube for UV protection with clearance for tube assembly
Inner Spreader Element (thickest)
Middle Spreader Element
Outer Spreader Element (thinnest)

Chords

Aramid Fibre Chord (aka Kevlar (R)) with an UV resistant jacket – breaking strength = 400kg

During the design we used a cherry picker lift to lift the hexagonal beam and to verify the design and performance.

And we even tried to put the antenna only on a tripod with the 20m band only 1.5m of the ground. We were able to talk in SSB voice to Bulgaria via Long Path ( Distance 25071 km)